benefits of food for the human body
on Rabu, 26 Agustus 2009
How Phytonutrients and Bio-Energy Benefit the Human Body
(Natural News) There is much talk about phytonutrients lately. What are phytonutrients and why are they so important? Well simply put, phytonutrients are certain compounds found in plants that evidence has shown to increase overall health and protect against certain diseases including cancer. The term “Phyto” comes from the Greek work for plant so phytonutrients are plant nutrients, though they’re of a different class then the traditional nutrients of fats, proteins, vitaminsand minerals.
These nutrients are not considered “essential for life” but they are important for health and longevity. Fruits, vegetables, grains, legumes, nuts, and teas are rich sources of phytonutrients. Fruits and vegetables that are high in carotenoids appear to protect humans against certain cancers, heart disease, and age-related macular degeneration.
So what does this have to do with bio-energy? Everything actually. Bio-energy is the actual energy source of the body that keeps you alive every second. Science knows that the body not only uses and generates electricity but also electromagnetic energy. The Chinese call this energy Chi. It is derived and absorbed from nature including the Sun, moon, stars, heavens, the earth, and most importantly from the air itself, also known as ionic energy.
Plants absorb this energy as they grow in the ground from the earth and absorb this energy from the sun and transfer it to their fruits. We then consume this energy when we eat the fruits which is extracted from the food during digestion via the spleen, something that it little known in western medical circles.
That is why these nutrients from natural plant sources are so important and beneficial to human health and longevity. It’s the same reason why drinking herbal and natural teas are so popular in China which has the greatest number of centenarians (people who live to be one hundred years old or older) in the world.
All processes in the body require energy, just like any chemical reaction does in chemistry. We get this energy from the foods that we eat and the air we breathe. The body also must have enzymes to break food down, kill viruses, bacteria, dissolve tumors and even to break down and build up muscle tissue and everything else in the body. A diet of at least fifty percent raw, unprocessed foods is vital to make sure that we're getting enough enzymes, phytonutrients, and the all important Chi or bio-energy for the body's processes to function optimally.
Some of the main sources of phytonutrients are as follows: Carrots, leafy green and yellow vegetables (e.g. broccoli, sweet potato, pumpkin, and carrots), peaches, apricots, leafy greens such as kale, spinach, turnip greens, tomato products, pink grapefruit, watermelon, guava, green vegetables, eggs, citrus.
I take food enzymes with every meal to aid digestion. This also takes a big load off the pancreas which makes most of the enzymes in the body. The more live, unprocessed food that we eat; the more phytonutrients, enzymes and bio-energy we take in. All natural foods contain this all important bio-energy or chi and without it no life could exist. This is how these foods help to increase our immune system, health, strength and regeneration of the body itself and ultimately help us feel better and live longer.
So to boost your own immune system and cell regeneration of the body, eat more phytonutrients, practice deep breathing exercises daily and make sure that your diet is at least fifty percent raw, unprocessed natural foods (preferably organic whenever possible) and you too can soon be singing the praises of phytonutrients.
Grape Seed Extract: Benefits to the Human Body
The food supplement known as grape seed extract is taken from the seeds and skins of red grapes. For those of you who are unsure of the various types of grapes that are on the market, this is the type that’s generally used in the production of wine.
This is a very popular food supplement in Europe and is considered by some to be more effective than Vitamin C and Vitamin E in its response to the body’s needs, since its rich in flavonoids – which contain powerful antioxidant properties. Among the most effective of these flavonoids are PCOs (procyanidolic oligomers). These PCOs, which are present in the grape seed extract food supplement, also help to improve blood circulation and provide strengthening of the vessels.
Health Benefits
Prescribed by doctors in Europe for a variety of vascular disorders, grape seed extract is of some benefit to heart and cancer patients, when the food supplement is administered regularly. Grape seed extract also helps to reduce or eliminate the symptoms of leg cramps, varicose veins, diabetes, numbness in the extremities – an even the effects of impotence, since this food supplement is designed to improve the body’s blood flow.
