Chapter 20 UNIFYING CONCEPTS OF ANIMAL STRUCTURE AND FUNCTION
I. Life is based on many structural levels Levels of animal structure: Atoms and molecules Cells Tissues Organs Organ systems Organism: May consist of a single cell or a complex multicellular organism.
Levels of Structural Organization in an Animal
TISSUES: Most animal cells are organized into tissues. Cooperative unit of very similar cells that perform a specific function. Tissue comes from Latin word meaning weave. Cells of tissues may be held together by: Fibers Glue-like substance Plasma membrane structures Tissue structure is related to its function.
TISSUES: There are four main types of animal tissue: 1. Epithelial 2. Connective 3. Muscle 4. Nervous
1. Epithelial Tissue Cells are tightly fitted together in continuous layers or sheets. Cover outside of body (skin), line organs and internal body cavities (Mucous membranes of digestive, respiratory, and reproductive systems). Tight packaging allows tissue to act as a barrier to protect against mechanical injury, infection, and fluid loss. Two surfaces: Free surface: Exposed to air or fluid. Bottom surface: Attached to underlying tissues by a basement membrane, a dense layer of protein and polysaccharides.
1. Epithelial Tissue Can be classified based on two criteria: A. Number of layers: Simple: One layer. Stratified: Several layers B. Shape of cells: Squamous: Flat cells. Cuboidal: Cube shaped cells Columnar: Column shaped cells Example: Simple squamous epithelium Stratified columnar epithelium
Epithelial Tissue Covers and Lines the Body and its Parts A. Simple squamous (Lung air sacs) B. Simple cuboidal (Kidney tubes) D. Statified squamous (Lining esophagus) C. Statified columnar (Lining intestine)
1. Epithelial Tissue Some epithelial tissues, such as mucous membranes, absorb and secrete chemical solutions. Mucous membranes: Digestive tract epithelium (mucous membranes) secretes mucus and digestive enzymes. Respiratory tract epithelium secretes mucous that helps trap dust particles before they reach the lungs.
2. Connective Tissue Relatively few cells surrounded by large amounts of nonliving material (matrix). Cells secrete the matrix, which can be solid, liquid, or gelatinous. Diverse functions. Mainly bind, support, and connect other tissues. Six types of connective tissue in humans: 1. Loose Connective Tissue: Most widespread connective tissue in vertebrates. Loose matrix with fibers, packing material. Attaches skin to muscles, binds and holds tissues and organs in place. 2. Adipose (fat): Pads and insulates body. Energy storage.
Connective Tissue Binds and Provides Support A. Loose Connective Tissue D. Fibrous Connective Tissue B. Adipose Tissue E. Cartilage C. Blood F. Bone
Types of connective tissue in humans (Continued): C. Blood: Fluid matrix (plasma) has water, salts, and proteins. Red and white blood cells. D. Fibrous Connective Tissue: Matrix of densely packed collagen fibers. Strong and nonelastic. Found in: Tendons: Attach muscles to bones. Ligaments: Attach bone to bone. E. Cartilage: Rubbery matrix with collagen fibers. Found on end of bones, nose, ears, and between vertebra. F. Bone: Supports the body of most vertebrates. Solid matrix of collagen fibers and calcium, phosphate, and magnesium salts. Bone is harder than cartilage, but not brittle because of collagen.
3. Muscle Tissue Most abundant type of tissue in most animals. Accounts for two-thirds (2/3) of human weight. Specialized for contraction. Made up of long cells that contract when stimulated by nerve impulses. Muscle cells have many microfilaments made up of actin and myosin. Muscle contraction accounts for much of energy consuming work in animals. Adults have a fixed number of muscle cells. Weight lifting doesn t increase number of muscle cells, only their size.
3. Muscle Tissue There are three types of muscle tissue: A. Skeletal (striated) muscle : Attached to bones by tendons. Responsible for voluntary movements. B. Cardiac muscle: Forms contractile tissue of heart. Not under voluntary control. C. Smooth muscle: Found in walls of digestive tract, bladder, arteries, uterus, and many internal organs. Responsible for peristalsis and labor contractions. Contract more slowly than skeletal muscle, but can remain contracted longer. Not under voluntary control.
Three Types of Muscle B. Cardiac muscle A. Skeletal muscle C. Smooth muscle
4. Nervous Tissue Senses stimuli and transmits signals from one part of the animal to another. Controls the activity of muscles and glands, and allows the animal to respond to its environment. Neuron: Nerve cell. Structural and functional unit of nervous tissue. Consists of: Cell body : Contains cell s nucleus. Dendrite: Extension that conveys signals towards the cell body. Axon: Extension that transmits signals away from the cell body. Supporting cells: Nourish, protect, and insulate neurons.
Nervous Tissue Forms a Communication Network
Organs are made up of different tissues Organ: Several tissues that act as a unit and together perform one or more biological functions. Perform functions that component tissues can t carry out alone. Example: The heart is an organ made up of: Muscle Tissue: Contraction Epithelial Tissue: Lines heart chambers to prevent leakage and provide a smooth surface. Connective Tissue: Makes heart elastic and strengthens its walls and valves. Nervous Tissue: Direct heart contractions.
Organs are Made of Several Different Tissues
Animals Regulate their Internal Environment Homeostasis: Steady state. Internal environment of animal remains fairly constant despite changes in the external environment. Control systems maintain internal conditions within a range in which life s metabolic activities can occur. Homeostasis is a dynamic state resulting from changes in the outside environment and internal control mechanisms that oppose such changes.
