Menstrual Cycle (PDF)

Dr/ Dorreia AbdAlla Mohamed Zaghloul General Embryology MENSTRUAL (UTERINE) CYCLE Learning objectives After this lecture, student should be able to: Describe the uterus at time of implantation. Know the hormona...

Dr/ Dorreia AbdAlla Mohamed Zaghloul General Embryology MENSTRUAL (UTERINE) CYCLE Learning objectives After this lecture, student should be able to: Describe the uterus at time of implantation. Know the hormonal control of the uterine cycle. Know the middle pain (pain near the middle of the menstrual cycle). Contents: Uterine cycle and its hormonal control. Pain near the middle of the menstrual cycle. STRUCTURE OF UTERINE WALL: The wall of the uterus is formed of 3 layers: 1- Inner mucosal layer called the endometrium. The endometrium has three layers: stratum compactum, stratum spongiosum(whichmakeup the stratum functionalis) & stratum basalis. a-Stratum compactum is the most superficial layer that formed from closely packed cells around necks of endometrial glands. b-Stratum spongiosum contains loose epithelial cells around the bodies of the endometrium glands c-Stratum basalis is the deepest and thinnest layer that lies against the myometrium and contains fundi (blind ends) of the endometrial glands. 2- Middle muscular layer called the myometrium. 3- Outer fibrous layer BLOOD SUPPLY OF UTERUS By uterine arteries that give rise to arcuate arteries, then branch to 1. The straight arteries that supply the basal zone of endometrium. 2. The spiral arteriesthat supply the functional zone of the endometrium. They are connected with the uterine veins through arterio-venous anastomoses. The spiral arteries and veins pass between the uterine glands. 1  Dr/ Dorreia AbdAlla Mohamed Zaghloul General Embryology MENSTRUAL (UTERINE) CYCLE DEFINITION: It is the periodic changes occurring in the endometrium of the uterus in fertile female. These changes are for preparation for the implantation of a fertilized egg. TIME AND DURATION: ♦It occurs for the first time at the age of Menarche in females between 12 to 15 years. ♦Then it occurs regularly in a cycle of about 28 days all over the fertility period of the female till the age of 45 to 50 years (age of menopause). However the cycle can vary from 21-35 days based on the individual female. ♦The menstrual cycle begins by blood flow, followed by regeneration of endometrium and ends by degeneration of the endometrium and its shedding. This is repeated every month under the influence of ovarian hormones (oestrogen& progesterone). PHASES: 3 phases: Menstrual phase, proliferative phase and secretory phase. ♦The menstrual and proliferative phases occur during the follicular phase of the ovarian cycle. ♦The secretory phase is synchronized with the luteal phase of the ovarian cycle. 1. THE MENSTRUAL PHASE (1st -5th days) ♣Menstruation is the first phase of the uterine cycle. The first day of menstruation is considered as the beginning of menstrual cycle. ♣It is called the destructive phase and it lasts for a few days (usually 3 to 5 days, but anywhere from 2 to 7 days is considered normal). ♣The functional layer (the entire compact layer and most of spongy layer of the uterine wall) is sloughed off and discarded during menstruation. ♣The basal layer containing basal ends of endometrial glands remains to undergo regeneration during subsequent proliferative phase of endometrium. ♣The menstrual discharge contains ♦ Unclotted blood form uterine blood vessels, 2  Dr/ Dorreia AbdAlla Mohamed Zaghloul General Embryology ♦ Epithelial cells from the endometrium and ♦Mucous secretions from the degenerated uterine glands. These contents are discharged from the vagina. The average blood loss during menstruation is 35 milliliters with 10–80 ml considered normal. 