Download Answers to Mastering Concepts Questions

Mastering Concepts
25.1
1. What is the difference between anatomy and physiology?
Anatomy is the study of the physical arrangement of the body’s parts; physiology
explains how those parts function.
2. What is the relationship among cells, tissues, organs, and organ systems?
Multiple types of specialized, interacting cells form tissues. Multiple tissues working
together form organs, and organ systems are groups of related organs that interact to
produce a specific body process.
3. Trace the body’s early development from one fertilized egg to a many-celled organism.
A fertilized egg divides multiple times to form an embryo consisting of identical cells.
The cells eventually begin to specialize, forming three primary germ layers (endoderm,
ectoderm, and mesoderm). Each germ layer, in turn, gives rise to several organ types that
are connected in the body’s organ systems.
25.2
1. If you were given a microscope slide with a slice of tissue on it, how would you
classify it into one of the four main tissue types?
If it is anchored to a basement membrane on one side, then it is epithelial tissue. If the
cells are not attached to one another and are embedded in an extracellular matrix, then it
is connective tissue. If the cells have multiple nuclei and/or are striated, then it is muscle
tissue. If the cells have branching extensions from a cell body, then it is nervous tissue.
2. Suppose you determine that a tissue sample consists of unconnected cells embedded in
an extracellular matrix. What criteria would you use to classify it into a specific subtype
of tissue?
The sample represents connective tissue. Loose connective tissue has a loose matrix of
fibers, whereas dense connective tissue has a more compact matrix of fibers. Fibers are
less obvious in other types of connective tissue. Cartilage has cells loosely dispersed in
fine fibers. Bones have rings of cells in a mineralized extracellular matrix. Blood has red
and white cells in a liquid matrix. Adipose tissue consists mostly of fat cells embedded in
minimal matrix.
25.3
1. Which organ systems contribute to each of the five general functions of life?
The five general functions of life and the corresponding organ systems are:
communication (nervous and endocrine systems); movement and support (muscular and
skeletal systems); acquiring energy (circulatory, respiratory, and digestive systems);
protection (urinary, integumentary, and immune/lymphatic systems); reproduction
(reproductive system, although all other systems contribute indirectly to this function).
2. What are three examples of interactions between organ systems?
Answers may vary, but here are three examples. (1) The circulatory system brings blood
to the urinary system, where the chemical composition of the blood is adjusted. The
functions of the urinary system are controlled by hormones produced by endocrine
glands. (2) The respiratory system exchanges gases with the bloodstream. The nervous
system works with the endocrine system to control the breathing rate; voluntary and
involuntary muscles enable breathing to occur. (3) The digestive system breaks food into
particles that are absorbed into the bloodstream and carried to cells that need nutrients (or
stored in the liver and in fat deposits). The digestive system is controlled by hormones
and influenced by the nervous system, and muscles propel food along the digestive tract.
25.4
1. Use figure 25.9 to explain which materials enter and exit the body, and how they do so.
Food and water enter the digestive tract through the mouth. Most nutrients and water are
absorbed into the bloodstream, but feces (undigested food) leaves the body through the
anus. Oxygen enters the body, and carbon dioxide leaves the body, at the lungs. Heat
leaves the body through the skin. Metabolic wastes and excess water, salts, and nutrients
pass from the circulatory system into the urinary system, which combines these
substances into urine that leaves the body.
2. What happens to an organism that fails to maintain homeostasis?
An organism that fails to maintain homeostasis will stop functioning and will eventually
die.
3. Distinguish between negative and positive feedback.
In negative feedback, the body reacts to a change by triggering action that reverses the
change. In positive feedback, the body reacts to a change by amplifying the change.
25.5
1. How does the integumentary system help the body maintain homeostasis?
The integumentary system blocks the entry of foreign substances into the body. It also
prevents the loss of body fluids and helps to maintain body temperature. The production
of vitamin D in skin helps to keep the skeleton strong.
2. What tissue types and specialized cells occur in each layer of human skin?
The two main layers of human skin are the epidermis and the dermis. The epidermis
consists mainly of stratified squamous epithelium. Specialized cells called keratinocytes
produce keratin and melanocytes produce melanin. The dermis consists mainly of
collagen but also contains elastin, smooth muscle, blood vessels, and glands. Specialized
cells in the dermis make up hair follicles and glands. Muscle cells and nerve endings also
occur in the dermis.
25.6
1. Describe how vitamin D and folic acid nutrition might explain the variation in
human skin pigmentation.
Deficiencies in vitamin D can cause death or pelvic deformities; deficiencies in folic acid
can lead to infertility in men or birth defects in babies. Ultraviolet radiation has two
simultaneous effects: it stimulates vitamin D production and destroys folic acid. Selection
for pigmentation therefore probably represents an evolutionary trade-off between
maximizing the two vitamins. In tropical areas, darkly pigmented skin blocks UV
radiation and therefore protects against folic acid destruction. In higher latitudes, lightly
pigmented skin maximizes vitamin D production.
2. Suggest a specific prediction related to folic acid that follows from the nutritional
trade-off hypothesis.
People with dark skin living in northern areas should have a greater concentration of folic
acid in their blood as compared to people with lighter skin living in the same area.
Write It Out
1. Distinguish between: (a) organs and organ systems; (b) simple squamous and stratified
squamous epithelial tissue; (c) loose and dense connective tissue; (d) skeletal and cardiac
muscle tissue; (e) neurons and neuroglia; (f) negative and positive feedback.
