MALE GENITAL SYSTEM
a. External Genitalia. The penis and the scrotum are the external parts of the
male genital system. See figure 1-7.
Figure 1-7. Male genital system.
(1) Penis. The penis is the male organ of copulation and urination. The
shaft of the penis is made up of three cylindrical masses of tissue bound together by
fibrous tissue. The two back and side tissue masses are called the corpora cavernosa
penis. The smaller third tissue mass is the corpus spongiosum penis located toward the
middle of the shaft and containing spongy urethra. These three tissue masses are
erectile (capable of erection) and contain blood sinuses (channels). When sexually
stimulated, the arteries of the penis dilate. Large quantities of blood enter the blood
sinuses. Expansion of these spaces compresses the veins draining the penis, causing
most entering blood to be retained. An erection is caused by these vascular changes,
the erection being a parasympathetic reflex. When the arteries constrict and the
pressure on the veins is relieved, the penis returns to its flaccid (soft, limp) state. See