Different Types of Covering and Lining Epithelium:
Shapes of cells
1- Squamous
a) Thin cells, arranged like floor tiles
b) Allows for rapid passage of substances
2- Cuboidal
a) As tall as they are wide, shaped like cubes or hexagons
b) May have microvilli
c) Function in secretion or absorption
3- Columnar
a) Much taller than they are wide, like columns
b) May have cilia or microvilli
c) Specialized function for secretion and absorption
4- Transitional
a) Cells change shape, transition for squamous to cuboidal and back
b) Organs such as urinary bladder stretch to larger size and collapse to a smaller size
The function of glandular epithelium is secretion
A gland may be a single cell (e.g. goblet cells which secrete mucus) or a group of cells that secrete substance into tubes (‘ducts’)
Glands classified as
Exocrine: secrete into ducts that empty onto surface of a covering and lining epithelium (e.g. skin or lumen of hollow organ such as stomach)
Endocrine: No ducts. Secretions are called hormones; enter interstitial fluid and then diffuse into blood stream