Covering Epithelium
Covering epithelia form cellular sheets that line the cavities of organs and cover the body surface. All substances that enter or leave tissues and organs must cross an epithelium.
Locations: Covering epithelium is found on the external and internal surfaces of the body. It forms the outer layer of the skin (epidermis) and lines various cavities and tubes within the body, such as the digestive and respiratory tracts.
Functions:
Protection: Covering epithelium acts as a protective barrier against physical damage, pathogens, and dehydration.
Selective Permeability: Depending on the location, covering epithelium can regulate the passage of substances into and out of tissues.
Sensation: Some covering epithelium, especially in sensory organs, detects stimuli, such as touch, pressure, and temperature.
Secretion: Certain types of covering epithelium can secrete substances, such as mucus in the respiratory tract or enzymes in the digestive tract.
Stratified Epithelia
Stratified epithelia are classified according to the cell shape of the superficial layer(s): squamous, cuboidal, or columnar.