Penis

The penis is composed of three cylindrical bodies of erectile tissue:

• Corpora cavernosa contains irregular vascular channels, separated by trabeculae and surrounded by a fibrous capsule called the tunica albugínea.

■ The inner surface of the tunica albugínea has a plexus of small veins that drain the cavernous spaces.

• Corpus spongiosum exhibits a similar arrangement of erectile tissue.

■ The trabeculae of erectile tissue contain branches of the deep artery of the penis, which end in small arteries that open directly into the cavernous spaces.

Chapter Summary

The testes contain seminiferous tubules and connective tissue stroma. Seminiferous tubules are the site of spermatogenesis. The epithelium contains Sertoli cells and spermatogenic cells. Sertoli cells synthesize androgen-binding protein and provide the blood-testis barrier. Spermatogenic cells are germ cells located between Sertoli cells. They include spermatogonia, primary and secondary spermatocytes, spermatids, and spermatozoa. Spermatozoa number about 60,000 per mm3 of seminal fluid. Each one has a head, which contains chromatin. At the apex of the nucleus is the ; acrosome. The tail contains microtubules.

Interstitial cells of Leydig are located between the seminiferous tubules in the interslitial connective tissue. They synthesize testosterone and are activated by luteinizing hormone from the anterior pituitary.

The genital ducts are composed of tubuli recti, rete testis, efferent ductules, ductus epididymis, ductus deferens, and ejaculatory ducts. Spermatozoa undergo maturation and increased motility within the ductus epididymis. Spermatozoa are stored in the efferent ductules, epididymis, and proximal ductus deferens.

The urethra etfends from the urinary bladder to the tip of the penis, The prostatic urethra is composed of transitional epithelium and the distal urethra ojstratified epithelium.

Seminal vesicles secrete alkaline, viscous fluid rich in fructose. They do not store spermatozoa.

Secretions from the prostate gland are rich in citric acid, lipids, zinc, and acid phosphatase.

Bulbourethral gland secretes mucous fluid into the urethra for lubrication prior to ejaculation.

The penis is composed of three cylindrical bodies of erectile tissue: corpora cavernosa, corpus spongiosum, and trabeculae of erectile tissue. The corpora cavernosa is surrounded by the tunica albuginea.

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