Other benefits of grape seed extract are in the areas of endometriosis, since the effects of this can be inhibited by the food supplement’s ability to provide antioxidants that can also invade the membranes of the body. Brain cells may also be protected from certain forms of damage (known as free radical damage) when grape seed extract is administered.
For those who are interested in retaining a youthful appearance, the benefits of grape seed extract come into play, as well. This versatile food supplement helps to maintain the elasticity of the skin, and is a popular ingredient of many facial and skin creams.
In countries such as America, where heart disease is prevalent, there’s a great deal of need for products that prevent such illnesses. Grape seed extract is outstanding in its ability to maintain healthy heart performance, due to its ability to prevent the development of plaque, which is known to clog the arteries and endanger those who suffer from this condition. Stroke can also be avoided through the ongoing use of this particular food supplement, for the same reasons.
High cholesterol is another major health concern in some parts of the world today – including America – and the call for agents that can reduce cholesterol is ongoing. Grape seed extract can be used to replace regular cooking oils, and has been known to reduce cholesterol levels by up to 14% in the span of one month.
Other health benefits that are derived from this food supplement include the minimization of fibromyalgia, occurrences of cancer, and the skins ailments known as eczema and psoriasis. Additional health areas that are improved through the use of grape seed extract are eyesight – the effects of macular degeneration and cataracts are diminished; allergic reactions – this food supplement provides a natural antihistamine and anti-inflammatory; and many other illnesses.
A food supplement in the form of grape seed extract is known to be quite safe and is effective in the treatment of a wide number of illnesses. Currently, grape seed extract can be purchased in the form of liquid, tablet or capsule
ORGANIC FOOD
Is good nutrition important in your life? For me, it is one of the most important issue because good nutrition signifies better life in general. One of the main ways to improve your food products is buying organic products. In our time pesticides are part of our every day life. This is sad. But you have the power to make choices. One of them is refusing to have food products which were bombarded with insecticides and pesticides to name only a few.
Think about all the food or other things you put in your body. What do you eat on a regular basis? Are you a fast-food nut, or do you take the time to prepare healthy meals at home? This question is a crucial one simply due to the fact that you are what you eat. Now, this can be interpreted in many ways. Clearly I don't mean that if you consume McDonald's every day, you're a Big Mac. But, if you do resort to fats-food that often, you should be concerned with your health. There is a reason why some healthy nuts are totally into organic products and won't touch restaurant cuisine. It's time you got in-the-know.
About two years ago, I began purchasing organic products. It's not that I was eating horrible foods in the past, but I wanted to pass on to my children a healthier lifestyle. I pretty sure that everyone wants their children to live a healthy life. My wife finally agreed to join me in my organic food products crusade after a while. So we started shopping for groceries at a finer food market. You know, the ones that focus on organic products and superb cuts of meat. Now, just to be clear, this is of course a more costly way to shop. Most organic farmers don't have the major earnings that the rest of them do. They earn less capital because they are providing on a smaller scale.
A dairy farmer shooting his cattle full of hormones can clearly produce much more milk than a farmer who goes the natural route. So in short, organic products cost more. But hey, you get what you pay for. Now, you may wonder why you should care if you're consuming organic products or not. This is a simple one. When you eat foods such as dairy products and meat that are not organic, you're also eating loads of antibiotics and hormones that have been given to the animals. This is not good for your body, and it seems that it leads to cancer.
Think about making the switch. You may want to pick up a few items that you eat regularly, which are organic if you're not willing to buy organic products only. This way the cheese or milk you consume on a regular basis will not be damaging your system with unnatural hormones, which can seriously affect the growth rate of your kids. Teach them a healthy lifestyle by buying organic products. You will be rewarded with abetter health if you have good eating habits on the long run which will translate in a happier life. Go the organic products route and be happy!
RAW ORGANIC SPROUTS
It's easy to grow your own organic sprouts at home. Select the seed of your choice, soak in chemical free solution, drain after 24-48 hours and rinse with filtered water. The health advantages of adding raw organic sprouts have been well documented over the years. See list of a few popular seeds you can sprout.
