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B5 G) Puberty & the Menstrual Cycle
B5 G) Puberty & the Menstrual Cycle
Puberty
Puberty is where a child’s body develops into an adult’s body. Puberty happens over many years and usually takes place between the ages of 10 and 16. It happens slightly earlier for females than males. During puberty, the body releases sex hormones that starts the development of secondary sexual characteristics.
The table below gives a summary of what happens during puberty for both males and females.
Puberty is where a child’s body develops into an adult’s body. Puberty happens over many years and usually takes place between the ages of 10 and 16. It happens slightly earlier for females than males. During puberty, the body releases sex hormones that starts the development of secondary sexual characteristics.
- The main reproductive hormone for males is testosterone, which is produced by the testes. It stimulates sperm production.
- The main reproductive hormone for females is oestrogen, which is produced in the ovaries. Oestrogen brings about many physical changes in the body. It also causes eggs to mature and is involved in the menstrual cycle.
The table below gives a summary of what happens during puberty for both males and females.
The Menstrual Cycle
The menstrual cycle is the process of getting the uterus ready for a fertilised egg (pregnancy). It is a continuous cycle that takes around 28 days. The menstrual cycle has 4 stages, which are:
The menstrual cycle involves 4 different hormones; FSH (follicle-stimulating hormone), oestrogen, LH (luteinising hormone) and progesterone. FSH and LH are produced by the pituitary gland (found at the base of the brain). Oestrogen and progesterone are produced by the ovaries. The graph below shows how the levels of these 4 hormones change over the menstrual cycle.
The menstrual cycle is the process of getting the uterus ready for a fertilised egg (pregnancy). It is a continuous cycle that takes around 28 days. The menstrual cycle has 4 stages, which are:
- The first stage is menstruation, which is where the lining of the uterus is shed through the vagina. This stage is also known as a “period”. It lasts for about 4 days.
- The second stage is where the lining of the uterus builds itself backup to become thick and spongey with lots of blood vessels. The second stage is all about getting the lining of the uterus ready to receive a fertilised egg. The second stage goes from day 4 to day 14.
- The third stage is where an egg develops and is released from the ovary. This happens at day 14 and is known as ovulation.
- The fourth and final stage is where the lining of the uterus is maintained ready to receive a fertilised egg. The lining of the uterus is maintained from day 14 to day 28. If no eggs are fertilised by day 28, the lining of the uterus breaks down (menstruation) and the whole cycle starts again (we go back to stage 1 and continue this whole process).
The menstrual cycle involves 4 different hormones; FSH (follicle-stimulating hormone), oestrogen, LH (luteinising hormone) and progesterone. FSH and LH are produced by the pituitary gland (found at the base of the brain). Oestrogen and progesterone are produced by the ovaries. The graph below shows how the levels of these 4 hormones change over the menstrual cycle.
FSH (Follicle-Stimulating Hormone)
FSH causes an egg to mature in one of the ovaries, which creates a structure called a follicle. FSH also causes the ovaries to start producing oestrogen. FSH is produced in the pituitary gland.
Oestrogen
Oestrogen causes the lining of the uterus to grow into a thick spongey wall with lots of blood vessels. There are high levels of oestrogen between day 4 and day 14 when the lining of the uterus is being built (stage 2 in the cycle); the level of oestrogen peaks around day 12. Oestrogen stimulates the production of LH and inhibits the production of FSH. Oestrogen is produced in the ovaries.
LH (Luteinising Hormone)
LH causes an egg to be released on day 14 (ovulation). The level of LH peaks on day 14, which is why an egg is released. LH is produced in the pituitary gland.
Progesterone
Progesterone maintains the lining of the uterus between day 14 and day 28 (stage 4 in the cycle), which is why the levels of progesterone are high on the second half of the menstrual cycle. Progesterone inhibits the production of LH and FSH. Progesterone is produced in the ovaries by the remains of the follicle after ovulation. When the levels of progesterone fall, the lining of the uterus breaks down and the whole process starts again starting with menstruation.
FSH causes an egg to mature in one of the ovaries, which creates a structure called a follicle. FSH also causes the ovaries to start producing oestrogen. FSH is produced in the pituitary gland.
Oestrogen
Oestrogen causes the lining of the uterus to grow into a thick spongey wall with lots of blood vessels. There are high levels of oestrogen between day 4 and day 14 when the lining of the uterus is being built (stage 2 in the cycle); the level of oestrogen peaks around day 12. Oestrogen stimulates the production of LH and inhibits the production of FSH. Oestrogen is produced in the ovaries.
LH (Luteinising Hormone)
LH causes an egg to be released on day 14 (ovulation). The level of LH peaks on day 14, which is why an egg is released. LH is produced in the pituitary gland.
Progesterone
Progesterone maintains the lining of the uterus between day 14 and day 28 (stage 4 in the cycle), which is why the levels of progesterone are high on the second half of the menstrual cycle. Progesterone inhibits the production of LH and FSH. Progesterone is produced in the ovaries by the remains of the follicle after ovulation. When the levels of progesterone fall, the lining of the uterus breaks down and the whole process starts again starting with menstruation.