Homeostatic Mechanisms Counteract Changes in External Conditions
Animals Regulate their Internal Environment Homeostasis: Maintained by negative feedback mechanisms. A change in one condition (e.g.: low body temperature), results is a response that counteracts that change (e.g.: shivering, etc.). Internal conditions regulated by negative feedback: Body temperature (Normal range: 97-100 o F) Salt concentration ph Blood levels of sugar, calcium, oxygen, etc.
Negative Feedback as Homeostatic Mechanism
Body Temperature is Regulated by Homeostasis
Major Organ Systems in Mammals Digestive system Respiratory system Circulatory system Cardiovascular Lymphatic and Immune system Excretory system Endocrine system Reproductive system Nervous system Muscular system Skeletal system Integumentary
1. Digestive System Components: Mouth, salivary glands, throat, esophagus, stomach, intestines, liver, gallbladder, pancreas, rectum, and anus. Functions: Ingest and mechanically break down food. Digest food: Stomach and small intestine mainly. Absorb nutrients and water. Eliminate waste. Homeostatic Roles: Supplies energy for life s activities. Supplies building blocks for macromolecules
Human Digestive System
2. Respiratory System Components: Nose, throat, larynx, trachea, bronchi, and lungs. Functions: Exchange gases with the environment: Supplies blood with oxygen. Disposes of carbon dioxide (waste product from cellular respiration). Homeostatic Roles: Regulates blood ph. Regulates blood oxygen and carbon dioxide levels.
Human Respiratory System
3. Cardiovascular System Components: Blood, heart, arteries, veins, and capillaries. Functions: Exchange gases with the respiratory system. Supplies tissues with oxygen. Removes carbon dioxide from tissues. Transports materials (nutrients, hormones, etc.) inside body. Defends against infection. Homeostatic Roles: Provides nutrients and removes waste materials from tissues. Regulates body temperature, water and ion balance.
Human Cardiovascular System
4. Lymphatic and Immune System Components: Lymph, lymphatic vessels, bone marrow, thymus, spleen, and lymph nodes. Functions: Defends against infection: bacteria, fungi, viruses, etc. Destruction of cancer and foreign cells. Synthesis of antibodies and other immune molecules. Synthesis of white blood cells. Homeostatic Role: Returns fluid and proteins that have leaked from blood capillaries into tissues. Up to 4 liters of fluid every day. Fluid returned near heart/venae cavae.
Lymphatic and Immune Systems
5. Excretory (Urinary) System Components: Kidneys, bladder, urethra, and associated ducts. Functions: Kidneys remove nitrogen containing waste from blood. Urine with waste is temporarily stored in bladder. Excretion of urine. Homeostatic Role: Regulates water levels in body. Removes excess water Helps conserve water
Human Excretory System
6. Endocrine System Components: Pituitary, adrenal, thyroid, thymus, pancreas, ovaries, testes, and other ductless glands. Functions: Produce hormones that regulate: Blood chemistry: Levels of sugars, minerals, etc. Reproduction Growth Metabolism Digestion Homeostatic Role: With nervous system, regulates metabolism and blood chemistry.
Human Endocrine System
7. Reproductive System Components: Female: Ovaries, oviduct, uterus, vagina, and associated structures Male: Testes, seminal vesicles, prostate, urethra, penis, and associated structures. Functions: Only organ system that is not essential for individual survival. Continuation of species. Gamete formation (eggs and sperm cells). Homeostatic Role: Maintains secondary sexual characteristics.
Male Reproductive System
Female Reproductive System
Gamete Formation Occurs in Testis
8. Nervous System Components: Brain, spinal cord, nerves, sense organs, and associated structures. Functions: Works with endocrine system to coordinate body activities. Integrates and processes information from sense organs. Sends signals (instructions) to muscles and glands. Responds to internal stimuli. Homeostatic Role: Regulates most organ activities along with endocrine system.
Human Nervous System
Nervous System Allows Us to Respond to Our Environment
9. Muscular System Components: Skeletal muscles. Functions: Skeletal muscle contraction allows for voluntary movement: Movement and locomotion. Mechanical work: Lifting, pulling, pushing objects. Communication: Body language and facial expression. Homeostatic Role: Allows animals to respond to and control their environment.
Muscular System: Skeletal Muscle Allows Voluntary Movement
10. Skeletal System Components: Bones, ligaments, and cartilage. Functions: Along with muscular system: Movement and locomotion. Mechanical work: Lifting, pulling, pushing objects. Body support. Protection of delicate internal organs (brain, heart, lungs, etc.) Calcium storage Homeostatic Role: Helps maintain constant blood calcium levels.
Skeletal System: Protection, Movement, & Support
11. Integumentary System Components: Hair, skin, and nails. Functions: Protects the body from: Infection: Barrier to microbes. Mechanical injury Excessive heat or cold: Thermoregulation Water loss Communication: Receives stimuli from environment Gives out subtle signals (blushing, etc.). Homeostatic Role: Helps maintain constant body temperature.
Integumentary System: Skin, Nails, & Hair
Organ systems must be coordinated for animal to survive Organ systems interact with one another in order to maintain fairly stable conditions (homeostasis) that are required for life. Example: Interactions between: Respiratory Circulatory Digestive
Relationships Between Several Major Organ Systems