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Section 1 Section 1 Body Organization Focus Levels of Structural Organization Objectives Overview Before beginning this section review with your students the objectives listed in the Student Edition. Students will distinguish among the structure and function of the four tissue types found in the body. They will recognize how tissues are organized into organs and then further into organ systems, the structure and function of the body’s cavities, and how endothermy helps maintain homeostasis. Bellringer Ask students to write down what causes a black eye. Instruct them to read the Real Life feature on the next page when they have finished and compare their answer to the one given there. ● Identify four levels of structural organization within the human body. 5C ● Analyze the four kinds of body tissues. 5A ● List the body’s major organ 10B TAKS 2 systems. ● Evaluate the importance of endothermy in maintaining 4B 11A TAKS 2 homeostasis. Epithelial tissue There are many different kinds of epithelial (ehp ih THEE lee uhl) tissue. Epithelial tissue lines most body surfaces, epithelial tissue nervous tissue connective tissue muscle tissue body cavity and it protects other tissues from dehydration and physical damage. An epithelial layer is usually no more than a few cells thick. These cells are typically flat and thin, and they contain only a small amount of cytoplasm. Epithelial tissue is constantly being replaced as cells die. Figure 1 Body tissues Cells of the body are grouped into different kinds of tissues. Connective tissue Nervous tissue GENERAL Lead a class discussion about all of the activities that occur in the stomach. Ask students if they have muscle tissue in their stomach and, if so, what it does. (Yes; muscle tissue in the stomach mixes food and stomach secretions and moves the food into the small intestines.) Ask them if they have nervous tissue in their stomach and, if so, what it does. (Yes; nervous tissue in the stomach stimulates muscles to contract and glands to secrete, and sends signals such as hunger and satiety to the brain.) TAKS 2 Bio 4B, 10A, 10B (grade 11 only); Bio 5A pp. 846–847 Student Edition TAKS Obj 2 Bio 4B TAKS Obj 2 Bio 10A TEKS Bio 4B, 5A, 5C, 10A, 11A Teacher Edition TAKS Obj 1 Bio/IPC 2C TAKS Obj 2 Bio 4B, 10A, 10B TEKS Bio 4B, 5A, 10A, 10B TEKS Bio/IPC 2C 846 Four Kinds of Tissues Key Terms Motivate Discussion/ Question The human body contains more than 100 trillion cells and more than 100 kinds of cells. How do these cells work together? The body is structurally organized into four levels: cells, tissues, organs, and organ systems. Recall that a tissue is a group of similar cells that work together to perform a common function. The cell types of the body are grouped by function into four basic kinds of tissues: epithelial, nervous, connective, and muscle tissues. These tissues, shown in Figure 1, are the building blocks of the human body. Skeletal muscle Cardiac muscle Epithelial tissue Smooth muscle 846 Chapter Resource File • Lesson Plan GENERAL • Directed Reading • Active Reading GENERAL Transparencies TT Bellringer TT Human Body Tissues TT Major Organ Systems of the Human Body Chapter 37 • Introduction to Body Structure Planner CD-ROM • Reading Organizers • Reading Strategies Nervous Tissue The nervous system is made of nervous tissue. Nervous tissue consists of nerve cells and their supporting cells. Nerve cells carry information throughout the body. You will learn more about the nervous system in Chapter 41. Connective Tissue Various types of connective tissue support, pro- tect, and insulate the body. Connective tissue includes fat, cartilage, bone, tendons, and blood. Some connective tissue cells, such as those in bone, are densely packed. Others, such as those found in blood, are farther apart from each other. Muscle Tissue Three kinds of muscle tissue enable the movement of body structures by muscle contraction. The three kinds of muscle tissues are skeletal muscle, smooth muscle, and cardiac muscle. Real Life A black eye is the common name for bruised tissues around the eye that may also be swollen. The dark color of the bruise is caused by blood oozing into spaces between the tissues from tiny blood vessels that were broken when the eye was injured. 1. Skeletal muscle. Skeletal muscle is called voluntary muscle because you can consciously control its contractions. Skeletal muscles move bones in the trunk and limbs. 2. Smooth muscle. Smooth muscle is called involuntary muscle because you cannot consciously control its slow, long-lasting contractions. Some smooth muscles, such as those lining the walls of blood vessels, contract only when stimulated by signal molecules. Other smooth muscles contract spontaneously. 3. Cardiac muscle. Cardiac muscle is found in the heart. The powerful, rhythmic contractions of cardiac muscle pump blood to all body tissues. Groups of neighboring cardiac cells contract all at once, stimulating adjacent groups of cells to contract. Teach Teaching Tip Fast-Twitch and Slow-Twitch There are two types of skeletal muscle fibers, fast-twitch and slowtwitch. Fast-twitch muscle fibers work quickly and powerfully for performing tasks such as weightlifting. Slow-twitch muscle fibers contract slowly, use less energy, and are used for longer activities, such as distance running. Both types of fibers exist in each of the body’s skeletal muscles in varying proportions depending on the muscle type. TAKS 2 Bio 4B, 10A; Bio 5A READING SKILL BUILDER Interactive Reading Assign Chapter 37 of the Holt Biology Guided Audio CD Program to help students achieve greater success in reading the chapter. Stem Cells Every human starts life as a single fertilized egg, which rapidly divides into a small cluster of cells. After about 5 days, a small ball of a few hundred cells is formed, which encloses a mass of embryonic stem cells. These early, undifferentiated cells will give rise to all of the types of cells of the developing body. Embryonic stem cells are immortal—that is, they divide indefinitely. And embryonic stem cells are not yet specialized. Indeed any embryonic stem cell is capable of becoming any type of tissue found in the adult body. Because they can develop into any tissue, embryonic stem cells offer the possibility of repairing damaged tissues. Stem cell therapy in mice has been shown to repair heart muscle and to produce functional nerve cells in the brain. The use of human embryonic stem cells is very controversial. Because obtaining embryonic stem cells destroys an early embryo, therapeutic use of embryonic stem cells raises serious ethical issues. Adults also have stem cells. Stem cells in bone marrow produce different types of blood cells. The adult brain contains stem cells that develop into new nerve cells. Adult stem cells are not as versatile as embryonic stem cells, and they are not immortal. Most stop reproducing after fewer than 100 cell divisions. Scientists are now at work on several therapeutic applications of adult stem cells. INCLUSION Strategies 847 • English as a Second Language • Attention Deficit Disorder Have students design a class chart of the four kinds of tissue found in the body. The chart should include the kind of tissue, where in the body the tissue is found, the body organs made-up of this tissue, and the function of each type of tissue. Students may also create a chart to identify the different types of muscle and where in the body the different muscle tissues are found. TAKS 1 Bio/IPC 2C; TAKS 2 Bio 4B, 10A, 10B (grade 11 only) Cultural Awareness Qi and The Body In some Asian countries, many people believe that the body has an energy field, call qi (chee), which moves through the body through channels called meridians. The function of qi is thought to be similar to the functions of the nervous and circulatory systems—moving information and energy within the body. Acupuncture, an ancient treatment for pain and many other ailments, is based on the concept of qi. Many scientists now believe that acupuncture is effective for pain because it activates the body’s endogenous opiates. LS Verbal Chapter 37 • Introduction to Body Structure 847 Organ Systems Teach, continued continued Teaching Tip GENERAL Tissue and Organ Transplants Ask students to think of body parts that have been transplanted in humans. Have them identify whether the part is a tissue or an organ. (Their list may include organs such as the heart, kidney, liver, lung, skin, and pancreas, and tissues such as blood, bone marrow, cornea, and bone.) LS Visual Bio 5A Activity Organizational Hierarchy Have students make a Graphic Organizer similar to the one at the bottom of this page to demonstrate that simpler structures in the body are components of more complex structures. Ask students to use the terms cell, tissue, organ, organ system, and body. LS Visual TAKS 1 Bio/IPC 2C; TAKS 2 Bio 4B, 10A, 10B (grade 11 only) Teaching Tip Homeostasis Point out to students that the maintenance of homeostasis in a multicellular organism is a complex process. Communication must be maintained among organ systems, organs, tissues, and even individual cells. Multicellular organisms have elaborate signaling systems that are only now being discovered. Many diseases result from the disruption of homeostasis. Have students select an endocrine or metabolic disorder and write a short report about it. Diseases to suggest include diabetes mellitus, goiter, and porphyria. LS Verbal TAKS 2 Bio 10B (grade 11 only); Bio 4B pp. 848–849 Student Edition TAKS Obj 2 Bio 4B TAKS Obj 2 Bio 10A TAKS Obj 2 Bio 10B TEKS Bio 4B, 5A, 5C, 10A, 10B, 11A Teacher Edition TAKS Obj 1 Bio/IPC 2C TAKS Obj 2 Bio 4B, 10A, 10B TAKS Obj 5 IPC 4B TEKS Bio 4B, 5A, 5C, 10A, 10B, 11A TEKS Bio/IPC 2C; IPC 4B 848 Body organs are made of combinations of two or more types of tissues working together to perform a specific function. The heart, for example, contains cardiac muscle tissue and connective tissue, and the heart is stimulated by nervous tissue. Each organ belongs to at least one organ system, which is a group of organs that work together to carry out major activities or processes. The different organs in an organ system interact to perform a certain function, such as digestion. The digestive system is composed of the mouth, throat, esophagus, stomach, intestines, liver, gallbladder, and pancreas. Some organs function in more than one organ system. The pancreas, for example, functions in both the digestive system and the endocrine system. Table 1 lists the body’s major organ systems. www.scilinks.org Topic: Organ Systems Keyword: HX4131 Table 1 Major Organ Systems of the Body System Major structures Functions Circulatory Heart, blood vessels, blood (cardiovascular) lymph nodes and vessels, lymph (lymphatic) Transports nutrients, wastes, hormones, and gases Digestive Mouth, throat, esophagus, stomach, liver, pancreas, small and large intestines Extracts and absorbs nutrients from food; removes wastes; maintains water and chemical balances Endocrine Hypothalamus, pituitary, pancreas and many other endocrine glands Regulates body temperature, metabolism, development, and reproduction; maintains homeostasis; regulates other organ systems Excretory Kidneys, urinary bladder, ureters, urethra, skin, lungs Removes wastes from blood; regulates concentration of body fluids Immune White blood cells, lymph nodes and vessels, skin Defends against pathogens and disease Integumentary Skin, nails, hair Protects against injury, infection, and fluid loss; helps regulate body temperature Muscular Skeletal, smooth, and cardiac muscle tissues Moves limbs and trunk; moves substances through body; provides structure and support Nervous Brain, spinal cord, nerves, sense organs Regulates behavior; maintains homeostasis; regulates other organ systems; controls sensory and motor functions Reproductive Testes, penis (in males); ovaries, uterus, breasts (in females) Produces gametes and offspring Respiratory Lungs, nose, mouth, trachea Moves air into and out of lungs; controls gas exchange between blood and lungs Skeletal Bones and joints Protects and supports the body and organs; interacts with skeletal muscles, produces red blood cells, white blood cells, and platelets Texas SE page TK 848 Graphic Organizer Use this graphic organizer with Activity on this page. is composed of Body are composed of Organ systems Chapter 37 • Introduction to Body Structure are composed of Organs are composed of Tissues Cells Body Cavities The body contains four large fluid-filled spaces, or body cavities, that house and protect the major internal organs. Within the body cavities, shown in Figure 2, organs are suspended in fluid that supports their weight and prevents them from being deformed by body movements. These organs are also protected by bones and muscles. For example, your heart and lungs are protected by the rib cage and the sternum inside the thoracic (thoh RAS ik) cavity. Your brain, encased within the cranial (KRAY nee uhl) cavity, is protected by the skull. Your digestive organs, located in the abdominal cavity, are protected by the pelvis and abdominal muscles. Your spinal cord is protected by the vertebrae that make up the spinal cavity. Endothermy Like all mammals, humans are endotherms. Humans maintain a fairly constant internal temperature of about 37°C (98.6°F). Your body uses a great deal of energy to maintain a stable internal condition. For example, a large percentage of the energy you consume in food is devoted to maintaining your body temperature. You would not survive very long if your temperature fell much below the normal range. Very high temperatures, such as occur with fever, are also dangerous because they can inactivate critical enzymes. Your body maintains a constant temperature Texas SE page due TK to the flow of blood through blood vessels just under the skin. To release heat to the air, blood flow is increased to these vessels. To retain heat, blood is shunted away from the skin. As an endotherm, you can remain active at external temperatures that would slow the activity of ectotherms. Endothermy enables you to sustain strenuous activity, such as exercise, for a long time. To maintain homeostasis, the body’s organ systems must function smoothly together. The nervous system and the endocrine system operate on negative feedback with other organ systems. This promotes stability throughout the body. In addition to temperature regulation, homeostasis involves adjusting metabolism, detecting and responding to environmental stimuli, and maintaining water and mineral balances. Close Reteaching Figure 2 Body cavities. Many organs and organ systems are encased in protective body cavities. Quiz Cranial cavity epithelial tissue? (to protect other tissues from dehydration and physical damage.) 2. What type of tissue is blood? (connective) 3. Which organ system regulates the concentration of body fluids? (excretory) Spinal cavity Thoracic cavity Diaphragm IPC Benchmark Fact Abdominal cavity Summarize the four levels of structural Critical Thinking Inferring Why should fever organization in the body. be controlled during an illness? List the four different kinds of body tissues, and give an example of each kind. 5A Describe the relationship between organs and organ systems. 10B Relating Concepts How is endothermy advantageous to humans? 4B 11A 4B TAKS Test Prep In which part of the body would you most likely find flat, thin cells that contain only a small amount of cytoplasm? A bone B cardiac muscle C digestive tract lining D skeletal muscle 5A 849 TAKS 2 Bio 10B (grade 11 only) Point out to students that just as bones and muscle protect organs, seat belts also provide vital protection, since according to Newton’s first law of motion, an object in motion maintains its velocity unless it experiences an unbalanced force. The tendency to continue moving is called inertia and explains the need for seat belts because they provide the unbalanced force necessary to stop you from moving once the car has stopped. Without seat belts disastrous consequences—such as being thrown from a car—could result. TAKS 5 IPC 4B Transparencies TT Cavities of the Human Body TT Inside the Human Coelom Answers to Section Review 1. cell—individual unit; tissue—group of similar cells that work together to perform a common function; organ—combination of two or more types of tissues that work together; organ system—group of organs that work together to perform a specific function Bio 5C 2. epithelial—lines body surfaces; nervous—nerve cells; connective—fat, cartilage, bone, tendon, blood; muscle—skeletal, smooth, cardiac Bio 5A 3. An organ system is composed of two or more organs that work together. GENERAL 1. What is the main function of Section 1 Review 5C Use a relationship with which students are more familiar to help them learn the levels of organization in the body. For example, a house is part of a city, which is part of a county, which is part of a state, which is part of the United States. 4. Endothermy allows humans to function in many environments and to engage in strenuous activities for long periods. TAKS 2 Bio 4B; Bio 11A 5. It is important to control a fever because high temperatures can inactivate essential enzymes. TAKS 2 Bio 4B 6. A. Incorrect. Bone tissue is composed of densely packed cells. B. Incorrect. Cardiac muscle tissue is composed of interconnected cells. C. Correct. The lining of the digestive tract is epithelial tissue, which is composed of thin, flat cells. D. Incorrect. Skeletal muscle is not composed of flat, thin cells. Bio 5A Chapter 37 • Introduction to Body Structure 849 Section 2 Section 2 Skeletal System Focus Overview Before beginning this section review with your students the objectives listed in the Student Edition. Students will describe the components of the skeletal system and the structure of bone, how bones grow and how they lose density, and the structure and function of the body’s joints and how they can become damaged. Bellringer Have students try to perform several activities without bending their fingers, such as picking up a pencil, taking off or putting on a jacket, or turning a page in a book. Then, have them write two or three sentences about joints and their importance. Objectives The Skeleton ● Distinguish between the axial skeleton and the appendicular skeleton. 10A ● ● ● ● What keeps your body from collapsing like a limp noodle? An internal skeleton of bones shapes and supports your body. Your skeleton provides protection for internal organs and, along with muscles, TAKS 2 enables movement with a versatile system of levers and joints. MusAnalyze the structure of cles pull against bones at joints, moving the limbs and the trunk. bone. 10A TAKS 2 Your skeleton is made mostly of bone, a type of hard connective Summarize the process tissue that is constantly being formed and replaced. The human skel10A of bone development. TAKS 2 eton, shown in Figure 3, contains 206 individual bones. Of these, 80 List two ways to prevent bones form the axial skeleton , which includes bones of the skull, 10A 10B osteoporosis. spine, ribs, and sternum. The other 126 bones, including those of the TAKS 2 Identify the three main arms, legs, pelvis, and shoulder, form the appendicular (ap uhn classes of joints. 10A TAKS 2 DIHK yoo luhr) skeleton . Key Terms axial skeleton appendicular skeleton bone marrow periosteum Haversian canal osteocyte osteoporosis joint ligament Skeleton Skull Clavicle Scapula Sternum Humerus Vertebra Radius Motivate Ulna Discussion/ Question Pelvic girdle Ask students what they already know about different types of joints. Tell them the names of the types of joints. Ask them to provide an example of each type and to describe the movement for which each type is adapted. Axial Skeleton The most complex part of the axial skeleton is the skull. Of the 29 bones in the skull, 8 bones Texas SE page TK form the cranium, which encases the brain. The skull also contains 14 facial bones, 6 middle-ear bones, and a single bone that supports the base of the tongue. The skull is attached to the top of the spine, or backbone, which is a flexible, curving column of 26 vertebrae that supports the center of the body. Curving forward from the middle vertebrae are 12 pairs of ribs, which form a protective rib cage around the heart and lungs. Metacarpals Carpals Femur Patella Tibia TAKS 2 Bio 10A, 10B (grade 11 only) Fibula Tarsals Figure 3 Skeleton. Bones of the appendicular skeleton “hang” from bones of the axial skeleton (purple). Metatarsals Appendicular Skeleton The appendicular skeleton forms the appendages or limbs—the shoulders, arms, hips, and legs. The arms and legs are attached to the axial skeleton at the shoulders and hips, respectively. The shoulder attachment, called the pectoral girdle, contains two large, flat shoulder blades, or scapulas, and two slender, curved 850 Chapter Resource File • Lesson Plan GENERAL • Directed Reading • Active Reading GENERAL pp. 850–851 Student Edition TAKS Obj 2 Bio 10A TAKS Obj 2 Bio 10B TEKS Bio 10A, 10B Teacher Edition TAKS Obj 2 Bio 4B, 10A, 10B TEKS Bio 4B, 5A, 5C, 10A, 10B, 11C 850 Transparencies TT Bellringer TT The Structure of Bone Tissue TT Compact Bone Chapter 37 • Introduction to Body Structure Planner CD-ROM • Reading Organizers • Reading Strategies • Occupational Application Worksheet Physical Therapist GENERAL collarbones, or clavicles. The clavicles connect the scapulas to the upper region of the sternum and hold the shoulders apart. This arrangement enables full rotation of the arms about the shoulder. The hip attachment, called the pelvic girdle, contains two large pelvic bones. The pelvic bones distribute the weight of the upper body evenly down the legs. The word periosteum is from the Greek peri, meaning “around,” and osteon, meaning “bone.” Teach Teaching Tip Tissues in Bone Point out to students that, while bone is composed primarily of connective tissue, it also contains the other three types of body tissues. Bone has nerve cells that can send pain signals to the brain if a bone is broken. Bone also contains smooth muscle tissue in the walls of the blood vessels that carry materials into and out of bone, as well as epithelial tissue in the walls of these blood vessels. Bone also has a wide variety of connective tissues, including blood, fat, mineralized connective tissue, as well as ligaments and tendons attached to the bones. Structure of Bone As shown in Figure 4, bones are made of a hard outer covering of compact bone surrounding a porous inner core of spongy bone. Compact bone is a dense connective tissue that provides a great deal of support. Spongy bone is a loosely structured network of separated connective tissue. Some cavities in spongy bone are filled with a soft tissue called bone marrow. Red bone marrow begins the production of all blood cells and platelets. The hollow interior of long bones is filled with yellow bone marrow. Yellow bone marrow consists mostly of fat, which stores energy. Bones are surrounded and protected by a tough exterior membrane called the periosteum (pair ee AHS tee uhm). The periosteum contains many blood vessels that supply nutrients to bones. Figure 4 Structure of bone Many bones contain bone marrow, blood vessels, and both compact and Texas SE page TK spongy bone tissue. TAKS 2 Bio 4B; Bio 5A, 5C Teaching Tip Bone marrow Mnemonics for Bone Names Tell students some simple ways to remember the names of bones. For example, the scapula is large and flat like a spatula; the ulna ends at the elbow (both first letters are vowels); the radius radiates around the ulna; the metacarpals are where fingers