Animal Structure and Function: An Introduction Chapter 38

KEY CONCEPTS Structure and function are closely linked at every level of organization

Learning Objective 1 Compare the structure and function of the four main kinds of animal tissues: epithelial, connective, muscle, and nervous

Tissue A group of similarly specialized cells Associated to perform one or more functions

Epithelial Tissue (Epithelium) A continuous layer (sheet) of cells covering a body surface lining a body cavity Functions in protection, absorption, secretion, or sensation

Connective Tissue 1 Relatively few cells separated by intercellular substance fibers scattered throughout a matrix Intercellular substance fibers collagen fibers elastic fibers reticular fibers

Connective Tissue 2 Contains specialized cells Functions: such as fibroblasts and macrophages Functions: joins other body tissues supports body and organs protects underlying organs

Muscle Tissue Consists of cells specialized to contract Each cell is an elongated muscle fiber many contractile units (myofibrils)

Nervous Tissue Neurons Glial cells elongated cells specialized for transmitting impulses Glial cells support and nourish neurons

Learning Objective 2 Compare the structure and function of the main types of epithelial tissue

Epithelial Tissue Epithelial cell shapes Epithelial tissue structure squamous, cuboidal, columnar Epithelial tissue structure simple, stratified, pseudostratified (See Table 38-1)

Simple Squamous Epithelium Lines blood vessels and air sacs in lungs Permits exchange of materials by diffusion

Simple Cuboidal and Columnar Epithelia Line passageways Specialized for secretion and absorption

Stratified Squamous Epithelium Forms outer layer of skin Lines passageways into the body Provides protection

Pseudostratified Epithelium Lines passageways Protects underlying tissues

Glands 1 Specialized epithelial tissue Goblet cells unicellular exocrine glands that secrete mucus

Glands 2 Exocrine glands Endocrine glands secrete product through a duct onto exposed epithelial surface Endocrine glands release hormones into interstitial fluid or blood

Glands

Unicellular glands (goblet cells) Cilia Basement membrane (a) Goblet cells. Skin Figure 38.1: Glands. A gland consists of one or more epithelial cells. (b) Sweat gland. (c) Parotid salivary gland. Fig. 38-1, p. 809

Membranes Epithelial membrane Mucous membrane Serous membrane sheet of epithelial tissue layer of underlying connective tissue Mucous membrane lines cavity that opens to outside of body Serous membrane lines cavity that does not open to the outside

Learning Objective 3 Compare the main types of connective tissue Summarize their functions

Connective Tissues Cells embedded in intercellular substance microscopic collagen fibers, elastic fibers, reticular fibers (thin branched fibers) scattered through a matrix (thin gel of polysaccharides)

Loose Connective Tissue Consists of fibers running in various directions through a semifluid matrix Flexible tissue forms a covering for nerves, blood vessels, and muscles

Dense Connective Tissue Stronger, less flexible than loose connective tissue Collagen fibers arranged in definite pattern Forms tendons (connect muscles to bones) ligaments (connect bones to bones)

Dense Connective Tissue

Elastic Connective Tissue Consists of bundles of parallel elastic fibers Found in lung tissue, walls of large arteries

Reticular Connective Tissue Consists of interlacing reticular fibers Forms support framework for many organs

Adipose Tissue Consists of fat cells Found with loose connective tissue in subcutaneous tissue

Cartilage and Bone Form skeletons of vertebrates Cartilage consists of chondrocytes in lacunae (small cavities in hard matrix) nonvascular Osteocytes secrete and maintain bone matrix vascular

Cartilage and Bone Cartilage Bone

Bone

(a) The human skeleton consists mainly of bone. Figure 38.2: Bone. (a) The human skeleton consists mainly of bone. (b) A bone is cut open, exposing its internal structure. Fig. 38-2ab, p. 814

Blood and Lymph Circulating tissues fluid intercellular substances Help parts of an animal communicate with one another

Learning Objective 4 Contrast the three types of muscle tissue and their functions

Skeletal Muscle Striated and under voluntary control Elongated, cylindrical fibers with several nuclei Skeletal muscles contract, move parts of the body

Cardiac Muscle Striated, contractions are involuntary Elongated, cylindrical fibers branch and fuse; one or two central nuclei Muscle contracts, heart pumps blood

Smooth Muscle No striations, contractions involuntary Elongated, spindle-shaped fibers with a single central nucleus Smooth muscle moves body organs (example: pushes food through digestive tract)

Muscle Tissues

Learning Objective 5 How does the structure of the neuron relate to its function?