(Radish, Celery, Cauliflower, Mustard, Peas, Wheat, Alfalfa, Soybean, Garlic, Onion and Cabbage)
Many health professionals agree that sprouts can offer your body important nutrients. Some of these nutrients are the building blocks of life and provide numerous health benefits for a several functions of the body. Vitamins, minerals and amino acids a few of the building blocks. If you sprout in an organic environment, the seeds will sprouts will not have any harmful chemicals. This will help reduce the intake of toxic chemicals into the body.
Dietitians and doctors agree that the consumption of organic sprouts is safe and effective while incorporating raw foods into your lifestyle. Eating a diet consisting of raw foods is less likely to cause any experience of such illness, disease as well as other uncomfortable conditions. A very successful aspect for this type of diet is the consumption of organic sprouts. The consumption of these types of foods, aid in losing weight, as well as preventing different types of cancers and preventing heart disease, which are all beneficial to good health.
Did you know you could do your own sprouting when you enjoy eating the raw foods of nature? Many people enjoy sprouting their own seeds. Sprouting your own seeds is helpful as you can sprout your own seeds while saving a great deal of money, without having to buy sprouts someone else processed. The Easy-Sprouter is one item that is most helpful when you begin your own organic sprouting. Even if you have no experience with organic sprouting, the Easy-Sprouter is effective and wallet friendly. One of the best benefits of using an Easy-Sprouter is that you do not have to have any experience to use it and it does not require you to rinse the seeds.
The Easy-Sprouter establishes an ideal growing environment for an assortment of seeds. This environment removes the need to have experience in organic sprouting. Not only are you saving time and money while using the Easy-Sprouter, but you will also be making a practical contribution to our environment.
Stem-cell Genes That Help Form Plant Organs Identified
on Senin, 24 Agustus 2009Stem-cell Genes That Help Form Plant Organs Identified
ScienceDaily (Mar. 6, 2009) — Plant stem-cells are master cells located at the tip of the stem and are part of a structure called the shoot apical meristem (SAM). Here, the stem cells—all clumped together—divide throughout the life of the plant to give rise to other cells, resulting in the formation of above-ground organs such as leaves, flowers, branches and stem.
But despite the important role the stem cells play in plant development, their molecular composition has eluded researchers for long.
Now, working on Arabidopsis, a mustard-like plant that is a model for studying plant biology, a team of researchers at UC Riverside has identified all the genes expressed in the plant's stem cells.
The researchers also identified all the genes expressed in two other SAM cells: niche cells (which are located just beneath the stem cells and which provide signals that regulate the stem cells), and differentiating cells (which are generated by, and surround, the stem cells).
The final product of the researchers' work is a genome-scale, expression map of SAM—an achievement that paves the way to developing better varieties of crops and plants.
Besides revealing the molecular pathways that stem cells employ, the discovery also can help scientists better understand why stem cells—in both plants and animals—give rise to specialized cells at all.
Study results appear online this week in the early edition of the Proceedings of the National Academy of Sciences.
"Our study is the first to reveal the stem-cell signatures for any plant and the first to provide a global view of which genes are expressed, and where, within the SAM," said G. Venugopala Reddy, the lead author of the study and an assistant professor of plant cell biology in the Department of Botany and Plant Sciences. "Since SAM stem-cells are responsible for forming plant organs and determining plant architecture, further analysis of their genes may provide a handle in altering growth rates and growth patterns in economically important crop-species in order to maximize yield."
Reddy stressed that understanding the function and regulation of stem-cell-specific genes is critical to gaining insights into basic questions such as what constitutes stem-cell identity (the ability of cells to remain unspecialized) and what makes them differentiate into specialized cells.
"A comparative analysis of stem-cell-specific genes between plant and animal systems may also lead to a better understanding of stem-cell identity, a concept common to both the systems," he said.
The study breaks ground also in the way Reddy's research team pinned down the stem-cell genes in Arabidopsis.
