Unit 3 Lecture Study Guide

1. List the 4 primary tissue types and give the general characteristics and functions of each one.

I. EPITHELIUM

Functions (jobs):

1) It protects us from the outside world – skin.

2) Absorbs – stomach and intestinal lining (gut) 3) Filters – the kidney 4) Secretes – forms glands

II. CONNECTIVE TISSUE
Functions (jobs):
1) Wraps around and cushions and protects organs
2) Stores nutrients
3) Internal support for organs
4) As tendon and ligaments protects joints and attached muscles to bone and each

III. NERVOUS TISSUE
Functions (jobs):
1) Conducts impulses to and from body organs via neurons

IV. MUSCLE TISSUE
Functions (jobs):
1) Responsible for body movement
2) Moves blood, food, waste through body’s organs
Responsible for mechanical digestion

How are epithelial tissues classified?

Classified by cell shape and by the arrangement of layers in the cell.

2. How does the type of epithelial tissue relate to its function? Give at least 1 example of where you would find each type of epithelial tissue.

Squamous epithelium has two types, simple and stratified. Simple squamous epithelium consists of one layer of thin, flat epithelial cells resting on a basement membrane formed of connective tissue. It is found in such places as the alveoli of the lung and lining blood vessels. Squamous epithelial cells are flat, tightly adherent to each other, thin, and have a smooth surface. Their minute thickness serves them well in the lung alveoli. The alveoli are the site of gas exchange between the air in the lungs and the gases in the blood, which occurs by diffusion. The rate of diffusion is inversely dependent on the thickness of the surface through which diffusion occurs; the thicker the layers, the slower the diffusion. Gas exchange requires quick diffusion, therefore thin squamous epithelial cells are excellent for the job. Blood flow in blood vessels requires the lining surface of the vessels to be smooth, to reduce friction and aid blood flow. the smooth surface of squamous epithelial cells serves them well for this job as well. Other examples are numerous. Stratified squamous cells are multi-layered, and can have a layer of keratin on its outer surface or it may not. The underlying layers of stratified squamous epithelium are formed of cubical or columnar cells but the upper layer is formed of squamous cells. Keratinized stratified squamous epithelium is present in skin, where the keratin acts as a protective, water-proof layer. Non-keratinized stratified squamous epithelium is present in the mouth and rectum, among other places. Keratin is not required in such places as the presence of mucus keeps the cells lubricated.

3. Differentiate between exocrine and endocrine glands. Give an example of each.

ENDOCRINE GLANDS secrete their products to the bloodstream directly. The Endocrine Glands control the homeostasis and metabolism of the body, and they are the chief checkpoints of equilibrium of chemical substances in the bloodstream.

Examples: Pituitary Gland, Pineal Gland, Thyroid Gland, Adrenal Gland, Testes, Ovary

EXOCRINE GLANDS secrete their products through ducts. They are relatively less important than Endocrine Glands, but still maintain normal function, such as smooth passage of food or feces inward to outward, respectively.

Examples: Salivary Glands, Tear Glands, Mammary Glands, Stomach Pit, Anal Glands.

4. What is the difference between apocrine, merocrine and holocrine glands? Which is the most common?

Merocrine secretion - cells secrete their product through exocytosis and remain intact after secretion (digestive juices) Apocrine secretion - cells secrete their product by destroying their apex membrane so that the product flows out of the cell into the excretion duct; after