meet the carpals; the sternum looks like a tie (stern people wear ties); the fibula is the little bone in the lower leg (a little lie is a fib); tarsals are bones in your feet (you get tar on the soles of your feet) LS Verbal Periosteum (outer layer) Spongy bone Compact bone Blood vessels Using the Figure 851 INCLUSION Strategies • Gifted and Talented Using reference materials or the Internet, have students research the condition known as osteoporosis. The students should learn about the condition and its cause, why it affects women more than men, and what types of action can be taken to prevent the onset of osteoporosis. Students can then develop a taped or live public service announcement or brochure to share the information they have learned with others. did you know? Hyoid Bone The hyoid bone is the origin for the tongue muscles. You can find it by feeling the neck, lateral to the Adam’s apple, directly beneath the carotid arteries. If you push gently on one side of the throat, you can feel the bone easily on the opposite side. This bone can be broken by choking, making it very painful to speak or swallow. LS Kinesthetic Direct students’ attention to Figure 3. Point out the bones of the axial skeleton. (bones of the skull, spine, and rib cage) Ask students to identify the functions of these bones. (to enclose and protect internal organs and provide vertical support) Point out the bones of the appendicular skeleton. (the bones of the pectoral and pelvic girdles, arms, and legs) Ask students to identify the functions of these bones. (to provide attachment of the limb bones to the axial skeleton and to enable gross motor movement) LS Visual TAKS 2 Bio 10B (grade 11 only); Bio 5A Bio 11C Chapter 37 • Introduction to Body Structure 851 Growth of Bones Teach, continued continued Real Life Answer Bio 3D GENERAL Answers will vary. Encourage students to use the media center to find nonfictional accounts of crime solving. LS Verbal Teaching Tip Living Bones Students may think that bone has few of the traits of living tissue. Emphasize that the bony endoskeleton of vertebrates grows as the animal matures. This is unlike the hard exoskeleton of invertebrates, which must be shed for the animal to grow. The non-living components of bone— crystalline material that surrounds the living bone cells—give bone its strength and hardness. Real Life Years after an unsolved murder is committed, the victim’s bones may hold clues to the crime. Forensic anthropologists have solved many cases by analyzing bones and other human remains found at crime scenes. Finding Information Read some accounts of crimes solved by forensic anthropologists to learn how these scientists analyze bones. 3D In early development, the skeleton is made mostly of cartilage, a type of connective tissue that serves as a template for bone formation. During development, most cartilage is gradually replaced by bone as minerals are deposited. Deposits of calcium and other minerals harden bones, enabling them to withstand stress and provide support. In compact bone, new bone cells are added in layers around narrow, hollow channels called Haversian canals. Haversian canals extend down the length of a bone, and they contain blood vessels that enter the bone through the periosteum. As shown in Figure 5, layers of new bone cells form several concentric rings around Haversian canals. These rings form columns that enable the bone to withstand tremendous amounts of stress. Eventually, bone cells called osteocytes (AHS tee oh siets) become embedded within the bone tissue. Osteocytes maintain the mineral content of bone. The blood vessels that run through each Haversian canal supply the osteocytes with nutrients needed to maintain bone cells. Bones continue to thicken and elongate through adolescence as bone cells replace cartilage. Bone elongation occurs at the ends of long bones. Cartilage degenerates as new bone cells are added, causing bones to lengthen. Figure 5 Compact bone In compact bone, concentric rings of bone surround Haversian canals. Bone marrow TAKS 2 Bio 4B; Bio 5A READING SKILL Haversian canal BUILDER Paired Reading Pair each student with a partner. Have each student read silently about bone growth and osteoporosis. After students finish reading, ask one student from each pair to summarize what he or she understood, referring to the text when needed. The second student should add anything omitted. Both students should then describe what they found confusing and should work together to understand all the passages. Have them prepare a list of questions to pose to the class about passages that are still unclear after their collaboration. LS Interpersonal Osteocytes Periosteum Vein Artery Haversian canals 852 MISCONCEPTION ALERT pp. 852–853 Student Edition TAKS Obj 2 Bio 10A TEKS Bio 3D, 10A, 11C Teacher Edition TAKS Obj 1 Bio/IPC 2C TAKS Obj 2 Bio 4B, 10A, 10B TEKS Bio 3D, 3E, 4B, 5A, 10A, 10B, 11C TEKS Bio/IPC 2C 852 Calcium in Bones Most people know that calcium is needed for healthy bones. However, most people don’t know that bone tissue serves as a storage site for calcium. If calcium is needed elsewhere in the body (such as for nerve or muscle function), it may be released from the bones in a process called reabsorption. Conversely, if calcium is abundant in the body, it may be added to the bones. Parathyroid hormone, produced in Chapter 37 • Introduction to Body Structure the parathyroid glands, stimulates the release of calcium from bone cells into the blood. This hormone is released in response to low blood calcium levels detected by the parathyroid glands. Calcitonin, produced in the thyroid gland, stimulates the absorption of calcium into bone cells from the blood. This hormone is released in response to high blood calcium levels detected by the hypothalamus. TAKS 2 Bio 4B, 10A Teaching Tip Normal bone Bone in osteoporosis Dowager’s hump Osteoporosis In young adults, the density of bone usually remains constant. However, around the age of 35, bone replacement gradually becomes less efficient and some bone tissue is lost. Severe bone loss, as shown in Figure 6, can lead to a condition called osteoporosis (ahst ee oh puh ROH sihs), which means “porous bone.” Bones affected by osteoporosis become brittle and are easily fractured. Although both women and men lose bone tissue as they age, more women than men are affected by osteoporosis. Because women’s bones are usually smaller, women cannot afford to lose as much bone tissue as men. In addition, the production of sex hormones decreases after menopause. This decrease in hormone production has been linked to an increased rate of bone loss in women following menopause. You can take action now to prevent future osteoporosis. Building strong bones now will make you less likely to be affected by osteoporosis later in life. A mineral-rich diet that includes dairy products, green leafy vegetables, whole grains, and legumes such as those shown in Figure 7, together with regular exercise throughout your life will help maintain bone density. Figure 6 Effects of osteoporosis. Compare the density of a normal bone with that of a bone weakened by osteoporosis. One sign of osteoporosis is the familiar “dowager’s hump” of the back, caused by curvature of the spine. Figure 7 Preventing osteoporosis. A proper diet and regular exercise help reduce the risk of osteoporosis. 853 LS Logical Group Activity Spinal Flexibility Have students work in groups to create models of the vertebral column. Provide each group with empty or partly filled sewing thread spools and a very long shoelace or cording. (about 2 feet long) Instruct students to thread the lacing or cording through successive spools, tying a knot between each spool. (It might be necessary to tie one knot on top of another in order to keep the knot from slipping through the spools.) Have each group create a string of spools on their lacing or cording. Next ask students to make observations on the flexibility of each individual “joint” in the string of spools and on the whole length of spools, and to compare this flexibility to that of the human vertebral column. Point out that the small range of motion of the joints between each vertebra has a compounding effect. Although each joint allows only a small amount of movement between two individual bones, when added across all 26 vertebrae, the human spine is very flexible. TAKS 1 Bio/IPC 2C TAKS 2 Bio 10A, 10B (grade 11 only); Bio 3E Demonstration REAL WORLD CONNECTION Exercise is as important for building and maintaining strong bones as it is for building strong muscles. Exercise becomes especially important as people grow older, when bone mass begins to decrease due to hormonal and other physiological changes. Two types of exercises are important for maintaining healthy bones: weight-bearing and resistance exercises. Weight-bearing exercises Strong Bones Tell students that, although bones are lightweight, they are very strong. A human long bone has the tensile strength of cast iron, but it weighs only onethird as much. A bone can resist 25,000 lb/in.2 (1,800 kg/cm2) of compression and 15,000 lb/in.2 (1,100 kg/cm2) of tension. are exercises in which your bones and muscles bear your body weight and include activities such as jogging, walking, soccer, tennis, stair climbing, and dancing. Swimming and bicycling are not weight-bearing exercises. Resistance exercises involve using the bones and muscles to work against a force or weight and include activities such as free weights and weight machines found at gyms and health clubs. Soak a cooked, clean chicken bone in vinegar overnight to remove much of the calcium from the bone. Compare the flexibility of the soaked bone with that of a cooked, clean bone that has not been soaked. Relate these ideas to what happens to bone due to osteoporosis. LS Visual Bio 3E Bio 11C Chapter 37 • Introduction to Body Structure 853 Joints A joint is where two bones meet. Pads of cartilage cushion the ends of the bones of a joint, enabling the joint to withstand great pressure and stress. The bones of a joint are held together by strong bands of connective tissue called ligaments . Ligaments not only help stabilize joints but also prevent joints from moving too far in any one direction. Many sports-related injuries to ligaments are caused by an impact that forces a joint to overextend. Injury occurs because the impact exceeds the tension that the ligaments can withstand. Teach, continued continued Teaching Tip The Soft Spot Many students who have younger siblings know that a baby has a soft spot on the top of its head. Explain that the soft spot is an area where sections of the skull have not grown together and fused. This area will become an immovable joint as the baby matures. Tell students that several layers of tough membranes protect the brain, but care must be taken not to injure the baby’s vulnerable head. TAKS 2 Bio 10B (grade Three Main Types of Joints The skeletal system contains three main types of joints that enable varying degrees of movement: immovable joints, slightly movable joints, and freely movable joints. Examples of the three types of joints are shown in Figure 8. Figure 8 Types of joints. The body contains immovable, slightly movable, and freely movable joints. Immovable joint 11 only); Bio 5B Pivot joint Group Activity Orthopedic Sports Injuries Have students work in small groups to research sports injuries to the skeletal or muscular systems. Ask each group to choose a specific type of injury (e.g., jumper’s knee, shin splints, runner’s knee, tennis elbow), or a category of injuries (e.g., injuries to a specific body part, injuries commonly associated with a specific sport, or injuries of a particular tissue such as bones, muscles, tendons, or ligaments). Ask each group to prepare a poster or brochure that describes the injury