His lab initially labeled the three different SAM cell types—stem cells, niche cells and differentiating cells—by using different fluorescent proteins. Next, the researchers isolated the three discrete cell populations by first stripping the cell walls to release the cells as free populations. Then, using an instrument called Fluorescence Activated Cell Sorter, they separated each set of cells from the rest of the cell populations.
"Plant biologists have found it difficult to isolate the approximately 35 stem cells in the Arabidopsis shoot system for two main reasons: this is an extremely low number of stem cells and this clump of cells is tightly packed with a waxy coating covering its outer layer," Reddy said. "To meet this challenge, we used specific mutants of Arabidopsis that make more SAMs per plant. In the lab, we also formulated specific combinations of enzymes that efficiently digest away the cell walls."
Reddy explained that the gene expression map his team generated can help researchers track how genes give rise to complex tissues. It also will allow researchers to determine the expression patterns of SAM genes by a mere click of a button on a computer.
"Development of an organ such as SAM is a complex process in which cells constantly exchange information through regulated gene activities," he said. "What we have done so far is to find out which genes are expressed and where. One of the future challenges is to represent the gene expression on actual templates of plant cells, which would generate a dynamic atlas of stem-cell development. Such an atlas can be used to explore how genes function as a network to bring about stem-cell function."
Reddy acknowledged that developing the atlas is a difficult venture, requiring a synthesis of multiple disciplines such as genomics, live-imaging and informatics sciences.
"But our work breaks ground to make this a reality and we have already initiated some work in this direction," he said.
Reddy, who is also a member of UCR's Center for Plant Cell Biology, was joined in the research by Ram Kishor Yadav, Thomas Girke, Sumana Pasala and Mingtang Xie. The 24-month research project was funded by a grant from the National Science Foundation.
Basic Nutrition
on Senin, 17 Agustus 2009Basic Nutrition
Jump to: Introduction : Protein : Carbohydrate : Dietary Fibre : Fats & Oils : Vitamins : Minerals
Introduction
Many people worry that when they stop eating meat and fish, they might be in danger of some nutritional deficiency. This is not the case as all the nutrients you need can easily be obtained from a vegetarian diet. In fact research shows that in many ways a vegetarian diet is healthier than that of a typical meat-eater.
Nutrients are usually divided into five classes: carbohydrates, proteins, fats (including oil), vitamins and minerals. We also need fibre and water. All are equally important to our well-being, although they are needed in varying quantities, from about 250g of carbohydrate a day to less than two micrograms of vitamin B12. Carbohydrate, fat and protein are usually called macro-nutrients and the vitamins and minerals are usually called micro-nutrients.
Most foods contain a mixture of nutrients (there are a few exceptions, like pure salt or sugar) but it is convenient to classify them by the main nutrient they provide. Still, it is worth remembering that everything you eat gives you a whole range of essential nutrients.
Meat supplies protein, fat, some B vitamins and minerals (mostly iron, zinc, potassium and phosphorous). Fish, in addition to the above, supplies vitamins A, D, and E, and the mineral iodine. All these nutrients can be easily obtained by vegetarians from other sources, as this Information Sheet shows.
Protein
Women need about 45g of protein a day (more if pregnant, lactating or very active), men need about 55g (more if very active). Evidence suggests that excess protein contributes to degenerative diseases. Vegetarians obtain protein from:
• Nuts: hazels, brazils, almonds, cashews, walnuts, pine kernels etc.
• Seeds: sesame, pumpkin, sunflower, linseeds.
• Pulses: peas, beans, lentils, peanuts.
• Grains/cereals: wheat (in bread, flour, pasta etc), barley, rye, oats, millet, maize (sweetcorn), rice.
• Soya products: tofu, tempeh, textured vegetable protein, veggieburgers, soya milk.
• Dairy products: milk, cheese, yoghurt (butter and cream are very poor sources of protein).
• Free range eggs.
You have may have heard that it is necessary to balance the complementary amino acids in a vegetarian diet. This is not as alarming as it sounds. Amino acids are the units from which proteins are made. There are 20 different ones in all. We can make many of them in our bodies by converting other amino acids, but eight cannot be made, they have to be provided in the diet and so they are called essential amino acids.
