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2. The Animal Body and Principles of Regulation Chapter 42

3. 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

4. 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

5. 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. 6 Organization of Vertebrate Body Cardiac Muscle CellHeartCardiac MuscleCirculatory System CellOrganOrgan System Tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

7. 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. 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

9. 9 All vertebrates have dorsal and ventral body cavities Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. Section 1 Section 2 Section 3 Brain Thoracic cavity Diaphragm Pericardial cavity Vertebrae Cranial cavity Vertebral cavity Spinal cord Dorsal body cavity Right pleural cavity Peritoneal cavity Ventral body cavity

10. 10 Cross sections through three body regions Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b. Brain Muscles Rib Pharynx Epiglottis Esophagus Lungs Sternum Spleen Kidney Spinal cord Cecum Colon Mandible Muscles Section 1 Section 2 Section 3 Cranial cavity Vertebral cavity Pleural cavity Vertebra Trachea Anterior vena cava Thoracic cavity Small intestines Abdominal cavity

11. 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

12. 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

13. 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

14. 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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16. 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

17. 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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19. 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

20. 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

21. Connective Tissue Proper Adipose cells (fat cells) also occur in loose connective tissue –Develop in large groups in certain areas, forming adipose tissue 21 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 200 µm © Biophoto Associates/ Photo Researchers, Inc.

22. 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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24. 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

25. 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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27. 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

28. 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

29. 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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31. Heartbeat intrinsic to the heart 31 Heart continues to contract with no connection to the nervous system. Isolated heart Heart placed in solution with nutrients and oxygen. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

32. 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 32

33. 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 33

34. 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 34

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36. 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 36

37. 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 37

38. Overview of Organ Systems Reproduction and development –The biological continuity of vertebrates –In females, the system also nurtures the developing embryo and fetus 38

39. 39 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

40. 40 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

41. 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

42. 42 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

43. 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 43

44. 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

45. 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. 46 Homeostasis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. SensorIntegrating CenterStimulus Response ( – ) Move system towards set point Deviation from set point Constantly monitors conditions Compares conditions to a set point based on a desired value Causes changes to compensate for deviation Effector Negative feedback

47. 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

48. 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

49. 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. 50 Homeostasis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Integrating Center Stimulus Sensor Furnace turns on If Below Set Point Response Integrating Center Stimulus Sensor If Below Set Point Response a.b. ( – ) Room temperature changes from set point Negative feedback Negative feedback Room warms, temperature increases toward set point Thermometer in wall unit detects the change in temperature Room cools, temperature decreases toward set point Set Point = 70  F Thermostat compares temperature with set point Effector AC turns off Effector If Above Set Point AC turns on Furnace turns off Negative feedback Negative feedback Body temperature deviates from set point Body temperature drops Neurons in hypothalamus detect the change in temperature Body temperature rises If Above Set Point Blood vessels to skin dilate Glands release sweat Effector Set Point = 37  C Neurons in hypothalamus compare input from sensory neurons with set point Effector Blood vessels to skin contract Muscles contract, shiver

51. 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. 52 Homeostasis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Integrating Center Stimulus Sensor Response ( + ) Fetus is pushed against the uterine opening Receptors in the inferior uterus detect increased stretch Positive feedback loop completed— results in increased force against inferior uterus (cervix), promoting the birth of the baby Oxytocin causes increased uterine contractions Effector If Above Set Point The pituitary gland is stimulated to increase secretion of the hormone oxytocin The brain receives stretch information from the uterus, and compares it with the set point

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54. Regulating Body Temperature Temperature is one of the most important aspects of the environment Some organisms have a body temperature that conforms to the environment Other organisms regulate their body temperature 54

55. Q 10 is a measure of temperature sensitivity –The rate of any chemical reaction is affected by temperature –The rate increases with increasing temperature –Every 10°C increase in temperature doubles the reaction rate 55

56. Temperature determined by internal and external factors –Overall metabolic rate and body temperature are interrelated –Organisms must deal with external and internal factors that relate body heat, metabolism, and the environment 56 body heat = heat produced + heat transferred

57. Mechanisms of heat transfer Radiation. The transfer of heat by electromagnetic radiation Conduction. The direct transfer of heat between two objects. Energy is transferred from hotter objects to colder ones. Convection. Convection is the transfer of heat brought about by the movement of a gas or liquid. Evaporation. Heat of vaporization or the amount of energy needed to change them from a liquid to a gas phase 57

58. Ectotherms regulate temperature using behavior –Low metabolic rates –Regulate their temperature using behavior 58 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Flight Full-range movement of wings Warm up Shiver-like contraction of thorax muscles Preflight No wing movement 40 35 30 25 –101234 Time (min) Temperature (ºC) of thorax muscles

59. Endotherms create internal metabolic heat –Conservation or dissipation –Heat transfer is controlled by amount of blood flow to the surface of the animal Countercurrent exchange –Allows sustained high-energy activity –Tradeoff is the high metabolic rate 59

60. 60 Countercurrent heat exchange Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Artery Core body temperature 36°C Warm blood Cold blood Veins Capillary bed 5°C Temperature of environment Cold blood

61. Body size and insulation –Changes in body mass have a large effect on metabolic rate –Smaller animals consume much more energy per unit –body mass than larger animals –Summarized in the “mouse to elephant” curve Nonproportionality of metabolic rate versus size of mammals 61

62. 62 Relationship between body mass and metabolic rate in mammals Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Shrew 8 7 6 5 4 3 2 1 0 0.010.11101001000 Harvest mouse Kangaroo mouse Cactus mouse Mouse log Mass (kg) Flying squirrel Rat ElephantHorseHuman Sheep Dog Cat Rabbit Mass-specific metabolic rate (mL O 2 × g –1 × h –1 )

63. Mammalian thermoregulation is controlled by the hypothalamus –Neurons in the hypothalamus detect the temperature change –Stimulation of the heat-losing center Peripheral blood vessel dilation Sweating –Stimulation of heat-promoting center Thermogenesis Constriction of blood peripheral blood vessels Epinephrine production by adrenal glands Anterior pituitary produces TSH 63

64. 64 Control of body temperature by the hypothalamus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. () () Stimulus Sun Perturbing factor Snow and ice Perturbing factor Stimulus Sensor Hypothalamus Integrating Center Blood vessels dilate Glands release sweat Blood vessels constrict Response Body temperature rises Body temperature drops Thermoreceptors Negative feedback Negative feedback Body temperature rises Skeletal muscles contract, shiver Effector Body temperature falls