Epithelial Tissue Histology

Squamous

flat/scale-like

Cuboidal

cube shaped. as wide as it is tall

Columnar

column-like. taller than it is wide

Transitional

a type of epithelial tissue that can change shape, typically found in the bladder, allowing it to stretch and accommodate fluctuating volumes of liquid.

Apical surface

the surface of an epithelial cell facing the lumen or external environment

Basal surface

The surface of an epithelial cell facing the basement membrane.

Basement membrane

Formed from the epithelial and underlying connective tissue layers. It aids in attachment of the epithelial tissue and as a selective molecular barrier to underlying connective tissue.

Simple squamous Epithelium

Structure

Single layer of thin, flat cells resembling irregular floor tiles; the single nucleus of each cell bulges at its center

Function

Thinnest possible barrier to allow for rapid diffusion and filtration; secretion in serous membranes

Location

Air sacs in lungs (alveoli); lining of lumen of blood vessels and lymph vessels (endothelium); serous membranes of body

Simple cuboidal Epithelium

Structure

Single layer of cells about as tall as they are wide; spherical and centrally located nucleus

Function

Absorption and secretion; forms secretory tissue of most glands and small ducts

Location

Kidney tubules, thyroid gland follicles; surface of ovary; secretory regions and ducts of most glands

Simple columnar Epithelium

Structure

Single layer of cells taller than they are wide; oval-shaped nucleus oriented lengthwise in basal region of cell; apical regions of cell may have microvilli; may contain goblet cells that secrete mucin

Function

Absorption and secretion; secretion of mucin

Location

Inner lining of most digestive tract (stomach, small intestine, and large intestine)

Ciliated Simple Columnar Epithelium

Structure

Single layer of ciliated cells taller than they are wide; oval-shaped nucleus oriented lengthwise in basal region of cell; may contain goblet cells

Function

Secretion of mucin and movement of mucus along apical surface of epithelium by cilia; oocyte movement through uterine tube

Location

Lining of the larger bronchioles (air passageways) of the lung and the uterine tubes

Keratinized Stratified Squamous Epithelium

Structure

Multiple cell layers; basal cells are cuboidal or polyhedral, whereas apical cells are squamous; apical cells are dead and filled with the protein keratin

Function

Protection of underlying tissue from abrasion

Location

Epidermis of skin

Nonkeratinized Stratified Squamous Epithelium

Structure

Multiple cell layers; basal cells are cuboidal or polyhedral, whereas apical (superficial) cells are squamous; cells lack keratin; superficial cells are alive and kept moist

Function

Protection of underlying tissue from abrasion

Location

Lining of oral cavity, part of pharynx, part of larynx, esophagus, lining of vagina, and anus

Stratified Cuboidal Epithelium

Structure

Two or more layers of cells; cells at the apical surface are about as tall as they are wide

Function

Protection and secretion

Location

Ducts of most exocrine glands and ovarian follicles

Stratified Columnar Epithelium

Structure

Two or more layers of cells; cells at the apical surface are taller than they are wide

Function

Protection and secretion

Location

Large ducts of salivary glands, conjunctiva covering the eye, and membranous part of male urethra

Transitional

Structure

Epithelial appearance varies, depending upon whether tissue is relaxed or distended (stretched); relaxed epithelium (top) has cuboidal or polyhedral cells and the apical cells are large and rounded, whereas distended epithelium (bottom) has flattened cells at the apical surface; some cells are binucleated

Function

Accomodates urine volume changes (by distending or relaxing) in the urinary bladder, ureters, and part of urethra

Location

Lining of urinary bladder, ureters, and part of urethra