Anatomy and Physiology: Tissues
Body tissues are groups of cells that are similar in structure and function.
Epithelial tissues are the tissues that lines or covers the body. It is the lining, covering and the glandular tissue of the body. Primarily, epithelial tissues functions include:
- Forms continuous sheet by fitting together closely with the exception of glandular tissues.
- Have one free surface or edge in the membranes called an apical surface.
- Has a basement structure where the lower surface of the epithelium rests.
- Have no blood supply.
- Depends on diffusion from the capillaries in the underlying connective tissue for food and oxygen.
- Regenerates themselves if well nourish.
The epithelium is classified into simple and stratified epithelium. The classification is based on the cell arrangements.
- Simple Epithelium
This type of epithelium is very thin. It functions for absorption, secretion and filtration. Protection is not one of their specialties.
- Simple squamous epithelium – forms the membranes where filtration or exchange of substances by rapid diffusion takes place.
- Simple cuboidal epithelium – this is one layer of cuboidal cells which lies on the basement of the membrane. It forms the walls of the tubules in the kidney and the one that covers the surface of the ovaries in females.
- Simple columnar epithelium – this is one layer of columnar cells (tall cells) that fits closely together. It covers the entire area of the digestive tract from the stomach to the anus. In this type of epithelium, goblet cells are found. Goblet cells are the one which produce lubricating mucus.
- Pseudistratified Columnar Epithelium – this type of epithelium gives the impression that it is stratified. The main function of this epithelium is on absorption and secretion.
- Stratified Epithelium
This epithelium consists of two or more layer of cells. These epithelia mainly functions for protection. It is more durable than the simple epithelia making it possible to carry out its function of protection.
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