Examine a section of the penis (slide 109) and identify the folded mucosa of the urethra (Fig. 21-18 and 21-19). What type of epithelium is present? Near the urethra, identify the small paraurethral glands (Fig. 21-19).

What larger glands supplement the paraurethral glands and what is the function of these glands?

Identify the corpus cavernosum urethrae (or corpus spongiosum) surrounding the urethra (Figs.21-17 and 21-18). Next to this, dorsally, identify the paired corpora cavernosa penis. These bodies together represent three cylinders of erectile cavernous tissue. Within them identify the helicine arteries and the large vascular sinuses in the connective tissue surrounding the arteries (Fig. 21-19).

Would you classify the helicine arteries as actual arteries or as arterioles?

How does the action of these blood vessels lead to erection of the penis?

Clinical note: The target of the drug Viagra, used to treat impotence or erectile dysfunction, is the population of smooth muscle cells in the microvasculature of the corpora cavernosa, increasing the contractility of these cells and facilitating the events that lead to the cavernous tissue filling with blood.

Now for the female reproductive system.