This note briefly describes about the
gross anatomy of male and female urethra
along with its blood supply, lymphatic drainage and innervation.
General Consideration
Urethra is the terminal part of the urinary
tract and conducts urine from bladder to exterior.
Male urethra and female urethra are considered
separately below.
MALE URETHRA
•
Muscular tube
•
18-20 cm long
•
Extends from internal urethral
orifice of the urinary bladder to the external urethral orifice at
the tip of the glans penis
•
Divided into four parts
•
Preprostatic urethra
•
Prostatic urethra
•
Spongy urethra
Preprostatic Urethra or Intramural part of urthra
•
1-1.5 cm long
•
Extends vertically from bladder neck to
the superior aspect of prostate
•
Associated with internal urethral
sphincter
–
Prevents retrograde movement of semen to
the bladder
Prostatic urethra
•
4 cm long – widest and most dilatable
part
•
Descends through the anterior part of
the prostate
•
Forms a gentle curvature with anterior
concavity
Internal features
•
Posterior wall presents
–
Urethral crest
–
Prostatic sinus
on each side of the crest
–
Seminal colliculus
in middle part of the crest
•
Presents slitlike orifice which leads to
Prostatic Utricle
•
Ejaculatory duct open
on/within prostatic utricle
Membranous part
•
Shortest and narrowest part, 1-2 cm long
•
Lies in the perineal region
•
Begins at the apex of prostate and ends
at the bulb of the penis
•
Traverses the deep perineal pouch and
passes through the external urethral sphincter and perineal membrane
•
Associated with the external urethral
sphincter
•
Posterolaterally related with Bulbourethral
or Cowper’s gland
Spongy urethra
•
The longest part (15-16 cm and 5 mm in
diameter)
•
Passes through the bulb (Bulbar part of spongy urethra) and corpus
spongium of the penis (Penile part of spongy urethra)
•
Ends at the external urethral orifice
•
Expanded
• in the bulb of penis – intrabulbar
fossa and
•
In the glans penis – navicular fossa
•
Proximal part receives opening of ducts
of bulbourethral glands
•
Also receives openings of urethral
glands
Arteries, veins, lymph nodes and nerves
•
Proximal two parts
–
Arterial supply by Prostatic branches of
inferior vesical and middle rectal arteries
–
Veins follow the arteries and have same
name
–
Lymph drains mostly to internal iliac
lymph nodes
–
Nerves are derived from pudendal nerves
and prostatic plexus
•
Distal two parts
–
Artery: Branches of internal pudendal
artery
–
Vein: Internal pudendal veins
–
Lymph nodes: Membranous urethra drains
to internal iliac lymph nodes and most of spongy urethra drains to deep
inguinal lymph nodes
–
Nerves: are branches of pudendal nerve
–
Also derived from prostatic plexus
–
Afferent fibers passes through pelvic
splanchnic nerves
FEMALE
URETHRA
•
4 cm long and 6 mm in diameter
•
Begins at the bladder neck and passes
anteroinferiorly from the internal urethral orifice
•
Ends at external urethral orifice
in the vestibule of vagina
–
Lies anterior to the orifice of vagina
•
Lies anterior to the vagina
•
Its axis is parallel to that of vagina
•
Receives the openings of urethral
and paraurethral galnds
Arteries, veins, lymph nodes and innervation
•
Veins – follow the arteries and have
similar names
•
Lymph nodes – sacral and internal iliac
•
Innervation – pudendal nerve
REFERENCES:
Following resources are used while preparing this post (readers are strongly recommended to go through them for more details):
Gray's Anatomy for Students
K. L. Moore's Clinically Oriented Anatomy
R. Snell's Clinical Anatomy