FEMALE REPRODUCTIVE ANATOMY & PHYSIOLOGY
The Female Reproductive System
Development of a Baby
Hormone Control Centres: Hypothalamus & Pituitary
Fertilisation to Implantation
Menstrual Hormones: The Hormonal Axis
THE FEMALE REPRODUCTIVE SYSTEM
The first day of a period is known as the FIRST day of the NEXT menstrual cycle. In Family Planning, this is an important day for a woman to note each month – not the last day of a period. You will always be asked for this date when visiting a qualified medical practitioner or health professional for related health care.
Not all women have regular 28-day menstrual cycles.
Not all women ovulate on day 14 of their cycle.
If they did, then planning a family would be simple; no mistakes would be made when calculating safe times for unprotected sex, and the vast numbers of unplanned pregnancies worldwide would drop to zero.
Development of a Baby
From the 10th week of life, in utero, the external genitalia of a foetus start to show.A baby girl should be born with an intact vagina, cervix, uterus and fallopian tubes, with two ovaries already buried deep within her pelvic cavity.To be able to view any of these female reproductive organs, access is through the vulva – the well protected vaginal opening.
The vulva consists of several outer folds to protect the vagina.They are:
the mons pubis.
the outer and inner lips (labia majora and labia minora).
vestibule and urethra.
two pairs of lubricating glands – Skene’s glands and Bartholin’s Glands.
Generally, the mons pubis is covered with pubic hair in the shape of a triangle, with a straight line across the top, level with the woman’s stomach.
If the pattern is more diamond-shaped, with hair growing towards the tummy button (umbilicus), as in men, it may indicate an increase in testosterone production.
This may be symptomatic of very common fertility problems, such as Polycystic Ovary Syndrome (PCOS).
The increase in testosterone level has no effect on a woman’s femininity or sexual preference, but she may have a stronger sex drive.
However, her fertility may be affected because an increased level of testosterone may interfere with ovulation.
The labia majora are two large round pads which merge at the top to form the mons pubis.
They are called labia majora or ‘large lips’ and can be found either side of the vaginal entrance.
They are the female equivalent to the male scrotum.
They are firm and covered with pubic hair.
They become more flaccid with the fat pads thinning out as a woman gets older.
They contain sebaceous or oil and sweat producing glands around the hair follicles.
They cover the vaginal opening to protect against general infection and disease.
The labia minora are smaller, inner lips which do not have pubic hair covering them.
They fold over the vagina completely, sealing it and protecting it from general bacteria in the surrounding area.
They gently cover the urethra, like a small tent, to ensure that urine, when passed, is directed downwards.
Their upper portion covers the clitoris and is the equivalent of an uncircumcised man’s foreskin.
They are highly erotic and respond instantly to sexual stimulation.
On arousal, the veins within them constrict.
The blood that has rushed to them cannot escape – much the same way as when a penis becomes erect.
The engorged lips grip the penis during intercourse. The swelling helps to stop semen spill out of the vaginal vault after ejaculation.
The sebaceous glands in the labia minora release smegma – a white lubricant – just as men’s sebaceous glands do underneath their foreskin.
If the smegma isn’t washed away each day, its build-up can irritate and inflame the skin.
As a young woman develops, her labia minora become more obvious and extend beyond the labia majora.
The size of the labia minora is not related to the frequency of masturbation, as was once suggested.
It is normal for both men and women to masturbate. When a couple is emotionally close they can also empower each other with the knowledge of what each like. Therefore, sexual pleasure can be enhanced through mutual masturbation.
The clitoris is situated just below the mons pubis. This is where the top of the large and small lips join.Having developed from the same foetal tissue as the penis, the clitoris consists of highly erotic tissue which is comparable to the glans penis.
For protection, it is covered by a small hood or prepuce.
The prepuce is tight in young women – but loosens with maturity.
The clitoris, like the penis, can vary in shape and size.
During sexual arousal, the clitoris expands from about 2 cm to 4 cm.
