FEMALE REPRODUCTIVE SYSTEM

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1 FEMALE REPRODUCTIVE SYSTEM The External Genitalia ( page 925 ) Vulva The female external genitalia are known collectively as the vulva or pudendum. Mons pubis a rounded elevation of adipose tissue over the pubic symphysis and covered by pubic hairs Labia majora (singular = labium majorum) two large folds of skin, also covered by pubic hairs, that extend back from the mons pubis on each side enclose and protect the other external reproductive organs Labia minora (singular = labium minorum) two small, flattened, hairless folds between the labia majora deep pink in color due to a rich blood supply merge anteriorly to form the prepuce (hood) of the clitoris Clitoris glans clitoris - a small mass visible externally at the anterior margin of the vestibule - has a rich supply of nerve endings and is extremely sensitive - is enclosed by a hoodlike covering called the prepuce, which is formed by extensions of the labia minora where they merge anteriorly body of the clitoris - the portion embedded internally - the clitoris contains two columns of erectile tissue, each called a corpus cavernosum, which become engorged during sexual excitement. The clitoris is homologous to the penis, meaning that both develop from the same embryonic structure. Vestibule the vestibule is a central space bounded by what? the vestibule contains the: - urethral opening - vaginal opening posterior to the urethral opening may be covered to varying degrees by a thin membrane called the hymen openings of vestibular glands that produce a mucous secretion for lubrication Perineum The clinical perineum is the area between the vaginal orifice and the anus (It is important in obstetrics because it may be torn during childbirth. To prevent damage and ensure proper healing, a surgical incision, called an episiotomy, is often made in the perineum to enlarge the vaginal opening for delivery.) Chapter 26 The Reproductive System Part II Female 1

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3 The Mammary Glands (Page 925) define lactation: the mammary glands are modified sweat glands in the breasts consist of lobes with adipose tissue in between (see Fig ) each lobe has several lobules with milk-secreting glands milk is transported through ducts ending at the nipple the darker pigmented area around the nipple is called the areola Ovaries ( back to page 915) describe the appearance and location of the ovaries: list the first two of the three numbered functions of the ovaries given on p. 915: the tunica albuginea is the capsule of CT that surrounds each ovary ovarian follicles are in the cortex of the ovary; each consists of an oocyte surrounded by cells called follicular cells Oogenesis ( we will get back to most of this later!) define oogenesis: when does it begin and when does it end? examine Fig and my diagram on the next page: is an oogonium haploid or diploid? is a primary oocyte haploid or diploid? is an ovum (egg) haploid or diploid? is a zygote haploid or diploid? Chapter 26 The Reproductive System Part II Female 3

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5 The Uterine Tubes ( page 919) what are the uterine tubes also called? they are paired; approx. 5 inches long; they convey oocytes from the ovaries to the uterus each has an opening into the peritoneal cavity near the ovaries and passes medially to the uterus to open into the uterine cavity Name the three segments of each uterine tube: the funnel-shaped open end near the ovary - is fringed with fingerlike processes called fimbriae that extend from the free margin of the infundibulum. Their movement creates currents in the peritoneal fluid that carry the oocyte into the uterine tube following ovulation. - the middle segment - this short segment is connected to what? Histology of the Uterine Tubes does the epithelium have cilia? oocyte transport involves a combination of what? The Uterus list the functions of the uterus: the uterus is the size and shape of what? Chapter 26 The Reproductive System Part II Female 5

6 Internal Anatomy of the Uterus there are two regions of the uterus: 1. body - the large main portion the cavity within the body of the uterus is the uterine cavity 2. cervix - the more narrow, inferior part of the uterus that opens into the vagina the cervical canal is the cavity/passageway within the cervix The Uterine Wall there are three layers of the wall of the uterus (see Fig ): endometrium - consists of an epithelium and underlying, well-vascularized connective tissue - the epithelium forms glands called endometrial glands - the endometrium is divided into: 1) functional zone - the inner layer closer to the uterine cavity; is shed during menstruation 2) basilar zone - the deeper layer; does not shed and gives rise to a new functional layer during each menstrual cycle myometrium - the middle layer formed by smooth muscle perimetrium - the thin outer layer The Vagina ( p. 924) describe the vagina: what are its three major functions? Hormones and the Female Reproductive Cycle GnRH = gonadotropin-releasing hormone produced in the hypothalamus of the brain stimulates the release of gonadotropins (LH and FSH) from the anterior pituitary gonadotropins -produced by the cells of the anterior pituitary: FSH = follicle-stimulating hormone initiates growth of ovarian follicles and stimulates ovarian follicles to secrete estrogens Chapter 26 The Reproductive System Part II Female 6

