Life begins in the female reproductive tract. Sperm travels into the fallopian tubes and fertilizes the egg, called an ovum. The fertilized egg begins cell division and travels into the uterus to implant on the inner lining of the uterus, called the endometrium.
Even in the absence of a pregnancy, the female reproductive organs continually change. The appearance of the uterus and ovaries changes in response to changing hormone levels. These changes occur every month and in the same order. This is called the menstrual cycle.
The Uterus
The uterus is located low in the pelvis, midline, and behind the bladder. While its location in the uterus is consistent, the position of the uterus can vary. It is a muscular organ that is approximately eight centimeters long, five centimeters wide, and three centimeters in diameter. The size of the uterus can vary from person to person and may be larger in those who have previously given birth.
The uterus is divided into three anatomical sections. The lower section of the uterus, about one-third of its length, is the cervix. The cervix remains closed during pregnancy and dilates in preparation for childbirth. The upper two-thirds of the uterus is the body. The top portion of the body is called the fundus.
The uterus has three layers. The perimetrium is the outer capsule of the uterus. The myometrium is the thick, middle, muscular layer. The endometrium is the glandular, inner lining that proliferates throughout the menstrual cycle and is shed during menstruation.
The Vagina
The vagina is a tube-like structure that is approximately nine centimeters long. It provides an opening to the outside from the uterine cervix. During menstruation, the endometrial tissue passes through the vaginal canal. Other vaginal secretions also pass to the outside, especially during ovulation or sexual intercourse. The vagina also serves as the birth canal during childbirth.
The Ovaries
The ovaries are located on either side of the uterus, called the adnexa. They vary in size throughout the menstrual cycle and can measure approximately three centimeters in the longest dimension.
During fetal development, several million primordial follicles form. These consist of a primary oocyte surrounded by a layer of follicular cells. They begin the process of meiosis, which is the process of dividing the genetic material of a cell to form two cells containing half of the material. This material is later joined with that of a sperm during fertilization to form the genetic material of a new person.
Many of the primordial follicles deteriorate before birth and many more deteriorate before puberty. With the onset of puberty, oogenesis begins. Oogenesis is the development of a mature egg cell, called an ovum, in preparation for fertilization.
Fallopian Tubes
During ovulation, an ovary releases an egg that is swept into the fallopian tube by projections called fimbriae. The egg travels the length of the tube to the uterus. Cilia are hair-like projections within the fallopian tubes that help move the ovum toward the uterus.
The ovaries, fallopian tubes, uterus, and vagina are all involved in the monthly menstrual cycle. Each month, an ovary and the endometrial lining of the uterus undergo changes during the development of a mature ovum and preparation for pregnancy.
When gynecological problems arise, pelvic ultrasound is often done to examine the uterus and ovaries. It is the preferable method of diagnostic imaging of the female pelvis because it does not use ionizing radiation, which could negatively affect fertility. Using ultrasound, signs of the different phases of the menstrual cycle are seen because of the changing appearances of the ovaries and the uterus.
Reference
Shier, D., Butler, J., Lewis, Ricki. Hole's Human Anatomy & Physiology. New York: McGraw-Hill, 2002.
Diane Ursu - Diane Ursu joined Suite101 as a contributing writer in August 2009 and became a Feature Writer in January 2010. She is a freelance writer ...
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