Histology Of Ureter, Urinary Bladder And Urethra By Dr. Roomi 265k3b

Histology of Ureter, Urinary bladder and urethra By Dr. Mudassar Ali Roomi (MBBS, M.Phil)

Ureter • The wall of ureter is composed of following three coats: 1. Mucosa 2. Muscularis 3. Adventitia Note: no submucosa.

1. Mucosa • Mucosa is thrown into longitudinal folds, due to which the lumen appears star-shaped in t.s. • Transitional epithelium • Lamina propria is fibroelastic C.T. • No glands in lamina propria

2. Muscularis • It is thick and consists of two layers of smooth muscle. • Inner longitudinal and outer circular smooth muscle • Near the lower end of ureter, a third longitudinal smooth muscle layer is added outer to the circular layer. • Ureteric muscle undergoes regular peristaltic movements to help the flow of urine towards the bladder.

3. Adventitia • It is the outermost layer • It consists of loose C.T. containing blood vessels.

Ureter

Ureter

URETERIDENTIFICATION POINTS

HOW TO DRAW IT!

URINARY BLADDER • Like ureter the wall of urinary bladder is also composed of following three coats: 1. Mucosa 2. Muscularis 3. Adventitia Note: no submucosa.

1. Mucosa • Epithelium is of transitional variety • In the empty bladder, the epithelium is thicker and consists of 6-8 layers of cells • In the distended bladder, the epithelium consists of only 2-3 layers of cells • Lamina propria is fibroelastic C.T. • A few small mucus secreting glands are found in the lamina propria near the ureteric and internal urethral orifices

2. Muscularis • It comprises three layers of smooth muscle collectively called the detrusor muscle, which contract to empty the bladder : an inner longitudinal, a middle circular and an outer longitudinal layer. • Middle circular layer is well developed around the internal urethra orifice to form a sphincter.

3. Adventitia/serosa • Adventitia consists of fibroelastic C.T. • The superior surface of bladder is covered by peritonium (Serosa).

Urinary bladder

TRANSITIONAL EPITHELIUM •

The urothelium is composed of the following three layers: 1. a single layer of small basal cells resting on basement membrane. 2. an intermediate region containing from one to several layers of polygonal cells 3. a superficial layer of very large bulbous cells called umbrella cells which are occasionally bi- or multinucleated and are highly differentiated to protect underlying cells against the cytotoxic effects of hypertonic urine.

TRANSITIONAL EPITHELIUM (cont...) • •

•

•

Umbrella cells are especially well developed in the bladder where with urine is the greatest. In umbrella cells, apical membrane plaques are present which are impermeable and protect cytoplasm and underlying cells from hyperosmotic effects of urine. When the bladder is emptied, not only does the mucosa fold extensively, but individual umbrella cells decrease their apical surface area by folding the membrane and internalizing the folded plaques in discoidal vesicles. As the bladder fills again the discoidal vesicles re the apical membrane, increasing its surface area as the cell shape changes from round to flat. The urothelium becomes thinner, apparently the result of the intermediate cells being pushed and pulled laterally to accommodate the increased volume of urine.

HOW TO DRAW IT!

URINARY BLADDERIDENTIFICATION POINTS

MALE URETHRA •

The urethra is a tube that carries the urine from the bladder to the exterior. • In men, the two ejaculatory ducts the urethra at the prostate gland . • The male urethra is longer and consists of three segments: 1. The prostatic urethra, 3–4 cm long, extends through the prostate gland and is lined by urothelium. CLINICAL POINT: BPH in old age compresses on the prostatic urethra which creates difficulty in urination. 1. The membranous urethra, a short segment, es through an external sphincter of striated muscle and is lined by stratified columnar and pseudostratified epithelium. 2. The spongy urethra, 15 cm in length, is enclosed within erectile tissue of the penis and is lined by stratified columnar and pseudostratified columnar epithelium, with stratified squamous distally.

FEMALE URETHRA • In women, the urethra is exclusively a urinary organ. • The female urethra is a tube 4 to 5 cm long, lined initially with transitional epithelium, then by stratified squamous epithelium and some areas of pseudostratified columnar epithelium. • Increased chances of UTI in females due to short urethra!