Ovary
For Ovary as part of plants see Ovary |
Human female internal reproductive anatomy |
Ovaries are
egg-producing reproductive organs found in
female organisms.
Ovaries are part of the
vertebrate female
reproductive system. Normally, a female will have two ovaries, each performing two major functions: producing
eggs, or (
exocrine function) and secreting
hormones, or (
endocrine function). 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 (the process called
puberty in humans), eggs will periodically mature and be released from the ovary (a process called
ovulation) 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.
 |
Internal reproductive organs of human female |
Animal and human 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.
See also:
Oophorectomy,
polycystic ovary syndrome,
Turner syndrome,
hypogonadism,
menopause,
ovum,
ovarian cancer,
corpus luteum,
cervix,
vagina
