Ovaries, the female gonads, are located below the digestive system in the abdominal
cavity. Inside each ovary are many follicles, which consist of a single egg cell, and one
or more layers of follicle cells. Follicle cells protect and nourish the egg cells. A
woman is born with about 400,000 follicles and cannot produce more.
 Ovulation is the process in which an egg is expelled from a follicle. The egg
is expelled directly into the abdominal cavity and is picked up by the fallopian tubes.
Inside the fallopian tubes are cilia, which sweep the egg into the uterus. At the neck of
the uterus is the cervix, which leads into the . The vagina has very thin walls,
much thinner than those of the uterus.
At the end of the are two pairs of folded skin, the libia minora and the libia
majora. At the top of the libia is glans clitoris, a small bulb of erectile tissue. Like
glans penis, glans clitoris is very sensitive to stimuli.
At ejaculation, millions of sperm are propelled into the female’s reproductive
tract. Some sperm immediately leak out of the . The rest then are able to propel
themselves up through the towards the cervix. Sperm travel through the female
reproductive tract, then are killed by the acidity of the vaginal fluids. The few sperm
that are able to make it to the cervix are then exposed to contractions of the uterus that
cause a washing machine effect in the uterine cavity. Here thousands of sperm are hunted
down and killed by phagocytes, which recognize them as foreign. Of the millions of
sperm that are ejaculated, only a few thousand are able to reach the egg.
When the sperm reaches the egg, it cannot immediately fertilize it. Instead it must
wait in order to allow their membranes to become capacitated, or weakened. The cervical
mucus facilitates this, and in the following 6-8 hours the sperm are gradually
capacitated.
After capacitation has occurred, a reaction called the acrosomal reaction can occur.
This reaction releases enzymes in the area surrounding the egg weakening its membrane.
Once weakened a single sperm is allowed to penetrate the egg and fertilize it.
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