- Epithelial Tissues are important for the trichologist to understand as they include the skin epidermis.
- General Features:
- Closely packed cells
- Avascular---without blood vessels
- nutrients and waste must move by diffusion
- Good nerve supply
- Rapid cell division (high mitotic rate)
Functions of Epithelium
- Functions of epithelial tissue:
- protection, filtration, lubrication, secretion, digestion, absorption, transportation, excretion, sensory reception, and reproduction.
- covering and lining epithelium
- epidermis of skin
- lining of blood vessels and ducts
- lining respiratory, reproductive, urinary & GI tract
- glandular epithelium
- secreting portion of glands
- thyroid, adrenal, and sweat glands
Classification of Epithelium
Epithelial tissue can be classified in two ways:
- Classified by arrangement of cells into layers
- simple = one cell layer thick
- stratified = two or more cell layers thick
- pseudostratified = cells contact basement membrane but all cells don’t reach apical surface
- nuclei are located at multiple levels so it looks multilayered
- Classified by shape of surface cells
- squamous =flat
- cuboidal = cube-shaped
- columnar = tall column
- transitional = shape varies with tissue stretching
Diagram of Epithelium Tissue
