The menstrual cycle
The Recurring series of events in the human female reproductive system. is a recurring process which takes around 28 days.
During the process, the lining of the Also known as a womb. This is where the fertilised egg (ovum) develops. is prepared for pregnancy. If implantation of the fertilised egg into the uterus lining does not happen, the lining is then shed. This is known as Also called a 'period'. The loss of blood and tissue from the lining of the uterus through the vagina during the menstrual cycle..
Several Chemical messenger produced in glands and carried by the blood to specific organs in the body. are involved in the menstrual cycle of a woman:
- Follicle Stimulating Hormone. It stimulates oestrogen production and the growth of follicles (egg-sacs) in the ovary. It is secreted by the pituitary gland. causes the maturation of an egg in the ovary
- Luteinising Hormone, secreted by the pituitary gland, which stimulates ovulation. stimulates the release of the egg
- A female sex hormone produced in the ovaries, which is responsible for puberty in girls and the regulation of the menstrual cycle. is involved in repairing and thickening the uterus lining, while Sex hormone produced by the ovaries and placenta. maintains it
| Hormone | Where produced | Role |
| FSH (follicle stimulating hormone) | Pituitary gland | Causes an egg to mature in an ovary; stimulates the ovaries to release oestrogen |
| Oestrogen | Ovaries | Stops FSH being produced (so that only one egg matures in a cycle); repairs, thickens and maintains the uterus lining; stimulates the pituitary gland to release LH |
| LH (luteinising hormone) | Pituitary gland | Triggers ovulation (the release of a mature egg) |
| Progesterone | Ovaries | Maintains the lining of the uterus during the middle part of the menstrual cycle and during pregnancy |
| Hormone | FSH (follicle stimulating hormone) |
|---|---|
| Where produced | Pituitary gland |
| Role | Causes an egg to mature in an ovary; stimulates the ovaries to release oestrogen |
| Hormone | Oestrogen |
|---|---|
| Where produced | Ovaries |
| Role | Stops FSH being produced (so that only one egg matures in a cycle); repairs, thickens and maintains the uterus lining; stimulates the pituitary gland to release LH |
| Hormone | LH (luteinising hormone) |
|---|---|
| Where produced | Pituitary gland |
| Role | Triggers ovulation (the release of a mature egg) |
| Hormone | Progesterone |
|---|---|
| Where produced | Ovaries |
| Role | Maintains the lining of the uterus during the middle part of the menstrual cycle and during pregnancy |
If a woman becomes pregnant, the The organ in the uterus of pregnant mammals that allows the transfer of nutrients and waste products between the mother and the fetus through the umbilical cord. produces progesterone. This maintains the lining of the uterus during pregnancy and means that menstruation does not happen.
The interactions of hormones - Higher
The menstrual cycle lasts for approximately 28 days. Graphs can be used to follow changes to the hormones during this process.
Question
Describe the relationship between the different hormones during the 28 days.
Days 1 to 12 - oestrogen gradually increases and peaks approximately on the 12th day. Progesterone, LH and FSH stay approximately at the same levels and begin to increase slightly from around day 12.
FSH and LH patterns are very similar and peak during ovulation at approximately 14 days during this cycle. They drop sharply on day 15 and stay constant until day 28.
Oestrogen drops during days 13 and 14, and progesterone continues to gradually increase until about day 21, when it slowly beings to decrease again. Oestrogen mirrors this shape and also has a second lower peak at about day 21.
Greg Foot describes the interaction of FSH, LS, oestrogen and progesterone in the menstrual cycle