The World of Pregnancy

Ovaries: What Are They & What They Do!

You probably have heard of the term “ovary” and their importance in the conception of a human being. In this article, we`ll go over a few important aspects related to this female reproductive organ.

What Is an Ovary?

The ovaries, together with the fallopian tubes and the uterus, constitute the female internal genital system.

In the adult woman, the ovaries are small formations with a length of 4 cm, a width of 2 cm and a thickness of 1 cm. They are situated on each sides of the uterus, and their internal face corresponds to the trumpet pavilion. The ligaments to the neighboring organs (uterus, tubes), but they remain mobile. An ovary is composed from 2 layers of tissue: in the center, the medulla contains blood vessels that provide irrigation; at the periphery the cortical part occupies 2/3 from the gland; at the person`s birth, it contains all the follicles that will ensure during each menstrual cycle the maturation of an ovocyte and the expulsion of an egg, the female reproductive element.

Their Structure

The ovarian area is covered by a unilateral cavitary/cubic epithelium known as ovarian germinating epithelium. Below it`s a layer of dense connective tissue known as albuginee tunica (which is the one determining the whitish color of the ovaries). Under albuginee is ovarian cortical, which is mostly of composed of ovarian follicles. The medulla is the central part of the ovary and is made up of a vascular rich lax connective tissue matrix. – Read more!

The ovary has 2 sides (lateral and medial) and 2 margins (anterior and posterior) and 2 extremities (tuber and uterus). This is a mobile organ maintained in position by:

  • The ovarian susceptor ligament.
  • Ovarian ligament (utero-ovarian).
  • Tubo-vascular (infundibulo -ovarian).
  • Mesovarium.

What Is the Role of the Ovaries?

The ovary`s role is double: on one hand, it releases a mature egg in the follicle each month from the puberty to the menopause, while on the other hand, it secretes estrogen. The ovaries` function is controlled by hCG released from nerve cells located in the hypothalamus that send their own messages to the pituitary gland for the production of follicle stimulating hormone and luteinizing hormone. These two are carried in the cardiovascular system to control the menstrual cycle.

They release an egg at the middle of each menstrual cycle. Generally, only a single egg from a single ovary is released during every menstrual cycle, and each ovary take turns when releasing the egg (oocyte). A baby of female gender is always born having all the eggs that she`ll ever have, which is estimated to be about 2.000.000. However, by puberty, the number will decrease to around 400.000 eggs in the ovaries. Between puberty and menopause, just 400 – 500 eggs will ever reach maturity, be released from the ovaries and be fertilized in the uterine tubes of the woman`s reproductive tract.

In the ovaries, the eggs are at first enclosed in one layer of cells called follicle that supports the eggs. In time, they start to mature and an egg is released from an ovary in every menstrual cycle. As they mature, the follicle`s cells divide quite rapidly and the follicle starts to increase in size. A lot of them lose their ability of functioning during the process that may take a few months, but one will dominate in every menstrual cycle and the contained egg is released during the process of ovulation.

During their development, the follicles start producing estrogen. As soon as the egg was released during ovulation, there is an empty follicle which is left behind in the ovary known as corpus luteum. This one will released a higher amount of progesterone and a lower amount of estrogen. These 2 hormones will prepare the uterine lining for a possible pregnancy, if the egg that has just been released is fertilized. If this doesn`t happen, the corpus luteum will break down and then both the estrogen and progesterone secretion will stop. Due to the fact that these 2 hormones won`t by present anymore, the uterine lining will start to fall away and be eliminated from the body through the process of menstruation. After your period ends, a new menstrual cycle will start.

The menopause is nothing more than the ending of the reproductive years of a woman after her last menstruation. This is generally caused by the loss of the follicles that remained in the ovary, containing eggs. If there`s no more follicles and eggs, the 2 hormones are no longer secreted by the ovary. This will lead to a cease of menstruation.

Regulation of Ovarian Secretion

  • At puberty:

– From the age of 8 – 9 years, the secretion of pituitary gonadotropic hormone secretion increases, reaching puberty at the age of 12 to 14. These days, as a result of increased estrogen section, the development of breasts and pubic hair occurs, and due to the increased secretion of adrenal cortical androgenic hormones underarm hair (axillary hair) occurs.

  • During pregnancy:

– The yellow body is no longer atrophic; it develops secreting large amounts of estrogen and progesterone; ovulation is inhibited, so the menstrual cycle no longer occurs.

– After around 3 months of pregnancy, the placenta secretes estrogen, progesterone, human chorionic somatotropin (HCS) and gonadotropic hormone (similar to LH): human chorionic gonadotropin (hCG).

– Estrogens develop the mammary glands and increase the uterus.

– Progesterone lowers the contractility of the uterus, prepares the breast for lactation.

– hCG prevents involution of the yellow body and stimulates it to secrete large amounts of progesterone and estrogen.

– HCS stimulates protein anabolism and lowers the use of glucose for the body, leaving high levels of fat.

  • At menopause:

-Before the menopause is installed, the ovarian cycle starts to be rather irregular, which might take a few months or years.

– Menopause occurs physiologically between 45 -55 years.

– Once menopause is installed, the ovaries become small, and estrogen and androgen levels are low.

Pathology Associated with the Ovary

– Primary: having genetic causes, such as enzyme deficiencies or autoimmune diseases.

– Secondary: caused by hypothyroidism by GnRH.

  • Ovarian hyperfunction has different manifestations depending on the period in which it occurs.

– Before puberty: the onset of puberty, the early occurrence of menarche, ovulation, and secondary sexual characteristics.

– After puberty: it often occurs because of a secretory estrogen tumor.

Ovarian hyperfunction may be:

– Primary: caused by ovarian malignancies.

– Secondary: caused by a hypersecretion of GnRH or FSH and LH.

  • Hyperandrogenism occurs most commonly in adults and is characterized by masculinization.

The ovary may be the site of some inflammatory lesions in a salpingitis (inflammation of one or both uterine tubes), benign or malignant tumors. Ovarian failure causes disorders related to the menstrual cycle, and frequently sterility. – More here!

Evaluation of Ovarian Function (Specific Diagnostics)

Lab investigations:

– dosing of circulating estrogens (basal level of 20 – 60 picograms/ml and ovulatory peak > 200 picograms/ml). – Click here!

– serum progesterone dosing on day 21 (normal value: 18 nanograms/dl).

– dosage concentrations of FSH and LH (radioimmunization, fluorimmunization or ELISA).

Clinical investigations:

  • Cervical mucus exam on day 14 of the menstrual cycle.
  • Citovaginal smear.
  • Recording the basal temperature curve.

The palpation of the abdomen allows the search for ovarian cysts. The 2 main ovarian examinations are ultrasound and celioscopy, a procedure that allows the insertion of an optical system through a small abdominal incision.

Image courtesy of WiseGeek.org
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