Epithelial Tissue - Anatomy + Physiology I

Epithelial tissue

Sheets of closely packed cells; cover surfaces, line cavities, form glands; avascular but nourished by underlying connective tissue

Functions of epithelium

Protects tissues, secretes and excretes substances, absorbs nutrients, filters, senses stimuli

Basement membrane

Layer anchoring epithelium to connective tissue; made of collagen and glycoproteins

Apical surface

Cell surface facing away from basement membrane

Basal surface

Cell surface facing the basement membrane

Simple epithelium

One cell layer; all cells touch basement membrane

Stratified epithelium

Two or more layers; only deepest cells contact basement membrane

Simple squamous epithelium

Thin, flat cells; rapid diffusion and transport; secretes serous fluid; found in alveoli, glomeruli, endothelium, serosa

Simple cuboidal epithelium

Cube-shaped cells; absorption, secretion, mucus production, movement; found in liver, thyroid, glands, bronchioles, kidney tubules

Simple columnar epithelium

Tall, narrow cells; may have microvilli, cilia, goblet cells; absorption, secretion, mucus; found in GI tract, uterus, kidney, uterine tubes

Pseudostratified columnar epithelium

Appears multilayered but all cells touch basement membrane; has cilia and goblet cells; secretes and propels mucus; found in respiratory tract, male urethra

Keratinized stratified squamous epithelium

Multiple layers; surface cells dead and scaly; protects against abrasion, pathogens, water loss; found in epidermis, especially palms and soles

Nonkeratinized stratified squamous epithelium

Multiple layers; surface cells alive; resist abrasion and pathogens; found in tongue, oral mucosa, esophagus, vagina

Stratified cuboidal epithelium

Two or more layers; surface cells cuboidal; secretes sweat, produces sperm and ovarian hormones; found in sweat gland ducts, ovarian follicles, seminiferous tubules

Stratified columnar epithelium

Rare; surface cells columnar; found in parts of male urethra and some gland ducts

Urothelium (transitional epithelium)

Multilayered; surface cells change shape from round to flat when stretched; allows filling of urinary tract; found in ureter and bladder