The internal genitalia or genital organs comprise the deferent ducts, seminal vesicles, and ejaculatory ducts. The external genital organs comprise the penis, testis, and scrotum.
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.
It is about 45 cm long and ascends in the spermatic cord. It passes through the inguinal canal and then crosses over the external iliac vessels to enter the pelvis minor. It passes along the lateral wall of the pelvis where it lies external but adherent to the parietal peritoneum and medial to the vessels and nerves.
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.
It then joins the duct of the seminal vesicle to form the ejaculatory duct.
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.
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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.
The duct of each seminal vesicle joins the ductus deferens to form the ejaculatory duct. This opens into the posterior wall of the prostatic urethra, near the opening of the prostatic utricle.
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
These ducts are formed by the union of the ducts of the seminal vesicle and ductus deferens. The ejaculatory ducts are about 2.5 cm long and are formed near the neck of the bladder.
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.
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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 about the size of a walnut and surrounds the prostatic urethra.
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.
This separates the bladder, seminal vesicles, and prostate from the rectum.
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 apex of the prostate is inferior and is related to the superior fascia of the urogenital diaphragm. It rests on the sphincter urethrae muscle and is embraced by the medial margins of the levator ani muscles.
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.
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The Bulbourethral Glands
These are 2 pea-sized, yellowish glands (Cowper's glands). They lie posterolateral to the membranous urethra.
They are superior to the bulb of the penis and embedded in the fibres of the sphincter urethrae muscle.
The ducts of the bulbourethral glands are relatively long (2.5 to 3 cm). They pass through the inferior fascia of the urogenital diaphragm with the urethra. These ducts open by minute apertures into the proximal part of the spongy urethra in the bulb of the penis.
The blood supply of the bulbourethral glands is from the arteries to the bulb of the penis.