Single plant foods do not contain all the essential amino acids we need in the right proportions, but when we mix plant foods together, any deficiency in one is cancelled out by any excess in the other. We mix protein foods all the time, whether we are meat-eaters or vegetarians. It is a normal part of the human way of eating. A few examples are beans on toast, muesli, or rice and peas. Adding dairy products or eggs also adds the missing amino acids, eg macaroni cheese, quiche, porridge.
It is now known that the body has a pool of amino acids so that if one meal is deficient, it can be made up from the body's own stores. Because of this, we don't have to worry about complementing amino acids all the time, as long as our diet is generally varied and well-balanced. Even those foods not considered high in protein are adding some amino acids to this pool.
Carbohydrate
Carbohydrate is our main and most important source of energy, and most of it is provided by plant foods. There are three main types: simple sugars, complex carbohydrates or starches and dietary fibre.
The sugars or simple carbohydrates can be found in fruit, milk and ordinary table sugar. Refined sources of sugar are best avoided as they provide energy without any associated fibre, vitamins or minerals and they are also the main cause of dental decay.
Complex carbohydrates are found in cereals/grains (bread, rice, pasta, oats, barley, millet, buckwheat, rye) and some root vegetables, such as potatoes and parsnips. A healthy diet should contain plenty of these starchy foods as a high intake of complex carbohydrate is now known to benefit health. The unrefined carbohydrates, like wholemeal bread and brown rice are best of all because they contain essential dietary fibre and B vitamins.
The World Health Organisation recommends that 50-70% of energy should come from complex carbohydrates. The exact amount of carbohydrate that you need depends upon your appetite and also your level of activity. Contrary to previous belief a slimming diet should not be low in carbohydrates. In fact starchy foods are very filling relative to the number of calories that they contain.
Dietary Fibre
Dietary fibre or non-starch polysaccharide (NSP), as it is now termed, refers to the indigestible part of a carbohydrate food. Fibre can be found in unrefined or wholegrain cereals, fruit (fresh and dried) and vegetables. A good intake of dietary fibre can prevent many digestive problems and protect against diseases like colon cancer and diverticular disease.
Fats & Oils
Too much fat is bad for us, but a little is necessary to keep our tissues in good repair, for the manufacture of hormones and to act as a carrier for some vitamins. Like proteins, fats are made of smaller units, called fatty acids. Two of these fatty acids, linoleic and linolenic acids, are termed essential as they must be provided in the diet. This is no problem as they are widely found in plant foods.
Fats can be either saturated or unsaturated (mono-unsaturated or poly-unsaturated). A high intake of saturated fat can lead to a raised blood cholesterol level and this has been linked to heart disease. Vegetable fats tend to be more unsaturated and this is one of the benefits of a vegetarian diet. Mono-unsaturated fats, such as olive oil or peanut oil, are best used for frying as the poly-unsaturated fats, like sunflower or safflower oil are unstable at high temperatures. Animal fats (including butter and cheese) tend to be more saturated than vegetable fats, with the exception of palm oil and coconut oil.
Vitamins
Vitamin is the name for several unrelated nutrients that the body cannot synthesise either at all, or in sufficient quantities. The one thing they have in common is that only small quantities are needed in the diet. The main vegetarian sources are listed below:
Vitamin A (or beta carotene): Red, orange or yellow vegetables like carrots and tomatoes, leafy green vegetables and fruits like apricots and peaches. It is added to most margarines.
B Vitamins: This group of vitamins includes B1 (thiamin), B2 (riboflavin), B3 (niacin), B6 (pyridoxine), B12 (cyanocobalmin), folate, pantothenic acid and biotin.
All the B vitamins except B12 occur in yeasts and whole cereals (especially wheat germ), nuts & seeds, pulses and green vegetables.
