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The Animal Body and Principles of Regulation Chapter 43 Organization of Vertebrate Body Organization of Vertebrate Body There are four levels of organization: 1. Cells 2. Tissues 3. Organs 4. Organ systems Tissues are groups of cells that are similar in structure and function The three fundamental embryonic tissues are called germ layers -Endoderm, mesoderm and ectoderm In adult vertebrates, there are four primary tissues -Epithelial, connective, muscle and nerve 3 Bodies of vertebrates are composed of different cell types -Humans have 210 2 Organization of Vertebrate Body Organization of Vertebrate Body Organs are combinations of different tissues that form a structural and functional unit The body plan of all vertebrates is essentially a tube within a tube -Inner tube = Digestive tract -Outer tube = Main vertebrate body -Supported by a skeleton -Outermost layer = Skin and its accessories Organ systems are groups of organs that cooperate to perform the major activities of the body -The vertebrate body contains 11 principal organ systems 4 Organization of Vertebrate Body Inside the body are two identifiable cavities 5 6 8 9 Organization of Vertebrate Body Dorsal body cavity: Within skull & vertebrae Ventral body cavity: Bounded by the rib cage and vertebral column -Divided by the diaphragm into: -Thoracic cavity: Heart and lungs -Abdominopelvic cavity: Most organs -Peritoneal cavity: Coelomic space -Pericardial cavity: Around the heart -Pleural cavity: Around the lungs 7 1 Epithelial Tissue An epithelial membrane, or epithelium, covers every surface of the vertebrate body -Can come from any of the 3 germ layers -Some epithelia change into glands Cells of epithelia are tightly bound together -Provide a protective barrier Epithelia possess remarkable regenerative powers replacing cells throughout life 10 Epithelial Tissue 11 Epithelial Tissue Epithelial tissues attach to underlying connective tissues by a fibrous membrane -Basal surface = Secured side -Apical surface = Free side -Therefore, epithelia have inherent polarity, which is important for their function Simple Epithelium Simple Epithelium Two general classes -Simple = One layer thick -Stratified = Several layers thick Subdivided into: -Squamous cells = Flat -Cuboidal cells = Cube-shaped -Columnar cells = Cylinder-shaped 13 Simple squamous epithelium -Lines lungs and blood capillaries Simple cuboidal epithelium -Lines kidney tubules and several glands Simple columnar epithelium -Lines airways of respiratory tract and most of the gastrointestinal tract -Contains goblet cells: secrete mucus 14 Simple Epithelium (Cont.) 16 12 15 Simple Epithelium 17 18 2 Simple Epithelium (Cont.) Simple Epithelium Stratified Epithelium Glands of vertebrates form from invaginated epithelia -Exocrine glands -Connected to epithelium by a duct -Sweat, sebaceous and salivary glands -Endocrine glands -Ductless; lost duct during development -Secretions (hormones) enter blood 19 Stratified Epithelium 20 Connective Tissues Connective Tissue Proper Derive from embryonic mesoderm Divided into two major classes -Connective tissue proper -Loose or dense -Special connective tissue -Cartilage, bone and blood All have abundant extracellular material called the matrix -Protein fibers plus ground substance 22 Connective Tissue Proper Fibroblasts produce and secrete extracellular matrix Loose connective tissue -Cells scattered within a matrix that contains large amounts of ground substance -Strengthened by protein fibers such as: -Collagen – Supports tissue -Elastin – Makes tissue elastic 23 Connective Tissue Proper 24 Connective Tissue Proper Adipose cells (fat cells) also occur in loose connective tissue -Develop in large groups in certain areas, forming adipose tissue 25 Named according to the features of their apical cell layers -Epidermis is a stratified squamous epithelium -Characterized as a keratinized epithelium -Contains water-resistant keratin -Note: Lips are covered with nonkeratinized, stratified squamous epithelium 21 26 Dense connective tissue -Contains less ground substance and more collagen than loose connective tissue -Dense regular connective tissue -Collagen fibers line up in parallel -Makes up tendons and ligaments -Dense irregular connective tissue: -Collagen fibers have different orientations -Covers kidney, muscles, nerves & bone 27 3 Connective Tissue Proper Special Connective Tissue Connective Tissue Proper (Cont.) 28 Special Connective Tissue 29 Special Connective Tissue Cartilage -Ground substance made from characteristic glycoprotein, called chondroitin, and collagen fibers in long, parallel arrays -Flexible with great tensile strength -Found in joint surfaces and other locations -Chondrocytes (cartilage cells) live within lacunae (spaces) in the ground substance30 Special Connective Tissue Bone -Osteocytes (bone cells) remain alive in a matrix hardened with calcium phosphate -Communicate through canaliculi Blood -Extracellular material is the fluid plasma -Erythrocytes = red blood cells -Leukocytes = white blood cells -Thrombocytes = platelets 31 Special Connective Tissue 32 Muscle Tissue Muscle Tissue Muscles are the motors of vertebrate bodies -Three kinds: smooth, skeletal and cardiac Smooth muscles are found in walls of blood vessels and visceral organs -Cells are mono-nucleated Skeletal muscles are usually attached to bone by tendons, so muscle contraction causes bones to move -Muscle fibers (cells) are multi-nucleated -Contract by means of myofibrils, which contain ordered actin & myosin filaments -Skeletal and cardiac muscles are also known as striated muscles -Skeletal muscle is under voluntary control, whereas contraction of the other two is involuntary 34 33 35 36 4 Muscle Tissue Cardiac muscle is composed of smaller, interconnected cells -Each with a single nucleus -Interconnections appear as dark lines called intercalated disks -Enable cardiac muscle cells to form a single functioning unit 37 38 Nerve Tissue 39 Nerve Tissue Cells include neurons and their supporting cells, called neuroglia Most neurons consist of three parts -Cell body: contains the nucleus -Dendrites: highly branched extensions -Conduct electrical impulses toward the cell body -Axon: single cytoplasmic extension -Conducts impulses away from cell body Neuroglia do not conduct electrical impulses -Support and insulate neurons and eliminate foreign materials in and around neurons -Associate with axon to form an insulating cover called the myelin sheath -Gaps, known as nodes of Ranvier, are involved in acceleration of impulses 40 41 42 43 44 45 5 Nerve Tissue Overview of Organ Systems Nervous system is divided into: -Central nervous system (CNS) -Brain and spinal cord -Integration and interpretation of input -Peripheral nervous system (PNS) -Nerves and ganglia (collections of cell bodies) -Communication of signal to body 46 Overview of Organ Systems Communication and integration -Three organ systems detect external stimuli and coordinate the body’s responses -Nervous, sensory and endocrine systems Regulation and maintenance -Four organ systems regulate and maintain the body’s chemistry -Digestive, circulatory, respiratory and urinary systems Support and movement -The musculoskeletal system consists of two interrelated organ systems 47 Defense -The body defends itself with two organ systems: integumentary and immune Overview of Organ Systems Overview of Organ Systems 48 Overview of Organ Systems (Cont.) Reproduction and development -The biological continuity of vertebrates is the province of the reproductive system -In females, the system also nurtures the developing embryo and fetus 49 Overview of Organ Systems (Cont.) 52 50 Overview of Organ Systems 51 Overview of Organ Systems (Cont.) 53 54 6 Overview of Organ Systems (Cont.) Overview of Organ Systems 55 Overview of Organ Systems (Cont.) 56 Overview of Organ Systems 58 Overview of Organ Systems (Cont.) Overview of Organ Systems (Cont.) 57 Overview of Organ Systems (Cont.) 59 Homeostasis 60 Homeostasis As animals have evolved, specialization of body structures has increased For cells to function efficiently and interact properly, internal body conditions must be relatively constant -The dynamic constancy of the internal environment is called homeostasis -It is essential for life 61 62 63 7 Homeostasis Homeostasis To maintain internal constancy, the vertebrate body uses negative feedback mechanisms -Changing conditions are detected by sensors (cells or membrane receptors) -Information is fed to an integrating center, also called comparator (brain, spinal cord or endocrine gland) -Compares conditions to a set point -If a deviation is detected, a message is sent to an effector (muscle or gland) -Increase or decrease in activity brings internal conditions back to set point -Negative feedback to the sensor terminates the response 64 Homeostasis 65 66 Homeostasis Homeostasis Homeostasis Humans have set points for body temperature, blood glucose concentrations, electrolyte (ion) concentration, tendon tension, etc. Negative feedback mechanisms often oppose each other to produce finer degree of control -Many internal factors are controlled by antagonistic effectors -Have “push-pull” action -Increasing activity of one effector is accompanied by decrease in the other Antagonistic effectors are involved in the control of body temperature -If hypothalamus detects high temperature -Promotes heat dissipation via sweating, and dilation of blood vessels in skin -If hypothalamus detects low temperature -Promotes heat conservation via shivering and constriction of blood vessels in skin 69 We are endothermic: can maintain a relatively constant body temperature (37oC or 98.6oF) -Changes in body temperature are detected by the hypothalamus in the brain 67 Homeostasis 68 Homeostasis 70 In a few cases, the body uses positive feedback mechanisms to enhance a change -These do not in themselves maintain homeostasis -However, they are generally part of some larger mechanism that does! -Examples: -Blood clotting -Contraction of uterus during childbirth 71 Homeostasis 72 8