Physiology of menstruation

Only humans, closely related primates, some species of bats, and elephant shrews visibly menstruate. The processes that drive the monthly maturation, slough, and renewal of the endometrium that results in menses are ultimately orchestrated by a complex interaction of hormones, tissues, and molecular signaling, all designed to ensure the possibility of securing a pregnancy should a timely mating occur. Menstrual pain and excessive menstrual bleeding are both extremes of a normal continuum. Understanding their development requires a familiarity with the processes that create the normal menstrual cycle. This discussion will focus primarily on the uterus, leaving many of nuances of the complex interactions of the hypothalamus, pituitary, and ovary to others. Keywords • Physiology • Pituitary • Hypothalamus • Ovary • Follicle stimulating hormone (FSH) • Luteinizing hormone (LH) • Endometrium • Prostaglandin • Ovulation • Anatomy • For excellent images and an overview of the anatomy of the female reproductive organs: • Smith RP, Turek P. The Netter Collection of medical illustrations: reproductive system. Philadelphia, PA: Elsevier—Global Medicine Group; 2011. • For a review of the structure and functions of FSH and LH: • Padmanabhan V, Karsch FJ, Lee JS. Hypothalamic, pituitary and gonadal regulation of FSH. Reprod Suppl. 2002;59:67–82. • Pierce JG, Parsons TF. Glycoprotein hormones: structure and function. Annu Rev Biochem. 1981; 50(1):465–95. • An excellent overview of the ro...

The purpose of the monthly menstrual cycle is to prepare for pregnancy. Menstrual cycles vary in length and intensity. During each menstrual cycle, an egg develops and is released from the The menstrual cycle is divided into four phases: • menstrual phase • follicular phase • ovulation phase • luteal phase The length of each phase can vary and change over time. The menstrual phase is the first stage of the menstrual cycle. It’s also when you get your period. This phase starts when an egg from the previous cycle isn’t fertilized. Because pregnancy hasn’t taken place, levels of the hormones estrogen and progesterone drop. The thickened lining of your uterus, which would support a pregnancy, is no longer needed, so it sheds through your vagina. During your period, you release a combination of blood, mucus, and tissue from your uterus. You may have period symptoms like these: • cramps (try these • tender breasts • bloating • mood swings • irritability • headaches • tiredness • low back pain The follicular phase starts on the first day of your period (so there is some overlap with the menstrual phase) and ends when you ovulate. It starts when the hypothalamus signals your pituitary gland to release Only the healthiest egg will eventually mature. (On rare occasions, a female may have two eggs mature.) The rest of the follicles will be reabsorbed into your body. The maturing follicle sets off a surge in estrogen that thickens the lining of your uterus. This creates a nutrient-ric...

The day count for menstrual cycle begins on the first day of menstruation when blood starts to come out of the vagina. In this section, the length of menstrual cycle has been assumed to be 28 days (which is the average among women). The entire duration of a Menstrual cycle can be divided into four main phases: • Menstrual phase (From day 1 to 5) • Follicular phase (From day 1 to 13) • Ovulation phase (Day 14) • Luteal phase (From day 15 to 28) Menstrual phase (day 1-5) Menstrual phase begins on the first day of menstruation and lasts till the 5th day of the menstrual cycle. The following events occur during this phase: • The uterus sheds its inner lining of soft tissue and blood vessels which exits the body from the vagina in the form of menstrual fluid. • Blood loss of 10 ml to 80 ml is considered normal. • You may experience abdominal cramps. These cramps are caused by the contraction of the uterine and the abdominal muscles to expel the menstrual fluid. Follicular phase (day 1-13) This phase also begins on the first day of menstruation, but it lasts till the 13th day of the menstrual cycle. The following events occur during this phase: • The pituitary gland secretes a hormone that stimulates the egg cells in the ovaries to grow. • One of these egg cells begins to mature in a sac-like-structure called follicle. It takes 13 days for the egg cell to reach maturity. • While the egg cell matures, its follicle secretes a hormone that stimulates the uterus to develop a lining ...

Do you know when your last menstrual period began or how long it lasted? If not, it might be time to start paying attention. Keeping track of your menstrual cycles can help you understand what's typical for you. You also can record your ovulation and find important changes — such as a missed period or menstrual bleeding that isn't typical. While irregularities in your period usually aren't serious, sometimes they are caused by other health problems. The menstrual cycle is the monthly series of changes the body goes through to prepare for pregnancy. Each month, one of the ovaries releases an egg. This is called ovulation. Hormonal changes at this time get the uterus ready for pregnancy. If the released egg isn't fertilized during ovulation, the lining of the uterus sheds through the vagina. This is a menstrual period. The menstrual cycle is counted from the first day of one period to the first day of the next. The cycle isn't the same for everyone. Menstrual bleeding might happen every 21 to 35 days and last 2 to 7 days. For the first few years after menstruation begins, long cycles are common. However, menstrual cycles tend to shorten and become more regular as people age. Your menstrual cycle might be regular — about the same length every month — or somewhat irregular. Your period might be light or heavy, painful or pain-free, long or short, and still be considered typical. Within a broad range, "typical" is what's typical for you. Certain kinds of birth control, such as ...

What is the menstrual cycle? The menstrual cycle is a complex series of physiological changes that occur in women of reproductive age on a monthly basis. The end result is the production of an ovum and thickening of the endometrium to allow for implantation, should fertilisation should occur. The menstrual cycle is orchestrated by the endocrine system through the complex interaction of the hypothalamus, pituitary and gonads ( You might also be interested in our over 1000 flashcards that cover key medical topics. Hypothalamic-pituitary-gonadal axis (HPG Axis) 1. The hypothalamus secretes GnRH. 2. GnRH travels down to the anterior pituitary gland and binds to receptors on the gland. 3. This promotes the release of LH (luteinizing hormone ) and FSH (follicle-stimulating hormone ). 4. LH and FSH travel in the bloodstream to the ovaries. 5. When LH and FSH bind to the ovaries they stimulate the production of oestrogen and inhibin: • Oestrogen helps to regulate the menstrual cycle and is an essential component in many other physiological processes • Inhibin causes inhibition of activin which is usually responsible for stimulating GnRH production • FSH also stimulates the development of ovarian follicles, with the follicle most sensitive to FSH becoming the dominant Graafian follicle • LH causes the Graafian follicle to change into the corpus luteum, which begins to produce progesterone • Progesterone stimulates the endometrium to become receptive to the implantation of a fertili...

menstrual cycle, recurring fluctuations in Phases of the menstrual cycle The normal human menstrual cycle is 28 days, but no woman is always precisely regular, and cycles as short as 21 days or as long as 40 days are not abnormal. It is customary to call the first day of the menstrual period the first day of the cycle, although menstruation is the end rather than the beginning of a process. On this basis the cycle is described as starting with about five days of menstruation, followed by a proliferative phase that lasts to about the 14th day, and then a secretory phase that lasts until the next menstruation. The external Facts You Should Know: The Human Body Quiz At the end of menstruation, just at the beginning of the proliferative phase, the endometrium is thin, with short, straight glands, and the see At about mid-cycle ovulation occurs: The ovum is luteus, “saffron-yellow.” The altered follicle is called When the ovum dies, the corpus luteum degenerates and ceases to produce hormones. On the withdrawal of estrogens and After menstruation the endometrium regenerates from the residual basal layer during the proliferative phase of the next cycle. Get a Britannica Premium subscription and gain access to exclusive content. Hormonal control of menstrual cycle The ovarian hormones circulate in the blood and are excreted in modified forms in the urine. Estimation of the urinary output by chemical methods gives an indication of the blood levels and of the total production of th...