The penis contains the urethra, which serves as a conduit for urine and semen, and three bodies of erectile tissue that produce erection when their abundant vascular sinuses fill with blood. The urethra is lined by pseudostratified columnar epithelium that transitions to stratified squamous epithelium. Small urethral glands are present in the lamina propria whose secretions function to lubricate the urethra.

• Examine the images below and a section of the penis, and identify the two corpora cavernosa (CC) and the corpus spongiosum (CS) surrounding the urethra. These three bodies are cylinders of erectile, cavernous tissue. Within them identify the helicine arteries and the large vascular sinuses in the connective tissue surrounding the arteries. Fibroelastic connective tissue, the tunica albuginea (TA), surrounds the three corpora.

• Next, identify the folded mucosa of the urethra. Near the urethra, note the small paraurethral glands that secrete mucus.

Clinical note: The drug Viagra treats impotence or erectile dysfunction by targeting the population of smooth muscle cells in the microvasculature of the corpora cavernosa. Increasing the contractility of these cells facilitates the events that lead to the cavernous tissue filling with blood.
 

Try this self-assessment quiz to practice what you have learned.

Now for the Endocrine System.