Epithelium is an animal tissue and is one of the four basic types of tissues in animal. These tissues cover the structures in the whole body and line cavities. They also form different types of glands. Selective absorption, secretion , transport across cells, protection and detecting sensation are its functions. A special category of this epithelial tissue is epidermis. The epithelial tissue is located above the connective tissue. These two tissues are divided by basement membrane. Epithelial tissue consists of cells which are linked by desmosomes and tight junctions. This tissue has cells that are clustered tightly. This tissue is avascular which implies that it should get nourishment through the diffusion of the substances from the connective tissue that is underlying via basement membrane.
Types of Epithelia in Digestive tract
Epithelium lines up the digestive tube. The epithelium is continuous at skin located at mouth as well as anus. The nature of epithelium changes with body parts. In some parts it works as protective layer and in some other parts it performs the role of absorption. Mucus secretions by individual glands or cells provide protection to the epithelial membranes. The process of digestion which changes the form of food to subtler substances that can be assimilated by the body is done by glands which are located inside the tract as well as its outside.
Transitional epithelium is a tissue that is stratified. In this tissue the cells will be fairly round while the organ that this tissue lines up is not stretched out. With the stretching of tissue, the cells become flat especially the ones which are on the surface. This stretching makes the organs that are lined up with this tissue(transitional epithelium) to alter shape with damaging or affecting the epithelial lining. For this reason, transitional epithelium is well-suited to line urinary tract as well as the bladder.
Endocrine glands do not have duct system while in exocrine glands, ducts release the products. In endocrine glands, secretions move into vascular system and are directed into the basal side while in exocrine glands, the secretions move from the ducts to the environment outside. In these glands, the secretions will be released to the surface of the apical cell.
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