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Human Body
They are small ovoid structures, lying one on either side of the uterus. Each ovary is suspended from below by an ovarian ligament.
(1) Oogenesis
Oogenesis is the process by which primitive female gametes become mature ova. Very little development takes place between childhood and puberty. During puberty the internal organs reach maturity, become active and menstruation begins. The mature ovary has a cycle of activity which occupies approximately 28 days.
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At birth, the ovaries of every girl contain about 2 million primordial follicles, each containing a primary oocyte. During the reproductive years, some 500 of the follicles will mature and expel their ova.
The secretion of follicle stimulating hormone (FSH) by the anterior pituitary gland stimulates primordial follicle, which begins to grow and develop. By the time ovulation occurs, the oocyte undergoes the first phase of meiosis.
2. Ovulation
Luteinizing hormone (LH), also from the anterior pituitary, assists FSH to promote final follicular growth and ovulation. The follicle ruptures expelling the ovum which enters the uterine tube.
If the ovum is fertilised by the male sperm, it implants itself in the uterus. Large amount of oestrogen and progesterone are produced during the early months of pregnancy. If the ovum is not fertilized, production of hormones ceases, menstruation occurs and the next cycle begins.
3. Secretion of Hormones
Ovarian endocrine activity is mainly concerned with the secretion of oestrogen and progesterone. Oestrogen is a collective name for a group of hormones which are of similar structure. It is responsible for the development of secondary sexual characteristics, female reproductive tract and mammary glands.
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