Intratesticular ducts
The sperm-conveying ducts originate directly within the testis, serving as a direct continuation of the spermatogenic tissue.
- Straight tubules (tubuli recti): short segments following the convoluted seminiferous tubules. Their internal lining is formed by a simple columnar epithelium, and the lumen has a smooth contour.
- Rete testis (rete testis): a system of anastomosing channels located in the mediastinum testis. The epithelium here becomes flattened, forming a simple cuboidal or even squamous epithelium.
System of epididymal ducts (Epididymis)
The epididymis is attached to the upper surface of the testes and is responsible for the final maturation of spermatozoa. In addition, the epithelial cells secrete components of the seminal fluid, while smooth muscle elements participate in ejaculation.
- Efferent ductules (ductuli efferentes): emerge from the rete testis (typically 12–15 in number). Their initial straight segment is located within the testis, while the long, convoluted segment forms the head of the epididymis. On histological slides, they exhibit a characteristic uneven, "scalloped" contour. This is due to the alternation of tall ciliated cells and low glandular cells with microvilli that secrete via an apocrine mechanism.
- Epididymal duct (ductus epididymidis): a long tube (up to 3–4 meters) that repeatedly twists to form the body and tail of the epididymis. The contour of its lumen is even, as the epithelium (pseudostratified ciliated) consists of evenly distributed tall ciliated cells (type I) and low intercalated cells (type II).
Vas deferens (Ductus deferens)
The ductus deferens originates from the tail of the epididymis as a dense, tubular structure 40–50 cm in length. It ascends as part of the spermatic cord, passes through the inguinal canal, and enters the pelvic cavity before emptying into the upper (prostatic) part of the urethra.
The structure of the wall of the ductus deferens has distinct features:
- Mucosa forms longitudinal folds. The epithelium remains pseudostratified, but a well-developed connective tissue lamina propria appears.
- Muscular coat is very thick and consists of three layers of smooth myocytes: an inner longitudinal, a middle circular, and an outer longitudinal layer. Such musculature is necessary for the forceful expulsion of semen (ejaculation).
- Adventitia is formed by loose fibrous connective tissue.
Changes in epithelium and musculature in the urethra
In the male urethra, there is a sequential change in the epithelial lining and a reduction of the muscular layer.
Epithelial dynamics:
- In the prostatic urethra, the epithelium is transitional (similar to the urinary bladder).
- In the membranous and most of the spongy urethra, it transitions to pseudostratified columnar with abundant goblet cells.
- In the area of the navicular fossa, stratified squamous epithelium appears.
Muscular dynamics: Smooth muscle tissue gradually regresses. In the prostatic part, there are longitudinal and circular layers forming the involuntary sphincter. In the membranous part, only isolated bundles of smooth myocytes remain, but a voluntary skeletal muscle sphincter appears. In the spongy part, the smooth muscle layer almost completely disappears.
Briefly: answers to topical questions
With which duct does the ductus deferens merge to form the ejaculatory duct?
The ductus deferens merges with the excretory duct of the seminal vesicle to form the ejaculatory duct (ductus ejaculatorius). Prior to this merger in its pelvic portion, the terminal segment of the ductus deferens forms a dilation known as the ampulla of the ductus deferens (ampulla ductus deferentis). The resulting ejaculatory duct then pierces the prostate gland and opens onto the seminal colliculus directly into the prostatic urethra.
What other structures are part of the spermatic cord along with the ductus deferens?
Along with the ductus deferens (ductus deferens), the spermatic cord contains blood and lymphatic vessels, neural structures, and other elements enclosed within the fascia derived from the fascia transversalis:
- Arteries (a. testicularis, a. cremasterica, a. ductus deferentis) — testicular artery, cremasteric artery, and artery of the ductus deferens.
- Venous structures (vv. deferentiales, plexus venosus pampiniformis) — veins of the ductus deferens and the pampiniform venous plexus.
- Nerves (r. genitalis n. genitofemoralis, plexus sympathicus deferentialis, plexus sympathicus testicularis) — genital branch of the genitofemoral nerve, sympathetic plexuses of the ductus deferens and testis.
- Lymphatic vessels — provide lymphatic drainage.
- Remnant of the processus vaginalis of the peritoneum — an additional structural element of the cord.
Class and exam questions
Why does the lumen of efferent ductules appear irregular on histological slides?
The uneven, "scalloped" contour is due to the structure of the epithelium: it alternates between tall ciliated cells forming protrusions and low glandular cells (with microvilli) forming crypts.
How many muscle layers are in the wall of the ductus deferens?
In the ductus deferens, the muscular coat is robust and consists of three layers: an inner longitudinal, a middle circular, and an outer longitudinal layer.
How does the duct of the epididymis differ from efferent ductules under a microscope?
The duct of the epididymis has a smooth, distinct internal luminal contour, whereas the efferent ductules are characterized by a tortuous, scalloped edge due to the alternation of cells of varying heights.
What else to study on this topic
- Features of apocrine secretion in the low cells of the efferent ductules.
- The relationship between the structure of urethral muscles and the regulation of urination and ejaculation.
- Topography and functions of the rete testis in the context of the mediastinum testis.
- Differences between ciliated (type I) and intercalated (type II) cells of the epididymal duct.
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