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Epithelial Tissue
Term | Definition |
---|---|
two types | Covering & Lining epithelium and glandular |
Covering and lining epithelium | found on free surfaces of the body such as the outer layer of skin; dips into open cavities of the digestive and respiratory tracts; lines blood vessels and the heart; covers walls of body cavities and the organs |
Glandular | makes up the glands of the body |
functions of epithelial tissue | protection, absorption, filtration, and secretion |
6 special characteristics | cellularity, specialized contacts, polarity, avascularity, basement membrane, and regneration |
Cellularity | epithelium composed almost entirely of cells; very little extracellular matrix |
Specialized contacts | adjacent cells are bound together by lateral contacts |
Polarity | has one free surface exposed to the body exterior or cavity of organ |
Avascularity | no blood vessels within; receives nourishment from underlying connective tissue |
basement membrane | epithelium rest on a basal lamina (non-living, adhesive material) which separates it from connective tissue |
Regeneration | as long as there is adequate nutrition lost cells can be replaced |
Classification of epithelia (2 criteria) | Shape of cell and number of cell layers present |
Classification on shape | Squamous, Cuboidal, columnar |
squamous | flattened, scale-like cells |
cuboidal | cells that are as tall as they are wide |
columnar | cells that are tall and column-shaped |
Classification on number of layers | simple and stratified |
Simple | consists of single layer |
stratified | consists of multiple layers of cells stacked on top of each other |
simple squamous | single layer of flattened cells; functions in diffusion and filtration (lungs, kidneys, and blood vessels) |
simple cuboidal | single layer of cube like cells; functions in secretion and absorption (kidney, small glands, and ovaries) |
simple columnar | single layer of tall cells; functions in secretion and absorption (digestive tract, bronchi, uterine tubes) |