Menstrual Cycle PDF

MENSTRUAL CYCLE Out Line  Introduction  Endocrine control of menstrual cycle.  Hypothalamic-Pituitary Ovarian Axis  The ovarian cycle  Menstrual cycle and Feedback mechanism  The uterine cycle  Normal and Abnormal menstruation 3/25/1446 2 Introduction  Me...

MENSTRUAL CYCLE Out Line  Introduction  Endocrine control of menstrual cycle.  Hypothalamic-Pituitary Ovarian Axis  The ovarian cycle  Menstrual cycle and Feedback mechanism  The uterine cycle  Normal and Abnormal menstruation 3/25/1446 2 Introduction  Menstrual cycle is the process in which females ripen or release one mature egg and the preparation of the uterus for pregnancy.  The menstrual cycle occurs repeatedly between the age of menarche, until menopause when it ends.  Menarche is the first menstrual period in a female. 3/25/1446 3  The average age of menarche is 12-13 years, but it is considered normal to occur between ages 8 - 16 years.  Factors such as hereditary, diet and overall health can accelerate or delay the menarche. 3/25/1446 4  The length of menstrual cycle varies greatly among women (ranging from 21 to 35 days) with 28 days designated as the average length.  The cessation of menstrual cycles at the end of a woman’s reproductive period is termed menopause.  The average age of menopause is 52 years with range between 45 and 55 being common. Menopause before age 45 is considered premature. 3/25/1446 5 Endocrine control of menstrual cycle  Hypothalamus:  Gonadotrophin releasing hormone (Gn.R.H) or called Luteinizing releasing hormone (LHRH)  Pituitary:  Follicle Stimulating hormone (FSH)  Luteinizing hormone (LH)  Ovary:  Estrogen Progesterone 3/25/1446 6 HYPOTHALAMIC- PITUITARY- OVARIAN AXIS 3/25/1446 7  The hypothalamus: the hypothalamus can either stimulate or inhibit the secretion of the pituitary hormones, and the hypothalamus itself is influenced by other parts of the central nervous system.  From the hypothalamus gonadotropin-releasing hormone (GnRH) passes to the anterior lobe of the pituitary gland, where it causes release of the gonadotropins.  The anterior lobe of the pituitary gland controls the ovarian function by a cyclic secretion of the gonadotropins. The pituitary gonadotropins are: FSH , LH, and Prolactin. 3/25/1446 8  Follicle-stimulating hormone (FSH): FSH begins to be secreted towards the end of the previous menstrual cycle, and rises to a peak at about day 5 of the new cycle, then the level falls slightly before rising to a second peak at about day 12. FSH is responsible for: 1. Ripening & maturation of Graafian follicle of the ovary, 2. Stimulating estrogen secretion by the growing Graafian follicle, 3. In combination with luteinizing hormone, it causes ovulation. 3/25/1446 9  Luteinizing hormone (LH): The level of LH in the blood is fairly constant throughout the cycle except there is a sudden peak at about the mid-cycle (day 12 or 13). LH is responsible for: 1. In combination with FSH, it promotes follicular ripening, 2. LH surge brings rupture of the mature Graafian follicle (ovulation). 3. Turning the ruptured Graafian follicle to a corpus luteum. 4. Stimulating the corpuse luteum to secreate estrogen & progesterone. 3/25/1446 10 Prolactine hormone: The release of FSH& LH, inhibit the release of prolactine. The exact role of prolactine in the control of ovulation is not exactly known, but may be an agent which prevents further ovulation once fertilization has happened. 3/25/1446 11 PHYSIOLOGY OF MENSTRUAL CYCLE The normal menstrual cycle is divided into:  The ovarian cycle a. The follicular phase b. Ovulation c. Luteal phase  The uterine cycle a. Menstruation b. Proliferative phase c. Secretory phase 3/25/1446 12  1. THE OVARIAN CYCLE The changes that occur in the ovary during each cycle can be divided into three stages: A. Follicular phase (day 1 to 13), B. Ovulatory phase (day 14) C. Luteal phase (day 15 to 28). 3/25/1446 13 The ovarian cycle 3/25/1446 14  A.The follicular phase (day 1 to 13)  During this phase, a primordial follicle, under the effect of FSH, changes into a full mature Graafian follicle. In the early part of this phase up to 50 follicle or more start to ripe & mature, but normally only one follicle matures fully and ovulates while the others retrogress.  