Neuron Elongated cell Receives and transmits information Synapse a junction between neurons

Neuron Dendrites Axon receive signals transmit signals to cell body transmits signals away from cell body to other neurons, muscles, glands

Neuron

Neurons Dendrite Nuclei of glial cells Axon 100 µm Fig. 38-3, p. 817 Figure 38.3: LM of nervous tissue. Neurons transmit impulses. Glial cells support and nourish neurons. Axon 100 µm Fig. 38-3, p. 817

KEY CONCEPTS The main types of tissues in a complex animal are epithelial, connective, muscle, and nervous

Learning Objective 6 Describe the organ systems of a mammal Summarize the homeostatic actions of each organ system

Organ Systems Tissues and organs working together In mammals, 11 organ systems work together in the organism Each organ system functions to maintain homeostasis

11 Organ Systems Integumentary Respiratory Skeletal Urinary Muscular Nervous Digestive Endocrine Cardiovascular Reproductive Immune (lymphatic)

11 Organ Systems

11 Organ Systems

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KEY CONCEPTS Tissues and organs form the 11 main organ systems of a complex animal

Learning Objective 7 Define homeostasis Contrast negative and positive feedback systems

Homeostasis Balanced internal environment (steady state) Homeostatic mechanisms control processes that maintain conditions

Negative Feedback Systems 1 Maintain dynamic equilibrium (homeostasis) 1. Stressor causes change in some steady state 2. Triggers a response that opposes the change

Negative Feedback Systems 2 3. Sensor detects change a deviation from desired condition (set point) 4. Sensor signals an integrator (control center) 5. Integrator activates effectors organs or processes that restore steady state

Negative Feedback

Normal condition (set point) restored. Stressor HOMEOSTASIS 5 Normal condition (set point) restored. 1 Stressor causes deviation from set point. 4 Integrator activates effectors (homeostatic mechanisms). Figure 38.5: Negative feedback. 2 Sensor detects change from set point. 3 Sensor signals integrator (control center). Fig. 38-5, p. 821

Positive Feedback System Deviation from steady state causes changes that intensify (rather than reverse) the changes

Positive Feedback

Loss of blood causes blood pressure to decrease. Stressor: hemorrhage Homeostasis 1 Loss of blood causes blood pressure to decrease. 4 Cardiac output decreases (heart pumps less blood). Figure 38.7: Positive feedback. In positive feedback, the changes that occur amplify the deviation from the set point. Loss of blood causes blood pressure to decrease. Less blood reaches the heart, so heart function decreases. The resulting decrease in cardiac output further decreases blood pressure, bringing about conditions farther from homeostasis. 2 Less blood circulates to heart. 3 Heart function declines. Fig. 38-7, p. 822

KEY CONCEPTS Homeostatic mechanisms are responsible for the body’s automatic tendency to maintain a relatively stable internal environment

Learning Objective 8 Compare the costs and benefits of ectothermy

Thermoregulation Process of maintaining body temperature within certain limits despite changes in surrounding temperature Animals have different structural, behavioral, and physiological strategies

Ectotherms In ectotherms, body temperature depends on temperature of environment Use behavioral strategies to adjust body temperatures

Costs and Benefits Benefits of ectothermy Disadvantage of ectothermy very little energy used to maintain the metabolic rate ectotherms can survive on less food Disadvantage of ectothermy activity limited by daily and seasonal temperature conditions

Learning Objective 9 Compare the costs and benefits of endothermy Describe strategies animals use to adjust to challenging temperature changes

Endotherms Have homeostatic mechanisms regulate body temperature within a narrow range

Costs and Benefits Benefits of endothermy Disadvantage of endothermy high metabolic rate constant body temperature allows higher rate of enzyme activity active even in low winter temperatures Disadvantage of endothermy high energy cost

Temperature Regulation in Humans

HOMEOSTASIS Decreased muscle activity Increased sweating/ panting Nerves Evaporation Smooth muscle in blood vessels relaxes Blood vessels dilate Sensors signal temperature- regulating center in hypothalamus (integrator) Specialized nerve cells (sensors) detect change from set point Figure 38.9: Regulation of temperature in the human body. Body temperature increases Body temperature decreases (normal condition restored) Stressors Stressors HOMEOSTASIS Fig. 38-9, p. 823

Body temperature increases (normal condition restored) Body temperature decreases Specialized nerve cells (sensors) detect change from set point Sensors signal temperature- regulating center in hypothalamus (integrator) Increase in voluntary movement; shivering Blood vessels constrict Figure 38.9: Regulation of temperature in the human body. Nerves Smooth muscle in blood vessels contracts Increase in metabolic rate Anterior pituitary gland Thyroid gland Fig. 38-9, p. 823

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Acclimatization Process of adjustment to seasonal changes

Torpor Torpor Hibernation Estivation adaptive hypothermia (in small endotherms when surrounding temperature drops) Hibernation long-term torpor in response to winter cold Estivation torpor due to lack of food or water during summer heat

KEY CONCEPTS Thermoregulation contributes to homeostasis

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