type they have researched and includes labeled illustrations. Have students present their findings to the class or display their projects so that other class members can examine them all. TAKS 1 Bio/IPC 2C Slightly movable joints Immovable Joints Tight joints that permit little or no movement of the bones they join are called immovable joints. The cranial bones of the skull are joined by sutures, a type of immovable joint in which the bones are separated by only a thin layer of connective tissue. Slightly Movable Joints Joints that permit limited movementTexas of theSE bones pagethey TKjoin are called slightly movable joints. For example, the vertebrae of the spine are joined by cartilaginous joints, which are a kind of slightly movable joint in which a bridge of cartilage connects the bones. Slightly movable joints are also located between bones of the rib cage. Freely Movable Joints In joints that permit movement, Hinge joint the direction of bone movement is determined by the structure of the joint. Joints that permit the most movement are called freely movable joints. Some kinds Saddle joint Table 2 Movable Joints Ball-andsocket joint Gliding joint Joint Type of movement Examples Ball-and-socket joint All types Shoulders and hips Pivot joint Rotation Top of spine (turning of head) Hinge joint Bending and straightening Elbows, knuckles of fingers and toes Gliding joint Sliding motion Wrists and ankles Saddle joint Rotation, bending, and straightening Base of thumbs 854 did you know? pp. 854–855 Student Edition TAKS Obj 2 Bio 10A TAKS Obj 2 Bio 10B TEKS Bio 10A, 10B, 11C Teacher Edition TAKS Obj 1 Bio/IPC 2C TAKS Obj 2 Bio 10A, 10B TAKS Obj 5 IPC 4C TEKS Bio 3E, 3F, 5B, 10A, 10B, 11C TEKS Bio/IPC 2C, 3C; IPC 4C 854 Artificial Hip Joint In 1963, a British orthopedic surgeon revolutionized arthritic hip therapy when he created an artificial hip joint. He created a metal (vitalium) ball and plastic (polyethylene) socket. The plastic socket is cemented to the pelvis. This invention has helped many people, including children who are born with a hip socket that is too shallow and bones that are not aligned properly as well as arthritis patients who suffer disabling pain in the hip joint. Bio 3F, Bio/IPC 3C Chapter 37 • Introduction to Body Structure IPC Benchmark Review To prepare students for the TAKS and accompany the discussion of joints and movement, have students review Types of Simple Machines TAKS 5 IPC 4C on p. 1057 of the IPC Refresher in the Texas Assessment Appendix of this book. Figure 9 Knee. The knee is an example of a freely movable joint. Muscle Tendon Close Reteaching Cartilage Have students examine prepared slides of cartilage and bone. Ask them to explain how the structure of cartilage and bone is related to the function each performs in the body. (Students’ responses will vary but should describe the hardness of bone, the role of bone in support and protection, the flexibility of cartilage, and the role of cartilage as a precursor of bones.) LS Visual Patella (kneecap) Ligaments Fibula (bone) Tibia (bone) of freely movable joints are listed in Table 2. The structure of one freely movable joint, the knee, is shown in Figure 9. Disorders of Joints TAKS 2 Bio 10A www.scilinks.org Topic: Joint Disorders Keyword: HX4107 Quiz Recall that ligaments hold the bones of a joint together. A lining of SE page TK tissue that surrounds the jointTexas secretes a lubricating fluid that reduces friction at the ends of the bones. When a disease afflicts the bones, connective tissue, or lubricating tissues in a freely movable joint, the joint’s ability to move may be greatly impaired. Rheumatoid arthritis is a painful inflammation of freely movable joints. This condition occurs when cells of the immune system attack the tissues around joints, severely damaging the joints. Symptoms of rheumatoid arthritis include stiffening and swelling of the joints. Osteoarthritis is a similar disorder that causes the degeneration of cartilage that covers the surfaces of bones. As the cartilage wears away, the bones rub together, causing pain. GENERAL 1. Name one major function of the axial skeleton. (vertical support, protection of internal organs) 2. What is the relationship between cartilage and bone? (In vertebrates, the skeleton of the embryo is composed of cartilage. As the young animal grows, most of the cartilage is generally replaced by bone tissue.) 3. Which kind of joint has the greatest range of motion? (freely movable joints) Section 2 Review Distinguish between the axial skeleton and Critical Thinking Relating Concepts the appendicular skeleton. The bones of a newborn baby are made mostly of cartilage. Why is that an advantage during 10A 10B childbirth? 10A Differentiate between compact bone and spongy bone. 10A Describe how bones elongate in development. 10A List the three main types of joints, and give an example of each type. 10A Analyzing Information Why are women more likely than men to develop osteoporosis? 10A 10B TAKS Test Prep What effect does regular 11C exercise have on the skeletal system? A reduces bone mass B leads to osteoporosis C maintains bone density D makes bones more porous 855 GENERAL Have students make models of joints and bone cross sections using door hinges, old antennas, poster board, plastic foam, marking pens, and other readily available materials. On cross sections, students should label the parts of the bone. Place the models into their portfolios. TAKS 1 Bio/IPC 2C; Bio 3E Transparencies Answers to Section Review 1. The axial skeleton makes up the axis or center of the skeleton and is composed of the skull, spine, ribs, and sternum. The appendicular skeleton is composed of the remainder of the bones. TAKS 2 Bio 10A 2. Compact bone is dense; spongy bone is loosely connected and porous. TAKS 2 Bio 10A 3. Bone cells gradually replace cartilage at the ends of the bones. TAKS 2 Bio 10A 4. immovable—cranium; slightly movable— vertebrae; freely movable—knee, elbow, hip, and shoulder TAKS 2 Bio 10A Alternative Assessment 5. Women usually have less bone tissue to lose, and after menopause their production of sex hormones decreases. TAKS 2 Bio 10A, 10B 6. Cartilage is more flexible than bone, making passage through the birth canal easier. TT Effects of Osteoporosis TT The Human Knee TAKS 2 Bio 10A, 10B 7. A. Incorrect. Regular exercise increases bone mass. B. Incorrect. Regular exercise helps protect against osteoporosis. C. Correct. Regular exercise throughout life helps to maintain bone density. D. Incorrect. Regular exercise makes bones less porous. Bio 11C Chapter 37 • Introduction to Body Structure 855 Section 3 Section 3 Muscular System Focus Objectives Overview Before beginning this section review with your students the objectives listed in the Student Edition. Students will understand how the skeleton is moved by muscles, how muscle tissue is constructed, and how muscle tissue contracts. They will describe aerobic and anaerobic muscle contraction and develop an appreciation for how exercise affects muscle health. Bellringer Have students alternately bend and straighten their arms or legs while feeling the muscles in the front and the back. Tell them to write a description of what they feel when the limb is straightened versus bent. This activity can lead to a discussion of how muscles work in opposition to bend and straighten the limbs at the joints. ● Describe the action of muscle pairs in moving 10A TAKS 2 the body. ● Relate the structure of a skeletal muscle to the muscle’s ability to contract. 10A TAKS 2 ● Describe how energy is supplied to muscles for contraction. 4B TAKS 2 Key Terms tendon flexor extensor actin myosin myofibril sarcomere TAKS 2 Bio 10A, 10B (grade 11 only) Muscles and Movement Every time you move, you use your muscles. Walking and running, for example, require precisely timed and controlled contractions of many skeletal muscles. When you lift a heavy object, the total force produced by muscle contractions in your arm must overcome the weight of the object. Muscles in your jaw contract and enable you to chew food with your teeth. Even when you are idle, many skeletal muscles, including those in your back and neck, remain partially contracted to maintain balance and posture. Movement of the Skeleton Muscles can move body parts because muscles are attached to bones of the skeleton. As shown in Figure 10, most skeletal muscles are attached to bones by strips of dense connective tissue called tendons . One attachment of the muscle, the origin, is a bone that remains stationary during a muscle contraction. The muscle pulls against the origin. The other attachment, the insertion, is the bone Texas SE page TK that moves when the muscle contracts. Movement occurs when a muscle contraction pulls the muscle’s insertion toward its origin. Skeletal muscles are generally attached to the skeleton in opposing pairs. One muscle in a pair pulls a bone in one direction, and the other muscle pulls the bone in the opposite direction. In the limbs, each opposing pair of muscles includes a flexor muscle and an extensor muscle, as shown in Figure 10. A flexor muscle causes a joint to bend. An extensor muscle causes a joint to straighten. Figure 10 Muscle pair Pairs of opposing muscles work together to move bones at joints. Motivate Have a volunteer hold his or her right arm straight out, palm up, at shoulder level. Ask him or her to place the left thumb and index finger lightly on the right biceps about two inches apart and raise the right palm to the shoulder. Have the student explain what happens to the fingers. (The fingers should move closer together, demonstrating that the muscle is actually shortening.) The demonstration works best with the sleeve rolled up. LS Kinesthetic TAKS 2 Bio 10A Triceps muscle (extensor) Biceps muscle (flexor) Tendon Biceps contraction Triceps contraction 856 Chapter Resource File pp. 856–857 Student Edition TAKS Obj 2 Bio 4B TAKS Obj 2 Bio 10A TAKS Obj 2 Bio 10B TEKS Bio 4B, 10A, 10B Teacher Edition TAKS Obj 2 Bio 6D, 8C, 10A, 10B TEKS Bio 5A, 5C, 6D, 8C, 10A, 10B Triceps muscle (extensor) Insertion • Lesson Plan GENERAL • Directed Reading • Active Reading GENERAL 856 Origin Biceps muscle (flexor) Demonstration Transparencies TT TT TT TT Bellringer Opposing Muscles of the Arm Structure of Skeletal Muscle Contraction of a Muscle Chapter 37 • Introduction to Body Structure Planner CD-ROM • Reading Organizers • Reading Strategies Figure 11 Skeletal muscle In skeletal muscle, contraction occurs within the sarcomeres of muscle fibers. Teach Using the Figure Muscle fiber Z line Myosin filament Actin filament Texas SE page TK Sarcomere TAKS 2 Bio 10A, 10B; Bio 5A, 5C Myofibril Muscle Structure Muscles contain some connective tissue, which holds muscle cells together and provides elasticity. Muscle tissue also contains large amounts of contractile protein filaments. These protein filaments, called actin and myosin (MIE oh sihn), enable muscles to contract. Actin and myosin are usually found in the cytoskeleton of eukaryotic cells, but they are far more abundant in muscle cells. Other characteristics of muscle tissue include the ability to stretch or expand and the ability to respond to stimuli, such as signal molecules released by nerve cells. Skeletal muscle tissue consists of many parallel elongated cells called muscle fibers. As shown in Figure 11, each muscle fiber contains small cylindrical structures called myofibrils (mie oh FIE bruhlz). Myofibrils have alternating light and dark bands that produce a characteristic striated, or striped, appearance when viewed under a microscope. In the center of each light band is a structure called a Z line, which anchors actin filaments. The area between two Z lines is called a sarcomere (SAHR koh mihr). Thus, a myofibril is a grouping of sarcomeres linked end to end. Each