Final answer:
Sperm are capable of surviving within the female reproductive tract for 3 to 5 days. They face various challenges such as vaginal acidity and immune defenses before potentially fertilizing an oocyte, which necessitates capacitation. Fertility in both sexes varies with age, with female fertility peaking in the twenties.
Step-by-step explanation:
During the transit of sperm through the female reproductive tract, many obstacles are encountered. Initially, millions of sperm released into the vagina are faced with high acidity and barriers of cervical mucus. The few that manage to enter the uterus are then subject to attack by phagocytic uterine leukocytes.
Despite these challenges, the ones that reach the uterine tubes, typically where fertilization occurs, can survive there from 3 to 5 days after ejaculation. This means that fertilization can still happen if intercourse occurs a few days before the ovulation cycle peak, taking into consideration that an oocyte can only survive for about 24 hours post-ovulation.
Furthermore, for sperm to successfully fertilize an oocyte, they must undergo a priming process called capacitation. This process enhances their motility and modifies the membrane to allow the release of enzymes needed to penetrate the oocyte. Therefore, sperm have to be correctly prepared before they can fertilize an egg.
It is important to note that fertility, both male and female, changes with age, with female fertility typically peaking in the twenties. Understanding the complex journey and lifespan of sperm within the female reproductive system allows for better insight into the fertilization process and fertility planning.