5.1.2  Ova: the female sex cells

As you learned in Study Session 3, a baby girl is born with all the ova that she will have in her lifetime, but they are in an immature state. Each ovum is a large cell, with an external cell membrane, and is full of liquid which is rich in protein. It has a nucleus which contains the female genetic material.

The ova are stored in ovarian follicles in the ovaries, and a few begin to mature each month after a girl reaches puberty at about 12 to 15 years of age. This process continues until the menopause at about age 48 to 50 years, when the menstrual cycles end.

  • Which hormones are involved in stimulating the maturation of ova?

  • The hypothalamus in the brain produces gonadotropin-releasing hormone (GnRH), which stimulates the pituitary gland (also in the brain) to produce follicle-stimulating hormone (FSH) and leutenizing hormone (LH). These two hormones act on the ovarian follicles and cause a few of the immature ova to begin maturation.

  • If the first day of the last menstrual period is called ‘day 1’, after how many days will a mature ovum be released from one of the ovaries?

  • Ovulation occurs at around day 14 of the cycle in most women.

5.1.1  Sperm: the male sex cells

5.2  Fertilisation