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The Animal Body and Principles of Regulation Chapter 43

Organization of Vertebrate Body There are four levels of organization 1.Cells 2.Tissues 3.Organs 4.Organ systems Bodies of vertebrates are composed of different cell types –Humans have 210 3

Organization of Vertebrate Body Tissues –Groups of cells that are similar in structure and function –3 fundamental embryonic tissues are called germ layers Endoderm, mesoderm, and ectoderm –In adult vertebrates, there are four primary tissues Epithelial, connective, muscle, and nerve 4

Organization of Vertebrate Body Organs –Combinations of different tissues that form a structural and functional unit Organ systems –Groups of organs that cooperate to perform the major activities of the body –Vertebrate body contains 11 principal organ systems 5

6 Organization of Vertebrate Body

General 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 7

8 Organization of Vertebrate Body 2 main body cavities –Dorsal body cavity Forms within skull and vertebrae –Ventral body cavity Bounded by the rib cage and vertebral column Divided by the diaphragm into –Thoracic cavity – heart and lungs »Pericardial cavity: Around the heart »Pleural cavity: Around the lungs –Abdominopelvic cavity – most organs »Peritoneal cavity – coelomic space

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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 11

Epithelial Tissue Epithelia possess remarkable regenerative powers replacing cells throughout life Epithelial tissues attach to underlying connective tissues by a fibrous membrane –Basal surface – secured side –Apical surface – free side –Inherent polarity important for their function 12

Epithelial Tissue Two general classes –Simple – one layer thick –Stratified – several layers thick Each class subdivided into –Squamous cells – flat –Cuboidal cells – about as wide as tall –Columnar cells – taller than they are wide 13

Simple Epithelium Simple squamous epithelium –Lines lungs and blood capillaries –Delicate nature permits diffusion 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

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Simple 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 16

Stratified Epithelium 2 to several layers thick Named according to the features of their apical cell layers Epidermis is a stratified squamous epithelium –Terrestrial vertebrates have a keratinized epithelium Contains water-resistant keratin –Lips are covered with nonkeratinized, stratified squamous epithelium 17

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Connective Tissues 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 19

Connective Tissue Proper Fibroblasts produce and secrete extracellular matrix Loose connective tissue –Cells scattered within a matrix that contains a large amount of ground substance –Strengthened by protein fibers Collagen – supports tissue Elastin – makes tissue elastic Reticulin – helps support the network of collagen 20

Connective Tissue Proper Adipose cells (fat cells) also occur in loose connective tissue –Develop in large groups in certain areas, forming adipose tissue 21

Connective Tissue Proper Dense connective tissue –Contains less ground substance 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, and bone 22

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Special Connective Tissue Cartilage –Ground substance made from characteristic glycoprotein (chondroitin) and collagen fibers in long, parallel arrays –Firm and flexible tissue that does not stretch –Great tensile strength –Found in joint surfaces and other locations –Chondrocytes (cartilage cells) live within lacunae (spaces) in the ground substance 24

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 25

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Muscle Tissue Muscles are the motors of vertebrate bodies Three kinds: smooth, skeletal, and cardiac –Skeletal and cardiac muscles are also known as striated muscles –Skeletal muscle is under voluntary control, whereas contraction of the other two is involuntary 27

Muscle Tissue Smooth muscle –Found in walls of blood vessels and visceral organs –Contain a single nucleus Skeletal muscle –Usually attached to bone by tendons, so muscle contraction causes bones to move –Muscle fibers (cells) are multinucleated –Contract by means of myofibrils, which contain ordered actin and myosin filaments 28

Muscle Tissue Cardiac muscle –Composed of smaller, interconnected cells –Each with a single nucleus –Interconnections appear as dark lines called intercalated disks Gap junctions link adjacent cells –Enable cardiac muscle cells to form a single functioning unit 29

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Nerve Tissue Cells include neurons and their supporting cells (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 31

Nerve Tissue 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 (nodes of Ranvier) are involved in acceleration of impulses 32

Nerve Tissue 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 and from the CNS to the rest of the body 33

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Overview of Organ Systems Communication and integration –Three organ systems detect external stimuli and coordinate the body’s responses –Nervous, sensory, and endocrine systems Support and movement –Musculoskeletal system consists of two interrelated organ systems 35

Overview of Organ Systems Regulation and maintenance –Four organ systems regulate and maintain the body’s chemistry –Digestive, circulatory, respiratory, and urinary systems Defense –The body defends itself –Integumentary and immune systems 36

Overview of Organ Systems Reproduction and development –The biological continuity of vertebrates –In females, the system also nurtures the developing embryo and fetus 37

38 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Skull Sternum Pelvis Femur Nervous SystemEndocrine SystemSkeletal System Ovary (female) Pituitary Hypothalamus Thyroid Thymus Pancreas Brain Nerves Testis (male) Adrenal gland Spinal cord

39 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Arteries Heart Circulatory System Esophagus Liver Stomach Small intestine Digestive SystemMuscular System Gastrocnemius Biceps Sartorius Quadriceps Salivary glands Pectoralis major Rectus abdominus Large intestine Veins

40 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lymph nodes Thymus Spleen Bone marrow Lymphatic/Immune System Penis Reproductive System (male)Reproductive System (female) Ovary Uterus Vas deferens Lymphatic vessels Vagina Fallopian tube Testis

41 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lymph nodes Thymus Spleen Bone marrow Lymphatic/Immune System Penis Reproductive System (male)Reproductive System (female) Ovary Uterus Vas deferens Lymphatic vessels Vagina Fallopian tube Testis

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 42

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Homeostasis 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 conditions deviate too far from a set point, biochemical reactions are initiated to change conditions back toward the set point 44

Homeostasis Humans have set points for body temperature, blood glucose concentrations, electrolyte (ion) concentration, tendon tension, etc. Integrating center is often a particular region of the brain or spinal cord Effectors (muscles or glands) change the value of the condition in question back toward the set point value 45

46 Homeostasis

Mammals and birds are endothermic –Maintain a relatively constant body temperature independent of the environmental temperature –Humans 37 o C or 98.6 o F –Changes in body temperature are detected by the hypothalamus in the brain 47

Homeostasis 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 48

Homeostasis 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 49

50 Homeostasis

Positive feedback mechanisms –Enhance a change – not common –These do not in themselves maintain homeostasis –Important components of some physiological mechanisms Blood clotting Contraction of uterus during childbirth 51

52 Homeostasis

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