sarcomere contains overlapping thin and thick protein filaments that move and interact with each other. The thin filaments are actin, and the thick filaments are myosin. The filaments run parallel to one another along the length of the sarcomere. The dark bands that occur in the middle of the sarcomere are regions where the thick filaments and the thin filaments overlap. Demonstration www.scilinks.org Topic: Muscle Structure Keyword: HX4126 857 did you know? Achilles Tendon The Achilles tendon is the thickest and strongest tendon in the human body. According to ancient Greek mythology, Achilles’ mother dipped him in the magical River Styx to make him an invulnerable warrior. As she immersed him, she held him by one heel and forgot to dip him a second time so the heel she held could become wet too. Therefore, Direct students’ attention to Figure 11. Point out the muscle fibers, myofibrils, sarcomeres, Z lines, actin, and myosin. Make sure that students understand the separate levels of organization shown in the figure. Help students understand that muscles comprise many bundles of muscle fibers, that a muscle fiber contains many myofibrils, and that a myofibril consists of actin and myosin. Remind students that muscle contractions begin at the microscopic level—with actin and myosin. the place where she held him remained untouched by the magic water of the Styx and that part stayed mortal or vulnerable. He was killed when an arrow pierced his one weak point, the place on his heel where his mother held on to him. To this day, any weak point is called an “Achilles’ heel.” The Achilles tendon is named for this mythical hero. GENERAL Provide students with diagrams of part or all of a few insects’ skeletal and muscular systems, including at least one flying insect. Provide them also with diagrams of parts or all of a few vertebrate’s skeletal and muscular systems, including at least one bird. Ask students to compare the attachments of muscles to skeleton in the insects and the vertebrates. (The insects’ muscles are attached to their exoskeletons and the vertebrates’ muscles are attached to their endoskeletons.) Ask students to compare skeletal movements in the insects and the vertebrates. (Both types of animals move their skeletons by contracting muscles; the insects’ muscles are inside of their exoskeletons and the vertebrates’ muscles are external to their endoskeletons.) Ask students to compare the muscle and skeletal structures and functions involved in flight in an insect and a bird. (The insect does not have muscles in its wing as the bird does. The insect moves it wings by the actions of muscles attached to different points on the exoskeleton. These actions cause the wings to move back and forth. The bird moves it wings by the actions of muscles in the chest area of the body and in the wings.) TAKS 2 Bio 8C, 10A, 10B, 6D (grade 10 only); Bio 5C Chapter 37 • Introduction to Body Structure 857 Muscle Contraction How does a muscle contract? Muscle contraction occurs in the sarcomeres of myofibrils. The overlapping arrangement of the thick and thin protein filaments in a sarcomere enables muscle contraction. The events of a muscle contraction are summarized in Figure 12. Teach, continued continued Teaching Tip GENERAL Sarcomeres Ask students to research muscle contraction using the Web site in the Internet Connect box on the next page. Have them draw a diagram of a sarcomere before and during a contraction, and ask them to annotate their drawings. LS Visual TAKS 1 Bio/IPC 2C Using the Figure Direct students’ attention to Figure 12. Interlace the fingers of your hands to show how actin and myosin slide past each other in the sarcomeres. Have students contract a muscle (such as the gastrocnemius of the calf), and point out that they should feel the muscle become shorter and thicker. Explain that this is the result of the contraction of many sarcomeres within the muscle. LS Kinesthetic TAKS 2 Bio 4B, 10A; Bio 3E Activity Have students curl their middle finger under and place their fingertips down on a table. Have them try to raise their fingers one by one. They should be able to lift all fingers except the ring finger. Explain that each finger has a tendon, and those tendons attach to a muscle in the arm. The tendons in the middle and ring finger are linked together in the hand, connecting their movement. LS Kinesthetic TAKS 2 Bio 10A Step Before a muscle is stimulated, the sarcomere is relaxed. Myosin and actin filaments partially overlap one another. Step A muscle contraction usually begins when a muscle fiber is stimulated by signal molecules released by a nerve cell. This causes myosin and actin filaments to “slide” along one another so that they overlap even more. The sarcomere becomes shorter as the Z lines are pulled closer together. Step The sarcomere is fully contracted, and myosin and actin completely overlap one another. This shortening of sarcomeres occurs down the entire Figure 12 Figure 38-12 length of the muscle fiber. What determines the force of conMuscle Contraction traction? A muscle exerts the greatest ic h p a r g During a muscle contraction, force when all of its fibers are consarcomeres in myofibrils shorten. tracted. When a fiber is stimulated, its sarcomeres contract. The total Sarcomere Myofibril amount of force a muscle exerts depends on how often muscle fibers are stimulated and how many muscle fibers contract. How is the force of muscular conMyosin Actin traction controlled? As different numbers of fibers in a muscle con1 The sarcomere is relaxed. Z line tract at one time, the total force generated by contraction varies. For example, the total amount of force needed to lift a pencil is much less than the force needed to lift a brick. Thus, fewer muscle fibers in your 2 Contraction begins as actin and myosin overlap. arm contract when you lift a pencil than when you lift a brick. The set of muscle fibers activated by a nerve cell is called a motor unit. Every time a nerve cell activates its motor unit, all the fibers in that unit contract. Muscles that require a finer degree of control, 3 Contraction is completed. such as muscles that move the fingers, have only a few muscle fibers in each motor unit. Large muscles, such as muscles in the leg, have several hundred muscle fibers in each motor unit. BIO 858 MEDICINE CONNECTION pp. 858–859 Student Edition TAKS Obj 2 Bio 4B TAKS Obj 2 Bio 10A TAKS Obj 2 Bio 10B TEKS Bio 4B, 10A, 10B Teacher Edition TAKS Obj 1 Bio/IPC 2C TAKS Obj 2 Bio 4B, 6D, 10A TAKS Obj 3 Bio 7B TAKS Obj 5 IPC 4D TEKS Bio 3E, 3F, 4B, 6D, 7B, 9A, 10A TEKS Bio/IPC 2C; IPC 4D 858 Because movement requires energy, students might assume that ATP is consumed at the moment muscles contract. A key discovery made by the British physiologist and biophysicist Archibald V. Hill, however, helped biologists determine the sequence of events. Hill discovered that muscle cells use ATP after, not during, contraction. ATP does not Chapter 37 • Introduction to Body Structure cause contraction, rather ATP prepares the muscle for the next contraction. In 1922 Hill received a Nobel Prize in medicine and physiology for his work on muscles. His work was continued by Hugh Huxley, who formulated a theory that explained the role of ATP in cocking myosin heads prior to the contraction of the sarcomere. TAKS 2 Bio 4B; Bio 3F, 9A Interaction of Myosin and Actin How do actin and myosin cause sarcomeres to shorten during a muscle contraction? Myosin filaments have long, finger-like projections with an enlarged “head” at one end. Actin filaments contain many sites to which myosin can bind during a muscle contraction. Stimulation of a muscle fiber leads to the exposure of these binding sites on actin filaments. As shown in Figure 13, the myosin heads attach to the binding sites on actin filaments and then rotate, causing myosin to move relative to actin. Step Muscle contraction begins as a myosin head attaches to an exposed binding site on an actin filament. Step The myosin head rotates, causing the actin filament to “slide” against the myosin filament. This sliding causes the filaments to overlap one another. Step ATP is used as the myosin head detaches and snaps back into its original position. The myosin head reattaches to actin at a binding site farther along the actin filament. When the myosin heads cannot move farther, they release momentarily and reposition themselves to grab the actin and pull again. Thus, the myosin heads “walk” along actin filaments, essentially “stepping” at each available binding site. This grabbing and pulling action is repeated, causing the sarcomere to shorten as the Z lines are pulled closer together. www.scilinks.org Topic: Muscle Contraction Keyword: HX4125 1 Using the Figure Have four students stand in a straight line, one behind the other, with their hands on their hips. Have a fifth student face the leader of the line and slowly pull herself along the line by grasping the elbow of each member of the line in succession. Ask students to relate Figure 13 to the demonstration. (The fifth student represents myosin; the others are actin. The fifth student’s hand is the myosin head.) LS Kinesthetic TAKS 2 Bio 10A; Bio 3E Figure Figure13 38-13 Interaction of Muscle Protein Filaments IPC Benchmark Fact During a muscle contraction, myosin and actin move against one another. Muscle contraction begins as a myosin head attaches to a binding site on an actin filament. 2 The myosin head rotates, causing the actin filament to "slide" against the myosin filament. 3 Explain to students that resistance exercises such as weight lifting often involve a simple machine known as a human forearm, which is an example of a third-class lever. Your biceps muscle attaches near the elbow, which is the fulcrum. It contracts a short distance to move the forearm a long distance. Have students identify other third-class levers of the human body. Ask them if any human body joints are like other simple machines such as the inclined plane or pulley. TAKS 5 IPC 4D (grade 11 only) ATP is used as the myosin head detaches from the binding site and snaps back into its original position. Myosin head Myosin filament Myosin head Z line Binding site Actin filament Rigor Mortis After death, ATP production stops. Without ATP, myosin heads attach to actin filaments but cannot detach. As a result, all the muscles are locked in their contracted position, making the body rigid. This condition is known as rigor mortis (“stiffness of death”), and it persists for up to 25 hours after death. TAKS 2 Bio 4B; Bio 9A A lot of energy is needed to power a muscle contraction. ATP is used each time a myosin head moves from one binding site on an actin filament to another. Without ATP, myosin heads would remain attached to actin filaments, keeping the muscle contracted. ATP is also used to move calcium ions into muscle cells. Calcium ions are needed for binding sites to be exposed on actin filaments. Without calcium ions and ATP, a muscle could not contract. IO B graphic Teaching Tip ATP ATP Binding site 859 Transparencies Face Muscles The human face has 44 separate muscles, four of which are devoted to chewing and 40 to facial expression. No other species has such capacity for making faces. It is now clear that extraordinary amounts of information can be gleaned by systematically measuring facial expression. Researchers have recently found a way to measure changes in facial muscle tension that are too small to create visible movements. They have discovered that when normal people merely think about certain mildly emotional topics, such as recalling happy or sad experiences, tension increases slightly in some facial muscles. Sensitive facial expression measurement techniques such as this aid in determining subtleties of feelings and attitudes, especially when verbal reports are untrustworthy