It is extremely sensitive and direct manipulation (touching) can sometimes cause pain.
The entire vulval area is covered with nerve endings which adjoin the clitoris. Therefore, sexual stimulation anywhere in the vulval area can increase response sufficiently to produce an orgasm.
During foetal development, there are two separate areas of vaginal development – upper and lower tissue development. Where these areas meet – approx 12 mm inside the vaginal opening – a membranous plate forms.This is called the hymen. Usually, as a young girl develops, this plate opens in the middle and the membrane shrinks away. In babies, this hole is tiny but, as a young girl grows, the opening is usually big enough to allow menstrual blood to pass through.
Often, the hymen enlarges naturally, without penetration.
If a young woman uses tampons, the hole will increase a little at a time.
She may not experience any pain or bleeding when she first has penetrative sex.
If she has pain and difficulty, gentle finger insertion can increase the size of the opening and eventually she will be able to allow a penis entry without discomfort.
Some young women have a particularly thick hymen or solid hymenal plate, which does not allow blood to escape during menstruation. Blood flows back through the uterus into the pelvic cavity, causing recurrent pelvic pain. Therefore, hymenotomy (surgical opening of the hymen) may be necessary.
Once the hymen is open (broken) the remnants leave a fleshy ring – called a circle of maidens (carunculae mytriformis) – which can be felt as rugged tissue inside the small vaginal lips. If the remnants are long and annoying they can be removed surgically.
In some parts of the world, where proving virginity by bleeding on the wedding night is important women, who have had sexual intercourse previously, may find a surgeon who is prepared to ‘repair’ or sew together the hymen remnants, so they can be ‘broken’ during intercourse. This may, however, be considered a form of FGM (female genital mutilation), and it illegal in most countries around the world now. In other areas, young women practice anal sex in the belief that this will ensure that they will retain their virginity. They hope to bleed on their wedding night if they preserve their hymen by not having penetrative vaginal sex.
Penetrative anal sex carries serious health risks.
See also SEXUALLY TRANSMITTED INFECTIONS.
Situated between the pubic bone and the vaginal entrance, the urethra (urine passage) carries urine out of the body from the bladder.
Women have a much shorter urethra than men.
Being only 4 to 6 cm long, it is also prone to infection.
Bacteria can travel easily up the urethra to the bladder, particularly during sex or through poor hygiene after opening the bowels.
During vigorous and/or occasional sex:
The penis may hit the base of the bladder, causing irritation (similar to bruising) although the reproductive organs are not affected. This condition is known as honeymoon cystitis.
Vaginal fluid may be massaged into the entrance of the man’s urethra – or into the woman’s cervix from his urethra – allowing bacteria easy passage to the uterus, fallopian tubes and pelvic cavity.
In particular, the bacterial sexually transmitted infection Chlamydia, may be transmitted during cervical massaging.
Chlamydia can cause recurrent urethritis (inflammation of the urethra).
Chlamydia can cause tubal infection, and subsequent infertility, in women and men.
See also Sexually Transmitted Infections: Chlamydia.
Two small ducts known as Skene’s glands, lie alongside the urethra. They secrete a lubricating fluid during sexual stimulation.
The ducts can become blocked if a bacterial infection, such as gonorrhoea, is caught.
As the glands swell, the ducts may close, trapping pockets of bacteria.
This can lead to infection of the vagina, cervix, uterus and fallopian tubes.
This, in turn, may cause Pelvic Inflammatory Disease (PID) which can result in infertility. See also Sexually Transmitted Infections: Pelvic Inflammatory Disease (PID).
There is another pair of glands at the lower vaginal opening called Bartholin’s glands. These ducts surface on the small lips – ie. the labia minora.
Any vaginal infection can seep into these ducts and cause swelling – sometimes to the size of a golf ball.
If a cyst forms, this is unlikely to be painful. However, if an abscess forms, this will be very painful.
