Male Internal Genital Organs

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Female external
genital organs | Main Anatomy Index | Male external genital organs
Last updated 30 March 2006
Male Internal Genital Organs
The Ductus Deferens
- This is a thick-walled muscular tube (also known as vas
deferens) that is the continuation of the duct of the epididymis.
- The ductus deferens (L. defero, to carry down) begins in the tail
of the epididymis and ends by joining the duct of the seminal vesicle to form the ejaculatory
duct.
- During its course no other structure intervenes between
it and the peritoneum.
- The ductus deferens crosses the ureter
near the posterolateral angle of the bladder.
- At first it lies superior to the seminal vesicle and then it descends
medial to the ureter and this vesicle.
- The ductus deferens enlarges to form the ampulla of the ductus deferens as it passes posterior
to the bladder.
Arterial
Supply and Venous Drainage of the Ductus Deferens
- The artery of the ductus deferens is closely
applied to its surface.
- It is tiny and arises from the superior (or inferior) vesical artery.
- It terminates by anastomosing
with the testicular artery, posterior
to the testis.
- The veins accompany the arteries.
Innervation of the
Ductus Deferens
- Innervation is derived from the inferior hypogastric plexus.
- The ductus deferens is richly innervated by autonomic nerve fibres, thereby facilitating its rapid
contraction for expulsion of sperm cells during ejaculation.
Lymphatic
Drainage of the Ductus Deferens
- Lymph vessels from the ductus deferens end in the external iliac
lymph nodes.
The Seminal Vesicles
- Each vesicle is a thin-walled, pear-shaped
structure, about 5 cm long.
- It consists of a tube (10 to 15
cm long), which is coiled to form the vesicle-like mass.
- It lies between the fundus of the bladder and the rectum.
- The seminal vesicles do not store sperm cells.
- They secrete a thick alkaline
fluid that mixes with the sperm cells as they pass into the ejaculatory ducts and then the urethra.
- These secretions provide most of the volume of the
semen.
- The superior ends of the seminal vesicles are covered with peritoneum and lie posterior
to the ureters.
- Here, they are separated from the rectum by the peritoneum
of the rectovesical pouch.
- The inferior ends of the seminal vesicles are closely related to the rectum
and are separated only by the rectovesical septum.
Arterial
Supply and Venous Drainage of the Seminal Vesicles
- The arteries are derived from the inferior vesicle and middle rectal arteries.
- The veins accompany the arteries.
Innervation of the
Seminal Vesicles
- The walls of these vesicles contain a plexus of nerve fibres and some sympathetic
ganglia.
- The preganglionic sympathetic fibres emerge from the superior lumbar nerves.
- The parasympathetic fibres are from the pelvic splanchnic nerves.
Lymphatic
Drainage of the Seminal Vesicles
- The lymph from these vesicles drainage primarily to the iliac
lymph nodes, especially the internal iliac lymph nodes.
The Ejaculatory Ducts
- They run close together as they pass anteroinferiorly
through the posterior part of the prostate
along the sides of the prostatic utricle.
- The ejaculatory ducts traverse the main part of the prostate and converge to open by slit-like apertures into the posterior
wall of the prostatic
urethra.
The Prostate
- This is the largest accessory gland of the male reproductive system.
- The prostate (prostate gland) is partly glandular and partly fibromuscular.
- It is enveloped in a thin, dense
fibrous capsule (true capsule), which is enclosed within a loose
sheath derived from the pelvic fascia called
the prostatic sheath (false capsule).
- It is continuous inferiorly with the superior
fascia of the urogenital diaphragm.
- Posteriorly, the prostatic sheath
is part of the rectovesical septum.
- The prostatic venous plexus lies between
the fibrous capsule and the prostatic
sheath.
- The prostate has a base, apex,
and 4 surfaces (posterior,
anterior, and 2 inferolateral
surfaces).
The Base of the Prostate
- The base of the prostate (its vesicular surface) is closely related to the neck of the urinary bladder.
- The prostatic urethra
enters the middle of the base near its anterior
surface.
The Apex of the Prostate
The Posterior Surface of
the Prostate
- This is triangular and flattened
transversely.
- It faces posteriorly and slightly
inferiorly toward the urogenital
diaphragm.
- It rests on the ampulla of the rectum.
- Thus, this surface can be palpated by a digit in the rectum.
- Usually, the posterior surface has a shallow median groove,
demarcating the lateral lobes.
- The lateral lobes are often fused
and clinicians often refer to them as the posterior lobe.
- Superiorly on the posterior surface, there is a shallow groove where the ejaculatory
ducts enter the prostate.
- This groove indicates the middle lobe, the small
section of the prostate between the ejaculatory ducts and
the urethra.
- The middle lobe lies posterior
to the uvula vesica of the urinary bladder.
- The prostatic utricle is located in the substance of the middle lobe.
The Anterior Surface of
the Prostate
- This is transversely narrow and convex
and extends from the apex
to the base.
The Inferolateral
Surfaces of the Prostate
- These meet anteriorly with the convex
anterior surface and rests on the fascia
covering the levator ani muscles.
The Prostatic Ductules or Ducts
- There are 20 to 30 of these in number.
- They open chiefly into the prostatic sinuses on each
side of the urethral crest on the posterior
wall of the prostatic
urethra.
- This occurs because most glandular tissue is located posterior and lateral to the prostatic urethra.
- The prostatic secretion, a thin
milky fluid, is discharged into the prostatic part of the
urethra by contraction of the smooth muscle.
- Prostatic fluid provides about 20% of the volume of the
semen.
Arterial Supply of the
Prostate
- The arteries are derived mainly from the inferior vesical
and middle rectal arteries.
- They are branches of the internal iliac artery.
Venous Drainage of the
Prostate
- These for the prostatic venous plexus around the sides and base of the
prostate.
- This plexus is located between the capsule of the prostate
and its fascial sheath.
- It drains into the internal iliac veins.
- It also communicates with the vesical venous plexus and
the vertebral venous plexus.
Lymphatic Drainage of
the Prostate
- The lymph vessels terminate chiefly in the internal iliac
and sacral lymph nodes.
- Some vessels from its posterior surface pass with the lymph vessels of the bladder
to the external iliac lymph nodes.
Innervation of the Prostate
- Parasympathetic fibres arise from the pelvic splanchnic nerves (S2, S3, and S4).
- The sympathetic fibres are from the inferior
hypogastric plexuses.
The Bulbourethral Glands
- These are 2 pea-sized, yellowish
glands (Cowper's glands).
- They lie posterolateral to the membranous urethra.
- The blood supply of the bulbourethral glands is from
the arteries to the bulb of the penis.
