A visual comparison of the human male body and the human female body reveals many similarities, but the differences are immediately apparent. The reproductive organs are the most obvious difference—the physical expression of the chromosomes that determine biological sex.
Anatomy specific to females relates to sexual function, reproduction, and hormone regulation, and includes the external genitalia—the vulva—and the internal reproductive organs—the ovaries and the uterus.
The breasts are considered ‘accessory’ reproductive organs, as their main function is to lactate—provide milk for a newborn baby.
The sexual anatomy of males and females differs, but all sex organs develop from the same set of cells. During foetal development these cells differentiate according to the specific hormonal environment they find themselves in.
A baby’s biological sex is determined at the moment the father’s sperm meets the mother’s egg. This is made possible by our genes and the chromosomes that carry them.
Of the 23 chromosome pairs of that carry all of the genetic information needed for humans to reproduce, there is only one pair that differentiates sex—an X chromosome provided by the mother’s ovum, and either an X or Y chromosome provided by the father’s sperm.
The sex chromosomes carry the genes responsible for sexual differentiation. The SRY gene (Sex-determining Region of the Y chromosome) is of particular importance as it produces a specific sex-determining protein that causes a foetus to develop male gonads (the testicles). Without the presence of a functional SRY gene the developing embryo becomes a girl by default.
Shortly after they are formed, the testicles begin secreting testosterone. Exposure to this hormone causes undifferentiated tissues to develop into the glans penis. Without the presence of testosterone, the same tissues develop into a clitoris.
The other reproductive organs develop similarly. Under the influence of hormones, the scrotum, testes, epididymis, vas deferens, prostate, seminal vesicles urethra, and penis develop for males, while the ovaries, fallopian tubes, uterus, cervix, vaginal canal, Bartholin’s glands, vagina, clitoris, and clitoral hood develop for females. The sex organs with which a person is born are called primary sexual characteristics.
Further sexual development occurs long after birth, at puberty. Once again, under the influence of sex hormones, the human body matures, and secondary sex characteristics appear in both genders.
The external genitals include the mons pubis, the labia majora, labia minora, the vaginal vestibule/orifice, the clitoris, and the perineum.
Together they are called the vulva (from the Latin for covering or wrapper).
The external genitalia play three main roles:
The mons pubis (pubic mound, mons veneris) is a rounded fleshy area formed of fatty tissue that covers the pubic bone and, from puberty, is covered with hair. Although the ‘short and curlies’ serve a purpose—to lessen friction during sex and prevent the transmission of bacteria and other pathogens—some women prefer to trim, shave, or wax it. What you do with yours, of course, is up to you.
Hair follicles in the underarms and pubis are also associated with apocrine sweat glands; these glands secrete pheromones, which are believed to play a role in sexual attraction, however many questions remain unanswered.
Labia majora—the fleshy outer lips on either side of the vaginal opening. They enclose and protect the other external genitalia and contain sweat and sebaceous glands, which produce lubricating secretions. After puberty, the outer surface of the labia majora is pigmented and covered with hair, while the inner surface is smooth and pink.
Labia minora—the inner lips that sit within the labia majora are smooth and pink and can vary in size. In some females, for example, the inner lips extend beyond the outer lips, while in others they are quite small.
A rich supply of blood vessels gives the labia minora a pinkish colour. The vessels fill with blood during sexual stimulation, causing the labia minora to swell and become very sensitive.
Clitoris. The labia minora join at the top to enclose the glans clitoris, which is usually the size of a pea, but this can vary from person to person. Actually, only the tip of the clitoris is visible—it also has two shafts that extend into the body as far as 12–13 centimetres. The clitoris contains many nerve endings, so it reacts to tactile stimulation by swelling, which contributes to sexual arousal in women.
Clitoral hood. The clitoral hood or foreskin is the fold of skin that surrounds the head of the clitoris. It protects the clitoris from friction.
The labia majora, labia minora, and clitoris are made up of erectile tissue that swells with blood when stimulated.