The most common bacterial sexually transmitted infections are Chlamydia and Gonorrhoea, and where the vaginal vault is infected, the risk of infertility is higher.
Early treatment of Chlamydia and Gonorrhoea is, therefore, essential.
See also Sexually Transmitted Infections: Gonorrhoea. Chlamydia.
Situated about an inch below the vagina, the anus is the opening to the rectum.
Like the clitoris and vagina, the anus is a sexually sensitive area.
It is essential that girls are taught from the earliest age, to wipe from front to back after defecation (opening the bowels), to avoid contracting urinary tract infections caused by poor hygiene.
If vaginal sex follows anal sex then the risk of vaginal infection is very high.
Condoms must always be used – and changed – before going from anus to vagina.
The vagina is a self-cleansing passage between the uterus and the outside of the body.
It is coated with moist secretions and cleans itself continuously.
It is approximately 10 to 12 cm long.
It is made of tissue similar to that which lines the mouth.
It acts as a channel for menstrual blood to leave the body.
It guides the penis and holds a pool of semen close to the cervix after ejaculation.
It is fantastically elastic – lined by rugae (folds) which expand to allow a baby to enter the world.
It can contract sufficiently to hug a slim finger tightly.
It can be squeezed at will and good pelvic muscle tone is important to prevent incontinence and prolapse.
The ability to control and squeeze during sex enhances mutual pleasure.
The cervix (neck of the womb) is a short, valve like organ, situated between the vagina and the body of the uterus.
It is approximately 4 cm in diameter, round and movable, with a dimple in the centre, which feels similar to the end of the nose.
Sperm pass to the uterus and menstrual blood escapes from the body through it.
Babies pass through the cervix during vaginal delivery.
It defends the pelvic organs from bacteria and other microscopic foreign matter.
The tiny central passage is blocked by infertile mucus until the fertile time of the menstrual cycle.
Then, it allows sperm passage to the fallopian tubes.
If it is damaged, production of cervical mucus may be upset, causing an increased risk of infertility.
This may be temporary or permanent, depending on the cause.
It is not fully mature until a female is approx 23 years of age.
It is particularly vulnerable to infection from sexually transmitted invisible strains of HPV (Human Papilloma Virus/Genital Wart Virus) – and nicotine.
See also Sexually Transmitted Infections: HPV (Human Papilloma Virus).
As a woman matures, so does the transformation zone of her cervix.
The uterus is a stretchy, pear-shaped organ about 7.5 cm long, which is suspended in the pelvic cavity by ligaments.
It holds approx one teaspoon of fluid.
Made of smooth muscle cells, it is elastic and vascular.
Under the influence of hormones, it moves constantly throughout the menstrual cycle, contracting and relaxing.
Each month, it contracts strongly to shed its lining (endometrium) during menstruation – unless pregnancy occurs – but it contracts even more strongly during labour.
In pregnancy, it can expand to 40 times its normal size.
Approximately 10 cm long, the fallopian tubes branch from the upper corners of the uterus.
Ova are transported along fallopian tubes and fertilisation occurs within them.
They are thickly lined with tall cells which have brush-like tips known as cilia.
The soft, invisible cilia sweep in a uniform direction towards the uterus. They waft an egg forward, yet go against any sperm that may be trying to gain access up the tube.
They secrete an enzyme-rich substance which devours some of the sticky coating surrounding the egg, making it more receptive to penetration by the sperm.
To assist sperm with their tracking system, there is a down flow of fluid to guide the sperm
Each fallopian tube has four segments:
An interstitial or inter-muscular portion inside the uterus, which has a pinhead sized opening into/from the uterus.
The isthmus – a narrow portion.
The ampulla – slightly larger and the usual site of fertilisation.
The fimbria – soft, flaring finger-like projections at the end. One fimbria is attached to the ovary, the rest hang free
An egg has no means of motion so it must rely upon the fimbria to catch it as it falls from the ovary.
