11.1.5. The menstrual cycle

The menstrual cycle

The menstrual cycle is the set of periodic changes that occur in the female reproductive system in order to prepare the body for fertilization of the ovum and pregnancy. It begins in women from 10 to 14 years, with menarche, and disappears between 45 and 55 years, with menopause .

The menstrual cycle usually has an average duration of 28 days, although it can vary. Only a single egg usually matures in each cycle.

The menstrual cycle consists of two phases:

Follicular phase. A group of follicles develop and a single follicle matures and increases in size until ovulation occurs, when the follicle ruptures and the mature egg is released. It occurs from day 1 (the first day of menstruation) to day 14 of the cycle.
- The pituitary gland secretes follicle-stimulating hormone (FSH), which stimulates the growth of follicles, although only one will mature.
- In the developing follicles, its cells begin to secrete estrogen, hormone that causes the increase of the endometrium of the uterus, which becomes thicker and filled with blood vessels.
- When the level of estrogens increases to its maximum, the pituitary gland secretes luteinizing hormone (LH), causing ovulation or expulsion of the ovum from the follicle, approximately in the middle of the menstrual cycle.
- The egg travels through the fallopian tubes to the uterus.
Luteal phase. It lasts from day 15 to 28 of the cycle, from ovulation until menstruation begins.
- After ovulation, the remnants of the follicle form the corpus luteum or yellow, which will last until pregnancy or menstruation occurs.
- The luteinizing hormone (LH) causes the corpus luteum begins to secrete progesterone, the hormone that prepares the endometrium for embryo by receiving it acquires its maximum thickness.
- If fertilization does not occur, about 14 days after ovulation, the production of progesterone will decrease, causing the lining of the uterus, the endometrium, to shed and go out through the vagina, causing a bleeding called menstruation or rule, which It lasts for about four days and will start another new menstrual cycle.
- If the egg meets a sperm in the fallopian tube, fertilization can occur and the embryo implants in the uterus, estrogen and progesterone will continue to be produced to prevent the endometrium from shedding, until the placenta is created.

The egg, after ovulation, is released and travels to the uterus. If you don't find a sperm within 24 hours, the egg dies. This occurs almost always, either because there has been no copulation or because the sperm has not found the egg due to the use of a contraceptive method or for other reasons.

The life of sperm is longer, about five days, so the days before ovulation and the day of ovulation are the most fertile days of the menstrual cycle and when there is the greatest chance of pregnancy.

By Chris 73 (File:MenstrualCycle.png) [CC BY-SA 3.0], via Wikimedia Commons

Activity: The menstrual cycle.

Activity: Period calendar.

Test and video: The menstrual cycle.

Video: Ovulation.

Animation: The menstrual cycle and destinations of the ovum.

Curiosity: Do all animals have menstruation?

The period, in addition to humans, appears in some primates (Catarrhini, our closest relatives), in some species of bats and Elephant shrews.

Almost all mammalian species have a reproductive cycle or estrous cycle , in which changes occur in the ovary as a result of hormonal changes that regulate the receptivity of the female. During this cycle, the uterine lining grows and, if there is no fertilization, it returns to its initial state without any bleeding. Unlike the human menstrual cycle, the estrous cycleIt is usually regulated by other factors, such as seasonal changes, temperature, food availability, male odors, etc. Mares, sheep, cats, goats, for example, only have one cycle in one season of the year. In some cases there is a certain periodicity, as in dogs (diesel, two estrus per year). Other species, on the other hand, such as the cow or the sow, have estrous cycles throughout the year.

You may have heard that bitches have periods, but that bleeding is not period. It occurs when the heat begins because it increases the concentration of estrogens that favor the dilation of blood vessels so that more blood reaches the female genital tract and passes through the walls of the vagina.

