FEMALE REPRODUCTIVE SYSTEM Objectives By the end if this lesson you should be able to: 1. Describe the role of the reproductive system 2. Describe the structural organization of the female reproductive system 3. Describe the gross anatomy of the , , fallopian tubes, and the perineum Role of the Female Reproductive System The female reproductive system produces gametes that may unite with a male gamete to form the first cell of the offspring. Provides protection and nutrition to the developing offspring. Structural Plan of the Female Reproductive System Reproductive organs can be classified as essential organs and accessory organs, depending on how directly they are involved in producing offspring. The essential organs of reproduction in women, the gonads, are the paired ovaries. The female gametes, or ova, are produced by the ovaries. Cont,d

The accessory organs of reproduction in women consist of the following structures: • Uterine tubes, uterus, and vagina. Along with the ovaries, these organs are sometimes collectively called the “internal genitalia.” • The , or external reproductive organs. These organs are often called the “external genitalia.” • Additional sex glands, including the mammary glands. . OVARIES Location of the ovaries The ovaries are nodular glands located on each side of the uterus, below and behind the uterine tubes, weigh approximately 3 g. Microscopic structure of the ovaries is covered by squamous-shaped epithelial cells called the germinal epithelium. Ovarian follicles contain the developing female sex Cells. Ovum — an oocyte released from the ovary. Microscopic Structure of the Ovaries

Ovary consists of two major layers of tissue—an outer cortex and inner medulla. Below the epithelial cells is a tough gray-white layer called the tunica albuginea that covers the ovarian cortex. Embedded in the connective tissue matrix of the cortex are thousands of microscopic structures called ovarian follicles which contain the immature female sex cells, or oocytes, and their surrounding cells. The ovarian medulla contains supportive connective tissue cells, blood vessels, nerves, and lymphatics. Functions of the ovaries 1. Ovaries produce ova — the female gametes 2. Oogenesis — process that results in formation of a mature egg 3. The ovaries are endocrine organs that secrete the female sex hormones (estrogens and progesterone) UTERUS Structure of the uterus  The uterus is pear shaped and has two main parts—the and the body.  The wall of the uterus is composed of three layers—the inner , the middle , and the outer incomplete layer of parietal peritoneum.  Cavities of the uterus—the cavities are small because of the thickness of the uterine walls.  The body cavity's apex constitutes the internal os and opens into the , which is constricted at its lower end and forms the external os that opens into the vagina.  The blood to the uterus is supplied by uterine arteries. Location of the uterus 1. The uterus is located in the pelvic cavity between the urinary bladder and the rectum. 2. The position of the uterus is altered by age, pregnancy, and distention of related pelvic viscera. 3. The uterus descends, between birth and puberty, from the lower abdomen to the true pelvis. 4. The uterus begins to decrease in size at menopause. Position of the uterus 1.Body lies flexed over the bladder. 2.Cervix points downward and backward, joining the vagina at a right angle. 3. Several hold the uterus in place but allow some movement. Functions of the uterus 1.Permits sperm to ascend toward the uterine tubes. 2. If conception occurs, an offspring develops in the uterus a. The embryo is supplied with nutrients by endometrial glands until the production of the placenta. b. The placenta is an organ that permits the exchange of materials between the mother's blood and the fetal blood but keeps the two circulations separate. Cont,d c. Myometrial contractions occur during labor and help push the offspring out of the mother's body. 3. If conception does not occur, outer layers of endometrium are shed during menstruation a. Menstruation is a cyclical event that allows the endometrium to renew itself. UTERINE TUBES  Uterine tubes are also called fallopian tubes, or oviducts  Uterine tubes are attached to the uterus at its upper outer angles and extend upward and outward toward the sides of the pelvis. Structure of the uterine tubes 1. Uterine tubes consist of mucous, smooth muscle, and serous lining. 2. Mucosal lining is directly continuous with the peritoneum lining of the pelvic cavity. a. Tubal mucosa is continuous with that of the vagina and uterus, which means it may become infected with organisms introduced into the vagina. 3. Each uterine tube has three divisions: isthmus, ampulla, and Infundibulum. . Function of the uterine tubes

Uterine tubes serve as transport channels for ova. The site of fertilization at the ampulla. VAGINA The vagina is a tubular organ located between the rectum, , and bladder Structure of the vagina 1. The vagina is a collapsible tube capable of distention, composed of smooth muscle, and lined with mucous membrane arranged in rugae. 2. The anterior wall is shorter than the posterior wall because the cervix protrudes into its uppermost portion. 3. —a mucous membrane that typically forms a border around the vagina. It is normally incomplete to allow for passage of menstrual flow. Functions of the vagina . The lining of the vagina lubricates and stimulates the penis during sexual intercourse and acts as a receptacle for semen. . The vagina transports tissue and blood shed during menstruation to the exterior. . Provides an elastic passageway through which the baby passes during childbirth. VULVA The vulva consists of the female external genitalia: Mon pubis, majora, , , urinary meatus, vaginal orifice, and greater vestibular glands. Functions of the vulva 1.Mon pubis, Labia protect the clitoris and Vestibular glands. 2.The clitoris contains sensory receptors that send information to the sexual response area of the brain. 3.The vaginal orifice is the boundary between the internal and external genitalia. . BREASTS

Location and size 1. The breasts lie over the pectoral muscles. 2. Estrogens and progesterone control breast development. 3. Breast size is determined by the amount of fat around glandular tissue. Function of the breasts 1. Lactation Mechanism of lactation a. The ovarian hormones make the breasts structurally ready to produce milk. b. Shedding of the placenta results in a decrease of estrogens and thus stimulates Prolactin. c. Prolactin stimulates production of milk and oxytocin stimulates the release of milk. . FEMALE REPRODUCTIVE CYCLES

The female reproductive system has many cyclical changes that start with the beginning of menses. 1. Ovarian cycle 2. Menstrual cycle (endometrial cycle) 3. Myometrial phase 4. Gonadotropic cycle Menstrual cycle Cont,d

• It is commonly divided into three phases: the follicular phase, ovulation, and the luteal phase; although some sources use a different set of phases: menstruation, proliferative phase, and secretory phase. Menstrual cycle.

