What Is The Function Of The Ovaries?
Ovaries are flattened ovoid bodies with dimensions of 4 cm, 2 cm and 1 cm. Each ovary is attached at hilum to the broad ligament by means of mesovarium and ovarian ligament. At hilum, the connective tissue of mesovarium and ovarian ligament is continuous with ovarian stroma. The mesovarium gives rise to germinal epithelium. On cross section, each ovary shows two zones of structures:
The medulla is otherwise known as zona vasculosa. It is the central deeper portion of the ovary. It has the stroma of loose connective tissues. It contains blood vessels, lymphatics, nerve fibers and bundles of smooth muscle fibers near the hilum.
It is the outer broader layer and has compact cellular layers. It is interrupted at the hilum, where the medulla is continuous with mesovarium. Cortex is lined by the germinal epithelium underneath a fibrous layer known as tunica albuginea. The cortex consists of the following structures:
- Glandular structures which represent ovarian follicles at different stages of development
- Connective tissue cells
- Interstitial cells which are clusters of epithelial cells with fine lipid granules formed mainly from theca interna.
In the intrauterine life, the outer part of cotex contains the germinal epithelium, which is derived from the germinal ridges. When the fetus develops, the germinal epithelium gives rise to a number of primordial ova. The primordial ova move towards the inner substance of cortex. A layer of spindle cells from the ovarian stroma gets arranged around the ova. The spindle cells are called granulosa cells. The primordial ovum along with granulosa cells is called the primordial follicle.
At 7th or 8th month of intrauterine life, about million primordial follicles are found in the ovary. But, at the time of birth, only 1 million primordial follicles are seen in both the ovaries and, the rest of the follicles degenerate. At the time of puberty, the number decreases further to about 3,00,000 to 4,00,000. After menarche, during every menstrual cycle, one of the follicles matures and releases its ovum. During every menstrual cycle, only one ovum is released from any one of the ovaries.
During every cycle, many of the follicles degenerate. The degeneration of the follicles is called atresia and the degenerated follicles are known as atretic follicles. The atretic follicles become fibrous and, the fibrotic follicles are called the corpus fibrosa. Atresia occurs at all levels of follicles. Usually, the degenerated follicles disappear without leaving any scar.
Functions of ovaries are:
- Secretion of female sex hormones
- Oogenesis and menstrual cycle.