Woman: Encyclopedia II - Woman - Biology and sex

Woman - Biology and sex

Biological factors are not the sole determinants of whether persons are considered, or consider themselves, women. Some women can have abnormal hormonal or chromosomal differences (such as congenital adrenal hyperplasia, complete or partial androgen insensitivity syndrome or other intersex conditions), and there are women who may be without, at least for an earlier part of their lives, typical female physiology (trans, transgendered or transsexual women). (See gender identity.)

In terms of biology, the female sex organs are involved in the reproductive system, whereas the secondary sex characteristics are involved in nurturing children or attracting a mate. Most women have the karyotype 46,XX, but around one in a thousand will be 47,XXX and one in 2500 will be 45,X.

Although fewer females than males are born (the ratio is around 1:1.05), women are more common in the adult population (about a 1.04:1 ratio). Women have a lower death rate than men, even in the uterus, living on average five years longer due to a combination of factors: genetics (redundant and varied genes present on sex chromosomes in women); sociology (such as not being expected in most countries to perform military service); health-impacting choices (such as suicide or the use of cigarettes and alcohol); the presence of the female hormone estrogen, which has a cardioprotective effect in premenopausal women; and the effect of high levels of androgens in men. Out of the total population there are 101.3 men for every 100 women (source: 2001 World Almanac).

After the onset of menarche, most women are able to become pregnant and bear children. The study of female reproduction and reproductive organs is called gynaecology. Women generally reach menopause in their late 40s or early 50s, at which point their ovaries cease producing estrogen and they can no longer become pregnant.

In general, women suffer from the same illnesses as men; however there are some sex-related illnesses that are found more commonly or exclusively in women.

Adapted from the Wikipedia article "Biology and sex", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki