The four main functions of epithelial tissue are to provide physical protection, control permeablility, provide sensations, and to produce specailized secretions. There are eight types of epithelium.
Simple squamous epithelium - found lining heart and blood vesses, lungs etc. the function is to reduce friction and to absorb and secrete.
Stratified squamous epithelium - found on the surface of the skin and all openings to the body. The function is physical protection against abrasions and pathogens.
Simple cuboidal epithelium - found in glands and ducts. The function is secretion and absorption.
Stratified cuboidal epithelium - found lining some ducts it is rare. Its functions are to protect, secrete, and absorb.
Transitional epithelium - found in the bladder and ureters. The function is to allow expansion and relaxation after stretching.
Simple columnar epithelium - found in the lining of stomach, intestine, and gallbaldder. The functions are protection, secretion and absorption.
Pseudostratified ciliated columnar epithelium - found in the lining of the nasal cavity, trachea, and bronchi. The function is protection and secretion.
Stratified columnar epithelium- found in the pharynx, epiglottis, anus, and urethra. Its function is protection.
Tissues in bodies animals refer to components formed out from same type of cells. The human body has four type of tissues - connective, epithelial, muscles and nervous.
Epithelial tissues form covering of the entire body, which we call the skin. These also form lining of body openings such as mouth and throat. Epithelial tissues also line all body cavities such as alimentary tract, urinary tract, and blood vessels.
The epithelial tissues performed various functions such as protection, secretion, selective absorption, transcellular transportation and detection of sensation.
Epithelium tissues are classified in three classes according to functions performed by them.
- Epithelial surface membrane that perform protective function. These are like sheets that cover the body and its parts. They protect internal fluids from flowing out, and don't allow external substances to get in.
- Glandular epithelial tissues contain cell that produce and release secretory products including hormones and perspiration.
- Sensory epithelial tissues contain receptor cells that transduce specific sensory stimuli into neural activity - for example, receptor cells of taste buds and olfactory cells.