The menstrual cycle
Some animations
hormones of the menstrual cycle
Video animation on the main events
Hormones affect the wall of the uterus
During the menstrual cycle, the wall of the uterus goes through four phases under the influence of two hormones, oestrogen and progesterone. During the first phase, which lasts about five days, the lining of the uterus is shed, accompanied by a loss of blood. This time is a woman’s period or more correctly the menstrual phase or menstruation. The other phases of the cycle prepare the uterus to receive and protect a zygote:
Menstruation: The uterus lining is shed. Blood and fragments of tissue leave the body through the vagina. Menstruation is triggered by a decrease in the concentration of progesterone. This phase last from 3 - 7 days.
During the menstrual cycle, the wall of the uterus goes through four phases under the influence of two hormones, oestrogen and progesterone. During the first phase, which lasts about five days, the lining of the uterus is shed, accompanied by a loss of blood. This time is a woman’s period or more correctly the menstrual phase or menstruation. The other phases of the cycle prepare the uterus to receive and protect a zygote:
Menstruation: The uterus lining is shed. Blood and fragments of tissue leave the body through the vagina. Menstruation is triggered by a decrease in the concentration of progesterone. This phase last from 3 - 7 days.
Make sure to understand this graph fully. Know the moment at which which hormone is active and the function of it. (So for FSH, LH, Estrogens ad Progesterone)
Repair phase: More blood vessels grow in the lining of the uterus, and the lining thickens and becomes more stable. These changes are triggered by an increase in the concentration of oestrogen, produced by the ovaries. This phase lasts about 10-11 days.
Following the development of a Graafian follicle (see ovarian cycle) an egg is released into the oviduct. Ovulation occurs at the peak of oestrogen concentration and is triggered by a hormone from the pituitary gland. (The release of the ovum is accompanied by a slight increase in temperature. Some women are actually aware of the moment of ovulation).
Following the development of a Graafian follicle (see ovarian cycle) an egg is released into the oviduct. Ovulation occurs at the peak of oestrogen concentration and is triggered by a hormone from the pituitary gland. (The release of the ovum is accompanied by a slight increase in temperature. Some women are actually aware of the moment of ovulation).
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Receptive phase: The lining of the uterus and its blood vessels are now well developed. If fertilisation has occurred the embryo can become implanted. This optimum set of conditions for implantation remains from 6-7 days after ovulation, and is maintained by an increasing concentration of progesterone (released by the corpus luteum; see ovarian cycle).
Premenstrual phase: The uterus lining degenerates as the progesterone concentration starts to fall unless embryo implantation has occurred, in which case progesterone (from the corpus luteum) keeps the lining intact to begin pregnancy. This is the last few days before menstruation. |
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