Office of Health Education & Promotion

Brad Archambault - Graphite on Paper

The Reproductive System

Specialized sex cells, called gametes are the ova in women and sperm in men. The ova and sperm fuse during fertilization to produce a cell called the zygote. The zygote contains genetic information from the sex cells of both parents, and allows for the development of new human life.

The reproductive systems of males and females have both essential organs and accessory organs . The essential organs of reproduction in both men and women are called gonads. The gonads of men are the testes or testicles. The testes produce the male sex cells, spermatozoa or sperm. Sperm are formed within the walls of the seminiferous tubules of the testes. From here, sperm enter, and then pass through the epididymis, a comma-shaped structure that lies along the top and behind the testes inside the sac that holds them called the scrotum. The epididymis is a single and very tightly coiled tube which, if stretched out, would be be about 20 feet in length. Next, sperm pass through the vas deferens, a thick, smooth, muscular tube that passes from the scrotal sac upward into the abdominal cavity. Once in the abdominal cavity, the vas deferens extend over the surface of the bladder where it joins the duct from the seminal vesicle to form the ejaculatory duct, which then passes from the prostate gland and permits sperm to empty into the urethra, and out of the body through the penis. Semen or seminal fluid is the mixture of sperm and secretion from accessory glands, including seminal vesicles, the prostate gland, and the Cowper’s glands.

The external reproductive organs or genitalia of the male includes the penis and the scrotum. The penis is made stiff or erect by the filling of its spongy tissue with blood during sexual arousal. At the end of the shaft of the penis is the glans or head, over which, at birth, the skin is folded to form a retractable casing called the foreskin or prepuse. The external urethral orifice is the opening of the urethra at the tip of the glans.

The gonads in women are the pair of ovaries where ova are produced. The ovaries resemble large almonds in size and shape and are attached to ligaments in the pelvic cavity on each side of the uterus, a muscular organ with a small cavity inside. The uterus is made of the body or upper portion, and the cervix, or lower portion. The uterus has three functions: menstruation, pregnancy, and labor.

Embedded in connective tissue just below the outer layer of each ovary are about 1 million ovarian follicles. Each follicle contains an oocyte, an immature stage of the female sex cell. During a female’s reproductive lifetime however, about 350-500 of these follicles fully develop, releasing an ovum for potential fertilization. Production of estrogen and progesterone, female sex hormones, is also a function of the ovaries. Estrogen is the sex hormone that causes the development of secondary sex characteristics, like breast development and the initiation of the first menstrual cycle. Progesterone stimulates the lining of the uterus and acts with estrogen to initiate the menstrual cycle in girls during puberty. The fallopian tubes are ducts for the ovaries, where ovum travel to the uterus.

The vagina is a muscular tube lined with mucous membrane. It lies in the pelvic cavity between the urinary bladder and the rectum, and connects from the uterus to the external genitalia.

Each breast consists of 15 to 20 lobes, and each lobe has several lobules, and each lobule has glandular cells that secrete milk. These cells are arranged in grapelike clusters called alveoli, and small lactiferous ducts drain the alveoli toward the nipple like the spokes of a wheel.

The external genitalia or vulva of females consists of the mons pubis, a skin-covered pad of fat over the public bone. Extending downward from the mons pubis are the labia major, elongated folds of skin, and the labia minora, smaller folks of skin within the labia majora. The clitoris, made of erectile tissue, is located just behind the upper junction of the labia minora, is the primary place of erotic and sexual stimulation. Between the clitoris above and the vaginal opening below is the urethral opening.

In some instances, babies are born with ambiguous genitalia and are called intersex individuals. The cause of this phenomenon can be hormonal or chromosomal.

More...

The Skeletal System
The Muscular System
The Nervous System
The Digestive System
The Respiratory System

The Endocrine System
The Lymphatic System
The Urinary System
The Reproductive System