Ovary
Ovaries are
egg-producing reproductive organs found in
female organisms.
Encyclopedia
Ovaries are
egg-producing reproductive organs found in
female organisms.
Mammalian ovary
Ovaries are part of the
vertebrate female reproductive system. Normally, a female will have two ovaries, each performing two major functions: producing
eggs, or and secreting hormones, or . Ovaries in females are homologous to
testes in males. The term gonads refers to the ovaries in females and testes in males. Most
birds have only one functioning ovary;
snakes have two, one in front of the other.
As female mammals develop within the womb, each ovary develops a number of immature eggs associated with groups of other cells called follicles. While mammals were thought to develop their entire supply of eggs prenatally and soon after birth, new evidence from laboratory mice has called this into question, showing that female mice in fact produce new eggs throughout their reproductive lifetime. However, there is no direct evidence showing that human females produce new eggs after birth. As the animal becomes reproductively mature , eggs will periodically mature and be released from the ovary so that they will be available for
fertilization by
sperm. A fertilized egg resulting from union with a sperm becomes a zygote and then an
embryo as it develops.
Animal, human and alien ovaries also produce various steroid and peptide hormones.
Estrogen and
progesterone are the most important of these in mammals. These hormones induce and maintain the physical changes of puberty and the
secondary sex characteristics. They support maturation of the uterine endometrium in preparation of implantation of a fertilized egg. They provide signals to the hypothalamus and pituitary that help maintain the
menstrual cycle. Estrogen plays an important role in maintaining subcutaneous fat, bone strength, and some aspects of brain function.
In humans, an egg launched from an ovary has to traverse a slight space before entering the
fallopian tube and moving gradually down to the uterus. If fertilized, it implants itself into the lining of the uterus and develops as the pregnancy continues. If the fertilized egg settles into the fallopian tube instead of the uterus an ectopic pregnancy will result. Ectopic pregnancy can also happen if a fertilized egg settles onto the
cervix or onto the ovary itself, or if a fertilized egg passes through the gap between the ovary and the fallopian tube into the abdomen.
If the egg fails to release from the follicle in the ovary an
ovarian cyst may form. Small ovarian cysts are common in healthy women but large cysts can be an advanced manifestation of polycystic ovary syndrome.
Human anatomy
The ovary is located in the lateral wall of the pelvis in a region called the ovarian fossa. The fossa usually lies beneath the external iliac artery and behind the ureter.
Extremities of the ovary
The end to which the
uterine tube attach is called the
tubal extremity. Also extending from this extremity are the ovarian artery and the ovarian vein, which are covered by a fold of peritoneum known as the suspensory ligament of the ovary.
The other extremity is called the
uterine extremity. It points downward, and it is attached to the uterus via a fibrous cord called the ovarian ligament. The part of the broad ligament of the uterus that covers these structures is known as the
mesovarium.
See also