or unavailable. TAKS 2 Bio 6D (grade 10 only), 10A; TT Filaments TAKS 3 Bio 7B Chapter 37 • Introduction to Body Structure 859 Aerobic and Anaerobic Energy Pathways The ATP used to power contractions is usually supplied by aerobic respiration. During prolonged exercises, such as a long-distance walk, oxygen is consumed at a sustainable, steady rate, and aerobic respiration yields most of the ATP. However, during brief, intense activities, such as sprinting and weight lifting, anaerobic processes take over. Most of the ATP used in such activities comes from glycolysis, as the oxygen available to muscle cells rapidly decreases. When both anaerobic and aerobic energy pathways become insufficient for muscle contraction, muscles can use only glycogen as an energy source. As glycogen is used up, the body begins to use fat as an energy source. When ATP consumption exceeds ATP production, muscle fatigue and soreness may result, leaving muscle fibers unable to recover from contraction. Real Life Close Reteaching Have students create a flip book of 20 pages showing the mechanics of muscle contraction. The first and last pages should have the following labels: actin, myosin, myosin head, and sarcomere. TAKS 1 Bio/IPC 2C Quiz What is the best way to increase muscle size, strength, and endurance? If you want to have large muscles and be strong enough to lift large loads, you should train with heavy weights. On the other hand, repeatedly lifting lighter weights builds muscle endurance. Exercise and Fitness GENERAL Consistent aerobic exercise makes the heart pump more efficiently and thus increases the energy available to muscles as a result of improved blood circulation. More oxygen is extracted by the body with each breath, increasing the oxygen supply to muscles. More ATP is available for muscle contractions, thereby reducing muscle fatigue. The increase in muscle efficiency results in greater endurance, or the ability continue Texas SEtopage TK exercising. Resistance exercises, such as weight lifting, shown in Figure 14, can increase muscle size and strength. Resistance exercises are mostly anaerobic, so they do not usually improve the uptake of oxygen to muscles. Muscle mass is increased by resistance training. The amount of tension and the rate of exercise are both important factors. However, the short-term demands of such strength training do not cause the circulatory changes that increase endurance. Excessive exercise or failure to warm up properly can lead to muscle injury. Muscles can tear if they are stretched too far during strenuous exercise. If excessive stress causes tendons to become inflamed, a painful condition called tendinitis results. 1. What are tendons? (They are strips of connective tissue that attach skeletal muscles to bones.) 2. What is a sarcomere? (A sarcomere is a very small subunit of a muscle cell.) Alternative Assessment GENERAL Ask students to draw a diagram to illustrate the role of ATP in muscle contraction. Their diagrams should show each step in the muscle contraction process and indicate where ATP is involved. TAKS 1 Bio/IPC 2C; TAKS 2 Bio 4B; Bio 9A IPC Benchmark Fact Describe how energy and work are related and distinguish both terms from power. Whereas energy or work is the ability to change or move matter (i.e., work ⫽ force ⫻ distance), power is a measure of how much work gets done in a certain amount of time. Power is therefore derived from the ratio of energy or work to time (i.e., power ⫽ work/time). TAKS 5 IPC 4B Figure 14 Resistance exercise. Weight lifting and other resistance exercises primarily involve anaerobic energy pathways in muscles. Section 3 Review Describe how muscle pairs work together to 10A move body parts. Compare the roles of thick and thin filaments in muscle contraction. 10A Identify the energy pathway that is primarily involved with exercises that increase muscle size 4B and strength. Critical Thinking Applying Information What causes muscle cramping after rigorous exercise or a repeated movement? TAKS Test Prep Which main organ systems are involved when you flex your arm 10B at the elbow? A muscular, skeletal, immune B nervous, muscular, skeletal C skeletal, excretory, nervous D endocrine, muscular, immune 860 Answers to Section Review pp. 860–861 Student Edition TAKS Obj 2 Bio 4B TAKS Obj 2 Bio 10A TAKS Obj 2 Bio 10B TEKS Bio 4B, 10A, 10B, 11A, 11C Teacher Edition TAKS Obj 1 Bio/IPC 2C TAKS Obj 2 Bio 4B, 10A, 10B TAKS Obj 5 IPC 4B TEKS Bio 4B, 9A, 10A, 10B TEKS Bio/IPC 2C; IPC 4B 860 1. Many skeletal muscles exist in opposing pairs. Flexors bend joints and extensors straighten them. TAKS 2 Bio 10A 2. Thick (myosin) filaments have heads that attach to thin (actin) filaments. The heads rotate, causing actin to slide against myosin. This process repeats many times during a single muscle contraction. TAKS 2 Bio 10A 3. the anaerobic pathway TAKS 2 Bio 4B Chapter 37 • Introduction to Body Structure 4. When ATP consumption exceeds ATP production, muscle cramping results. 5. A. Incorrect. The immune system is not involved in muscle contraction. B. Correct. All three of these systems are involved. C. Incorrect. The excretory system is not involved in muscle contraction. D. Incorrect. The endocrine and immune systems are not involved in muscle contraction. TAKS 2 Bio 10B (grade 11 only) Skin, Hair, and Nails Section 4 Section 4 Focus Skin Objectives The skin, which makes up about 15 percent of your total body weight, is the largest organ of the body. Many specialized structures are found in the skin, which along with the hair and nails, forms the integumentary system. The skin protects the body from injury, provides the first line of defense against disease, helps regulate body temperature, and prevents the body from drying out through evaporation. As shown in Figure 15, the skin is made mostly of connective tissue and layers of epithelial tissue. The two primary layers of skin are the epidermis and the dermis. Overview ● Analyze the structure and function of the epidermis. ● Describe how the dermis helps the body maintain homeostasis. 10A 11A TAKS 2 ● Summarize how hair and nails are formed. 10A TAKS 2 ● Identify various types of skin disorders. 10A 11C TAKS 2 Epidermis Key Terms The epidermis is the outermost layer of the skin. About as thick as this page, the epidermis is made of several layers of epithelial cells. The part of the epidermis you see when you look in a mirror is a thin layer of flattened, dead cells that contain keratin. Keratin is a protein that makes skin tough and waterproof. The cells of the epiTexas TK dermis are continuously damaged by SE thepage environment. They are scraped, ripped, worn away by friction, and dried out because of moisture loss. Your body deals with this damage not by repairing the cells, but by replacing them. epidermis keratin melanin dermis hair follicle subcutaneous tissue sebum Before beginning this section review with your students the objectives listed in the Student Edition. Students will examine the composition of the different layers of the skin as well of the functions of the skin. They will describe the structure of hair and nails. Finally, they will develop an understanding of skin disorders including their causes, symptoms, and treatments. Bellringer Ask students to write down all of the functions they can think of that involve the skin. (containing other organs, reduces water loss, regulates body temperature, removes toxins, protects against injury, protects against infection) TAKS 2 Bio 10A Figure 15 Structure of skin Skin has two distinct layers that contain many blood vessels, nerve cells, muscles, hairs, and glands. Motivate Discussion Hair follicle Hair shaft Pore Epidermis (outer layer) Oil gland Dermis (inner layer) Subcutaneous tissue Vein Nerve cells Muscle fibers Sweat gland Artery 861 Chapter Resource File • Lesson Plan GENERAL • Directed Reading • Active Reading GENERAL Planner CD-ROM • Reading Organizers • Reading Strategies • Supplemental Reading Guide Microbe Hunters Ask students for a show of hands to the following questions: Who likes to go to the beach? Who tans? Who burns? Explain that a suntan is actually a defense mechanism of the skin. Melanin is a dark pigment that is present in varying degrees in different individuals. Additional melanin is produced by the skin when it is exposed to ultraviolet radiation. We call this additional melanin a tan; the darkened skin protects the dermis somewhat from damaging radiation. Emphasize the importance of using SPF 15 or higher sunscreen to prevent sunburn. Burns early in life increase the chances of skin cancer later. LS Intrapersonal TAKS 2 Bio 4B; Bio 9A Transparencies TT Bellringer TT Structure of Skin Chapter 37 • Introduction to Body Structure 861 The outermost cells of the skin are continually shed and replaced by a layer of actively dividing cells at the base of the epidermis. As new skin cells form, they migrate upward and produce large amounts of keratin. These cells are shed about a month after they reach the surface. The inner layer of the epidermis also contains cells that produce the pigment melanin. Melanin (MEHL uh nihn) ranges in color from yellow to reddish brown to black, and it helps determine skin color. People with more melanin tend to have darker skin, and people with less melanin usually have lighter skin. Melanin also absorbs ultraviolet (UV) radiation, protecting the skin from exposure to sunlight. Exposure to UV radiation increases the production of melanin. This is why some people become “tan” after exposure to sunlight. However, UV radiation has been shown to cause skin cancer, especially in people with light skin. Thus, you should avoid excessive exposure to sunlight and wear sunscreen when outdoors. Teach Teaching Tip GENERAL Skin Layers Have students make a Graphic Organizer similar to the one at the bottom of this page to demonstrate the relationship between the skin’s two primary layers and the subcutaneous tissue. Below the name of each of the three layers, have students describe its components. LS Visual TAKS 2 Bio/IPC 2C, TAKS 2 Bio 10A, 10B Dermis The dermis is the functional layer of skin that lies just beneath the epidermis. Connective tissue in the dermis makes the skin tough and elastic. The dermis contains many nerve cells, blood vessels, hair follicles , and specialized skin cells. Sensations of touch, Courtroom Science Teaching Strategies Have students collect newspaper, magazine, or Internet articles about the uses of forensic technologies in the courtroom. Discussion Should these relatively new technologies be used in a courtroom? (Answers will vary but may include that although they are scientifically valid, they have not been tested sufficiently.) What are some of the drawbacks of using hair for drug testing? (Answers will vary but may include that some individuals may cut their hair to avoid detection of their drug use.) Should employers be able to do random drug testing on hair? (Answers will vary but may include that it is an accurate indicator of drug use and provides a long-term record, but it may violate an individual’s rights in certain cases.) Courtroom Science I n the United States, medical evidence is often used in criminal trials. Hairs left at a crime scene can provide enough information to make or break a case. To the unaided eye, the differences between hairs amount to no more than color, coarseness, and whether the hairs are curly or straight. Using a microscope, however, scientists can distinguish more than two dozen characteristics in a single hair. Experts compare hairs found at a crime scene with hairs of suspects. These comparisons can rule out a suspect when the hairs are different, but they usually are not enough to convict a suspect without other evidence. DNA Fingerprinting Hair consists of cells that contain DNA. Thus, scientists