The enzyme-inducing cilia then waft the egg along the fallopian tube towards the ampulla – where it may meet a sperm.
Fertilisation requires optimal conditions and damage from infection greatly reduces successful conception.
Hormone Control Centres: Hypothalamus & Pituitary
From puberty, the brain controls the many hormonal changes necessary for ovulation to take place each month.
The pea-sized pituitary gland – often referred to as the ‘leader of the hormonal orchestra’ – can be found at the base of the brain.
Its assistant, the hypothalamus, can be located nearby.
These two glands are responsible for stimulating the production of follicles in the ovaries and alter cervical mucus, every month. In men, they stimulate the production of sperm cells, continuously.
The female ovaries – also known as gonads – are similar to male testicles.
Supported by ligaments, they are suspended on both sides of the uterus, in the abdominal cavity.
They release eggs and produce the hormones oestrogen and progesterone.
A baby girl is born with her life’s supply of eggs – approx 300,000 – of which only about 1 in 1,000 will develop and mature later in life.
From puberty, approx 30 immature follicles attempt to ripen each month – but usually, only one egg out-sizes the others and is released.
Sometimes, one ovary is more active than the other. In which case, the woman may not ovulate alternately but will ovulate from the same ovary consecutively.
When a girl is young, her ovaries are small, round and white.
As she matures, they grow to between 2.5 and 5 cm long and, with increasing ovulation, the surface becomes pitted.
After the menopause, ovaries shrivel and become small again.
If one ovary is damaged or missing, the other compensates, increasing its hormone output to keep circulating levels stable.
The age of a woman’s menopause is pre-determined by her genetic make-up, generally following her mother’s pattern and biological time-clock.
Releasing Hormones (RH) triggered by the hypothalamus influence ovulation so the ovary knows how and when to ovulate.
These are FSH – RH (Follicle Stimulating Hormone – releasing hormone) and LH – RH (Leutenising/Lutenising Hormone – releasing hormone).
The hypothalamus sends RH messages known as gonodotrophics/gondoprophins – from gonad = ovary; trophic = nourishment – which feed and nourish the ovaries and support the secretion of oestrogen and progesterone.
The pituitary receives RH messages from the hypothalamus so that it can secrete stimulating hormones such as FSH and LH.
The ovaries produce oestrogen during the lead up to ovulation (follicular phase).
Just before ovulation, there is a surge of LH which signals the biggest follicle to burst and release its egg.
The empty follicle – the corpus luteum or yellow body – turns yellow.
The ovary produces progesterone, as well as oestrogen in this second half of her cycle (luteal phase).
If a fertilised egg embeds in the lining of the womb (endometrium), it has about a week to signal that it’s there, before the next period will occur as usual.
It does this by stimulating another hormone – hCG (human Chorionic Gonadotrophin).
The LH surge indicates the start of the ovulatory stage and is never signalled during ongoing pregnancy.
Progesterone production continues and, all being well, the lining of the womb remains intact.
The ovary regularly stops producing oestrogen and progesterone – approx 14 days after ovulation.
This causes the lining to shed and the first day of the next cycle begins.
Fertilisation to Implantation
Fertilisation occurs in the fallopian tube when one sperm binds to the outer membrane (cumulus oophorus/oophorous) of the egg.
It punctures the egg and shoots chemicals through the inner membrane (zona pellucida).
Instantly, the sperm head injects the ovum with its nuclear chromosomes.
Instantly, the shell of the ovum transforms into an impenetrable wall, which stops any further sperm from entering.
Strands of DNA flow through the shell fusing two cells.
Fertilisation has now occurred.
Nine days later, the fertilised ovum which is growing and multiplying, may implant in the lining of the womb, commencing pregnancy.
If the fertilised ovum does not implant, pregnancy does not commence – and the next period occurs.
Menstrual Hormones: The Hormonal Axis
The hypothalamus signals the pituitary, and then the pituitary signals the gonads (ovaries/testicles).
The gonads answer back, using different hormones.
