50 Fun Facts About Female Anatomy

The human uterus is usually described as being shaped like which fruit?

It measures roughly 7.6 cm long, 4.5 cm wide and 3 cm thick when not pregnant, then expands enormously to hold a full-term baby.

What is the inner lining of the uterus, shed during a period, called?

The three layers from inside out are endometrium, myometrium and perimetrium; the middle one is mostly smooth muscle and does the work in labour.

The thick muscular wall of the uterus that contracts during childbirth is called what?

Its innermost part, the junctional zone, thickens in the condition adenomyosis; the outer serous coat is the perimetrium.

Roughly how many oocytes (immature eggs) are present in the ovaries at birth?

Only around 500 of them will ever be ovulated; the rest quietly degenerate over a lifetime.

Approximately how many mature eggs will a woman release over her whole reproductive life?

The pool falls from a peak of several million before birth to about 300,000 at puberty; everything else undergoes atresia.

The fallopian tubes are named after Gabriele Falloppio, a 16th-century anatomist who was also what?

He called the organ 'tuba uteri' because it looked like a trumpet, and described it in his 1561 Observationes Anatomicae.

Fertilization normally happens in which part of the fallopian tube?

It is the widest section, about 5 cm long; the finger-like fimbriae at the far end sweep the egg in from the ovary.

What are the finger-like projections at the end of each fallopian tube called?

The egg is actually released into the abdominal cavity first; beating cilia on the fimbriae draw it into the tube.

Which surgical term describes removing a fallopian tube together with at least one ovary?

'Salpinx' is Greek for trumpet, the same image Falloppio used; a hysterectomy removes the uterus itself.

What is the median length of the human menstrual cycle?

Anything from 21 to 35 days is considered normal, and the average happens to be close to the lunar month.

Which day is counted as day one of the menstrual cycle?

The period itself lasts about five days; a first period, or menarche, arrives at around age twelve.

What is the medical term for a girl's first period?

The most common age is twelve, and in the first two years afterward about half of cycles happen without ovulation at all.

A surge in which pituitary secretion triggers ovulation?

Rising estrogen from the maturing follicle feeds back on the pituitary to produce the LH surge, along with a smaller spike in FSH.

After ovulation, the follicle's remains form a temporary progesterone gland called what?

The name means 'yellow body', from its carotenoid pigment; if no pregnancy follows it shrivels into the white scar called the corpus albicans.

The temporary gland left after ovulation gets its yellow colour from which pigments?

The same pigment colours the macula lutea of the retina, which is why both structures share the Latin word for yellow.

Mature ovarian follicles are also called Graafian follicles, after which 17th-century Dutch anatomist?

Working mostly on rabbits, he wrongly assumed fertilization happened inside the ovary, but his 1672 description of the follicles stuck.

Which estrogen becomes the predominant form circulating during pregnancy?

Estradiol dominates in the reproductive years; the three major natural estrogens are estradiol, estriol and a third that takes over after menopause.

Which estrogen becomes the predominant form in a woman's body after menopause?

It is far weaker than estradiol, roughly a tenth as potent in laboratory tests, which is part of why menopausal symptoms appear.

Which chemist first isolated pure crystalline progesterone in 1934?

Allen had discovered the hormone's action in 1929; Butenandt's Danzig lab did the purification and later shared a Nobel Prize for sex-hormone work.

Menopause is officially dated retroactively, once how long has passed since the last period?

It typically arrives between 45 and 55; the average age of the last period in the US is 51, in India 46.

What is the average age of a woman's final menstrual period in the United States?

Bone-density loss runs fastest from about a year before that last period through the two years after it.

A typical menopausal hot flash lasts how long?

They can bring shivering, night sweats and reddened skin; cognitive behavioural therapy and hypnosis have both been shown to blunt their impact.

Which bone is the most sexually dimorphic in the human skeleton, and so most reliable for determining sex from remains?

The female pelvis is wider, shallower and more circular, an evolutionary compromise between walking efficiently and giving birth known as the 'obstetrical dilemma'.

What is the wider female equivalent of the male subpubic angle called?

In 1939 Caldwell and colleagues classified female pelves into four types and found the round 'gynaecoid' shape in about half of specimens.

Which pelvic shape, considered ideal for childbirth, did Caldwell find in about half of women?

The study labelled every non-gynaecoid shape 'abnormal', a word that stuck even though at least half of women have one.

Compared with men, women have roughly what difference in red blood cell count?