• Stimulated by gradually increasing amounts of estrogen in the follicular phase, discharges of blood (menses) slow then stop, and the lining of the uterus thickens. Follicles in the ovary begin developing under the influence of a complex interplay of hormones. Approximately mid-cycle, 24–36 hours after the Luteinizing Hormone (LH) surges, the dominant follicle releases an ovum, or egg in an event called ovulation. After ovulation, the egg only lives for 24 hours or less without fertilization while the remains of the dominant follicle in the ovary become a ; this body has a primary function of producing large amounts of progesterone. Cont,d • Under the influence of progesterone, the endometrium (uterine lining) changes to prepare for potential implantation of an embryo to establish a pregnancy. If implantation does not occur within approximately two weeks, the corpus luteum will involute, causing sharp drops in levels of both progesterone and estrogen. These hormone drops cause the uterus to shed its lining and egg in a process termed menstruation. • In the menstrual cycle, changes occur in the female reproductive system as well as other systems (which lead to breast tenderness or mood changes, for example). Menstruation • Menstruation is also called menstrual bleeding, menses, catamenia or a period. • High circulating levels of progesterone and estrogen prevent maturation and the release of another ovum should the pregnancy occur. • Eumenorrhea denotes normal, regular menstruation that lasts for a few days (usually 3 to 5 days, but anywhere from 2 to 7 days is considered normal). The average blood loss during menstruation is 35 milliliters with 10–80 ml considered normal Follicular phase

• This phase is also called the proliferative phase. • Through the influence of a rise in follicle stimulating hormone (FSH) during the first days of the cycle, a few ovarian follicles are stimulated. • As they mature, the follicles secrete increasing amounts of estrogen. The estrogens initiate the formation of a new layer of endometrium in the uterus, identified as the proliferative endometrium. The estrogen also stimulates crypts in the cervix to produce fertile cervical mucus, which may be noticed by women practicing fertility awareness. Ovulation • During the follicular phase, estrogen suppresses production of luteinizing hormone (LH) from the anterior pituitary gland. When the egg has nearly matured, levels of estrogen reach a threshold above which they stimulate production of LH. In the average cycle this LH surge starts around cycle day 12 and may last 48 hours. • The release of LH matures the egg and weakens the wall of the follicle in the ovary, causing the fully developed follicle to release its secondary oocyte. The secondary oocyte promptly matures into an ootid and then becomes a mature ovum. • After being released from the ovary and into the peritoneal space, the egg is swept into the by the fimbria. After about a day, an unfertilized egg will disintegrate or dissolve in the fallopian tube. Cont,d

• Fertilization by a spermatozoon, when it occurs, usually takes place in the ampulla, the widest section of the fallopian tubes. A fertilized egg immediately begins the process of embryogenesis, or development. The developing embryo takes about three days to reach the uterus and another three days to implant into the endometrium. It has usually reached the blastocyst stage at the time of implantation. Luteal phase  The luteal phase is also called the secretory phase. An important role is played by the corpus luteum, the solid body formed in an ovary after the egg has been released from the ovary into the fallopian tube.  This body continues to grow for some time after ovulation and produces significant amounts of hormones, particularly progesterone.  Progesterone plays a vital role in making the endometrium receptive to implantation of the blastocyst and supportive of the early pregnancy; it also has the side effect of raising the woman's basal body temperature. There is a noted secretion of prolactin towards the end of the secretory phase. Cont,d  After ovulation, the pituitary hormones FSH and LH cause the remaining parts of the dominant follicle to transform into the corpus luteum, which produces progesterone. The increased progesterone in the adrenals starts to induce the production of estrogen. The hormones produced by the corpus luteum also suppress production of the FSH and LH that the corpus luteum needs to maintain itself. Consequently, the level of FSH and LH fall quickly over time, and the corpus luteum subsequently atrophies. Cont,d Falling levels of progesterone trigger menstruation and the beginning of the next cycle. From the time of ovulation until progesterone withdrawal has caused menstruation to begin, the process typically takes about two weeks, with 14 days considered normal. The loss of the corpus luteum can be prevented by fertilization of the egg; the resulting embryo produces human chorionic gonadotropin (hCG), which is very similar to LH and which can preserve the corpus luteum. Importance of the female reproductive cycles 1.The ovarian cycle's primary function is to produce ova at regular intervals. a. Its secondary function is to regulate the endometrial cycle through estrogen and progesterone. 2.The function of the endometrial cycle is to make the uterus suitable for implantation of a new offspring. Cont,d

3.The cyclical nature of the reproductive system and the fact that fertilization will occur within 24 hours after ovulation means that a woman is only fertile a few days of each month. N.B. Menstrual flow begins at puberty, and the menstrual cycle continues for about 3 decades.