NOTES FOR BIOLOGY 1002

SECTIONS 004, 005, 006

Spring 2006

DR. STEVEN POMARICO

CHAPTER 33

ANIMAL TISSUES AND ORGAN SYSTEMS

One of the characteristics of life is that organisms establish and maintain an internal environment. Part of this process includes homeostasis.

Homeostasis - tendency of life to try and maintain the structure and regulate the                                        internal environment.

                   Life is easier without a lot of changes to deal with.

This “maintenance of an internal environment” is a dynamic process which require continual regulation (and energy)

The basic scheme of organization involves cells organized into tissues organized into organs organized into organ systems

There are four general types of tissue:

                   Epithelial

                   Connective

                   Muscle

                   Nerve

>>>Epithelial tissue

Cells form continuous sheets called membranes (see fig.33.2)

Membranes cover the body and line all body cavities

The main function of the epithelial tissue is to form a barrier

         Because of this the epithelial tissue has no blood vessels

It’s either nourished by diffusion from capillaries beneath it or is continuously lost and replaced by cell division

There are many types of epithelial tissue

Some epithelial tissues form glands that are specialized for the secretion of substances.

The are two main types of glands

                   Exocrine glands

                   Endocrine glands

Exocrine glands (See fig. 33.4):

         These glands remain connected to the epithelial tissue and secrete their                    material either outside the body or into a cavity

                   salivary, sweat, and sebaceous (oil) glands.

Endocrine glands

         These glands have lost their connection to the epithelial tissue and secrete                    their material into the bloodstream

                                       hormones

>>>Connective tissue

         Includes soft connective tissue and specialized connective tissue

The soft connective tissue has three types:

         -loose or dermis

         -dense irregular

         -dense regular - tendons and ligaments,

There are four different types of specialized connective tissue:

         -cartilage,

         -bone

         -adipose tissue or fat

         -blood and lymph

The connective tissue is surrounded by large quantities of extracellular substances (between the living cells) that are secreted from the connective tissue.

-loose or dermis is found under all the epithelial tissues (See fig 33.2) and is

          responsible for nourishing the epithelial via capillaries and fluid-filled spaces.

Many of the other types (except blood and lymph) are interwoven with extracellular fibrous strands of collagen which is a protein secreted by the cells

-dense regular - tendons and ligaments contain densely packed collagen fibers in a parallel arrangement

-cartilage

         Covers ends of bones at joints.

         Supports respiratory passages.

         Supports ear and nose.

         Forms shock-absorbing pads between vertebrae

-bone (See fig 33.6)

         Resembles cartilage hardened by deposits of calcium phosphate.

-adipose tissue or fat

         Specially modified to act as storage sacs for triglycerides (fats).

-blood and lymph

         Largely composed of extracellular fluid called plasma (for blood) and Iymph

>>>Muscle tissue (See fig 33.8)

This tissue is specialized for contraction.

There are three types of muscle

                   skeletal also called striated

                   smooth

                   cardiac

>>>Nerve tissue

Composed of cells called neurons that are specialized to generate and conduct electrical signals.

A neuron has four major parts

                   Dendrites - receive signals

                   Cell body - maintains and repairs the cell

                   Axon - conducts electrical signal to target cell

                   Synaptic terminals - transmits the signal to target cell at a region                                                            called the synapse