Vitamin B12 is the only one that may cause some difficulty as it is not present in plant foods. Only very tiny amounts of B12 are needed and vegetarians usually get this from dairy produce and free range eggs. It is sensible for vegans and vegetarians who consume few animal foods to incorporate some B12 fortified foods in their diet. Vitamin B12 is added to yeast extracts, soya milks, veggieburgers and some breakfast cereals.
Vitamin C: Fresh fruit, salad vegetables, all leafy green vegetables and potatoes.
Vitamin D: This is vitamin is not found in plant foods but humans can make their own when skin is exposed to sunlight. It is also added to most margarines and is present in milk, cheese and butter. These sources are usually adequate for healthy adults. The very young, the very old and anyone confined indoors would be wise to take a vitamin D supplement especially if they consume very few dairy products.
Vitamin E: Vegetable oil, wholegrain cereals, eggs.
Vitamin K: Fresh vegetables, cereals and bacterial synthesis in the intestine.
Minerals
Minerals perform a variety of jobs in the body. Details of the some of the most important minerals are listed below:
Calcium: Important for healthy bones and teeth. Found in dairy produce, leafy green vegetables, bread, tap water in hard water areas, nuts and seeds (especially sesame seeds), dried fruits, cheese. Vitamin D helps calcium to be absorbed.
Iron: Needed for red blood cells. Found in leafy green vegetables, wholemeal bread, molasses, eggs, dried fruits (especially apricots and figs), lentils and pulses. Vegetable sources of iron are not as easily absorbed as animal sources, but a good intake of vitamin C will enhance absorption.
Zinc: Plays a major role in many enzyme reactions and the immune system. Found in green vegetables, cheese, sesame and pumpkin seeds, lentils and wholegrain cereals.
Iodine: Present in vegetables, but the quantity depends on how rich the soil is in iodine. Dairy products also have plenty of iodine. Sea vegetables are a good source of iodine for vegans.
Reproductive System
on Jumat, 14 Agustus 2009Reproductive System
Sexual reproduction is the process of producing offspring for the survival of the species, and passing on hereditary traits from one generation to the next. The male and female reproductive systems contribute to the events leading to fertilization. Then, the female organs assume responsibility for the developing human, birth, and nursing. The male and female gonads (testes and ovaries) produce sex cells (ova and sperm) and the hormones necessary for the proper development, maintenance, and functioning of the organs of reproduction and other organs and tissues.
The reproductive system comprises the reproductive organs. In the male, the organs include the testes, accessory ducts, accessory glands, and penis. In the female, the organs include the uterus, uterine tubes, ovaries, vagina, and vulva.
The testes are paired reproductive organs in the scrotum, which hangs outside the human body. Normal sperm production requires the cooler outside temperature. Each testis contains coiled seminiferous tubules where sperm (male reproductive cells) production occurs. Between the seminiferous tubules are Leydig cells, clusters of endocrine (secretory) cells. Leydig cells produce androgens (sex hormones), mostly testosterone.
Each sperm cell has three parts: a head, middle piece, and tail. An acrosome at the head tip produces enzymes that help penetrate the female ovum (egg). During conception, chromosomes (genetic material) in the nucleus (cell control center) join with chromosomes in the ovum. The middle piece contains mitochondria, structures that provide energy for the sperm. The mitochondria are tightly spiraled around the axial filaments (contractile portion) of the flagellum (tail). Centrioles form the tail, which moves the sperm toward the ovum. An ejaculation (ejection of sperm from the penis) has 300 to 500 million sperm.
The accessory ducts store secretions from the testes and accessory glands and deliver secretions to the penis. The epididymis, a coiled tube next to each testis, receives sperm from the seminiferous tubules. The epididymis has three parts: a head, body, and tail. The epididymis stores sperm and propels it toward the penis. Smooth muscle contractions in the epididymis walls move sperm through the duct. As sperm pass through the epididymis, the sperm mature and receive nourishment.
