Epithelial Tissue
It lines body surfaces (such as skin) and internal cavities (such as organs). Its main functions include protection (Skin), absorption (Intestine, absorbs nutrients), secretion (glands), sensitivity (Sensory epithelia, such as in the retina) and exchange of substances (Lung alveoli).
Features:
Juxtaposed cells: Little space between them.
Avascular: No blood vessels; nourished by connective tissue.
High renewal: Regenerates quickly.
Polarity: It has an apical side (facing surfaces) and a basal side (connected to the basement membrane).
Classification Regarding layers:
Simple: One layer of cells.
Stratified: Multiple layers.
Pseudostratified: Appears to have several layers, but all of them touch the basement membrane.
Regarding cell format:
Pavement: Flat cells.
Cubic: Cubic cells.
Columnar: Elongated cells.
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