More information about the female genital tract

The clitoris is a button of tissue which sits at the apex of the vulva, where the labia minora join together, which becomes erect due to increased blood flow during sexual arousal, and is analogous to the male penis. The bottom of the vulva is separated from the anus by a firm block of tissue called the perineal body. The whole of the area between this at the bottom and the clitoris at the top is called the perineum (because it’s this which is around the baby - or neonate - at birth).

The ovaries - one either side of the uterus - lie in a fold of tissue called the broad ligament, made up of peritoneum, the membrane that lines the abdomen. The surface of the ovary is not covered by peritoneum - if it were then the eggs would be trapped inside - rather the surface is bare, so that at ovulation an egg is released into the abdominal cavity, where (usually) it is swept up into the fallopian tube. Each ovary is almond-shaped and about three to four centimetres long, and each contains about 1-2 million cells called germ cells. These have been formed during the development of the foetus, starting at about three months' gestation. At six months there are roughly 7 million germ cells, but the number declines before birth and continues to decline throughout the woman's life until the menopause, when the ovaries cease to function. After puberty (which usually occurs when girls reach a certain body mass) hormones secreted by the hypothalamus stimulate the pituitary (see more information on the brain in the head section) to produce other hormones which act on the germ cells, wakening them up, as it were, from the state of suspended animation that they have been slumbering in since birth. One of the germ cells will develop, to produce a fluid filled space called a follicle, containing the egg, or ovum. At ovulation the follicle bursts and the egg is caught by the fallopian tube. Sometimes there is a little bleeding from the surface of the ovary, which irritates the peritoneum and causes pain - which is why some girls suffer pain in the middle of the menstrual cycle (called Mittel-Schmerz). After the egg has been released, the cells of the follicle continue to secrete hormones - oestrogen and progesterone - which act on the lining of the uterus to prepare it for the implantation of an embryo should fertilisation occur. The cells of this follicle appear yellow, and so it is called corpus luteum (meaning yellow body). Should fertilisation not occur, the corpus luteum shrinks, hormonal support for the lining of the uterus is withdrawn and it is shed - the process of menstruation. The first day of menstruation is termed day one of the menstrual cycle. In a normal cycle menstrual loss takes five to seven days and is heaviest at the start of the period. The amount of blood lost is very variable and depends, among other things, on the size of the uterus - so that if uterine size is increased by fibroids, for example, so is blood loss. Ovulation usually occurs around about day 12 of the cycle, and menstruation recurs after 28 days. Not every woman however has a 28-day cycle, and not all cycles are regular, particularly at either end of the reproductive life: they may be very irregular during adolescence, when not all cycles are ovulatary.

The fallopian tubes, each about 10 cm long, lie in the free edge of the ligament called the broad ligament, where the ovary sits. Each tube has 4 parts - the bell-shaped infundibulum, at the free end, which overlies the ovary and has a number of fronds, called fimbriae, designed to catch the egg when it’s freed from the follicle, a thin walled duct called the ampulla, which leads to a short, thicker walled part called the isthmus. This contains tiny hairs called cilia, which hold the egg up on its journey to the uterus, awaiting fertilisation. The region of the tube where it enters the uterus is called the interstitium.

The uterus is a muscular organ shaped like a pear, about 8 cm long when fully developed, divided into the fundus at the top, the body in the middle and the cervix, which protrudes into the vagina, at the bottom. The fallopian tubes enter at each side just below the fundus. The wall of the uterus is made up of smooth muscle, called the myometrium, and it has a glandular lining called the endometrium, designed to nourish a developing embryo. In the absence of fertilisation it is this lining which is shed during menstruation. The uterus usually leans forwards (called anteverted) but in 20% of women it leans backwards, towards the rectum (called retroverted). The cervix has a central canal: at the outer end, in the vagina, is the external os, while the end in the uterus is the internal os. This canal is about 2mm in diameter in the woman who has never been pregnant: it stretches to 10cm during labour and delivery.

The vagina is a muscular tube connecting the cervix of the uterus with the outside world. In the adult it’s about 7 cm deep at the front and 10cm at the back. It is sufficiently elastic to accommodate childbirth and has a mucosal lining which is lubricated partly by mucous secreted by the cervix - which changes and increases at ovulation - and partly by fluid from blood vessels below its surface, a process called transudation, which is increased during sexual arousal, and decreases after the menopause. The front wall of the vagina constitutes the back wall of the bladder and the tube - the urethra - which runs from the bladder to open just below the clitoris, lies within it. The floor of the vagina lays against the front wall of the rectum.

The vulva consists of the fleshy labia majora which run from the pubic mound to the perineal body, which sits just in front of the anus. Behind these lie two soft lips of flesh - the labia minora - which together at the top form the covering of the clitoris, and at the bottom meet to form what is called the fourchette. Between the labia majora and minora, on each side, are glands called Bartholin’s glands. These produce secretions which act as pheromones, or sexual attractants. The hymen is a thin fold of skin which covers the entrance to the vagina, and has an opening in the middle to allow the flow of menstrual blood.

At puberty the changes that occur are firstly the development of the breasts (between 9 and 13 - continuing until 18), a growth spurt which begins at 9 or 10 and continues until after periods are established, the appearance of pubic and axillary (armpit) hair which starts at around about 10 and reaches adult distribution by the age of 15 or 16, and menarche - the first period which occurs between 11 and 15, with a median age of 13. There is, of course, a wide variation in these ages - because there is a wide variation between individuals.