can get additional evidence from hair through DNA fingerprinting. First used as forensic evidence in the 1980s, DNA fingerprinting is now fairly common in many kinds of criminal trials. By 1997, DNA fingerprinting had been used in more than 50,000 cases in the United States. Drug Testing Hair can also provide evidence of drug use. Hair collects drugs that are delivered to hair follicles by blood. Hair provides a longer record of drug exposure than blood or urine does. Head hair grows an average of about 1 cm Forensic scientist (0.4 in.) per month; a 10 cm (4 in.) length of hair gives evidence of a person’s drug use during the last 10 months. Such evidence has been introduced in cases involving illegal drug use. www.scilinks.org Topic: Forensic Analysis Keyword: HX4087 862 Graphic Organizer pp. 862–863 Student Edition TAKS Obj 2 Bio 4B TAKS Obj 2 Bio 10A TAKS Obj 2 Bio 10B TEKS Bio 4B, 10A, 10B Teacher Edition TAKS Obj 1 Bio/IPC 2C TAKS Obj 2 Bio 4B, 10A, 10B TAKS Obj 5 IPC 5A, 5B TEKS Bio 4B, 9A, 10A, 10B, 11C TEKS Bio/IPC 2C, 3C TEKS IPC 5A, 5B 862 Use this graphic organizer with Teaching Tip on this page. Epidermis Dermis Subcutaneous layer Hair follicles Flattened, dead cells Chapter 37 • Introduction to Body Structure Sweat glands Oil glands Blood vessels Muscle fibers Fat and other connective tissue temperature, and pain originate in nerve cells within the dermis. The dermis also contains tiny muscles that are attached to hair follicles in your skin. When you get cold, these muscles contract and pull the hair shafts upright, helping to insulate the body. These muscles also cause goose bumps on the skin’s surface. A network of blood vessels in the dermis provides nourishment to the living cells of the skin. These blood vessels also help regulate body temperature by either radiating heat into the air or conserving heat. If your body gets too hot, blood vessels just under the skin dilate so that blood flows near the skin’s surface, releasing heat from the body. This is why people with light complexions turn slightly red during strenuous exercise, as shown in Figure 16. If your body gets too cold, the blood vessels constrict, reducing heat loss. Sweat glands in the dermis also help remove excess body heat. The evaporation of sweat from the skin’s surface removes heat more efficiently than the dilation of blood vessels. Most sweat is about 99 percent water and 1 percent dissolved salts and acids. Certain sweat glands located in body areas with dense hair, such as the armpits, also secrete proteins and fatty acids. Because these substances provide a rich food source for bacteria, stale sweat often releases the offensive odor of bacterial waste products. Teaching Tip Temperature Regulation Figure 16 Cooling mechanism. Flushed (reddened) skin is a sign that the body is overheated and is releasing heat from the skin. Hair Growth Tell students that hair grows at different rates in different regions of the body. The growth rate also differs with age and sex. Hair follicles go through cycles that average 4 years of growth followed by several months of inactivity. With the beginning of a new active growth cycle, the old hair is pushed out (if it has not fallen out already). Out of more than 100,000 hairs, only about 50 hairs a day are lost. Several factors can increase hair loss. These include dietary factors, high fever, stress, drugs, radiation, and some hormonal factors related to pregnancy. TAKS 2 Bio 4B, 10A Subcutaneous Tissue Subcutaneous tissue, located beneath the skin just under the der- mis, is a layer of connective tissue made mostly of fat. Subcutaneous tissue acts as a shock absorber, provides additional insulation to help conserve body heat, and stores energy. Subcutaneous tissue also anchors the skin to underlying organs. The thickness of subcutaneous tissue varies in different parts of the body. For example, the eyelids have very little, while the buttocks and thighs may have a lot. The pads of subcutaneous tissue in the soles of your feet may be more than 6 mm (0.25 in.) thick. Teaching Tip Homeothermy Tell students that when a person’s body temperature rises above 41ºC (106ºF), enzymes in the brain begin to denature. Have students describe the appearance of a raw egg white. (clear, runny, slimy) Then have them describe the appearance of a cooked egg white. (white, firm) Explain that the egg white changes when it is cooked because its proteins become misshapen, or denatured. Enzymes also are proteins, and at high temperatures they no longer function normally. Hair and Nails Hair and nails are derived from the epidermis. Hair follicles produce individual hairs, which help protect and insulate the body. Shown in Figure 17, hair is made mostly of dead, keratin-filled cells. A shaft of hair grows up from the hair follicle and through the skin’s surface. Each hair on your head grows for several years. Then the follicle enters a resting phase for several months, and the hair is eventually shed. Hair color is primarily determined by the presence of the pigment melanin. Blonde hair and red hair typically contain less melanin than brown hair and black hair. Nails are produced by specialized epidermal cells located in the light, semicircular area at the base of each nail. These cells become filled with keratin as they are pushed outward by new cells. Nails protect the tips of the fingers and toes and continue to grow throughout life. Bio 9A SKILL Figure 17 Hair. An average human head contains about 100,000 hairs. 863 IPC Benchmark Fact Remind students that UV radiation is an electromagnetic wave or disturbance that carries energy through space and therefore does not need a medium in order to travel. In addition, mention that the vibrations in electromagnetic waves are caused by fluctuations in electric and magnetic fields, which are perpendicular to the direction the wave travels and thus behave like transverse waves. TAKS 5 IPC 5A (grade 10 only), 5B (grade 11 only) Trends in Neurobiology New Technique Medical researchers have developed a technique for severing nerves within the chest cavity that appear to be connected with excessive sweating (especially of the palms) and flushing of the upper body (especially of the face). Surgeons use an endoscope to view the inside of the thoracic cavity, and as a result the procedure involves minimal invasion to surrounding tissue. The procedure has a success rate of about 95 percent. Bio/IPC 3C BUILDER Writing Skills Ask students to research skin cancer using the Web site in the Internet Connect box on the previous page. Have them write a paragraph on the risk factors and symptoms of two relatively common carcinomas: basal cell carcinoma and squamous cell carcinoma. Ask students to identify the primary risk factor for nearly all types of skin cancer. (exposure of the skin to the sun) LS Verbal Bio 11C Chapter 37 • Introduction to Body Structure 863 Skin Disorders Close www.scilinks.org Topic: Skin Cancer Keyword: HX4165 Reteaching Use rapid-fire questions to review the layers of the skin and the important structures in each layer. Some key items: artery (dermis), melanin (epidermis), dead cells (epidermis), fat (subcutaneous tissue), middle layer (dermis). TAKS 2 Bio 10A Quiz The skin is continuously exposed to damaging factors such as insect bites, microorganisms, and ultraviolet radiation. Injuries such as scrapes and blisters are often minor and usually heal rapidly without permanent scarring. Burns, however, can be very serious and can result in permanent scarring or even death. Some skin disorders are the result of changes that occur within the body over time. Acne Figure 18 Skin cancer. In its early stages, a carcinoma may look like a wart. A malignant melanoma often looks like a mole that changes in size, shape, or color. GENERAL 1. Identify one function of skin. (protects the body from injury, protects the body from disease, helps regulate body temperature, prevents the body from drying out) 2. What is melanin and what is its function? (Melanin is a skin pigment that absorbs ultraviolet radiation, thus protecting the skin against this radiation.) 3. What kind of tissue is hair made of? (epithelial) 4. What kinds of tissues are found in the skin? (nervous, muscular, epithelial, connective) The most common skin problem for teenagers is acne (AK nee), a chronic inflammatory condition that involves the skin’s oil-producing glands. Oil glands in the dermis release sebum (SEE buhm), an oily secretion that lubricates the skin. Sebum is released through ducts, or pores, into nearby hair follicles. These oil glands are especially active during adolescence. Acne is caused by excessive secretion of sebum, which blocks pores with oil, dirt, and bacteria. Makeup and other cosmetic products can contribute to clogging. As a result, the surrounding tissue becomes infected and inflamed, and the pores accumulate pus, producing pimples. Serious acne may need to be treated using antibiotics. Although acne cannot be prevented, it can usually be managed with proper skin care. Skin CancerTexas SE page TK Skin cancer can result from genetic mutations caused by overexposure to UV radiation. The most common types of skin cancer are carcinomas (kahr sih NOH mahz), which originate in skin cells that do not produce pigments. If they are detected early, carcinomas can be treated. A small percentage of skin cancers are caused by mutations that occur in pigment-producing skin cells. These cancers, called malignant melanomas (mehl uh NOH mahz), grow very quickly and spread easily to other parts of the body. About 8 out of 10 skin cancer deaths are from malignant melanomas. A carcinoma and a malignant melanoma are shown in Figure 18. You can reduce the risk of skin cancer by avoiding overexposure to either natural or artificial UV radiation and by using protective sunscreens. Carcinoma Alternative Assessment Malignant melanoma Have students make a threedimensional model of the skin using construction paper, tissue paper, yarn, glue, or other art materials. Ask them to show and explain their models to the class when they finish. TAKS 1 Bio/IPC 2C Section 4 Review Describe the structure of the epidermis. 10A List two ways that the dermis helps regulate body temperature. 10A 11A Summarize how nails are formed. 10A Identify the most common cause of skin cancer and how it can be avoided. 10A 11C Critical Thinking Recognizing Relationships Why is a third-degree burn, which destroys the epidermis and dermis of the 10A 10B 11C skin, such a serious injury? TAKS Test Prep When your body temperature becomes too low, blood vessels just under your 11A skin A dilate. C release sweat. B constrict. D raise hair shafts. 864 Answers to Section Review pp. 864–865 Student Edition TAKS Obj 2 Bio 6C TAKS Obj 2 Bio 10A TAKS Obj 2 Bio 10B TEKS Bio 6C, 10A, 10B, 11A, 11C Teacher Edition TAKS Obj 1 Bio/IPC 2C TAKS Obj 2 Bio 10A TEKS Bio 10A, 11A, 11C TEKS Bio/IPC 2C 864 1. The epidermis is composed of a thin layer of 5. The epidermis and dermis perform several vital dead, flattened, keratin-containing cells. functions, including waterproofing the body, TAKS 2 Bio 10A keeping pathogens out, and regulating body 2. The dermis helps regulate body temperature by temperature. Loss of the dermis and epidermis controlling the diameter of blood vessels. A removes the barrier between the interior tislarge diameter vessel dissipates heat; a small sues and the external environment. TAKS 2 Bio 10A, 10B; Bio 11C diameter vessel conserves heat. Also, the dermis releases sweat to cool the body. 6. A. Incorrect. These blood vessels TAKS 2 Bio 10A; Bio 11A dilate when the body temperature becomes too 3. At the base of each nail are specialized epiderhigh. B. Correct. Constriction helps to reduce mal cells. These cells fill with keratin, which heat loss. C. Incorrect. Blood vessels do not forms the nail, as they are pushed outward by release sweat; sweat is released when the body new cells. TAKS 2 Bio 10A temperature becomes too high. D. Incorrect. 