Stratified Epithelium Overview

Study Notes

It is composed of multiple layers of epithelial cells (2 or more).
Only the basal layer is in contact with the basal lamina.
The basal layer undergoes mitotic division, producing cells in the upper layers.
It is named according to the shape of the most superficial cells.

A thick type of stratified epithelium with multiple cell layers.
Cells rest on a clear wavy basement membrane.
The basal layer (Malpighian layer) is composed of columnar cells and is well nourished.
The intermediate layers (spongy layer) are made up of polygonal cells.
The superficial layers are flat squamous cells, either nucleated or not.
The surface can be covered with a keratinized or non-keratinized layer.
Its main function is protection against physical and microbial damage.
It is present in the outermost layer of the skin and the inner lining of the mouth, esophagus, and vagina.

The surface cells are very flat and are no longer alive. They lack a nucleus and organelles and are filled with keratin, making the skin waterproof.
It is present in: skin, epidermis of the palm of the hand and sole of the foot, external ear, external nose, outer surface of the lip.

The surface cells are living cells, with no keratin.
Cells produce mucus to keep the surface moist, and helps balance the surrounding pH.
It is present in: lining of the buccal cavity, pharynx, esophagus, tongue, gum, cornea, exposed parts of the conjunctiva, vagina, terminal parts of male and female urethrae, inner surface of the lip.

A rare type of epithelial tissue, composed of column-shaped cells in multiple layers.
It is present in the conjunctiva of the eye, parts of the pharynx, anus, uterus, male urethra and vas deferens.
It protects the conjunctiva of the eyes and other delicate structures.
It has secretory functions.

Consists of multiple layers of epithelial cells.
Dome-shaped superficial cells with specialized protective membranes, capable of contracting and expanding for adaptation.
Basal cubical to columnar cells attached to the basal lamina.
Its function is to stretch to accommodate liquid volume and return to normal state without damage.
It lines the organs of the urinary system (urothelium).

Glands are collections of epithelial cells modified to produce different types of secretion.

Multiprotein complexes that provide contact or adhesion between neighboring cells or a cell and the extracellular matrix.
Types: tight junctions, adherens junctions, desmosomes, gap junctions, hemidesmosomes.

Impermeable seals that encircle cells, binding them together into leak-proof sheets.
Plasma membranes of adjacent cells fuse together tightly to limit leakage of substances.
They play vital roles in holding cells together, forming protective and functional barriers.
Major proteins: claudins and occludins.

Bundles of protein complexes at cell-cell junctions, strongly binding and adhering cells.
Usually more basal than tight junctions.
Cytoplasmic face is linked to the actin cytoskeleton.
Allow cells within a tissue to respond to forces, biochemical signals, and structural changes in their microenvironment.

Intercellular junctions that provide strong adhesion between cells.
Form links between cells, connecting intermediate filaments of the cell cytoskeletons of adjacent cells.
Also known as macula adherens.
Responsible for maintaining the mechanical integrity of tissues.

Aggregates of intercellular protein channels that permit direct cell-cell transfer of ions and small molecules.
Expressed in all tissues and cells, particularly in cell types involved in direct electrical communication, such as neurons and cardiac muscle.