When sperm enters the female body, a complex journey begins with the ultimate goal of fertilization.
Here's a breakdown of the events:
- Initial Deposition: Semen, containing sperm, is deposited in the vagina during sexual intercourse.
- Liquefaction: The semen initially coagulates, but then liquefies within 15-30 minutes, allowing the sperm to swim freely.
- Cervical Passage: Sperm must navigate the cervix, the opening to the uterus. Cervical mucus can either aid or hinder sperm passage depending on the stage of the menstrual cycle. Around ovulation, the mucus becomes thinner and more receptive to sperm.
- Uterine Transit: Contractions of the uterine muscles help propel the sperm through the uterus towards the fallopian tubes. The journey through the uterus is relatively quick, with some sperm reaching the fallopian tubes within minutes.
- Fallopian Tube Ascent: The sperm continue their journey into the fallopian tubes, aided by further muscular contractions and chemical signals.
- Capacitation: As sperm travel through the female reproductive tract, they undergo a process called capacitation. This process modifies the sperm, enabling them to fertilize an egg.
- Fertilization: If an egg is present in the fallopian tube, the capacitated sperm can attempt to penetrate its outer layers (corona radiata and zona pellucida). Only one sperm will typically successfully fertilize the egg.
- Sperm Survival: Sperm can survive in the female reproductive tract for up to five days, increasing the window of opportunity for fertilization. However, most sperm die relatively quickly.
In essence, sperm embark on a guided journey through the female reproductive system, facing numerous challenges, with the ultimate aim of uniting with an egg and initiating pregnancy.
