Reproductive System

Reproductive System



Female Reproductive System
- Menstrual Cycle
- The Hypothalamic-Pituitary Axis

Male Reproductive System

Fertilisation


Female Reproductive System

The female reproductive system is entirely internal.

The vagina is the canal that leads from the outside of the body to the cervix, the opening to the uterus.
The uterus is the muscular organ where a fertilised egg, or embryo, attaches and develops. It is the size and shape of a pear and lined with a rich and nourishing membrane, the endometrium.

The endometrium is the inner layer of the uterus and is attached to the muscle layer of the uterus. It is functionally divided into two distinct zones. The outer part is the part that sheds during the menstrual cycle, and the inner part contains stem cells that helps to regenerate the lost cells.

The fallopian tubes extend from the top of the uterus down over the ovaries, the two walnut-sized organs that contain the eggs.

The female ovaries are paired, flat, elliptical structures which measure approximately 5cm in diameter. The ovaries are in the abdomen and are suspended by various ligaments.

The ovary itself consists of two parts, the outer cortex and the inner medulla. The cortex is where development of the eggs occurs, and the medulla carries nerves and blood vessels.

Females are born with approximately 2 to 4 million primary follicles. These fetal follicles contain a developing egg called a primary oocyte surrounded by a layer of granulosa cells. These primary oocytes are part way through a cell division. This process of division doesn"?Tt resume until the time of ovulation. With each ovarian cycle, a handful of ovarian follicles are recruited and usually only one of these ovulates, the remaining unrecruited follicles remain in an inactive state. Development of follicles occurs until menopause.

The eggs in each ovary are made before a woman is born. A girl is born with about 2 million eggs. At the time she has her first period there are about 400,000.
Every month from puberty to menopause, eggs begin to mature inside several fluid filled 'cysts' within the ovaries, called follicles. Only one of these follicles will become dominant, while the others will shrink and be absorbed by the ovary. At mid cycle, the dominant follicle releases a single egg during ovulation, which then travels down the fallopian tube toward the uterus.
For a pregnancy to occur, fertilisation happens in the fallopian tube, when the egg meets sperm. The developing embryo then travels down the fallopian tube to the uterus, where it will implant in the endometrium approximately 7 days after ovulation.
Hormones control the highly complicated sequence of events leading to ovulation. The pituitary gland in the brain produces the two hormones that the ovary needs:
• Follicle stimulating hormone (FSH)
• Luteinising hormone (LH)

Menstruation Cycle

In humans the female egg or ovum is released once per month and if not fertilised both the unused egg and the lining of the uterus are shed and the body prepares itself again for the possible implantation of a fertilised egg.

"Menstruation is a phase of the menstrual cycle in which the uterine lining (endometrium) is shed. Menstrual cycles occur exclusively in humans and other apes. " http://en.wikipedia.org/wiki/Menstruation

Normal menstruation is a complex interactions between several hormones produced by three organs of the body; the hypothalamus; the pituitary gland and the ovaries. The optimal cycle has a duration of 28 days, but it is often found that women ahve a cycle between 21 to 35 days. Menstruation usually starts at an average age of 13 (called menarche) and lasts on until between 45 and 52 when a woman is said to go through menopause.
The inner lining of the uterus is called the endometrium and it goes through three phases during the menstrual cycle:

1.Follicular phase

    - this begins on Day 1 of the menstrual cycle, the first day of menstrual bleeding. FSH begins by stimulating the development of many follicles, but as levels of FSH gradually fall in a natural cycle only one follicle will dominate and go on to produces a mature egg. The non-dominant follicles are absorbed by the ovary and cannot be used again. The developing follicle also secretes estrogen, which has several functions. For example, estrogen develops the watery mid cycle changes in cervical mucus that assist the passage of sperm into the uterus and also causes the thickening of the endometrium required for implantation. The main estrogen the ovary produces is estradiol (E2).

2.Ovulatory phase
    - this phase is short. It begins when, in response to rising estrogen levels, the level of LH rises dramatically. This LH surge triggers the final maturation of the egg, the rupture of the follicle, and then the release of the egg. This usually happens 14 days before the next period is due, or on day 14 of a 28-day cycle.

3.Luteal phase
    - begins after ovulation. At this point, the ovarian follicle where the egg developed collapses and solidifies to become the corpus luteum. This very important structure mainly produces progesterone, the hormone necessary for transforming the endometrium so that a fertilised egg (the early embryo) can implant and develop. If conception does not occur, the corpus luteum stops functioning on about Day 26 of a 28 day cycle. Without the support of progesterone, the endometrium begins to break down and is shed in menstruation

Bleeding as a result of menstruation lasts 2 to 7 days on average, from which there is an average loss of 20 to 80mL of blood.

The Hypothalamic-Pituitary Axis

The Hypothalamus
There are five different hormones released from the hypothalamus that have an effect on the menstrual cycle. These hormones include:
• Gonadotrophin Releasing Hormone (GnRH)
• Thyrotropin Releasing Hormone (TRH)
• Somatotropin Release-Inhibitory Factor (SRIF) AKA Somatostatin
• Corticotrophin Releasing Factor (CRF)
• Prolactin Release-Inhibiting Factor (PIF)
Each of these have a different effect on the anterior pituitary gland, stimulating it to release or stop releasing a particular hormone.

