Epithelial tissues are widespread throughout the body.Thay form the coverin of all the body surfaces,line body cavities and hollow organs,and are the major tissue in glands.They perform a variety of functions that include : protection,secretion,absorption,excretion,filteration,diffusion,and sensory reception.
The cells in epithelial tissue are tightly packed together with very little intercellular matrix.Because the tissue form coverings and linings,the cells have one free surface that is not in contact with other cells.
opposite the free surface,the cells are attached to underlying connective tissue by a non-cellular basement membrane.This membrane is a mixture of carbohydrates and proteins secreted by the epithelial and connective tissue cell.
Epithelial cells may be squamaous,cuboidal,or columnar in shape and may be arranged in single or multiple layers.
Simple cuboidal epithelium is found in glandular tissue and in the kidney tubules. Simple columnar epithelium lines the stomach and intestines. Pseudostratified columnar epithelium lines portions of the respiratory tract and some of the tubesof the male reproductive tract.
Transitional epithelium can be distended or stretched. Glandular epithelium is specialized to produce and secrete substances.
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