The paired seminal vesicles are tortuous tubes surrounded by a connective tissue capsule. Their mucosa is highly folded, making it falsely appear as if these glands have multiple lumens. The lining epithelium is simple cuboidal/columnar or pseudostratified columnar epithelium. Underlying the mucosa is a fibroelastic lamina propria and two layers of smooth muscle. The seminal vesicles secrete a fluid that is rich in fructose, prostaglandins, and fibrinogen, and constitutes ~70% of the fluid component of semen.

• Examine the images at the right and a section of the seminal vesicle. Identify columnar/cuboidal epithelium (it may appear pseudostratified) in the thin, highly folded mucosa and the layers of smooth muscle surrounding the secretory components.
   

The prostate gland consists of tubuloacinar glands lined by a simple or pseudostratified columnar epithelium surrounded by a fibromuscular stroma. The ejaculatory duct, carrying sperm in seminal fluid, empties into the prostatic urethra that runs through the center of the gland. The prostate gland secretes a fluid containing enzymes, glycoproteins, and prostaglandins that is added to the semen during ejaculation. The lumens of the prostate gland sometimes contain small concretions, or corpora amylacea, which are helpful in identifying the prostate gland, but have no known functional or clinical significance.

 
• Examine the image at the right and this trichrome-stained section of prostate gland. Identify the tall epithelial cells with their lightly stained and "foamy" appearing apical cytoplasm. In the stroma, notice the smooth muscle fibers (red) mixed with dense connective tissue (blue). In the lumens, identify the calcified, proteinaceous concretions, corpora amylacea.

• The association between prostate and urethra can be seen in this specimen, which shows the region near the urethra. The urethra has been split and appears to be on the edge of the section. Notice the difference between the glandular tissue near the urethra and the glands throughout most of the organ further from the urethra.

Clinical note: Prostate glands provide urologists with plenty of work by being prone to three very common problems. (1) They are the sites of chronic, low-grade bacterial infections. (2) In older persons the secretory epithelium very frequently undergoes benign hyperplasia. This tissue overgrowth constricts the urethra, causing problems with urination. (3) Adenocarcinoma of the prostate epithelium is a very common form of cancer.
 

The penis and urethra are next.