FEMALE SEXUAL CYCLES 9 AUGUST 2024.ppt

MENSTURAL CYCLE EN OBIKILI  The female reproductive or sexual cycles are the monthly changes that occur in the ovaries, uterus, uterine tubes, the vagina and the breasts. They prepare the female reproductive system for potential pregnancy.  The cycles are under the i...

MENSTURAL CYCLE EN OBIKILI  The female reproductive or sexual cycles are the monthly changes that occur in the ovaries, uterus, uterine tubes, the vagina and the breasts. They prepare the female reproductive system for potential pregnancy.  The cycles are under the influence of hormones secreted by the hypothalamus and the pituitary gland. The hypothalamus secretes gonadotropin-releasing hormone (GRH) which stimulates the anterior pituitary gland to produce two hormones that act on the ovaries.  The two hormones produced by the anterior pituitary glands are the follicle stimulating hormone (FSH) and the luteinizing hormone (LH). The follicle stimulating hormone stimulates the growth of the ovarian follicles, and the production of estrogen by the follicular cells.  The luteinizing hormone induces or triggers ovulation, and stimulates the follicular cells and corpus luteum to produce progesterone. The FSH and LH stimulate changes that occur in the endometrium. The cyclic changes that occur in the ovaries are referred to as the ovarian cycle. They include maturation of ovarian follicles, ovulation, and formation of corpus luteum.  Menstrual or uterine or endometrial cycle is the monthly cyclic changes that occur in the uterus particularly the endometrium during the reproductive life of a female. It prepares the uterus for a potential pregnancy. It is called menstrual cycle because if fertilization does not occur, it ends in menstruation or menses. It is also called the endometrial cycle because the changes are most marked in the endometrium. The menstrual cycle on the average lasts for 28 ± 7 days. It may be as short as 21 days or as long as 35 days or more. In about 90 % of healthy women the range is 23 -35 days  The duration of the menstrual cycle varies from person to person. In the same person, it can change over time and with age. The menstrual cycle starts at puberty (11- 13 years) and ceases at menopause (45-55 years). Menarche is the first menstruation in the life of a female Menopause is the cessation of menstruation.  The wall of the uterus consists of three layers: a)Endometrium: mucosa or inner lining of the uterus b)Myometrium: a thick layer of smooth muscle c)Perimetrium: Serosa or peritoneal covering of the uterus  The endometrium when it is fully formed consists of three layers: i) Stratum compactum or compact layer ii) Stratum spongiosum or spongy layer iii) Stratum basale or basal layer  The menstrual cycle may be divided into 3 or 4 phases. The phases overlap because the changes that occur during the cycle are continuous. a) Menstrual phase b) Proliferative phase c) Secretary phase  Ovulation may be also be considered as a phase. If the menstrual cycle is considered in relation to the ovarian cycle, it has two phases: follicular and luteal phases The follicular phase begins on the first day of the menstruation and lasts until ovulation.  The changes during the menstrual phase and most of the proliferative phase are under the influence of estrogens produced by the developing ovarian follicles. This phase is referred to as follicular phase of the menstrual cycle.  During the follicular phase, the ovarian follicles grow and one of them reaches maturity and releases an ovum. The follicular phase is the longest phase of the menstrual cycle. It lasts for 14 to 21 days. The end of the follicular phase is the most fertile period for pregnancy  The luteal or pregestational phase begins after ovulation and ends with menstruation. It has an ischaemic phase at its end. It is under the influence of progesterone produced by the corpus luteum. Phases of the menstrual cycle Changes in the uterine mucosa in relation to the cyclic changes in the ovaries. Ref. Sadler  Menstrual phase. The first day of the menstrual phase is the first day of the menstrual cycle. The phase lasts for 3-7 days. If pregnancy does not occur, the corpus luteum degenerates. The endometrium is deprived of estrogen and progesterone.  Withdrawal or drop in the estrogen and progesterone levels leads to the onset of menstrual bleeding. The spiral arteries which supply the spongy and compact layers of the endometrium constrict and blood supply to these layers are cut off. This results in ishaemia, necrosis and fragmentation of endometrial tissue.  After a period of time, the spiral arteries suddenly dilate. Blood flows through the damaged walls of the arteries. There is bleeding into the uterine cavity and shedding of the compact and spongy layers of the endometrium. The basal layer is not shedded because it is supplied by the basal arteries and not by the spiral arteries. The basal arteries do not undergo spam.  