Gonadotrophin Releasing Hormone

Release of this hormone is responsible for the stimulation of specific cells called gonadotrophs in the pituitary gland. This stimulation results in the production of two important hormones called LH (luteinising hormone) and FSH (follicular stimulating hormone) from the pituitary.

GnRH is of great importance in the menstrual cycle. One of the most important features of GnRH release is the fact that its release occurs in a pulsatile fashion. At the start of puberty there is a marked increase in the frequency and amplitude of GnRH release. A part of the brain called the surge centre in the brain controls the timing of this increased release of GnRH. The surge centre is present in females very early in life, however it is only as puberty approaches that this centre becomes more responsive to hormonal changes.

Throughout the menstrual cycle there is pulsatile release of GnRH. Anything that interferes with the pulse frequency of GnRH can stop the menstrual cycle from occurring. Restoration of this pulsatile GnRH by administering hormones can produce a return to ovulation.

The Pituitary Gland

The pituitary gland is an outpouching of the base of the brain which lies under the hypothalamus. The close proximity of these two parts of the brain is a reflection of their closely linked function.

The pituitary gland is divided into two different parts, each of which have different functions. The anterior pituitary is responsible for housing the gonadotrophs, these are the cells that release hormones important in controlling the menstrual cycle.

The anterior pituitary gland is composed of six different cell types and produces six different hormones. The cell type that is of importance in menstruation is the gonadotroph. These cells release follicle stimulating hormone (FSH) and luteinizing hormone (LH) and are also responsible for production and storage of these hormones.

Follicle Stimulating Hormone (FSH):

The granulosa in the ovaries are the main target for the action of FSH. In response to FSH stimulation the granulosa cells release oestrogen. The combined effect of oestrogen and FSH is to cause growth and increased oestrogen production.

Luteinizing Hormone (LH)
LH stimulates cells in the ovary, called the theca cells, to produce hormones called androgens which are then transported to the granulosa cells in the ovary for conversion into oestrogens.

Gonadotrophin secretory patterns

The normal ovulatory cycle is divided into two phases called the follicular and luteal phases.
• Follicular phase - is initiated from the day bleeding stops and finishes with a mid cycle surge of LH.
• Luteal phase - this is initiated with the mid-cycle surge of LH which coincides with ovulation and ends with the first day of onset of the period.
Together they create the The Ovarian Cycle

Hormones in the ovarian cycle:
Estrogen:
This is low at the beginning of the menstrual cycle and peaks at the middle and then once again towards the end.

Progesterone:
There is little production of this in the first half of menstruation but a significant increase in the second half. The progesterone remains high if pregnancy occurs. Progesterone is responsible for an increased body temperature in pregnancy as well.

The Male reproductive System

The male reproductive system is both internal and external.
The testes lie in the scrotum, the pouch of skin located beneath the man's penis. The testes are the organs that produce sperm and testosterone.
From the testes, sperm pass slowly through the coiled channels of the epididymis, where they mature.
Once sperm are mature, they move into the vas deferens, a tube that connects the epididymis with the urethra via a common ejaculatory duct. The entire process of sperm formation takes approximately 72 days.

As with women, the hormones LH and FSH also control men's reproductive systems.

Fertilisation

After sperm are deposited into the upper vagina via ejaculation, they must travel through the cervical mucus into the uterus and then into the fallopian tube before they can meet with the egg. Sperm are transported on this long journey by their own rapid forward movement assisted by upward contractions of the uterine walls. During the trip, sperm prepare themselves to meet the egg by subtle alterations of their heads and movement patterns.
When they meet the outer membrane of the egg, the sperm start to burrow through it and then enter the egg itself. At the moment the first sperm successfully penetrates the egg, a reaction is triggered that makes the egg resistant to all other sperm. This single sperm absorbs into the egg, where the genetic material contained in its head fuses with that of the egg. Fertilisation is now complete.

The egg maintains its ability to be fertilised for about 12 hours after ovulation. Sperm can remain viable in the cervical mucus for 48-72 hours or more around the time leading up to ovulation.

Menopausal Hot Flushes

Menopausal Hot Flushes

Hot flushes affect about three-quarters of menopausal women and are likely to be as individual as the women who have them. Most women will agree that flushing is uncomfortable and at times embarrassing, and can interfere with your ability to concentrate and carry out activities. The way that a flush can feel will vary with the woman. Most women will experience episodes of heat which vary in intensity, often accompanied with perspiration. Other symptoms include headaches, nausea, fatigue, dizziness, anxiety, ‘butterflies in the stomach’, confusion and palpitations.

It is thought that hot flushes are related to the changes in your hormones, in particular oestrogen. Hot flushes are not caused solely by oestrogen withdrawal. An increase of luteinising hormone (LH) commonly causes the symptoms that are associated with a hot flush. Thyroid disorders can also aggravate menopausal symptoms.

