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Ovarian Follicles

Ovarian follicles contain a single oocyte (immature ovum or egg). These eggs/ova are developed only once every menstrual cycle. A woman begins puberty with about 400,000 follicles.

PubMed Health Glossary
(Source: Wikipedia)

Anatomy of the female reproductive system; drawing shows the uterus, myometrium (muscular outer layer of the uterus), endometrium (inner lining of the uterus), ovaries, fallopian tubes, cervix, and vagina. Click to enlarge

The female reproductive system National Institutes of Health

About Ovarian Follicles

According to present knowledge, ovaries already contain all the egg cells women will have in their lifetime when they are born. These egg cells lie in small pockets called follicles. Once puberty starts, different hormones cause the first follicle to mature and release an egg cell (ovum).

Hormones are substances produced by the body that act as chemical transmitters. They regulate body functions like the menstrual cycle and body temperature. Hormones also trigger ovulation.

What happens during ovulation?

Around the time when a mature egg cell has left the ovary, a woman can get pregnant. The egg cell travels down the fallopian tube into the uterus. The moment the egg cell leaves the ovary is called ovulation. Once a girl has had her first monthly period, ovulation usually occurs once a month. Institute for Quality and Efficiency in Health Care (IQWiG)

Terms to know

Cervix
The lower, narrow end of the uterus that forms a canal between the uterus and vagina.
Endometrium
The layer of tissue that lines the uterus.
Fallopian Tubes
A slender tube through which eggs pass from an ovary to the uterus. In the female reproductive tract, there is one ovary and one fallopian tube on each side of the uterus.
Follicle (Follicular)
A sac or pouch-like cavity formed by a group of cells. In the ovaries, one follicle contains one egg. In the skin, one follicle contains one hair.
Follicle-Stimulating Hormone
A hormone made in the pituitary gland. In females, it acts on the ovaries to make the follicles and eggs grow. In males, it acts on the testes to make sperm. Also called follitropin and FSH.
Follicular Phase
Follicular phase begins with the onset of menstruation and ends with ovulation.
Myometrium
The muscular outer layer of the uterus.
Oocyte
The developing female reproductive cell; an immature egg.
Ovaries
The ovaries are a pair of female reproductive glands in which the ova, or eggs, are formed. The ovaries are located in the pelvis, one on each side of the uterus.
Ovum
The egg cell, or ovum, is the female reproductive cell. The ovum is one of the largest cells in the human body, typically visible to the naked eye.
Uterus (Womb)
The small, hollow, pear-shaped organ in a woman's pelvis. This is the organ in which a fetus develops. Also called womb.
Vagina
The muscular canal that goes from the uterus to the outside of the body. During birth, the baby passes through the vagina.

Terms to know

Cervix
The lower, narrow end of the uterus that forms a canal between the uterus and vagina....
Endometrium
The layer of tissue that lines the uterus....
Fallopian Tubes
A slender tube through which eggs pass from an ovary to the uterus. In the female reproductive tract, there i...
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