Composition of menstrual flow: a) Blood b) Degenerated epithelium and stroma of the compact and spongy layers of the endometrium c) Secretions of the uterine glands. These secretions are rich in lipids, glycogen and mucopolysaccharides.  About 35-45 mls of blood is lost during menstruation. The range is 5-80 mls.  Proliferative phase It last for about 9 days (range 6- 14 days). It coincides with the growth of the ovarian follicles and is under the influence of estrogen produced by the ovarian follicles. Ovarian and uterine cycles  After menstruation the endometrium is thin. During the proliferative phase the endometrium increases progressively in thickness and becomes more vascular. The glands increase in length and dilate. The epithelium of the glands changes from cuboidal to columnar.  By the end of the proliferative phase the endometrium has increased threefold in thickness and has 3 layers: Compact, spongy and basal layers. The compact and spongy layers are the functional layer  Luteal or secretory or pregestational phase It begins after ovulation and is constant in duration and lasts for 14 days. It coincides with the formation and growth of the corpus luteum and is under the influence of progesterone produced by the corpus luteum. During this phase, the endometrium reaches its maximum thickness  The glands become tortuous and distended with fluid which is rich in glycogen, mucopolysaccharides and lipids. The stroma cells enlarge and become densely packed. The arteries become coiled and congested and are referred to as spiral arteries. They supply the compact and spongy layers  If pregnancy does not occur, the corpus luteum degenerates. The estrogen and progesterone falls and the endometrium enters ischemic phase. FSH, LH, estrogen and progesterone levels during the menstrual cycle  The level of the estrogen rises to a peak two days before ovulation. This leads to a surge or sudden increase in the level of LH 24-36 hours before ovulation. Ovulation occurs because of this surge in LH. Follicle stimulating hormone reaches a peak about 24 hours before ovulation Progesterone level increases and  If fertilization does not take place, the granulosa cells secrete a protein called inhibin which acts on the anterior pituitary gland and inhibits the secretion of gonadotropins. This results in the regression of the corpus luteum. Consequently there is a fall in the levels of estrogen and progesterone. This fall triggers the constriction of the spiral arteries and the onset of menstruation.  If fertilization occurs the corpus luteum does not regress and it continues to grow and secrete progesterone and estrogen.  SIGNS OF OVULATION 1. Body temperature. The body temperature has a biphasic variation during the menstrual cycle. At about the mid cycle, there is a sudden fall in the body temperature. The fall is followed by a rise some hours after ovulation. This rise persists until 2 days before Morning temperature of a woman during the menstrual cycle. There is a fall in temperature at ovulation. Thereafter it rises  The rise in body temperature is due to the metabolic effect of progesterone 2. Cervical mucus. It becomes profuse, thin, clear and viscid just before ovulation. Following ovulation it becomes scanty, thick and more cellular. 3. Some women may have slight uterine bleeding at the middle of menstrual cycle.  4. Mittelschmerz pains. In some women, at ovulation, there is slight bleeding into the peritoneal cavity. There is a sudden constant pain in the lower abdomen. The pain is due to the irritation of the peritoneum by the blood or follicular fluid that is released during ovulation. 5. There is increased ferning or epithelial cornification of vaginal smears at the time of ovulation.  The sexual cycles are controlled by the hypothalamus. The gonadotropin-releasing hormone (GnRH) produced by the hypothalamus acts on the cells of the anterior pituitary gland which secrete follicle stimulating hormone (FSH) and luteinizing hormone (LH). The hormones stimulate and control the cyclic changes in the ovary.  Anovulatory menstrual cycle: Anovulatory menstrual cycle is a menstrual cycle in which there is no ovulation and consequently no luteal phase. The ovary does not produce a mature ovum. There are minimal changes in the endometrium. The secretory phase is not formed. The proliferative phase continues until menstruation begins. The duration of the cycle may vary from the normal menstrual cycle. Calculation of Expected Date of Delivery (EDD) If a woman’s last menstrual period (LMP) is known, her expected date of delivery (EDD) can be calculated by adding 7 to the day and 9 to the month. E.g., If the LMP is 8 February 2024, the EDD is 15 November 2024. If the LMP is 28 March 2024 , the EDD is 4 January 2025.