Human A&P Types of Epithelia

Simple Squamous

• Structure - flat or oval with central nucleus.

• Location - places with little wear and tear and also in places where substances are diffused and filtered.

• Function - diffusion, filtration, secretion

• Body – alveoli (air sacs in the lungs), tiniest blood vessels (capillaries)

Simple Cuboidal

• Structure - cube-shaped with a central nucleus.

• Location - in tubules where they can reabsorb substances.

• Function - mainly absorption, active transport, secretion

  • full of mitochondria for active transport

• Body – in the kidney tubules,

Simple Columnar 

• Structure - nucleus near bottom of column shaped cells.

• Location - inside lining of digestive tract, also contain goblet cells.

• Function - secretion of mucous, absorption.

  • breaking down food into simple molecules

• Body - inside stomach, small intestines, large intestines

Pseudostratified

• Structure - all cells touch basement membrane but not all reach the free surface.

• Location - respiratory tract

• Function - specialized goblet cells release mucous that coat passageways.

• Body - respiratory tract in lungs

Stratified Squamous 

• Structure - many layers with outermost layer being flat and scale–like. Underlying layers are more cuboidal or columnar.

• Location - anywhere the outer layers can be abraded and generally wherever protection is needed.

• Function - protection against abrasion. In epidermis, the keratin also acts as a waterproofing agent to fight water loss.

• Body - throat, vaginal canal, anus canal (beginning and end of digestive tract), the outermost layer of our skin (epidermis)

  • Nonkeratinized v. keratinized

    • nonkeratinized = lacks keratin

    • keratinized = outermost layer of skin

Stratified Cuboidal - rare

• Structure - Cuboidal cells, but in layers.

• Location - wherever protection is needed.

• Function - protection and secretion.

  • secretes sweat; produces sperm and hormones

  • sweat gland ducts; ovarian follicles and seminiferous

• Body - some sweat glands, endocrine glands, ovarian follicles, seminiferous tubules

Stratified Columnar - rare

• Structure - layers of columns - only outer layer is columnar.

• Location- male urethra.

• Function - protection and secretions.

• Body - male urethra

Transitional

• Structure - looks like stacks of cuboidal cells when in relaxed state, layers closest to apical surface can distend as bladder fills.

  • look like teardrops 

• Location - bladder, urethra, ureters

• Function - allows stretching of urinary bladder as it fills.

• Body - ureter and bladder