BY5.2 Sexual Intercourse, Fertilisation and Implantation

Sexual Intercourse:

• penis becomes erects as blood under pressure fills the erectile tissue
• vagina widens and becomes lubricaed by the secreion of mucus
• movements of the penis results in eaculation of semen into vagina
• some semen ejeaculated trhough cervix and into vagina, rest is at the top of the vagina
• sperm swins through the uterus and into the fallopian tube by lashings of their tail
• only a small portion (hundreds) of 400 million sperm reach the site of fertilisation and surround the ovum

Fertilisation:

• internal fertilisation - sperm is deposited into the female reproductive tract and swim trhough the cervix, up the uterus and into the fallopian tube
• sperm are vibale for 48 hours
• ova are viable for 24 hours
• if ovulation recently occured, the secondary ocyte is in the fallopian tube
• the secondary oocyte is surrounded by follicle cells and a clear membrane called the zona pellucida
• several hundred dpern surround it but only one will penetrate the egg
• sperm fuse with the egg and a diploid gamete…