epithelium

Question 1

simple squamous epithelium

Answer 1

Structure:
Single layer of flat/hexagonal cells
Nuclei appear very flat

Function:
Mainly diffusion, filtration,
Some secretion, absorption
Little barrier/protection against friction

Location:
Lining of blood vessels and the heart
Alveoli
Lining of serous membranes of the body cavities
Lining of some kidney tubules, etc

Question 2

simple cuboidal epithelium

Answer 2

Structure:
Single layer of cube-shaped cells;
Some cells have microvilli (kidney tubules)

Function:
Good for diffusion, secretion and absorption;

Location:
Kidney tubules,
Glands and their ducts,
Lining of terminal bronchioles of the lungs,
Surfaces of the ovaries

Question 3

simple columnar epithelium

Answer 3

Structure: Single layer of tall, narrow cells;
Some cells have cilia (bronchioles of lungs, auditory tubes, uterine tubes, and uterus) or microvilli (intestines)

Function: Movement of substances, absorption and Secretion
Offer more protection than flatter cells

Location: Glands and some ducts, bronchioles of the lungs, auditory tubes, uterus, uterine tubes, stomach, intestines, gallbladder, bile ducts, ventricles of the brain

Question 4

stratified squamous epithelium

Answer 4

Structure: Multiple layers of cells that are cube-shaped in the basal layer and progressively flattened toward the surface

Can be nonkeratinized (moist) or keratinized;

Function: Protection against abrasion, a barrier against infection, reduction of water loss from the body

Location:
Keratinized— skin
Nonkeratinized— mouth, throat, larynx, esophagus, anus, vagina, inferior urethra, cornea

Question 5

pseudostratified epithelium

Answer 5

Structure: Technically single
layer - some cells reach the free surface others do not;
Nuclei at different levels so appears stratified
Almost always ciliated and associated with goblet cells (secrete mucus)

Function: Synthesize and secrete mucus & move mucus (or fluid) that contains foreign particles over the surface

Location: Lining of the nasal cavity, nasal sinuses, auditory tubes, pharynx, trachea, bronchi of the lungs

Question 6

transitional epithelium

Answer 6

A unique type of stratified epithelium

Structure: Cuboidal/columnar when not stretched
Squamous/flattenend when stretched
Number of layers also decreases on stretch from 5/6 – 2/3 – cell shift on top of one another

Function: Accommodate fluctuations in the volume of
fluid in organs or tubes (tolerates stretching & recoil without damage)
Protects against the caustic effects of urine

Location: Lining of the urinary bladder, ureters, superior urethra, pelvis of the kidney (i.e. structures where considerable expansion occurs)