Vaginal vestibule. Within the labia minora lies the vaginal vestibule, where the internal female sexual organs are housed:
The vagina can vary in size, but the average length is about 7 centimetres. It expands during arousal.
If you insert a finger into your vagina, it is perfectly normal to feel ridges and folds—it is not supposed to be smooth. These bumps are called rugae. Similar to accordion bellows or pleats on a skirt, the rugae stretch and contract to accommodate objects ranging in size from a finger or tampon to babies of 3,5 kg or even larger.
Hymen. The hymen is a membrane of tissue that covers the external vaginal opening. Not all women have a hymen, however, and those that do usually have a partial hymen and don’t even know it’s there.
The hymen can rupture as a result of pelvic injury, sports activity, pelvic examination, sexual intercourse, or childbirth. The absence of a hymen does not mean that a female has been sexually active.
Bartholin’s glands. These are located on either side of the vaginal opening and secrete a thick liquid that lubricates the vagina during intercourse.
Further inside the vaginal canal you will find:
The cervix is a roughly 2–3 cm rounded, convex ellipse-like structure at the internal base of the vaginal canal. This is where the uterus begins. There is a small depressed opening in the centre that connects the cervix with the vagina. The cervix changes shape and position throughout a woman’s lifetime under the influence of hormones and during menstruation and pregnancy.
During birth, the cervix dilates to 10 cm allowing the baby to pass from the uterus, into the vaginal canal, and then into the world.
The uterus is the muscular sac that holds the foetus during pregnancy. It is located in the centre of the pelvic cavity.
During a female’s monthly menstrual cycle, the lining of the uterus thickens with blood in preparation for the release of an egg from one of the ovaries. This is to prepare a nourishing environment for a foetus if pregnancy occurs.
If this is not the case, the uterine lining sheds and is evacuated through the vagina. This is called the menstrual period. It lasts 5–7 days and repeats approximately every 28 days. The length of the menstrual cycle varies from woman to woman and from cycle to cycle.
The two uterine tubes or fallopian tubes extend from either side of the upper portion of the uterus, connecting the ovaries to the uterus.
The ovaries are small, almond-shaped organs located on either side of the uterus. They are suspended by ligaments connecting to the Fallopian tubes and to the uterine wall.
At birth an ovary contains approximately 1 million oocytes or egg cells. When a woman goes through puberty her oocytes begin to mature, typically one at a time (although sometimes several mature at once) and are released from one of the ovaries into the corresponding fallopian tube, where it travels toward the uterus for potential fertilization. This process is called ovulation. Only about 500 eggs ovulate over the course of a woman’s lifetime; the rest are wasted.
The ovaries also produce hormones—oestrogen and progesterone. These hormones play a crucial role in the regulation of the reproductive system and the menstrual cycle.
Normally, a fertilized egg will make its way through the fallopian tube into the uterus, where it will implant in the uterine wall for development. When a fertilized egg mistakenly implants in the fallopian tube, it is called an ectopic pregnancy.
Perineum. The area between the vaginal opening and the anus is called the perineum.
After childbirth, a woman’s breasts supply milk for her infant.
Breasts are primarily made up of fat; the amount of fat (a combination of body mass and genetics) determines breast size. However, breast size has no bearing on the amount of milk a woman is able to produce.
Female breast tissue is sensitive to cyclical fluctuations in hormone levels, for most women breast tissue changes as they age.
Within each breast there are sections, or lobules, that branch out from the nipple. Each lobule holds a number of tiny hollow sacs, or alveoli, where milk is produced. The alveoli are linked by a network of tiny, thin tubes, or ducts. When a woman is breastfeeding, these ducts carry milk from the alveoli toward the areola, where they join into larger ducts ending in the nipple. When a baby sucks on the nipple to feed, it also stimulates the level or prolactin in the blood, which in turn stimulates milk production in the alveoli.
Breasts are not merely decorative, they are also practical—nothing short of magical, in fact!
Attention! Every woman should check her breasts regularly to detect any changes that could potentially be an early symptom of cancer. Your doctor or gynaecologist can show you how to do a breast self-exam so you can incorporate it into your health routine!
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