2. THE PROLIFERATIVE PHASE:(From 5th to 14th day) ♣It follows the menstrual flow, and lasts for about 10 days and ends by the time of ovulation. It is characterized by repair and growth of all the endometrium contents following menstruation. ♣ This phase is also called estrogenic phase because it is controlled by estrogen secreted by theca interna surrounding the follicles. It corresponds to follicular phase of ovarian cycle. ♣The deep basal part of the endometrium are not shedded in mensis. The epithelium forming the blind ends of the glands multiplies and repairs the denuded surface of the epithelium. ♣The uterine glands elongate down into a loose stroma to become straight tubular glands but without secretions inside. ♣The endometrium increases in thickness (more than 3 mm) as stromal cells divide and thus increase in number. ♣Blood vessels are reformed and elongated. They extend between glands but not reach the surface. 3. THE SECRETORY PHASE:15th to the 28th day) ♣It begins after ovulation, takes 14 days and it is under the influence of the progesterone hormone secreted by corpus luteum (called progestational or luteal phase). ♣Endometrial glands become elongated, wide, tortuous, and distended with secretion that is rich in glycogen and lipids. ♣The spiral arteries become much elongated and coiled. They reach the surface mucosa. 3  Dr/ Dorreia AbdAlla Mohamed Zaghloul General Embryology ♣The endometrium becomes thickened, edematous and congested with blood (the thickness is more than 5 mm). ♣By the end of this phase, the endometrium is prepared and ready to receive a fertilized ovum and nourish it or for another menstruation. ♣If pregnancy occurs, the corpus luteum continues to secrete progesterone until the 4thmonth of pregnancy and after that progesterone production is taken over by the placenta. As a result of this mechanism, the thick endometrium is maintained throughout pregnancy. ♣If fertilization does not occur, the corpus luteum starts to degenerate resulting in a sudden drop in the level of progesterone in the blood. This sudden drop of progesterone leads to constriction of the spiral arterioles which leads to ischemia and necrosis of the superficial (functional) layer of the endometrium. After short time the constricted arteries open up resulting in bleeding and shedding of the superficial layer of the endometrium. ♣The last one or two days of the secretory phase is referred to as the premenstrual phase. RELATION OF MENSTRUATION TO OVULATION ♦The cyclic uterine changes are closely related to the ovarian cycles. It is possible to relate the specific phases of the two cycles. ♦The proliferative phase corresponds to the follicular phase of the ovarian cycle. ♦The secretory phase corresponds to the formation and growth of the corpus luteum, and it lasts as long as the corpus luteum remains functioning. ♦The beginning of involution of the corpus luteum marks the onset of menstruation. ♦Ovulation occurs at the end of the proliferative phase. However, there are variations in the timing of ovulation from the 8th to the 20th day of the menstrual cycle (normally at the 14th day). N.B. Amenorrhea means absent menstruation. The most common cause in a normal fertile female is pregnancy. 4  Dr/ Dorreia AbdAlla Mohamed Zaghloul General Embryology (A)Hormonal regulation of changes in the ovary and uterus.(B) Changes in concentration of anterior pituitary and ovarian hormones Pain near the middle of the menstrual cycle Mittelschmerz is the pelvic and lower abdominal pain that some women experience during ovulation. Ovulation generally occurs about midway between menstrual cycles; hence the term mittelschmerz, which comes from the German words for "middle" and "pain.“ The pain of ovulation can range from a mild twinge to severe discomfort and usually lasts from minutes to hours. It is generally felt on one side of the abdomen or pelvis and may vary each month, depending on which ovary is releasing the egg during that cycle. In some cases, a small amount of vaginal 5  Dr/ Dorreia AbdAlla Mohamed Zaghloul General Embryology bleeding or discharge may occur. Some women experience nausea, especially if the pain is severe. What Causes Painful Ovulation? As an egg develops in the ovary, it is surrounded by follicular fluid. During ovulation, the egg and the fluid, as well as some blood, are released from the ovary. While the exact cause of mittelschmerz is unknown, it is believed that the fluid or blood may irritate the lining of the abdominal cavity, causing pain. The pain goes away soon after the egg is released or once the body absorbs the fluid or blood. 6