4. Overexposure to UV radiation is the most comHair shafts are not raised by blood vessels. Bio 11A mon cause of skin cancer. Using sunscreen and limiting sun exposure can help reduce the risk. TAKS 2 Bio 10A; Bio 11C Chapter 37 • Introduction to Body Structure Study CHAPTER HIGHLIGHTS ZONE Key Concepts Alternative Assessment Key Terms Section 1 1 Body Organization ● Cells are grouped into four types of body tissues: epithelial tissue, nervous tissue, connective tissue, and muscle tissue. ● Body organs contain several types of body tissues. ● Organs are grouped into organ systems in which organs interact to perform a certain function, such as digestion. ● Endothermy enables the body to maintain homeostasis at all times, regardless of the temperature outside the body. epithelial tissue (846) nervous tissue (847) connective tissue (847) muscle tissue (847) body cavity (849) Chapter Resource File • Science Skills GENERAL • Critical Thinking • Test Prep Pretest GENERAL • Chapter Test GENERAL Section 2 2 Skeletal System ● The skeleton supports the body, provides protection for internal organs, and enables movement. ● The 206 bones of the skeleton are divided into the axial skeleton and the appendicular skeleton. ● Bones are made of hard compact bone surrounding porous spongy bone. ● Early in development, the skeleton is mostly cartilage. Bones harden as calcium and other mineral deposits build up. ● Bones thicken and elongate as development continues. ● Three kinds of joints fasten bones together: immovable joints, slightly movable joints, and freely movable joints. GENERAL Have students write trivia questions for a review game. These questions can be based on the review questions found at the end of each section. axial skeleton (850) appendicular skeleton (850) bone marrow (851) periosteum (851) Haversian canal (852) osteocyte (852) osteoporosis (853) joint (854) ligament (854) Section 3 3 Muscular System ● Muscles are attached to bones by tendons. ● Muscle pairs move parts of the body by pulling on bones. ● Sarcomeres shorten during muscle contraction. ● During muscle contraction, actin and myosin interact. ● Energy is required for muscles to contract. tendon (856) flexor (856) extensor (856) actin (857) myosin (857) myofibril (857) sarcomere (857) Section 4 4 Skin, Hair, and Nails ● The skin consists of two layers: the epidermis and the dermis. ● Subcutaneous tissue anchors skin to underlying organs. ● Hair and nails are derived from the epidermis. ● Most skin disorders are caused by damage to the epidermis. epidermis (861) keratin (861) melanin (862) dermis (862) hair follicle (862) subcutaneous tissue (863) sebum (864) 865 Answer to Concept Map Human body The following is one of several possible answers to Performance Zone item 15. cells compose is composed of tissues compose organs compose organ systems include nervous tissue connective tissue is a component of epithelial tissue muscle tissue include digestive system nervous system respiratory system immune system circulatory system reproductive system Chapter 37 • Introduction to Body Structure 865 Performance ZONE CHAPTER 37 ANSWERS Using Key Terms Using Key Terms 1. b TAKS 2 Bio 10A 2. c TAKS 2 Bio 10A 3. c TAKS 2 Bio 10A 4. b TAKS 2 Bio 10A 5. a. A tissue is a group of cells working together; an organ is a group of tissues working together to perform a specific function. b. The epidermis is the outermost layer of the skin; the dermis is the layer of skin that lies just beneath the epidermis. c. The axial skeleton includes the bones of the skull, spine, ribs, and sternum; the appendicular skeleton includes the bones of the arms, legs, pelvis, and shoulders. d. A flexor is a muscle that causes a joint to bend; an extensor is a muscle that causes a joint to straighten. Understanding Key Ideas 6. c TAKS 2 Bio 10B (grade 11 only) 7. d TAKS 2 Bio 10A 8. c TAKS 2 Bio 10A; Bio 11C 9. a TAKS 2 Bio 10A 10. a TAKS 2 Bio 10A; Bio 11A 11. d Bio 11C 12. increased secretion of oil, clogged pores, dirt, makeup, and bacteria Bio 11C 13. ball and socket—shoulder, pivoting; hinge—knee, bending and straightening TAKS 2 Bio 10A 14. DNA fingerprinting and analysis of hair, blood, and urine samples. Answers will vary, but identification by DNA sampling is the most specific. TAKS 1 Bio/IPC 2C 15. The answer to the concept map is found on the previous page. TAKS 1 Bio/IPC 2C; Bio 3E pp. 866–867 Review and Assess TAKS Obj 1 Bio/IPC 2C TAKS Obj 1 Bio/IPC 2D TAKS Obj 2 Bio 4B, 6C TAKS Obj 2 Bio 10A TAKS Obj 2 Bio 10B TEKS Bio 3D, 3E, 4B, 5A, 5C, 6C, 10A, 10B, 11C TEKS Bio/IPC 2C, 2D 866 CHAPTER REVIEW 1. The bones of the arms and legs form a. the axial skeleton. b. the appendicular skeleton. c. the pectoral girdle. d. vertebrae. 10A 10A 2. The outer membrane of bone is the a. marrow. c. periosteum. b. spongy bone. d. Haversian canal. 3. The bone at the end of a muscle attach- ment that does not move during muscle 10A contraction is called the a. tendon. c. origin. b. insertion. d. flexor. 9. Shortening of sarcomeres causes a. muscles to contract. b. Z lines to move apart. c. muscles to relax. d. None of the above 10A 10. The dermis helps regulate body tempera- ture by producing a. sweat. b. acne. 10A 11A c. oil. d. sebum. 11. The risk of developing skin cancer is increased by 11C a. eating oily foods. c. exercising. b. using sunscreen. d. sunbathing. 12. What factors contribute to acne, shown in the photograph below? 4. Which of the following is made mostly 11C of connective tissue? 10A a. epidermis c. hair b. dermis d. None of the above Texas SE page TK 5. For each pair of terms, explain the differ- ences in their meanings. a. tissue, organ b. epidermis, dermis c. axial skeleton, appendicular skeleton d. flexor, extensor Understanding Key Ideas 10B 6. The thoracic cavity contains a. the spinal cord. b. the brain. c. organs of the respiratory system. d. organs of the reproductive system. 13. Give an example of a ball-and-socket joint and a hinge joint. What type of movement 10A is permitted by each of these joints? 14. What are some ways in which forensic science can help in identifying a criminal? Which method produces 2C the most compelling evidence. 15. Concept Mapping Make a concept map that illustrates the body’s four levels of structural organization. Try to include the following terms in your map: muscle tissue, connective tissue, epithelial tissue, nervous tissue, organ, and organ system. 2C 3E 7. Which of the following is a function 10A of the skeletal system? a. support c. movement b. protection d. All of the above 10A 11C 8. Resistance exercises a. decrease muscle endurance. b. decrease muscle strength. c. increase muscle size. d. increase the number of muscle cells. 866 Assignment Guide Section 1 2 3 4 Questions 5, 6, 15 1, 2, 7, 13, 17, 19, 21 3, 8, 9, 16, 20, 21 4, 10, 11, 12, 14, 18, 21, 22 Chapter 37 • Introduction to Body Structure Critical Thinking Alternative Assessment Critical Thinking 16. Inferring Relationships Relate the 20. Communicating Find out about the causes, 16. Muscle contraction requires ATP, which is produced when food is broken down during cellular respiration. events of muscle contraction to cellular respiration. 4B 10A symptoms, and treatment of muscular disorders such as muscular dystrophy and Lou Gehrig’s disease. Summarize your findings in an oral report. 2D 6C 10A 11C 17. Inferring Relationships Young thorough- bred horses that are raced too early in life have an increased risk of breaking the bones in their legs. Using this information, what can you infer about bone develop10A ment in horses? 21. Relating Structure to Function Use a compound light microscope to compare prepared slides of bone, muscle, and epithelial tissue. Write a short report that describes the structural differences between cells. Relate the structure of cells to their functions. 2D 5A 11C 18. Predicting Outcomes Oil glands in the skin secrete a substance that helps kill bacteria. What might happen if you 11C washed your skin too often? 22. Recognizing Patterns Research the inci- dence of skin cancer in different parts of the world. Identify similarities and differences in the types of skin cancer. Present your 2D 3D findings in a written or oral report. 19. Recognizing Relationships Red blood cells are produced in red bone marrow. How are red blood cells transported to the rest of the body? 10A Texas SE page TK 10A 1. The structure labeled X is a A myosin filament. C myofibril. B muscle fiber. D Z line. 2. When a sarcomere changes from condition A to condition B, what happens to the muscle cell that contains it? 10A F It relaxes. H It contracts. G It rotates. J It slides. 3. Which sequence identifies the levels X A 5C of organization found in the body? A muscle cell → muscular system → muscle → muscle tissue B muscle cell → muscle tissue → muscle → muscular system C muscular system → muscle tissue → muscle cell → muscle D muscle → muscle cell → muscle tissue → muscular system Test B For a question involving experimental data, determine the constants, variables, and control before you try to answer the question. 867 Standardized Test Prep 1. A. Correct. The structure is a myosin filament. B. Incorrect. A muscle fiber is a whole cell. C. Incorrect. A myofibril is made up of many of the units shown in the diagram. D. Incorrect. The Z line is a vertical line separating sarcomeres. TAKS 2 Bio 10A 2. F. Incorrect. Shortening of the sarcomere contracts the muscle rather relaxing it. G. Incorrect. These cells do not rotate. H. Correct. The diagram represents the shortening of a sarcomere, which causes muscle to contract. J. Incorrect. A muscle cell does not slide, it contracts. TAKS 2 Bio 10A 17. The bones thicken and become stronger with age as bone replaces cartilage. TAKS 2 Bio 10A 18. Washing skin too often can deplete the natural bacteriakilling substance, resulting in an overgrowth of bacteria. Bio 11C 19. Red blood cells enter small blood vessels in bone and are transported to the rest of the body by the circulatory system. Bio 10A Alternative Assessment TAKS Test Prep The diagram below shows a sarcomere under two conditions. Use the diagram and your knowledge of science to answer questions 1–3. TAKS 2 Bio 4B, 10A 3. A. Incorrect. The muscular system is the highest level of organization of structures that contain sarcomeres. B. Correct. The level of organization increases from muscle cell, to tissue, to muscle to muscular system. C. Incorrect. The muscular system is the highest level of organization of structures that contain sarcomeres, and the muscle cell is the lowest of those indicated. D. Incorrect. The muscular system is the highest level of organization of structures that contain sarcomeres, and the muscle cell is the lowest level of those indicated. Bio 5C 20. Neuromuscular disorders are usually genetic in nature, although some muscular dystrophies may be autoimmune in origin. Symptoms of Lou Gehrig’s disease (amylotrophic lateral sclerosis) include muscle tissue degeneration and paralysis, followed by death. In the muscular dystrophies, muscle tissue gradually is replaced by fat, leading to immobility. Muscle degeneration often affects the ability to breathe, leading to respiratory infections. TAKS 1 Bio/IPC 2D TAKS 2 Bio 6C, 10A; Bio 11C 21. Answers will vary. TAKS 1 Bio/IPC 2D; Bio 5A, 11C 22. Answers will vary. Skin cancer is more common in fair-skinned people and in places with intense sunshine, such as Arizona and Hawaii. It is very common in Australia because many residents are fair-skinned people of European descent who have little natural melanin to protect them from the sun. TAKS 1 Bio/IPC 2D; Bio 3D Chapter 37 • Introduction to Body Structure 867