ANATOMY, MALE GENITALIA

Model of the internal anatomy of an adult male pelvis (median section).
The pelvic musculature and vascular network, as well as the spinal column, are described in image no. 1149205.
The ureter (in greenish yellow) carries the urine from the kidney to the bladder. The urinary bladder wall is mainly composed of the bladder muscle (in orange-red), the contraction of which allows urine evacuation through the urethra. This muscle is inwardly covered by a mucous membrane (in orange) with many folds and, outwardly, by the perimetrium (in white).
The rectum is composed of two segments: the rectal ampulla in its upper part, storing the feces, and the anal canal, ending in the anus. The rectal ampulla forms curves, giving rise to folds of the inner rectal mucosa - the rectal valves. It also has vertical folds, the anal columns. The rectal wall includes three tissue layers: an outer muscularis (in orange-red), constituted by muscle fibers allowing defecation, a middle submucosa and an inner mucosa (in orange). The opening of the extremity of the anal canal, the anus, is controlled by an internal anal sphincter, composed of smooth muscle (in orange, reflex opening for defecation) and an external anal sphincter of striated muscle (in red, voluntary relaxation).
Outside the pelvic cavity, the testicles (in khaki), located in the scrotum, produce spermatozoa and secrete sex hormones. The scrotum wall is inwardly covered by the Colles' fascia (in white) including a bundle of muscle fibers, the dartos, in contact with the abdominal wall. Each testicle is wrapped in the tunica vaginalis (in white) and in a fibrous capsule, the tunica albuginea (in white), the projections of which form walls separating the testicle into lobules. Spermatogenesis takes place in these lobules, then the spermatozoa are propelled towards the duct of the epididymis. The epididymis (in grey) is mainly made up of this duct, a long curled-up tube which performs sperm maturation; it is formed by three parts: the head, above the testicle, the body, sideways, and the tail, the end of which continues with the vas deferens. The latter goes up inside the cavity of the pelvis, within the spermatic cord that also includes the testicular arteries (in red) and the pampiniform plexus (in blue), a network of testicular veins which drains the blood from the testicles.
The vas deferens carries the spermatozoa towards the prostate, where it joins the excretory duct of the seminal vesicle to form the ejaculatory duct (in beige). This crosses then the Denonvilliers' fascia (in white), wall separating the prostate from the rectum, in order to bring the semen towards the urethra through the prostate. Lying at the bladder neck, the prostate (in beige) surrounds the prostatic urethra (orange duct). It makes secretions contributing to semen production and expelled through the urethra.
The urethra carries both the urine coming from the bladder and the semen released by the ejaculatory ducts. It crosses the prostate then the urogenital diaphragm (in red), including the urethral sphincter and the perineal muscles, goes through the penis and at last ends by a dilated portion the navicular fossa, opening on the urethral meatus. These three parts are respectively called the prostatic, membranous and spongy urethrae. The membranous urethra is surrounding by the Cowper's glands (in orange-red).
The penis includes three parts: an inner part, the root (bulb and crura), then the body and the glans. The bulb of the penis is linked to the urogenital diaphragm. The body includes the two peripheral corpora cavernosa and the corpus spongiosum, surrounding the urethra; each is wrapped in a fibrous tissue (the tunica albuginea, in white). They are constituted by erectile tissue rich in blood vessels (arteries in red and veins in blue). The erectile tissues of the penis are covered together by a fibrous membrane, the Buck's fascia (in white). At its lower end, the corpus spongiosum forms a bulge, the glans, with a ridge: the corona. The glans is covered by a free fold of skin, the foreskin. The deep dorsal vein of penis (in blue), located between the Buck's fascia and the tunica albuginea, drains the blood out of the corpora cavernosa.