Structures and Functions of the Reproductive System
The Male Reproductive System
The testes (testicles) are the male sex glands (gonads). Male sex cells (sperm cells) are produced in the testes. So is testosterone, the male hormone. This hormone is needed for reproductive organ function and for the development of male secondary sex characteristics. The testes are suspended between the thighs in a sac called the scrotum.
Sperm travel from the testis to the epididymis. The epididymis is a coiled tube on top and the side of the testis. From the epididymis, sperm travel through a tube called the vas deferens. Eventually each vas deferens joins a semivesicle. The two seminal vesicles store sperm and produce semen. Semen is a fluid that carries sperm from the male reproductive tract. The ducts of the seminal vesicles join to form he ejaculatory duct. The ejaculatory duct passes through the prostate gland.
The prostate gland, shaped like a doughnut, lies just below the bladder. The gland secretes fluid into the semen. As the ejaculatory ducts leave the prostate they join the urethra, which also runs through the prostate. The urethra is the outlet for urine and semen. The penis contains the urethra.
The penis is outside the body and has erectile tissue. When the man is sexually aroused, blood fills the erectile tissue. The penis becomes enlarged, hard, and erect. The erect penis enter the vagina of the female reproductive tract. The semen, which contains the sperm, is released into the vagina.
The Female Reproductive System
The female gonads are two almond shaped glands called ovaries. There is an ovary on each side of the uterus in the abdominal cavity. The ovaries contain ova (eggs). Ova are female sex cells. One ovum (egg) is released monthly during the woman’s reproductive years. Release of an ovum from an ovary is called ovulation. The ovaries also secretes the female hormones estrogen and progesterone. These hormones are needed for reproductive system function and development of female secondary characteristics.
When an ovum is released from an ovary, it travels through a fallopian tube. There are two fallopian tubes, one on each side. The tubes are attached at one end to the uterus. The ovum travels through a fallopian tube to the uterus. The uterus is a hollow, muscular organ shaped like a pear.
The uterus is in the center of the pelvic cavity behind the bladder and infront of the rectum. The main part of the uterus is the fundus. The neck or narrow section of the uterus is the cervix. Tissue lining the uterus is called the endometrium. The endometrium has many blood vessels. If sex cells from the male and female unite into one cell, that cell implants into the endometrium. There it grows into a baby. The uterus serves as a place for the unborn baby to grow and receive nourishment.
The cervix projects into a muscular canal called the vagina. The vagina opens to the outside of the body and is located just behind the urethra. The vagina receives the penis during sexual intercourse and is part of the birth canal. Glands in the vaginal wall keep it moistened with secretions.
The external genitalia of the female are called the vulva. The mons pubis is covered with hair in the adult female. The labia majora and labia minora are two folds of tissue on each side of the vaginal opening. The clitoris is the small organ composed of erectile tissue. The clitoris becomes enlarged and hard when sexually stimulated.
The endometrium is rich in blood to nourish the cell that grows into an unborn baby (fetus). If pregnancy does not occur, the endometrium breaks up and is discharged through the vagina to the outside of the body. This process is called menstruation. Menstruation occurs about 28 days. Therefore it is also called the menstrual cycle.
The first day of the cycle starts with menstruation. Blood flows from the uterus through the vaginal opening. Menstrual flow last 3 to 7 days. Ovulation occurs during the next phase. An ovum is released from the ovary. Ovulation usually occurs on or about day 14 of the cycle. Meanwhile, the ovaries secrete estrogen and progesterone (female hormones). These hormones cause the endometrium to thicken for possible pregnancy. If pregnancy does not occur, the hormones decrease in amount. Bood supply to the endometrium decreases because of the decrease in hormones. The endometrium breaks up and is discharged through the vagina. Another menstrual cycle begins.
For reproducion to occur, a male sex cell (sperm) must unite with a female sex cell (ovum). The uniting of the sperm and ovum into one cell is called fertilization. A sperm and an ovum each have 23 chromosomes. When the two cells unite, the fertilized cell has 46 chromosomes.
During intercourse, millions of sperms are deposited in the vagina. Sperm travel up the cervix, through the uterus, and into the fallopian tubes. If a sperm and an ovum unite in a fallopian tube, fertilization occurs and pregnancy results. The fertilized cell travels down the fallopian tube to the uterus. After a short time, the fertilized cell implants in the thick endometrium and grows during pregnancy.