This is known as the hormonal axis or route.
Delicate blood vessels are used in both directions to carry the messages – ie. the hypothalamus signals the pituitary to send FSH to the ovaries.
The ovaries then develop follicles and make oestrogen, to signal back.
When the pituitary receives this message, it stops sending oestrogen and shuts down the FSH supply.
If no oestrogen comes back along the axis, it cleverly detects this signal as ‘we need more FSH – start sending it again’.
And so the production cycle goes throughout the woman’s reproductive years.
Natural oestrogens are produced in the ovaries by the maturing follicle and in increasing amounts.
They are produced in the form of:
Oestradiol – an inactive form
Oestrone – a relatively inert form found mostly after the menopause
Oestriol – not very active, but large amounts are found in pregnancy
Stimulates growth of the vagina, uterus and oviducts.
Facilitates development of primordial follicles in the ovaries.
Inhibits FSH (follicle stimulating hormone) secretion from the ovary.
Stimulates endometrial proliferation.
Increases myometrial contractivity.
Stimulates growth of breasts with duct proliferation.
Promotes calcification of bones, female fat distribution and hair distribution.
The stroma of the ovaries produce androgens, androstenedione and testosterone – which is synthesised to oestrogen in the ovary and, peripherally, in body fat.
Oestrogens are metabolised by the liver.
About two-thirds of all oestrogens are excreted in urine and 10% in faeces via bile.
The rest are metabolised in other substances.
Too much oestrogen for too long can cause:
Chloasma – large pale brown patches – on the face.
Increased cervical mucus.
Headaches on and off the Pill.
Raised blood pressure.
Thrombophlebitis – inflammation of a wall of a leg vein associated with thrombosis.
Altered visual contours.
Urinary tract changes.
Abnormalities of clotting.
Thrombosis – cerebral and/or myocardial.
Altered Glucose Tolerance (in diabetics and non-diabetics).
Changes in liver function tests, thyroid and fat metabolism.
Increased fibroid growths, oestrogen dependent uterine or breast growths.
Increased epilepsy and threshold lowered.
Increased changes in benign liver tumours and gall bladder disease.
Oestrogenic effects in Natural Family Planning/Fertility Awareness (NFP/FA) may cause:
The lining of the womb (endometrium) starts to grow.
Cervix becomes softer, higher, open, wet, mucus appears and changes to the fertile type
Occasional Pill related effects of Oestrogen are:
Weight gain (oedema).
Excessive vaginal discharge.
There are two kinds of progesterone – natural and synthetic (progestogen).
Each cycle after ovulation, progesterone is produced:
By the corpus luteum in large amounts.
From ovarian stroma in small amounts.
Progesterone produces secretory changes, in the lining of the womb (endometrium), which were previously stimulated by oestrogens
It increases the growth of the smooth muscle tissue of the womb (myometrium).
It increases the secretory activity of the fallopian tube.
It increases motility of fallopian tube.
It aids the development of the glandular areas of the breasts.
Far greater amounts come from the corpus luteum after ovulation.
They are metabolised in the liver to pregnanediol.
About 1/5 of the progesterone made is excreted through urine.
Other progestogenic effects in the presence of oestrogen – but NOT POP dose – may cause:
Absent or scanty periods.
Acne – oily skin.
Increased facial hair growth.
Altered glucose tolerance (diabetics and non-diabetics).
Altered liver function.
Altered cholesterol concentrations in bile – bile thickens.
Altered lipid and fat metabolism.
There is also some suggestion – though not proven – that progestogenic effects may be associated with:
Loss of head hair.
Increased likelihood of thrush.
Progestogenic effects in Natural Family Planning/Fertility Awareness (NFP/FA) may result in:
Enriched lining of the womb (endometrium).
Mucus changing to infertile thick white plug.
Cervix (neck of the womb )becoming low, closed and dry.
Rise in base body temperature by 0.2°C.
Occasional Pill related effects of progestogen may cause:
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