Prostate and Penis

Prostate Gland

Capsule

• Fibroelastic connective tissue and smooth muscle.
• Capsule is continuous with the central stroma.

Central stroma

• Gives rise to septa that divide the prostate tissue into lobules.

Tuboloalveolar glands

• Acini lined by pseudostratified epithelial lining.
  – The secretory cells, as their name implies, secrete a white serous fluid that contains substances, including PSA, that facilitate semen liquefaction. At a higher magnification, the prominent Golgi complex and abundant secretory vesicles are visible.
  – In acini, may see a corpora amylacea (aka, prostatic concretion), which is a lamellated mass of accumulated secretions. These deposits occur more frequently with age, and may become calcified.

Stroma

• Surrounds glands, comprises collagen and smooth muscle fibers.

Zones of the prostate:

• Fibromuscular zone = anterior.
• Transitional zone surrounds the prostatic urethra, into which the glands drain.
• Central zone surrounds the ejaculatory ducts.
• Peripheral zone includes the rest of the prostate gland.
• Zones have clinical relevance:
  – The transitional zone is most susceptible to benign prostatic hyperplasia, whereas the peripheral zone is most susceptible to inflammation and prostatic adenocarcinomas.
  – Elevated plasma prostate-specific antigen, which is produced by the secretory cells of the peripheral zone, is indicative of adenocarcinoma; surgery, radiation, and hormone therapy are used to treat).

Be aware of intertextual variation in prostate zoning, and that, because of its shape, sections from different levels and perspectives will show more or less of these zones.

Penis

Comprises three cylindrical bodies of erectile tissue:

• The dorsal bodies are the corpus cavernosa; they are wrapped in a thick fibrous layer of tunica albuginea.
  – In histological sample of the corpus cavernosum, can see a helicine artery and a nearby venous sinus.
• The ventral body is the corpus spongiosum; the penile urethra lies within it.
  – Houses the urethral glands of Littre, which secrete pre-ejaculatory mucus into the prostatic urethra.

Histology:

• The erectile bodies comprise fibroelastic connective tissue interspersed with smooth muscle and neurovascular structures; indicate the deep arteries within the corpus cavernosa, and the dorsal artery and veins dorsally.
• During an erection, parasympathetic stimulation dilates the helicine arteries and the venous sinuses become engorged, blocking venous drainage.
• It is possible to "fracture" the penis: force exerted on an erect penis can rupture the tunica albuginea; surgery may be necessary for repair.

Additional Resource: Knobil and Neill's Physiology of Reproduction, edited by Tony M. Plant, Anthony J. Zeleznik.

Images:

Histology (Mark Braun, MD, & Indiana University: http://medsci.indiana.edu/c602web/602/c602web/toc.htm; http://www.indiana.edu/~anat215/virtualscope2/start.htm)