Penis (Penis)
The organ is formed by three cavernous structures: two corpora cavernosa (corpus cavernosum penis) and one corpus spongiosum (corpus spongiosum penis).
- The corpora cavernosa are anchored by their proximal parts (crura) to the inferior rami of the pubis and ischium. Superiorly, they are covered by the ischiocavernosus muscles, while their distal ends are embedded in the depressions of the glans base.
- The corpus spongiosum encloses the urethra. Its posterior part is expanded to form the bulb of the penis (bulbus penis), which is covered by the bulbospongiosus muscle, while its anterior part forms the glans penis (glans penis).
The bodies are firmly fused together to form grooves for the passage of vessels, nerves, and the urethra. Externally, they are surrounded by a dense tunica albuginea (tunica albuginea), over which lies the fascia of the penis (a continuation of the deep perineal fascia). The skin of the organ is thin and mobile, forming a fold at the anterior end known as the prepuce (preputium).
Blood supply is provided by branches of the internal pudendal artery: the dorsal artery supplies the skin and glans, while the deep artery runs within the substance of the corpora cavernosa. Venous blood drains into the femoral and internal pudendal veins, as well as into the venous plexus of the urinary bladder.
Male urethra (Urethra masculina)
The urethra is a tube 20–22 cm long with alternating narrowings and dilatations. Anatomically, the canal is divided into three parts:
- Prostatic part (pars prostatica) — 3–4 cm long, passing through the prostate gland. On its posterior wall rises the urethral crest (seminal colliculus), flanked by the openings of the ejaculatory ducts and prostatic ducts.
- Membranous part (pars membranacea) — the shortest (1.5–2.5 cm) and narrowest segment, surrounded by the voluntary sphincter. The bulbourethral (Cowper's) glands lie adjacent to its posterior wall.
- Spongy part (pars spongiosa) — the longest section (14–15 cm). The excretory ducts of the bulbourethral glands empty into its initial bulbous part (pars bulbosa).
Along the course of the urethra, there are three physiological constrictions: at the membranous part, as well as at the internal and external orifices. The canal forms two curves: the upper (subpubic) and lower (prepubic). When the penis is retracted toward the anterior abdominal wall, these curves merge into one, allowing the safe insertion of rigid metal instruments (catheters, cystoscopes).
Scrotum (Scrotum) and Testis (Testis)
The scrotum is a cutaneous sac divided by a septum (septum scroti) into two halves. Its wall consists of seven layers that successively cover the testis and spermatic cord:
- Skin (cutis)
- Dartos fascia (tunica dartos)
- External spermatic fascia
- Cremasteric fascia
- Cremaster muscle (m. cremaster)
- Internal spermatic fascia
- Tunica vaginalis testis (tunica vaginalis testis)
The testis is covered by the tunica albuginea, superficial to which lies the tunica vaginalis, consisting of parietal and visceral layers. Between the layers is a serous cavity (a potential site for fluid accumulation in hydrocele). Along the posterior border of the testis lies the epididymis (epididymis), which continues into the ductus deferens.
Arterial blood supply to the testis originates from the testicular artery and cremasteric artery. Venous drainage is unique: blood collects into the pampiniform plexus (plexus pampiniformis), from which the right testicular vein carries blood to the inferior vena cava, and the left to the left renal vein.
Spermatic cord (Funiculus spermaticus)
This is an anatomical complex extending from the epididymis to the deep inguinal ring. In an adult male, its length reaches 15–20 cm. On palpation through the scrotum, it feels like a smooth, soft cord about the thickness of the little finger.
The spermatic cord consists of:
- Ductus deferens (ductus deferens)
- Arteries (testicular artery and artery of the ductus deferens)
- Veins (pampiniform plexus, testicular veins, veins of the ductus deferens)
- Nerve plexuses and lymphatic vessels
- Remnant of the processus vaginalis of the peritoneum and loose connective tissue
Externally, this complex of structures is enveloped by three layers: the external spermatic fascia, the cremaster muscle (with its fascia), and the internal spermatic fascia.
Briefly: answers to topical questions
Which nerves provide innervation to the penis?
Innervation of the penis is supplied by the pudendal neurovascular bundle, as well as branches of the autonomic and somatic nervous systems.
- Dorsal nerve of the penis (n. dorsalis penis) — runs on the dorsal surface as part of the neurovascular bundle.
- Pelvic splanchnic nerves — carry parasympathetic fibers (from segments S2–S4) to the corpora cavernosa, facilitating erection.
- Pudendal nerve — provides somatic innervation to the urethral sphincter, ischiocavernosus, and bulbospongiosus muscles.
Afferent pathways transmit sensory impulses from the organ to spinal cord segments L1 and S2–S4.
To which regional lymph nodes does lymph from the testis drain?
The regional lymph nodes for the testis are the retroperitoneal and lumbar nodes.
Lymph from the testis drains via efferent vessels within the spermatic cord:
- into nodes located around the aorta and inferior vena cava;
- into retroperitoneal lymph nodes at the level of the renal hila.
Inguinal lymph nodes are generally considered distant. They are considered regional if normal lymphatic drainage is disrupted due to prior surgeries in the inguinal region: orchidopexy or herniorrhaphy.
From which blood vessel does the artery of the ductus deferens originate?
The artery of the ductus deferens (a. ductus deferentis) originates from the umbilical artery (a. umbilicalis). It subsequently runs within the spermatic cord (funiculus spermaticus) alongside the testicular artery (a. testicularis), the pampiniform venous plexus, and nerves.
To quickly memorize the three constrictions of the urethra, use the "MIE" rule: Membranous part, Internal urethral orifice, External urethral orifice.
Class and exam questions
Why is the penis pulled toward the anterior abdominal wall during urethral catheterization with a rigid instrument?
This maneuver straightens the prepubic and subpubic curves of the urethra, merging them into a single curve with anterior and superior concavity. As a result, a rigid metal instrument passes without traumatizing the walls.
What is the specific feature of venous drainage from the testes?
Blood collects into the pampiniform plexus, forming the testicular vein. The right vein empties directly into the inferior vena cava, while the left drains into the left renal vein.
Where is the narrowest part of the male urethra located?
The narrowest segment is the membranous part (pars membranacea), measuring only 1.5–2.5 cm in length. This is precisely where the voluntary sphincter is located.
What else to study on this topic
- Topography and fasciae of the perineum in the context of the urogenital diaphragm
- Syntopy of the prostatic urethra and seminal colliculus
- Mechanism of hydrocele formation (fluid accumulation in the serous cavity)
- Lymphatic drainage from the pelvic structures and inguinal region
- Innervation of the scrotum by branches of the lumbar and sacral plexuses
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