Ovary

Physiology

• Ovary is an organ in the female reproductive system that produces an ovum.
• Ovaries also secrete hormones that play a role in the menstrual cycle and fertility.

Microanatomy

• The surface of the ovaries is covered with a membrane consisting of a lining of simple cuboidal-to-columnar shaped mesothelium, called the germinal epithelium.

Micrograph of the ovarian cortex from a rhesus monkey showing several round follicles embedded in a matrix of stromal cells. A secondary follicle sectioned through the nucleus of an oocyte is at the upper left, and earlier stage follicles are at the lower right. The tissue was stained with the dyes hematoxylin and eosin. The outer layer is the ovarian cortex, consisting of ovarian follicles and stroma in between them. Included in the follicles are the cumulus oophorus, membrana granulosa (and the granulosa cells inside it), corona radiata, zona pellucida, and primary oocyte. Theca of follicle, antrum and liquor folliculi are also contained in the follicle. Also in the cortex is the corpus luteum derived from the follicles. The innermost layer is the ovarian medulla. It can be hard to distinguish between the cortex and medulla, but follicles are usually not found in the medulla.

Follicular cells are flat epithelial cells that originate from surface epithelium covering the ovary. They are surrounded by granulosa cells that have changed from flat to cuboidal and proliferated to produce a stratified epithelium.

The ovary also contains blood vessels and lymphatics.

Function

• At puberty, the ovary begins to secrete increasing levels of hormones.
• Secondary sex characteristics begin to develop in response to the hormones. The ovary changes structure and function beginning at puberty. Since the ovaries are able to regulate hormones, they also play an important role in pregnancy and fertility. When egg cells (oocytes) are released from the Fallopian tube, a variety of feedback mechanisms stimulate the endocrine system which cause hormone levels to change. These feedback mechanisms are controlled by the hypothalamus and pituitary glands. Messages or signals from the hypothalamus are sent to the pituitary gland. In turn, the pituitary gland releases hormones to the ovaries. From this signaling, the ovaries release their own hormones.

Gamete production

• The process of ovulation and gamete production, oogenesis, in a human ovary.
• The ovaries are the site of production and periodical release of egg cells, the female gametes. In the ovaries, the developing egg cells (or oocytes) mature in the fluid-filled follicles. Typically, only one oocyte develops at a time, but others can also mature simultaneously. Follicles are composed of different types and number of cells according to the stage of their maturation, and their size is indicative of the stage of oocyte development.
• When an oocyte completes its maturation in the ovary, a surge of luteinizing hormone is secreted by the pituitary gland which stimulates the release of the oocyte through the rupture of the follicle, a process called ovulation. The follicle remains functional and reorganizes into a corpus luteum, which secretes progesterone in order to prepare the uterus for an eventual implantation of the embryo.

Hormone secretion

• At maturity, ovaries secrete estrogen, androgen, inhibin, and progestogen.
• In women before menopause, 50% of testosterone is produced by the ovaries and released directly into the blood stream.
• The other 50% of testosterone in the blood stream is made from conversion of the adrenal pre-androgens ( DHEA and androstenedione) to testosterone in other parts of the body.
• Estrogen is responsible for the appearance of secondary sex characteristics for females at puberty and for the maturation and maintenance of the reproductive organs in their mature functional state.
• Progesterone prepares the uterus for pregnancy, and the mammary glands for lactation.
• Progesterone functions with estrogen by promoting menstrual cycle changes in the endometrium.^{[medical citation needed]}

Clinical significance

• Ovaritis= Oophoritis

• Hypogonadism
  • Central : Improper function from the hypothalamus and pituitary gland.
  • Primary

• Premature ovarian failure
• Polycystic ovarian syndrome