The Female Body
Vulva is the correct name for the external genitals of women. Most people mistakenly call the external genitals the vagina. However, the vagina is an internal muscular tube that extends from the cervix to the opening of the vulva (about 3 inches).
The vulva comprises several different parts.
The mons is the layer of fatty tissue that covers the pubic bone.
The labia majora (outer lips) are two thick, fatty folds of skin that extend downward from the mons, forming the outer borders of the vulva.
The labia minora (inner lips) are two thin folds of skin endowed with blood vessels and nerve endings. As a result, they are quite sensitive to the touch. The minor lips merge at the top to form a single fold of skin that covers the clitoris. This fold is also called the clitoral hood.
The clitoris is located below the mons at the point where the inner lips meet. The clitoris is a short cylindrical organ composed mainly of erectile tissue that can quickly fill with blood and thus cause the organ to stiffen and increase in size. The clitoris plays an essential role in sexual excitement. It is analogous to the male penis, but it is the only human body part with the sole purpose of producing pleasure. Men have a penis for pleasure, but it is also used for urination.
The vaginal opening is the entrance to the vagina and is below the clitoris.
The Male Body
The male external genitals consist of the penis (the head and the shaft) and the scrotum.
The penis is a tube-like organ that contains erectile tissue. There are three elongated spongy bodies inside the penis that extend the length of the organ; two run parallel on top, and one runs along the underside. The one on the underside contains the urethra, which releases urine and semen. During sexual arousal, these spongy bodies quickly fill with blood, which causes them to stiffen. As a result, the penis becomes erect.
The glans is the head of the penis. It is highly sensitive to touch, due to it's high amount of nerve endings.
The foreskin (or prepuce) is a roll of skin that covers the head of the penis. It is rich in nerve endings, so is very sensitive to touch. Surgical excision (removal) of the foreskin is called circumcision.
The coronal ridge is a circular ridge of flesh demarcating where the head of the penis and the shaft join.
The frenulum is a thin strip of flesh on the underside of the penis that connects the shaft to the head.
Finally, the scrotum is a bag or pouch of skin that hangs between the thighs at the base of the penis. It contains the testicles. Inside the scrotum there are two separate compartments, each containing one testicle and its spermatic cord.