Anatomy of the male reproductive organs of the pelvis

Transcript

Content Reviewers:

Viviana Popa, MD

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.

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.

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.

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.

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.

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. 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.

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.

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.