Flashcards in Ex.1-Chapter 4, Tissue: The Living Fabric Deck (35):
an ensemble of similar cells that have a common function
study of the microscopic anatomy of tissue
What are the four main tissue types in the body?
Epithelia, Connective, Muscle, Nervous
What are the functions of the epithelia?
Covers surfaces, lines body cavities, protection (skin), absorption (small intestines), secretion (glands), filtration (kidneys) and sensory reception (nerve endings).
What are the epithelia characteristics?
polarity, specialized contacts, supported by connective tissue, being avascular but innervated, and having the ability to regenerate.
What is does "polarity" of the epithelia mean?
All epithelia have an apical surface and a basal surface. The two surfaces differ in both structure and function. For this reason, we say that epithelia exhibit apical-basal polarity.
What is the apical surface?
an upper free surface exposed to the body exterior or the exterior cavity of an internal organ- faces the surface
What is the basal surface?
a lower attached- lining the organ or inner cavity
What is the "specialized contacts" of the epithelia?
proteins, which help form continuous sheets, which are call "tight junctions" and "desmosomes". These bind adjacent cells together at many points
What does the tight junctions do?
help keep proteins in the apical region of the plasma membrane from diffusing into the basal region.
What is epithelia supported by?
What does the basement membrane do?
reinforces the epithelial sheet, and helps adhere the epithelia to the connective tissue
Although epithelium is avascular (no blood vessels) it is what?
innervated (supplied by nerve fibers). Epithelia cells are nourished by substances diffusing from blood vessels in the underlying connective tissue
If epithelium cells rub off, are damaged, or lateral contacts are destroyed what can the epithelium do?
Regenerate, by rapidly reproducing themselves (mitosis)
How is epithelium named?
First name indicates the number of layers, and the second name describes the shape of its cells.
Consist of a single layer?
Composed of two of more layers?
Where is simple epithelia typically found?
where absorption, secretion, and filtration occur and a thin epithelial barrier is desired.
Where is stratified epithelia typically found?
high abrasion areas where protection is important, such as the skin surface and the lining of the mouth
What are the three common shapes of epithelial cells?
Squamous (flat), cuboidal (boxlike), and columnar (tall and column shaped)
Describe simple squamous epithelia
single layer, flattened, cytoplasm is sparse, resemble fried eggs
What is the function of simple squamous epithelia?
Filtration and diffusion
Where is some places in the body that simple squamous epithelia can be found?
kidneys and lungs
What are the two simple squamous epithelia in the body that have special names that reflect their location?
Endothelium and Mesothelium
What does endothelium do?
provides a slick, friction reducing lining in lymphatic vessels and in hollow organs of the cardiovascular system-blood vessels and the heart.
What does mesothelium do?
is the epithelium found in serous membranes, the membranes lining the ventral cavity and covering its organs.
Describe simple cuboidal epithelia?
single layer of cells as tall as they are wide, spherical nuclei.
What is the function of simple cuboidal epithelia?
secretion and absorption
Where can you find simple cuboidal epithelia in the body?
walls of ducts of glands and may kidney tubules
Describe simple columnar epithelia?
single layer of tall, closely packed cells, aligned like soldiers in a row
What is the function of simple columnar epithelia?
absorption and secretion
Where can you find simple columnar epithelia?
lining the digestive track from the stomach to the rectum
Describe pseudo-stratified columnar epithelia?
vary in height, all of its cells rest on the basement membrane, but only the tallest reach the free surface. Because the cell nuclei lie at different levels above the basement membrane, the tissue gives the false (pseudo) impression that several layers are present
What is the function of pseudo-stratified columnar?
secretes and absorbs, can be ciliated or non-ciliated