The ovaries (female gonads) are two almond-shaped glands suspended by ligaments in the upper pelvic cavity, one on either side of the uterus, posterior and inferior to the fallopian tubes. Their prime function is to produce the ova and the female hormone estrogen and progesterone. Although these hormones are manufactured by the ovaries, their production is controlled by the anterior pituitary gland. These hormones play essential roles in the development of secondary sex characteristics, the reproductive cycle, gestation, and lactation.
The graafiau follicles are microscopic pockets in the ovaries. One a month, under hormonal influence, a follicle matures, ruptures, and expels its ovum into the uterus. Each ovary normally releases an ovum every 56 days, the right and left ovary alternately discharging an ovum every 28 days. The menstrual cycle in most women is therefore 28 days in length.
The fallopian (uterine) tubes are composed of internal mucous, middle muscular, and outer serous coats that are continuous with the layers of the uterus. They serve as ducts of the ovaries, providing a passageway to the uterus. These tubes are in contact with the ovaries, but are not continuous with them. Their funnel-shaped openings, called free openings, are fringed with fingerlike processes that pick up an ovum and draw it into the fallopian tubes, where it is transported to the uterus by peristalsis and gravity. Fertilization of an ovum normally takes place in the fallopian tubes.
The uterus (womb) is a hollow, pear-shaped organ with thick, muscular walls. It is lined with a specialized epitheliums, called endometrium, which undergoes partial destruction about every 28 days in the nonpregnant woman.
The uterus averages 7 cm in length and 5 cm in width. It has three openings: the openings of the fallopian tubes laterally and the opening into the vagina. The parts of the uterus are the body, which is the large upper portion, and the cervix, which is the smaller portion that projects into the upper part of the vagina. The cervical opening into the vagina is called the external os. The walls of the uterus arc highly flexible and are composed of three layers that are continuous with the respective layers of the fallopian tubes.
In addition to being the focal point of the endometrial (menstrual) cycle, the uterus is the site of implantation, growth, and development of the fertilized ovum. The muscular walls of the uterus produce powerful rhythmic contractions that are important in the expulsion of the fetus at birth.
The vagina is a musculomembranous, collapsible tube capable of great distention. It is lined with mucous membrane that extends from the cervix to the vulva. The canal is about 7.5 cm long, and its lining membrane, which is greatly folded, is continuous with the inner lining of the uterus. The vagina is the organ that receives the male sperm during intercourse. It also forms the lower portion of the birth canal, stretching widely during delivery. In addition, it serves as an excretory duct for uterine secretions and menstrual flow.
When females reach puberty, they begin to experience the two recurring female cycles, the ovarian and endometrial.
As previously mentioned, each ovary produces a mature ovum every 56 days. They expel their ova on an alternating basis, approximately one every 28 days. The length of this cycle may vary markedly from individual to individual and between cycles of the same individual. On the first days of menstruation, several ova within the graafian follicles begin to mature, and normally one will be expelled 14 days before the next menstrual flow. This is the ovarian cycle.
The endometrial cycle centers around the periodic development and breakdown of the endometrial lining of the uterus. The first phase of the cycle is the menses, or menstruation. It begins when the endometrial lining starts to slough off from the walls of the uterus, and it is characterized by bleeding from the vagina. This is day 1 of the cycle, and this phase usually lasts through day 5. The time between the last day of the menses and ovulation is known as the postmenstrual phase. It lasts from day 6 through day 13 or 14 and is characterized by proliferation of endometrial cells in the uterus, which develop under the influence of the hormone estrogen. Ovulation is the rupture of a graafian follicle with the release of a mature ovum into the fallopian tubes. It usually occurs on day 14 or 15 of the cycle. The