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The internal reproductive anatomy includes the uterus, two ovaries, two fallopian tubes, the urethra, the pubic bone, and the rectum. The uterus contains an inner lining called the endometrial (which builds ups and sheds monthly in response to hormonal stimulation). The lower portion of the uterus is called the cervix, which contains a small opening called the so. Menstrual blood flows through the so into the vagina during menstruation. Semen travels through the so into the uterus and the fallopian tubes following ejaculation during sexual intercourse.
The cervical so dilates (opens) during childbirth. The ovaries, two small almond-shaped structures located on each side of the uterus, are the female gonads (reproductive lands). Female babies are born with over 400,000 ova (the gametes, also referred to as egg cells or octets), which are stored in the ovaries. The female body does not produce any additional ova. The ovaries produce estrogen and progesterone. The ovaries are close to, but not actually connected to the fallopian tubes, thin tube-like structures that are the site of fertilization, the fusion of the male and female gametes.
During coitus (sexual intercourse) between a male and a female, semen is released into the vagina and transported through the uterus into the fallopian tube. Although many factors contribute to whether or not a single act of intercourse will result in pregnancy, most important is whether or not a sperm cell will “meet” an ovum in the fallopian tube (fertilization). Fertilization can only occur if intercourse takes place before the time of ovulation that usually occurs “mid-cycle”, or about 14 days before the woman’s next menstrual period.
At the time of ovulation, the ovum is released from the ovary and transported in the fallopian tube where it remains for about 24-48 hours. Pregnancy is most likely to occur if fresh semen is present when ovulation occurs. Sperm cells remain viable within the female reproductive tract for about 72 hours. Only a single sperm cell is needed to fertilize the ovum, even though the average ejaculation contains approximately 300 million sperm. During fertilization, the sperm enters the cell membrane of the ovum so the nuclei of the sperm and egg cells combine to form a zygote.