The empty follicle is known as the courpus luteum, courpus luteum will be then atrophy and becomes the courpus Albicans.  As the Graafian follicle matures its cell produce estrogen in gradually increasing amounts. This rasing estrogen level inhibits the secreation of FSH (Negative feedback). 3/25/1446 15 3/25/1446 16  B. Ovulatory phase (day 14)  Ovulation is the second phase of the ovarian cycle in which a mature ovum is released from the ovarian follicle into the fallopian tube. LH surge, starts around day 12 of the cycle and may last 48 hours. 3/25/1446 17  The mature ovum has a diameter of 20 mm. After being released from the ovary, the ovum is swept into the fallopian tube by the fambria. After about a day, an unfertilized ovum will disintegrate or dissolve in the fallopian tube.  Fertilization by a spermatozoon usually takes place in the ampulla, the widest section of the fallopian tube. A fertilized ovum immediately begins the process of embryogenesis. 3/25/1446 18  C. The luteal phase (day 15 to 28).  This is the final phase of the ovarian cycle. after ovulation The empty follicle is known as the courpus luteum. The cell of the courpus luteum produce estrogen & progesterone.  If the released ovum is not fertilized, the courpus luteum degenerates to corpus albicans, and the level of estrogen & progesteron fall, so ovarian cycle ends, and menstruation starts.  If the released ovum is fertilized (pregnancy), the fertilized ovum will secretes human chorionic gonadotropins (HCG). HCG prevents the degenerates to corpus luteum.  corpus luteum continuous to produce estrogen & progesterone, so menstruation doesn't happen at the expected time which is the early symptom suggesting pregnancy. 3/25/1446 19 Menstrual cycle and Feedback mechanism 3/25/1446 20  Positive and Negative feed-back  Decreased level of estrogen stimulate Hypothalamus to secrete high impulses rate of Gn.R.H (Positive)  Secretion of high impulses of Gn.R.H stimulate anterior pituitary to secrete FSH (Positive)  Increase level of estrogen decrease impulses rate of Gn.R.H (Negative) 3/25/1446 21  2.The uterine cycle a. Menstruation b. Proliferative phase c. Secretory phase 3/25/1446 22  A. Menstruation This is the first phase of the uterine cycle. The flow of menses normally serves as a sign that a woman has not become pregnant. Menstruation is a periodic shedding of endometrium accompanied by loss of blood, It is due to degeneration of corpus luteum. 3/25/1446 23 Menstrual flow  Normal menstruation 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 50- 80 ml.  Color :dark red  Composition: RBCs, cervical mucous, epithelial cells, and bacteria. 3/25/1446 24  B. Proliferative phase  The proliferative phase is the second phase of the uterine cycle when oestrogen causes the endometrium to grow or proliferate. As they mature, the ovarian follicles secret increasing amount of oestradiol.  The oestrogens initiate the formation of a new layer of endometrium in the uterus, The oestrogen also stimulates crypts in the cervix to produce fertile cervical mucus. 3/25/1446 25  Thin endometrium immediately after the menstruation stopped  The red lines represents blood vessels.  The purple inner line represents the cells covering the endometrium 3/25/1446 26  The endometrium about one week later (12-14 days) since the onset of menstruation. This is just before ovulation  The endometrium is now much thicker (usually more than 6 mm) 3/25/1446 27 The endometrium a few days after ovulation. Glands develop and the blood vessels become more prominent  The protein content (purple blotches) in the endometrium increases. 3/25/1446 28 Blood starts leaking out The bleeding stops and a new cycle begins Bleeding 3/25/1446 29  C. Secretory phase This is the final phase of the uterine cycle. During the secretory phase, the corpus luteum produces progesterone which plays a vital role in making the endometrium receptive to implantation of the blastocyst and supportive of the early pregnancy by increasing blood flow and uterine secretions and reducing the contractility of the smooth muscle in the uterus. 3/25/1446 30 3/25/1446 31 3/25/1446 32 3/25/1446 33 3/25/1446 34 3/25/1446 35 3/25/1446 36