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Skip navigation Biology and Geology 3rd compulsory secondary education Biology and Geology 3rd ESO 01. General organization of the human body 1.1. Levels of organization of the human body 1.2. The cell 1.2.1. The prokaryotic cell 1.2.2. The eukaryotic cell 1.2.2.1. The eukaryotic animal cell 1.2.2.2. The eukaryotic plant cell 1.3. Tissues 1.4. Organs, systems and apparatus 1.5. Bibliography and student work 02. Food and health 2.1. Feeding and nutrition 2.2. Nutrients 2.2.1. Types of nutrients 2.2.2. The energy of nutrients 2.3. The food 2.4. Diets 2.5. Food consumption 2.5.1. Labelled 2.5.2. How to shop and cook 2.6. Food preservation and hygiene 2.7. Food production 2.7.1. Intensive agriculture 2.7.2. Intensive livestock 2.7.3. Aquaculture 2.7.4. Transgenic foods 2.7.5. Organic food 2.8. Eating-related illnesses 2.9. Bibliography and student work 03. The digestive system and digestion 3.1. Nutrition function 3.2. Digestive system 3.2.1. Ingestion 3.2.1.1. Chewing 3.2.1.2. 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The menstrual cycle 11.1.6. Fertilization, pregnancy and childbirth 11.1.6.1. Fertilization 11.1.6.2. Pregnancy 11.1.6.3. Birth 11.2. Natality control 11.2.1. Contraceptive methods 11.2.2. Reproduction techniques 11.2.2.1. Exploratory techniques 11.2.2.2. Assistance techniques in childbirth 11.2.2.3. Assisted reproductive techniques 11.3. Adolescence and sexuality 11.4. Main sexually transmitted diseases and prevention 11.5. Prevention and sexual hygiene 11.6. Bibliography and student work 12. Health and disease 12.1. What is health? 12.1.1. Health indicators 12.1.2. Health determinants 12.2. The disease and types of diseases 12.3. Infectious diseases 12.3.1. Types of infectious diseases 12.3.2. Immunity and immune system 12.3.3. Prevention and cure of infectious diseases 12.4. Non-infectious diseases 12.5. First aid 12.6. Transplants and donation of cells, blood and organs 12.7. Bibliography and student work 13. Ecosystems 13.1. Ecosystem components 13.2. Types of ecosystems 13.3. Factors influencing the ecosystem 13.4. Balance in ecosystems 13.5. The soil as an ecosystem 13.6. Bibliography and student work 14. The external geological activity of the Earth 14.1. Solar energy on Earth 14.2. External geological processes 14.2.1. Weathering 14.2.2. Erosion, transport and sedimentation 14.3. Factors that condition the modeling of the relief 14.4. Forms of relief modeling 14.4.1. Wild or stream waters 14.4.2. Torrential modeling 14.4.3. River modeling 14.4.4. Karst modeling. Groundwater 14.4.5. Littoral modeling 14.4.6. Glacier modeling 14.4.7. Wind or desert modeling 14.5. Geological action of living beings 14.6. Geological action of the human being 14.7. Bibliography and student work 15. The internal geological activity of the Earth 15.1. The internal energy of the Earth 15.2. Volcanoes 15.2.1. Types of volcanoes 15.2.2. Volcanic risk 15.3. Earthquakes 15.3.1. Seismic risk 15.4. Bibliography and student work « Previous \| Next » 11.1.5. The menstrual cycle The menstrual cycle The menstrual cycle is the set of periodic changes that occur in the female reproductive system in order to prepare the body for fertilization of the ovum and pregnancy. It begins in women from 10 to 14 years, with menarche, and disappears between 45 and 55 years, with menopause . The menstrual cycle usually has an average duration of 28 days, although it can vary. Only a single egg usually matures in each cycle. The menstrual cycle consists of two phases: Follicular phase. A group of follicles develop and a single follicle matures and increases in size until ovulation occurs, when the follicle ruptures and the mature egg is released. It occurs from day 1 (the first day of menstruation) to day 14 of the cycle. The pituitary gland secretes follicle-stimulating hormone (FSH), which stimulates the growth of follicles, although only one will mature. In the developing follicles, its cells begin to secrete estrogen, hormone that causes the increase of the endometrium of the uterus, which becomes thicker and filled with blood vessels. When the level of estrogens increases to its maximum, the pituitary gland secretes luteinizing hormone (LH), causing ovulation or expulsion of the ovum from the follicle, approximately in the middle of the menstrual cycle. The egg travels through the fallopian tubes to the uterus. Luteal phase. It lasts from day 15 to 28 of the cycle, from ovulation until menstruation begins. After ovulation, the remnants of the follicle form the corpus luteum or yellow, which will last until pregnancy or menstruation occurs. The luteinizing hormone (LH) causes the corpus luteum begins to secrete progesterone, the hormone that prepares the endometrium for embryo by receiving it acquires its maximum thickness. If fertilization does not occur, about 14 days after ovulation, the production of progesterone will decrease, causing the lining of the uterus, the endometrium, to shed and go out through the vagina, causing a bleeding called menstruation or rule, which It lasts for about four days and will start another new menstrual cycle. If the egg meets a sperm in the fallopian tube, fertilization can occur and the embryo implants in the uterus, estrogen and progesterone will continue to be produced to prevent the endometrium from shedding, until the placenta is created. The egg, after ovulation, is released and travels to the uterus. If you don't find a sperm within 24 hours, the egg dies. This occurs almost always, either because there has been no copulation or because the sperm has not found the egg due to the use of a contraceptive method or for other reasons. The life of sperm is longer, about five days, so the days before ovulation and the day of ovulation are the most fertile days of the menstrual cycle and when there is the greatest chance of pregnancy. By Chris 73 (File:MenstrualCycle.png) [CC BY-SA 3.0], via Wikimedia Commons Activity: The menstrual cycle. Activity: Period calendar. Test and video: The menstrual cycle. Video: Ovulation. Animation: The menstrual cycle and destinations of the ovum. Curiosity: Do all animals have menstruation? The period, in addition to humans, appears in some primates (Catarrhini, our closest relatives), in some species of bats and Elephant shrews. Almost all mammalian species have a reproductive cycle or estrous cycle , in which changes occur in the ovary as a result of hormonal changes that regulate the receptivity of the female. During this cycle, the uterine lining grows and, if there is no fertilization, it returns to its initial state without any bleeding. Unlike the human menstrual cycle, the estrous cycleIt is usually regulated by other factors, such as seasonal changes, temperature, food availability, male odors, etc. Mares, sheep, cats, goats, for example, only have one cycle in one season of the year. In some cases there is a certain periodicity, as in dogs (diesel, two estrus per year). Other species, on the other hand, such as the cow or the sow, have estrous cycles throughout the year. You may have heard that bitches have periods, but that bleeding is not period. It occurs when the heat begins because it increases the concentration of estrogens that favor the dilation of blood vessels so that more blood reaches the female genital tract and passes through the walls of the vagina. Licensed under the Creative Commons Attribution Share Alike License 4.0 « Previous \| Next » You can ask, comment, contribute, get in touch with other users in the forum of this course. This course is translated from https://biologia-geologia.com/BG3/
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The menstrual cycle