Histology of urinary passage
Epithelium
Site
In empty bladder
In distended
bladder
Urinary bladder
Transitional epithelium
1. In major & minor calyces: 2-3 cells thick
2. In ureter: 4-5 layers.
3. In urinary bladder: 6, 8 or more layers
1. 4-8 layers of cells:
a. Superficial cells
 Cubical, may be binucleated
 Convex free border & concave base.
 Receives the convexity of underlying flask-shaped cells.
b. Intermediate layers:
 Polyhedral cells,
 Abundant mucous I.C. subst
c. Basal cells:
 Columnar with no apparent basement membrane
1. Top cells become flattened.
2. Intermediate cells slide on each other.
3. The epithelium is reduced to 2-3 layers; a top flat layer & a basal cubical layer.
Ureter
1. Characterized by a narrow stellate-shaped lumen due to longitudinal mucosal folds
2. Wall consist of 3 layers:
a. Mucosa:
i.
Transitional epithelium & lamina propria
b. Muscle layer:
i.
Sharply delimited mooth muscle layers
ii.
Inner longitudinal & outer circular
iii.
In lower 1/3 – third outer longitudinal layer
c. Adventitia:
i.
Fibro-elastic tissue with BV & NV
ii.
Merges with surrounding tissue
Male urethra
The male urethra is long (20cm) twisted tube, that conducts urine from the urinary bladder (& seminal fluid from male
genitalia) to outside of the body
Glands open in the 1. Prostatic gland.
course of the
2. Glands of Littré.
urethra
3. Bulbo-urethral gland (Cowper’s Gland)
Parts
1. Prostatic
a. 3-4 cm long.
b. Arise from neck of the bladder and passes through the prostate.
c. V- shaped in cross section.
d. Both ejaculatory duct & prostatic duct open into it.
e. Epithelium: It is lined with:
i.
Transitional epithelium.
ii.
Pseudostratified columnar  distally.
f. Surrounded by:
i.
I.L. layer of smooth muscle fibers.
ii.
O.C. layer of smooth muscle fibers
iii.
Condenses to form the Internal Sphincter of U.B.
2. Membranous
a. Very short (1.5 cm).
b. Lies within urogenital diaphragm.
c. Extends from apex of prostate to root of penis.
d. Lined with stratified columnar epithelium.
e. Surrounded by striated muscle which forms the external Sphincter of UB
f. Cowper’s glands are present outside its wall & open in penile urethra.
3. Penile
a. The longest part (15 cm).
b. Passes through corpus spongiosum.
c. Its proximal part is dilated - the bulb of urethra.
d. Its distal part is dilated to form - “fossa navicularis”.
e. Lined with:
i.
Proximally: Stratif. Colum. Epith.
ii.
Distally: Stratif. Squam. Epith.
f. The lamina propria of the urethra contains:
i.
Highly vascular C.T. rich in elastic fibers.
ii.
I.L. & O.C. of smooth ms.fibs
iii.
Mucus secreting glands of Littrè (Intramucosal & extramucosal)
Female urethra
Length: 2-6 cm
Opening: in vestibule anterior to vaginal opening
Epithelium
Lined with transitional epithelium at neck of bladder, changes into pesudostriatified columnar, then
striatified squamous at its termination
Corium
CT containing:
1. I.L & O.C smooth muscle fibre
2. Small mucus secreting glands which open into the lumen
3. At external orifice, striated muscle form external sphincter
The connective tissue of the corium blends with that of vagina
Prostate
1. Type: Compound tubulo-alveolar gland.
2. Site: Surrounds the V-shaped first part of male urethra.
3. Stroma
Capsule:
Trabeculae:
Reticular fiber:
a. Thick fibroelastic tissue
a. Thick CT septa
a. A network of reticular fibers
b. Rich in SMF & BV
b. Extend from capsule to
b. Support the parenchyma
urethra
c. Divide the gland into lobules
d. Rich in SMF which condense
around urethra to form
internal urethral sphincter
4. Parenchyma
a. The ejaculatory duct divides the gland into 3 lobes.
b. Each lobe is subdivided into lobules.
c. Each lobule contains 3 types of acini which are: Mucosal acini, Submucosal acini & Main acini
d. The acini are irregular in outline & variable in size.
e. Lining epithelium of prostatic acini: pseudostratified columnar, columnar or cubical depending on gland activity.
Mucosal acini:
Submucosal acini:
Main acini:
 The smallest type
 Lie outer to mucosal acini
 Lie at the periphery of the
lobule.
 Lie in periurethral tissue
 Larger in size than mucosal
acini.

The largest acini.
 Open by small ducts in
prostatic urethra.
 Open into the urethral sinus
 Their ducts open into the
by 2 separate ducts.
posterior margin of urethra.
 In old age, they enlarge 
urinary obstruction.
(prostatic adenoma BPH)