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.