Sperm that are released into the vagina during intercourse are stimulated to swim by calcium ions diffusing from vaginale fluids into their tail. The membranes of sperms can detect chemicals released by the egg by their receptor. This allows them to swim towards the egg. Once the egg is reached many reactions take place.
1. The acrosome reaction
The zona pellucida is glycoproteins that surround the egg. The acrosome is a large membrane-bound sac of enzymes in the head of the sperm. When the sperm makes contact with the zoa pellucida, the contents inside the acrosome are released and the enzymes then loosen the zona pellucida which allows sperm to force their way through by beating their tail.
2. Penetration of the egg membrane
The acrosome reaction exposes an area of membrane on the tip of the sperm that has proteins that bind to the egg membrane. The first sperm that gets pass the zona pellucida binds and the membranes of the sperm and egg fuse together. The sperm nucleus enters the egg cell and this is when fertilization occurs.
3. The cortical reaction
The sperm brings parental genes and causes the egg to become active. This causes an effect on the cortical granules which are vesicles located near the egg membrane. There are plenty of these vesicles and when activation of the egg occurs, the contents are released from the egg by exocytosis. The chemicals in the cortical granules interact with the glycoproteins in the zona pellucida turing into an impenetrable fertilization membrane.
Data-based question: maternal age and pregnancy
1. From ages 12-19 to 20-24 there is a rise. After this, at 20-24, births are most successful and continue to be around the 20s. Once a person is in their 30s, there is a significant drop and once they are older than 44, the successful birth rates are very low.
2. Mothers in their 20s are more suitable to have children as they are younger. As they get older, they may not be built to have babies anymore therefore successful births are very low.
3. This could be due to social factors. They may not be educated as much as others and not have jobs therefore are not sure how to take care of children and get the right medical treatment. Also, their bodies are yet developing therefore might not be ready to give birth.
4. One difference is that the education of a mother is better at an older age (35 or more) so this a better environment for children to be born it. Another difference is that mothers at an older age have less successful pregnancies than younger women because their bodies may not be as equip at younger mothers.
5. The ideal age to have children may be 20-29. This is because the live births rate is higher than any other age. Also, the miscarriage rate is lower than others. Though mothers that are older are more educated, people are this age are still educated and it is safer to have a baby at this age therefore this would be the ideal age.