Biology
31, Las Positas College, Fall 2003
Tissues, Organ Systems, and Homeostasis
Chapter 29
I-4 Tissue Types
A. Epithelial
B. Connective
C. Muscle
D. Nervous
II-Organ Systems
III-Homeostasis
A. General Considerations
B. Feedback Loops
Introduction
Body made up of many different types of cells. These cells are organized to
form the structures & perform the functions of the human body. Cells ->
tissues. Tissues -> organs. Organs -> organ systems. Organ systems ->
organisms.
Tissue = many similar cells that perform a special function.
All animals need to:
1. Maintain conditions in the internal environment within ranges that are most favorable for cell activities.
2. Acquire nutrients and other raw materials, distribute them throughout the body, and dispose of wastes.
3. Afford protection against injury or attack from viruses, bacteria, and other agents of disease.
4. Reproduce, then often help nourish and protect the new individuals during their early growth and development.
I-4 Tissue Types –
Epithelia, Connective, Muscle, Nervous
A. Epithelial
1. Covers and lines the surfaces of the body, both external (body surfaces) & internal (cavities & tubes). Guards & protects.
1. protection (skin)
2. absorption (intestine)
3. secretion (glands)
4. sensation (taste buds)
5. excretion (kidneys, lungs)
5. surface transport (cilia sweep thin layer of mucus & particles stuck in it along surface of respiratory tract)2. Cells relatively regular in shape, tightly packed in continuous sheets. Can be flat (squamous), elongated (columnar), cuboidal (cubical) or transitional (changeable-bladder). Cells held together by strong adhesions = fibers for strength & channels for communication. Stuck onto basement membrane (connective tissue) for strength, guards against tearing, guide for regeneration of cells. Often have surface specialization
1 free surface - faces environment or some type of body fluid
1 or more layers: 1 layer -> secretion & absorption; 2 or more -> protectionForms glands - indentation of epithelium, may remain open to outside (exocrine) or ductless & secrete into bloodstream (endocrine)
B. Connective tissue - -> structural & metabolic support for other tissues
& organs. Cells provide the body with structural building blocks & potent
defenses. Also joins other tissues of the body.
1. Provides a framework for the body
2. Joins its tissues
3. Helps defend it from foreign invaders
4. Acts as storage sites for specific substances
1. Cells & Tissues that shape & bond-Structural stay in one place & secret proteins into empty spaces between them.
a. Protein fibers of different types
Dense, regular connective tissue-tendons, ligaments attachments between organs & dermis of the skin
Dense, irregular connective tissue-supports liver, spleen, lymph nodes, bone marrow tissue,
Elastic connective tissue -> stretch & recoil in lungs, arteries
Loose connective tissue - elasticity, diffusion-under skinb. cartilage cells -> gel & fibers
Chondrocytes -> cartilage - a specialized connective tissue that is hard and strong. Provides support & aids in movement of joints.
Depend on diffusion through matrix for nutrition - no blood vessels
Forms skeleton of sharks & rays, skeleton of other animals
Extracellular matrix = semi-fluid gel -> flexibility & allows passage of fluids. Reinforced by fibers.c. bone cells-lay down a matrix of fibers that becomes coated with calcium. Collagen fibers -> flexibility, become coated with crystals of calcium -> rigidity. Some bones -> blood cells
2. Cells that defend-float in a matrix of blood plasma.
White blood cells. Lymphocytes attack foreign cells & viruses or produce antibodies. Macrophages engulf & digest the invader. Mast cells release histamine -> blood vessel dilation -> increased blood flow -> increased O2 & nutrients, dilutes toxins.
Necessary for functional immune system.
Plasma fluid part of blood-transports food & waste products, regulates body temperature. Consists of mostly H2O, some salts and proteins.
3. Cell & Tissues that act as storage sites for specific substances. Cells specialize in accumulating & transporting particular molecules, such as fat & pigments.
a. Red blood cells - transport O2.
b. adipose cells = fat cells-store lipids for energy. Also helps shape and pad body. Insulates against heat loss.C. MUSCLE TISSUE-moves body parts by contracting (only).
3 types-different organization, appearance, control, function.1. Skeletal-attached to bones by tendons & allow you to move your body. Voluntary.
2. Smooth-found in organs. Ex: blood vessels, eye pupils. Involuntary. Controlled by nerves or hormones
3. Cardiac-heart, involuntary
D. NERVOUS TISSUE-neurons & supporting cells. Receive, analyze & integrate messages; produce & coordinate appropriate response.Neurons transmit messages, nerve impulses. Neurons - excitable, electrical charge via ions. Send message from 1 neuron -> another or -> muscle via neurotransmitters. Clustered & bundled.
Protected, supported, insulated by several types of supporting cells (glia).
Controls voluntary & involuntary muscles.
II-Organ Systems
Organs-made of several tissue types.
Organ systems-groups of organs that function together to carry out the principle activities of the body.11 = digestive, respiratory, circulatory, immune, urinary, nervous, skeletal, integumentary, muscular, endocrine, reproductive.
III-Homeostasis
A. General Considerations
The organ systems interact with one another to maintain a stable internal environment or "steady state" called homeostasis.
Homeostasis = the maintenance of a stable internal environment.
Homeostasis occurs when the body's needs adequately met & its functions are occurring smoothly.
Nerves & hormones -> adjustments.
B. FEEDBACK LOOPS-general
control mechanism. Message received, interpreted, response, new condition registered.
System feeds back to the system so that appropriate adjustments can be made.
Positive or NegativeNegative: most common- response -> homeostasis, opposite condition of initial stimulus.
Positive: -> change, increased condition, self-limiting.