Reproduction in Humans
Reproduction in humans always happen sexually.
Hormones
Hormones released in the pituitary gland control reproduction. The two hormones produced here are the 'follicle stimulating hormone' (FSH) and the 'luteinising hormone' (LH).
In boys, FSH stimulates sperm production while LH secretes the male sex hormone, testosterone. Testosterone is responsible for many of the changes boys get in puberty, for example, body hair and muscle development. In girls, these two hormones are responsible for the changes in females in puberty, for example, breast development and the beginning of menstruation (periods).
In boys, FSH stimulates sperm production while LH secretes the male sex hormone, testosterone. Testosterone is responsible for many of the changes boys get in puberty, for example, body hair and muscle development. In girls, these two hormones are responsible for the changes in females in puberty, for example, breast development and the beginning of menstruation (periods).
Fertilisation in Humans
The sperm cell is specialised to reaching the ovum. It has a tail-like flagellum that moves through a fluid. When the sperm reaches the ovum, the two nuclei must fuse. Each cell carries half the required chromosomes, so when they fuse, they will have the full amount of chromosomes.
The Menstrual Cycle
The menstrual cycle is approximately a month long. It is the cycle woman go through after puberty. The menstrual cycle goes as follows:
- Day 1-5: Periods happen as a result of the uterus lining shedding
- Day 6-13: A new uterus lining is developed
- Day 14: The ovum is shed from the ovary. The ovum stays in the Fallopian tube until approximately Day 19
- Day 15-28: The blood supply develops in the new uterus lining
Pregnancy and Birth
During pregnancy, there is a membrane called the amnion that encloses the baby. It is like a sac that secretes a fluid called amniotic fluid. This fluid protects the baby from external bumps and jolts. The more time that passes in pregnancy, the more complex the sac becomes. At nine months, a hormonal signal is sent to initiate labour.
Firstly, the cervix gets wider to allow the baby to pass through. The muscles move strongly, rupturing the amnion and allowing the amniotic fluid to escape. This is called 'Breaking of the Waters'. The baby is then pushed out using the muscles, head first, into the outside world. After that, the uterus continues to push out the placenta and the baby's membranes left behind. This is known as afterbirth.
Firstly, the cervix gets wider to allow the baby to pass through. The muscles move strongly, rupturing the amnion and allowing the amniotic fluid to escape. This is called 'Breaking of the Waters'. The baby is then pushed out using the muscles, head first, into the outside world. After that, the uterus continues to push out the placenta and the baby's membranes left behind. This is known as afterbirth.
OxNotes Revision Notes Summary for Human Reproduction
Coming 5 April 2014.
