Anatomy of the male reproductive organs of the pelvis

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Introduction0:00–0:25

The male reproductive system consists of a number of external and internal organs. The male reproductive organs that lie within the pelvic cavity include the ductus deferens, seminal vesicles, ejaculatory ducts, and prostate.
These organs are all important in the transportation and protection of sperm cells as they move from the testis to eventually reach the penis.
Let’s start with the ductus deferens or the vas deferens, which are paired tubes that carry mature sperm from the epididymis to the ejaculatory ducts.

Ductus deferens0:25–1:53

The ductus deferens begins at the inferior pole of the testis as a continuation of the last part of the epididymis, called the tail of the epididymis.
Then, it ascends posterior to the testis and medial to the epididymis to enter the spermatic cord, which is a cord-like structure that connects the testes to the abdominal cavity.
Finally, the ductus deferens penetrates the anterior abdominal wall through the inguinal canal and crosses the external iliac vessels to enter the pelvic cavity.
Here, the ductus deferens runs along the lateral wall of the pelvis, external to the parietal peritoneum. At the posterolateral angle of the urinary bladder, the ductus deferens crosses the ureter, reaching the fundus of the bladder.
A way to remember the relationship between the ductus deferens and the ureter is the phrase, “Bridge over troubled water” where the ductus deferens is crossing over the ureter which is carrying urine to the bladder.
At the fundus of the bladder, the ductus deferens lies superior to the seminal vesicle, where it then descends medial to the seminal vesicle, and dilates to form the ampulla of the ductus deferens.
The ductus deferens then terminates by joining the ducts of the seminal vesicle, forming the ejaculatory ducts.Now, the arterial blood supply of the ductus deferens comes from the artery of the ductus deferens.

Blood supply of ductus deferens1:53–2:19

Typically, this small artery arises from the superior vesical arteries, but may arise from the inferior vesical arteries.
Venous blood from the majority of the ductus deferens drains into the testicular vein, while some venous blood from the upper part drains into the vesical or prostatic venous plexuses.

Seminal vesicles2:19–2:58

Next are the seminal vesicles, also called seminal glands, which are paired elongated glands that lie between the fundus of the urinary bladder and the rectum.
The seminal glands secrete an alkaline fluid that contains coagulating agents and fructose which serves as an energy source for the migrating sperm as they pass into the ejaculatory ducts and urethra.
Now, the upper part of the seminal vesicle is covered by peritoneum, lying posterior to the ureters. Here, the rectovesical pouch separates the seminal vesicles from the rectum.
Each seminal vesicle duct terminates by joining the ductus deferens, forming the ejaculatory ducts. Finally, the arteries for the seminal vesicles come from the inferior vesical and middle rectal arteries, and the veins draining the seminal vesicles mirror these arteries.

Blood supply of seminal vesicles2:58–3:10

Next are the ejaculatory ducts, which are paired tubes that form near the neck of the bladder resulting from the union of the ducts of the ductus deferens and the seminal vesicles.

Ejaculatory ducts3:10–3:59

The ejaculatory ducts run in an antero-inferior direction through the posterior part of the prostate. Here, they descend on either side of the prostatic utricle, which is a pouch that extends backwards from the prostatic urethra.
Then, each ejaculatory duct opens on a rounded elevation on the posterior surface of the prostatic urethra, called the seminal colliculus.
Although the ejaculatory ducts course through the prostate, the seminal fluid and prostatic secretions will not mix until the ejaculatory ducts have terminated in the prostatic urethra.The arterial blood supply for the ejaculatory ducts is derived from the arteries of the ductus deferens, which typically arise from the superior and inferior vesical arteries.

Blood supply of ejaculatory duct3:59–4:13

Veins of the ejaculatory ducts drain into the prostatic and vesical venous plexuses.Alright, now let’s take a quick break and see if you can identify the ductus deferens, the seminal vesicles and the ejaculatory ducts on this image.

Quiz4:13–4:29

Now, let’s discuss the prostate gland, which is about the size and shape of a walnut, and sits inferior to the bladder and anterior to the rectum.