7 LH = luteinizing hormone stimulates further development of ovarian follicles and stimulates the ovarian follicles to secrete estrogens triggers ovulation and stimulates the cells of the remnants of the ruptured follicle in the ovary to form the corpus luteum stimulates the cells of the corpus luteum to produce progesterone estrogens secreted by ovarian follicles list the first 3 functions of estrogens in Table 26-1 on p. 932: progesterone secreted mainly by cells of the corpus luteum influences the endometrium mainly during the luteal phase to continue building up and maintaining the endometrium Phases of the Female Reproductive Cycle During the female reproductive cycle (menstrual cycle), cyclic changes occur in the ovaries and uterus. Examine the timeline below, which uses an average of 28 days for the length of a menstrual cycle (although it typically varies from 24 to 35 days or so!). days with reference to the ovary: with reference to the uterus: ovulation Follicular Phase (Preovulatory Phase) Luteal Phase (Postovulatory Phase) Menstrual Proliferative Phase Secretory Phase Phase Here is my outline of the female reproductive cycle on the next pages; we will follow what happens in the ovaries during the menstrual cycle, then we will follow the changes that occur in the uterus; we will do drawings in class to help show all! Ready.? Chapter 26 The Reproductive System Part II Female 7

8 EVENTS IN THE OVARIES First, review oogenesis (page 16 of these notes). Before puberty, the ovary contains numerous primordial follicles that each contain a primary oocyte arrested in meiosis one. Follicular Phase (Preovulatory Phase) GnRH stimulates the anterior pituitary to release FSH and LH under the influence of mainly FSH, several primordial follicles begin to develop further; most die off (called atretic follicles) near the end of the follicular phase, typically only one follicle develops into a mature (Graafian) follicle about 4 hours before ovulation, the primary oocyte in the mature follicle completes meiosis I and becomes a secondary oocyte arrested in meiosis II; it will NOT complete meiosis II and become a haploid egg unless a sperm enters its cytoplasm just before fertilization! the follicle cells of the developing follicles secrete estrogens (that effect the endometrium of the uterus) Ovulation usually occurs on day 14 of a menstrual cycle ovulation is due to a large surge in blood levels of LH and a smaller surge in FSH released by the anterior pituitary this causes the rupture of the mature (Graafian) follicle and the release of the secondary oocyte (along with the zona pellucida and corona radiate) from the surface of the ovary (the ovulated oocyte and surrounding structures are swept into the uterine tube; we will follow what happens to them later! Luteal Phase (Postovulatory Phase) after ovulation, the remnant of the empty, collapsed follicle in the ovary differentiates into a corpus luteum (CL) under the influence of LH the CL secretes progesterone and estrogens (that effect the endometrium of the uterus) if the ovulated secondary oocyte is not fertilized, the CL in the ovary begins to degenerate about 10 to 12 days after ovulation (day 24 to 26 of the menstrual cycle) blood levels of estrogen and progesterone decrease and fail to maintain the endometrium menstruation occurs if fertilization does take place, the CL in the ovary persists due to the production of HCG (human chorionic gonadotropin) produced by cells of the trophoblast (that become the chorion) about 8 days after fertilization becomes the CL of pregnancy and produces Chapter 26 The Reproductive System Part II Female 8

9 higher levels of progesterone and estrogens this maintains the endometrium and brings about many of the changes that occur in pregnancy EVENTS IN THE UTERUS Menstrual Phase (Menstruation) occurs during the first 3 to 5 days of a menstrual cycle if the ovulated secondary oocyte is not fertilized (more often than not that is the case!), the CL in the ovary begins to degenerate (it regresses ) about 10 to 12 days after ovulation (day 24 to 26 of the menstrual cycle) blood levels of estrogen and progesterone decrease low blood levels of these hormones fail to maintain the endometrium of the uterus, and the stratum functionalis degenerates, breaks up and sloughs away menstrual flow contains: degenerated endometrial cells blood from vessels of the endometrium mucus from the cervix and vagina the beginning of menstrual flow marks the beginning (day 1) of a new menstrual cycle at the end of the menstrual phase, only the thin stratum basalis of the endometrium remains Proliferative Phase after menstruation, the endometrium is very thin, with only the stratum basalis remaining increasing blood levels of estrogen produced by cells of the developing follicles in the ovaries stimulate the stratum basalis to produce a new stratum functionalis, and the endometrium thickens ( builds up ): - the endometrium glands develop - blood vessels in the stroma lengthen Secretory Phase the endometrium builds up further, due to the stimulation of progesterone and estrogens produced by the corpus luteum in the ovary: - the endometrial glands develop further; they lengthen, become tortuous, and become swollen with a nourishing secretion of lipids and glycogen - blood vessels in the stroma lengthen further Chapter 26 The Reproductive System Part II Female 9 The End!