Most of the time the period when you experience hot flushes lasts for about 1-2 years, but some may experience these for up to ten years. Rest assured that you have the ability to lessen this time and to reduce the severity of your symptoms with natural methods such as diet and lifestyle modifications. There are also several herbal preparations that are effective at relieving uncomfortable menopausal symptoms, however it is important that these be sought from a qualified naturopath or herbalist as most over-the-counter preparations will not have the same quality, and a herbalist can design a tonic that is specific for your needs. Sage tea may help to reduce sweating.

Risk of Hot Flushes Occurring increases with:
A maternal history of hot flushes, early menopause, cigarette smoking, early menarche and alcohol use are considered to be risk factors for more severe hot flushes.

Improvement may be felt with:
Phyto-oestrogens
Phyto-oestrogens are structurally similar to the oestrogen molecule and because of this they can bind to the body’s oestrogen receptors. The effect that the phyto-oestrogens have is varied, but recent studies have shown that the oestrogen levels of the woman will determine what sort of action the phyto-oestrogens will have. In a postmenopausal woman who has very little oestrogen, then phyto-oestrogens will exert a pro-oestrogenic effect, whereas a woman who has an oestrogen dominant condition would experience an anti-oestrogen effect. In short, the phyto-oestrogens have a balancing action on oestrogen status.

Studies have shown that cultures with a high intake of soya products have significantly less menopausal symptoms than western cultures. Asian diets are high in soy based foods (40–100 mg per day of isoflavones in Asian diets as compared to <3 mg per day in western diets), and most women in these countries express minimal menopausal complaints. Several other studies have shown that soy can improve menopausal symptoms, in particular hot flushes. They suggest an intake of 10-15 g of soy protein or 60 mg isoflavones (range of 30-100 mg) per day.

There are several types of phyto-oestrogens and these are isoflavones, coumestans, lignans, flavones, flavonols and flavanones. Isoflavones are responsible for the cardio-protective activities, improving bone density and protecting against breast cancer. They are found mainly in soya products and legumes. Coumestans are the main phyto-oestrogen studied for menopausal symptoms, and these are found in legumes such as soya products, peas and beans, and are highest in sprouted legumes such as alfalfa, mung bean or snow pea. The western diet is generally very low in these foods, but it is not difficult to include them in your diet.

Increasing phyto-oestrogen intake can be easy. 100g of tofu per day has been shown to reduce hot flushes and vaginal dryness and can be prepared in many ways. You could also use soya milk, add miso and tempeh to your cooking, eat more alfalfa and snow-pea sprouts, or add 2 tablespoons of freshly ground flaxseed to your muesli or cereal every morning. It is possible to take soya supplements, however it is preferable to eat soya in its whole food form as this provides a synergistic blend of the protein and soy germ.

Vitamins
Several studies have shown that vitamin supplementation can reduce menopausal symptoms, including hot flushes. Vitamin E supplementation has shown a statistically significant advantage over placebo in reducing hot flushes over four weeks at a dose of 400 IU twice daily. It has also been shown to reduce other common symptoms of menopause including fatigue, dizziness, palpitations, and nervousness9.

Vitamin C and flavonoids may also be of assistance in reducing hot flushes because of their ability to improve vascular integrity. One study performed in the early 1960s showed that supplementation with the flavonoid hesperidin and vitamin C completely relieved hot flushes in 53% of the 94 women studied and reduced them in 34%9. Further research into this area is required.

Evening Primrose Oil
Evening primrose oil comes from seeds which contain the oils alpha-linolenic acid (an omega-3 fatty acid) and gamma-linolenic acid (GLA; omega-6 fatty acid), both precursors of eicosanoids, which are constituents of cell membranes. The biochemical pathway for metabolism of dietary GLA eventually leads to an anti-inflammatory prostaglandin. This is a very popular supplement for the treatment of hot flushes which many women swear by, however the evidence to support this is limited. Dosages required are between 1-3g daily and need to be taken over long periods of time3.

Aggravating foods
Some foods may aggravate hot flushes, and these should be avoided. These foods include alcohol, spicy foods, and coffee.

Lifestyle
Observational studies have shown regular aerobic exercise lessens the frequency and severity of hot flushes#. It has several other positive effects, such as an improvement of mood, memory, libido, energy and weight loss#.

Performing relaxation exercises every day, such as meditation and breathing exercises, can help to reduce the intensity of hot flushes.

It may be helpful to wear loose fitting clothing made from natural material such as cotton. Wearing outer layers that are easily removed allows you to easily cool down when you’re experiencing a flush.

Many women will experience night sweats that require them to change the sheets. By placing a towel under them, they can simply remove it if it becomes wet and this saves the trouble of changing the sheets every morning.

Stress and anxiety can bring on and worsen hot flushes therefore steps should be made to reduce stress in your life. Meditation, counselling and herbal medicine can help to reduce stress.

The Herbal Approach
Your Naturopath can create a treatment plan to ease your menopausal symptoms. The treatment may be a combination of hormone modulating, cooling and calming. A naturopath will also assess your adrenal and liver health as these are common underlying factors. An individual formula will not only be of high quality, it will be tailored to your specific needs.

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