Prostate 4:29–6:08

It also surrounds the prostatic portion of the urethra. The prostate produces a thin, milky fluid that helps activate and protect sperm cells, and combines with the fluids of the other reproductive organs to produce semen.
The prostate is covered by a capsule of tough connective tissue and smooth muscle. The prostatic venous plexus, as well as nerves, overlie the capsule and are incorporated within it.
All of this is surrounded by the visceral layer of pelvic fascia, called the prostatic sheath. Now, the prostate has a base that lies below the neck of the bladder, and an apex that touches the fascia covering the superior urethral sphincter and the deep perineal muscles.
From a posterior view we can see the ductus deferens and the seminal vesicles positioned superior to the prostate contributing to the formation of the ejaculatory duct which passes through the base of the prostate.
Now, if you look hard enough, a posterior view of the prostate kind of looks like an angry bird! The prostate also has an anterior, posterior, and two inferolateral surfaces.
The anterior surface of the prostate forms part of the urethral sphincter, and is separated from the posterior surface of pubic bones by the retropubic space.
The posterior surface is anterior to the ampulla of the rectum, and the two inferolateral surfaces are in close relation to the levator ani muscles which help form the pelvic floor.
Alright, now deep to the capsule, the prostate can be divided into two glandular lobes, which form two thirds of the prostate, and a fibromuscular lobe, which forms one third of the prostate.

Lobes of prostate 6:08–6:58

These lobes are named based on their relationship to the prostatic urethra. First is the isthmus, or anterior lobe of the prostate gland.
The isthmus represents the fibromuscular third of the prostate and lies anterior to the prostatic urethra. The muscle fibers are the superior continuation of the external urethral sphincter for the neck of the urinary bladder.
Next are the right and left lobes, which are separated anteriorly by the isthmus of the prostate, and posteriorly by a shallow median furrow.
The right and left lobes make up the glandular two thirds of the prostate gland.Now, some clinicians further divide the prostate into zones.

Lobes of prostate 6:58–7:27

The anterior muscular zone contains the fibromuscular tissue of the isthmus. The peripheral zone, which is the outermost posterior section, is the largest of the zones.
Moving inward, the next section is the central zone, which contains the ejaculatory ducts that join with the prostatic urethra.
Last, there’s the transitional zone, which contains a portion of the prostatic urethra. Now, the prostatic fluid produced by the glandular portion of the prostate flows through prostatic ducts that open into the prostatic sinuses, which are bilateral recesses on each side of the seminal colliculus in the posterior wall of prostatic urethra.

Prostatic fluid7:27–7:52

Here, in the prostatic urethra, the prostatic fluid mixes with sperm and fluid from the seminal vesicles. Alright, now the prostatic arteries typically branch off from the inferior vesical artery, but may also derive from the internal pudendal or middle rectal arteries.

Blood supply of prostate7:52–8:29

Prostatic veins merge together to form the prostatic venous plexus around the base and sides of the gland. This plexus lies between the capsule of the prostate gland and the prostatic sheath, and drains into the internal iliac veins.
The prostatic venous plexus is continuous superiorly with the vesical venous plexus, and posteriorly with the internal vertebral venous plexus.

Innervation of male reproductive organs8:29–9:19

Now, let’s switch gears and talk about the innervation of the male reproductive organs of the pelvis. Nerves supplying the ductus deferens, the seminal glands, the ejaculatory ducts, and the prostate contain both sympathetic and parasympathetic fibers.
Sympathetic nerve fibers originate from the T12 to L2 spinal segments. Then, these fibers become components of the abdominopelvic splanchnic nerves, the hypogastric plexuses and the organ-specific pelvic plexuses before eventually reaching the reproductive organs of the pelvis.
Parasympathetic fibers originate from S2 and S3 spinal segments and travel via the pelvic splanchnic nerves to also join the inferior hypogastric and pelvic plexuses before synapsing on the target organs.Alright, as a quick recap.
The ductus deferens is a tube that transfers mature sperm from the tail of the epididymis, upward through the spermatic cord into the pelvic cavity, and terminates by emptying into the ejaculatory ducts.

Review9:19–10:37

The seminal vesicles are paired glands that lie between the fundus of the urinary bladder and the rectum. The ducts of the seminal vesicles join the ductus deferens, forming the ejaculatory ducts.
Then, the ejaculatory ducts run anteroinferiorly through the prostate gland to drain into the prostatic urethra. The prostate is covered by a fibrous capsule and prostatic sheath which contain nerves and a venous plexus.
Deep to the capsule, the prostate is divided into lobes, including the isthmus, which lies anterior to the prostatic urethra, as well as the right and left lobes, which are separated posteriorly by a shallow median furrow.
The prostatic fluid moves through ducts that open into the prostatic urethra, on either side of the seminal colliculus. Finally, the internal male reproductive organs receive both sympathetic and parasympathetic innervation via hypogastric and pelvic plexuses.