(a) Organs are the individual structures that function together to make up an organ
system. (b) Simple squamous epithelium includes just one layer; stratified squamous
epithelial tissue contains more than one layer of cells. (c) Loose connective tissue binds
tissues together and fills spaces, whereas dense connective tissue builds ligaments and
tendons. (d) Skeletal muscle tissue is voluntary and has long cells, whereas cardiac
muscle is involuntary, and has electrically connected short cells. (e) Neurons are the
communicating cells of the nervous system, whereas neuroglia the supporting cells. (f)
Negative feedback maintains homeostasis by reversing the effects of a change; positive
feedback counters homeostasis by amplifying the change.
2. Use the Internet to research cosmetic surgery. Write a paragraph explaining how a
plastic surgeon might manipulate each of the four main tissue types.
[Many examples are possible; two examples are provided here.] During a facelift, mostly
epithelial and connective tissue are rearranged. A plastic surgeon cuts through the skin,
detaches it from the underlying muscle, removes excess skin, and reattaches it to the face.
Smile reconstruction surgery moves muscle and nerve tissue from one part of the body to
the face, allowing patients with partial face paralysis to smile again.
3. What is homeostasis, and how is it important?
Homeostasis is a state of internal constancy. Cells and tissues must have conditions
within a certain range if they are to function. If the body system cannot maintain
homeostasis, it may stop functioning, and the organism may die.
4. When a person gets cold, he or she may begin to shiver. If the weather is too hot, the
heart rate increases and blood vessels dilate, sending more blood to the skin. How does
each scenario illustrate homeostasis?
Both examples illustrate how the body maintains a constant temperature. Shivering is the
involuntary contraction of skeletal muscles; the muscle movement produces heat, which
helps increase the body temperature. In the second scenario, blood passing near the skin
surface releases heat to the atmosphere, which helps cool the overheated body.
5. Provide nonbiological examples of negative and positive feedback, other than those
presented in the chapter.
Most people adjust spending by negative feedback. After a big paycheck, spending
increases, whereas after a large expense, spending decreases. The transition from swiftly
moving traffic to a traffic jam is an example of positive feedback. When one person
slams on the brakes, for example, the car behind must also brake, and so on.
6. Explain how you use your organ systems (except your reproductive system) while you
are exercising at the gym, and provide three hypotheses that might explain why some
exercise sessions go better than others.
Nervous system: stimulates muscles to contract. Endocrine system: releases hormones
that make pain more tolerable. Skeletal system and muscular system: muscles pull on
bones to move body parts. Digestive system: breaks down food to provide energy for
movement. Circulatory system: pumps oxygen-rich blood to muscles, and carries carbon
dioxide away from muscles. Respiratory system: exchanges oxygen and carbon dioxide
between the atmosphere and the blood. Urinary system: collects nitrogenous wastes
produced as muscles are exerted. Integumentary system: regulates water loss through the
skin. Immune system: protects against bacteria on workout equipment. A workout might
be more successful if the respiratory system is free of obstructions, such as mucus; if the
digestive system has recently extracted nutrients from food; and if the urinary system
maximizes water retention.
7. Describe how the circulatory system connects the digestive system with the urinary
system.
Nutrients and water move from the digestive system into the circulatory system, which
carries these substances to body tissues. Excess water and nutrients move from the
circulatory system into the urinary system and are excreted in urine.
8. Which tissues make up skin, the largest organ of the body? How do these tissues
interact to provide each of the functions of skin?
The epidermis contains stratified squamous epithelial tissue. The dermis contains
connective tissue, smooth muscle tissue and nervous tissue. These tissues allow the body
to maintain temperature homeostasis as nerves in the skin detect temperature and send the
information to the hypothalamus. For example, if the body is too hot then blood vessels
will dilate and sweat glands will open. This will bring the body temperature back to
normal. The skin also plays a homeostatic role in water balance, nutrition, and defense
against disease.
9. Describe at least one interaction between skin and each of the 10 other organ systems.
Nervous system: sensory receptors in the skin are part of the nervous system and detect
stimuli. Endocrine system: hormones participate in vitamin D production in the skin.
Skeletal system: vitamin D production in skin indirectly influences bone structure.
Muscular system: muscle fibers that attach to the dermis produce facial expressions.
Digestive system: food allergies can produce hives or rashes on the skin. Circulatory
system: blood vessels in the skin constrict and dilate to maintain temperature
homeostasis. Respiratory system: exchanges the needed O2 with the CO2 waste from skin
cells. Urinary system: the loss of water through the skin is countered by water retention in
the urinary system. Immune/lymphatic system: the skin acts a first line of defense to keep
out pathogens. Reproductive system: mammary glands in the skin produce milk for
infants.
Pull It Together
1. What features distinguish the four types of tissue?
Epithelial tissues make wall-like layers of cells that surround all the organs and make up
the outer layer of skin. Connective tissues consist of cells embedded in a prominent
extracellular matrix. The cells that make up muscle tissue are elongated and synchronize
their activity to contract. The nervous tissues consist of cells that communicate with one
another and with muscles and glands.
2. Add skin to the concept map, making at least five connections to existing terms in the
map.
“Skin” connects with the phrase “is one of the body’s” to “Organs.” “Epithelial” connects
with the phrase “tissue secretes sweat in the” to “Skin.” “Connective” connects with
“tissue supports the” to “Skin.” “Muscle” connects with “tissue controls hair position in
the” to “Skin.” “Nervous” connects with “tissue senses temperature and touch in the” to
“Skin.”
3. Describe examples of organ system interactions that maintain homeostasis.
[Many answers are possible; this is one example.] The brain monitors levels of carbon
dioxide in the blood. When these levels are too high, the nervous system stimulates the
breathing rate to increase, returning the oxygen-carbon dioxide ratio to normal.