Men's higher haemoglobin means more oxygen-carrying capacity; women, on the other hand, carry a higher percentage of body fat, guided by estrogen at puberty.

What is usually the first physical sign of puberty in girls, at about age ten and a half?

This is Tanner stage 2 of breast development; reproductive maturity follows about four years after the first changes.

What is the medical term for the onset of breast development at puberty?

In the two years after it, the uterus, ovaries and follicles all grow; menarche follows later.

Which two tissue types make up most of the breast?

Connective tissue and the suspensory Cooper's ligaments hold it together; some women have a higher glandular proportion than others.

The suspensory bands that support the breast are named after which English surgeon?

They are named for the English surgeon Astley Cooper; sensation to the nipple-areola area comes from the fourth thoracic nerve.

What is the name of the pigmented area of skin surrounding the nipple?

About two-thirds of the milk-producing tissue lies within 30 mm of the base of the nipple.

What is colostrum?

By mid-pregnancy the breast is physically ready to lactate and some women can already express it.

Which hormone is the main driver of milk production during breastfeeding?

It also raises insulin resistance and IGF-1 in pregnancy to prepare the body; a different hormone handles the squeeze that ejects the milk.

Which hormone contracts the cells around the milk-producing alveoli in the "let-down" reflex?

Its name comes from Greek for 'swift childbirth' because it also drives uterine contractions in labour.

How many amino acids does the let-down hormone, synthesised by Nobel laureate Vincent du Vigneaud, contain?

It was the first polypeptide hormone ever synthesized, in 1953, and with vasopressin is one of only two hormones the posterior pituitary releases to act at a distance.

During childbirth the cervix must dilate to more than what diameter?

As labour progresses it also softens, shortens and swings forward; between pregnancies its mucus changes texture across the cycle to help or block sperm.

Around ovulation, cervical mucus becomes thin and more what, to help sperm survive?

Fertility-awareness methods track its stretchiness (Spinnbarkeit), transparency and 'ferning' pattern when dried on a slide.

The word 'vagina' comes from the Latin for what?

Its healthy environment is acidic, around pH 4, thanks to Lactobacillus bacteria that turn sugar into lactic acid.

Which bacteria keep the vaginal environment acidic by producing lactic acid?

Species such as Lactobacillus gasseri also secrete hydrogen peroxide and bacteriocins that fend off infections; disturbing this balance invites yeast infections.

Bartholin's glands were first described in 1677 by an anatomist from which country?

Caspar Bartholin the Younger described them; sources often wrongly credit his grandfather, Caspar the Elder. They are the counterpart of the male bulbourethral glands.

The PSA-secreting Skene's glands are sometimes called the 'female' version of which male organ?

The term 'female prostate' was formally added to Terminologia Histologica in 2002; the fluid is also rich in glucose and fructose.

Which embryonic structure develops into the fallopian tubes, uterus and upper vagina?

In a male embryo, testosterone drives the Wolffian duct instead and the Müllerian duct withers away.

A Barr body, seen in the cells of females, is what?

Murray Barr and his student Ewart Bertram spotted it in 1949; Mary Lyon later explained it as one X being switched off in every cell.

Which hormone, produced after implantation, do home pregnancy tests detect?

hCG's job is to keep the corpus luteum pumping out progesterone through the first trimester so the uterine lining is not shed.

The word 'placenta' comes from a Latin word for what, referring to the organ's shape?

A full-term placenta weighs about 500 grams and is delivered in the 'third stage of labour' after the baby.

Roughly how much does a full-term human placenta weigh?

It also makes progesterone and, in male fetuses, its hCG prompts the testes to make testosterone.

Helen O'Connell's late-1990s research changed anatomy textbooks by showing what about the clitoris?

MRI studies since have shown roughly ten times the erectile tissue that older diagrams depicted, most of it beneath the surface.

Roughly how much does a typical adult, non-pregnant human uterus weigh?

It is about 7.6 cm long and sits immediately behind and almost over the bladder, in front of the sigmoid colon.

The Latin word cervix, used for the lower part of the uterus, translates which Greek word for 'neck'?

Greek writers usually called the cervical canal the 'stomachos'; Hippocrates and Aretaeus described cervical cancer more than 2,000 years ago.

Which 17th-century anatomist proposed in 1667 that mammalian ovaries, like birds', contain eggs?

He later suggested she-mules are infertile because their ovaries produce no eggs, overturning the old idea of 'female semen'.