The vas deferens is the dilated continuation of the epididymis. The vas deferens travels out of the scrotum and into the abdomen (gut cavity) through the inguinal canal. Once in the abdomen, the vas deferens passes behind the urinary bladder and expands to form an ampulla (expanded end part). Each ampulla joins with a seminal vesicle (an accessory gland) to form an ejaculatory duct. The vas deferens is the main sperm carrier. Its walls contain three layers of smooth muscle innervated by sympathetic nerves. Stimulation of these nerves propels sperm into the ejaculatory ducts. Here, the ampulla of the vas deferens and seminal vesicles meet and secretions from the seminal vesicles and sperm are stored. From this junction, the ejaculatory ducts pass through the prostate gland, where they receive more secretions, then join with the single urethra (tube through which sperm and urine pass out of body).
The urethra is the final section of the duct system. It passes from the urinary bladder and the ends of the ejaculatory ducts through the prostate gland and into the penis. The urethra receives secretions from the ejaculatory ducts, the prostate gland, and the bulbourethral glands (accessory glands). The urethra carries sperm through the penis during intercourse; during urination, urine passes through it. The urethra cannot execute both functions simultaneously. During ejaculation, a muscular sphincter (ring of muscle) closes off the bladder.
The accessory glands produce fluids that nourish and energize the sperm for the journey to the ovum. For example, during sexual excitement the seminal vesicles add secretions to the sperm in the ejaculatory duct. These secretions provide energy for the sperm and a neutralizing chemical that reduces vaginal acidity.
The prostate gland lies under the urinary bladder and surrounds the first part of the urethra. Its secretions also help neutralize vaginal acidity and make sperm motile (able to move).
The bulbourethral glands secrete a clear fluid that neutralizes the acidity of remaining urine in the urethra. When secretions of these glands combine with sperm, the result is seminal fluid, or semen. Only 1 percent of semen is sperm. The remainder contains fructose to nourish the sperm, an alkaline component to neutralize vaginal and urethral acidity, and salts and phospholipids, substances that make sperm motile.
The penis (male sexual organ) deposits semen into the vagina during sexual intercourse and carries urine through the urethra during urination. It contains erectile tissue that becomes engorged with blood during sexual excitement, resulting in an erection. The penis includes the shaft (tubular portion), glans (penis tip and sexual sensation center), and the prepuce, or foreskin (loose skin fold over glans). In a circumcision procedure, the prepuce is removed.
The female reproductive system is more complex than that of the male. It produces ova (egg cells); nourishes, carries, and protects the developing embryo; and nurses the newborn after birth. The system structures are the ovary, uterine tubes, uterus, vagina, vulva, and mammary glands.
Ovaries, a pair of female gonads (sex organs), reside in the pelvic part of the abdomen on either side of the uterus. Ovaries produce ova and estrogen (female sex hormone).
At puberty onset, the menstrual (uterine) cycle, a series of cyclic changes to the endometrium (uterine lining) begins. The ovarian cycle, fluctuating levels of ovarian hormones in the blood, causes the menstrual cycle.
The ovarian and menstrual cycles begin each month when a follicle (developing ovum surrounded by a cluster of cells) develops in the ovary. The hypothalamus in the brain produces hormones that cause these cycles. The hypothalamus releases gonadotropin-releasing hormone (GnRH), which acts on the anterior pituitary gland. GnRH causes the pituitary to release two more hormones: follicle-stimulating hormone (FSH) and luteinizing hormone (LH). FSH causes the primary oocyte within the follicle to develop into a secondary oocyte. Development occurs through meiosis (cell division that reduces the chromosome number in the cell from 46 to 23). Each secondary oocyte completes this division only when sperm fertilizes it.
The developing follicle produces estrogen, which causes the endometrium to prepare to nourish a fertilized egg. Estrogen also inhibits pituitary gland production of FSH. The elevated estrogen level causes the anterior pituitary to release LH. This action causes ovulation, a process in which the follicle rapidly enlarges and releases the secondary oocyte. LH also causes the collapsed follicle to become the corpus luteum, an endocrine (secretory) body. The corpus luteum secretes estrogen and progesterone (hormone that stimulates endometrium thickening). These hormones complete the endometrium development and maintain the endometrium for 10 to 14 days.
Unless sperm fertilize the secondary oocyte, the corpus luteum begins to degenerate, dropping blood progesterone levels. Without progesterone to maintain the endometrial lining, the lining is shed with the degenerated oocyte approximately 14 days after ovulation.
After ovulation, estrogen and progesterone act in the bloodstream to inhibit anterior pituitary production of LH and FSH. This negative feedback control ensures that only one follicle develops each cycle. Each cycle lasts approximately 28 days.
The uterine tubes (oviducts or fallopian tubes) are paired tubes that receive the developing ovum from the ovary. The infundibulum end is beside the ovary; its fimbria (feathery structures) "sweep" the developing ovum into the tube. The ampulla, the middle part of the uterine tube, contains smooth muscle to move the egg. Cilia (inner wall little projections) also sweep the egg along the tube. The unfertilized ovum degenerates in the ampulla; the fertilized ovum resumes its journey to the uterus. The isthmus end of the uterine tube opens into the uterus.
The uterus is a hollow muscular organ in front of the rectum and behind the urinary bladder. The fundus is the wide upper portion. The body is the tapered middle part that ends at the cervix (junction between the vagina and uterus). The isthmus is the constricted region between the body and cervix. The round ligaments hold the uterus anteverted (inclined forward) over the urinary bladder.
The uterus has three layers. The outer serous layer forms ligaments that hold it to the pelvic walls. The middle muscular layer has three muscle layers used in labor to deliver a baby. The endometrium inner mucosal lining has two layers, the stratum functionalis and stratum basalis.
Every month the stratum functionalis is built up in response to estrogen secretion. It contains blood vessels and glands to nourish the fertilized ovum. Unless sperm fertilizes the secondary oocyte, the corpus luteum disintegrates into corpus albicans, and estrogen and progesterone secretion cease. Without these hormones, the endometrium breaks down and menstruation (expulsion of endometrial lining from the uterus through the vagina) occurs. After menstruation, progesterone and LH levels decrease. The inhibition of LH causes the anterior pituitary to secrete FSH, which stimulates development of another ovum. The monthly cycle begins again.
The vagina is a muscular tube from the uterus to outside the body. In some women, the hymen (thin tissue) partially covers the vaginal orifice. Initial sexual intercourse or other form of penetration ruptures the hymen. The vagina receives sperm from sexual intercourse, channels menstrual flow out of the body, and is a birth canal for the baby during childbirth. Normally collapsed, it can enlarge to accommodate an erect penis or a birth.
The vulva, external genitalia, includes the mons pubis, labia majora, labia minora, and clitoris. The mons pubis is a mound of fatty tissue at the junction of the thighs and torso. During puberty, pubic hair covers it. The labia majora are skin folds that form the vulva outer border. During puberty, pubic hair covers the labia majora, too. The labia minora are inner, smaller skin folds that surround the urethral and vaginal openings. The labia minora merge anteriorly to form the prepuce (foreskin) of the clitoris. This small erectile structure, comparable to the male penis, becomes engorged with blood during sexual excitement and is the female center of sexual sensation.
The mammary glands have 15 to 20 lobes of glandular tissue. The lobes contain lactiferous ducts that converge toward the nipple. These ducts dilate just before they reach the lactiferous sinus, then constrict again before passing out of the nipple through 15 to 20 openings.
The mammary glands are in the breasts. These glands overlie the pectoral muscles and are attached to them via fascia (connective tissue). The glands are connected to the skin by the suspensory ligaments of the breast. These glands are modified sweat glands that produce and secrete milk during the lactation process to feed the newborn. During pregnancy, high blood estrogen and progesterone levels stimulate lactation. The corpus luteum produces these hormones during early pregnancy; the placenta takes over later. The hormones stimulate the ducts and glands in the breasts, enlarging the breasts.
The formation of sex cells begins before birth; spermatozoa form in males and oocytes in females. Spermatogenesis (sperm cell production) occurs in the seminiferous tubules. Spermatogonia (stem cells) line these tubules at birth and contain 46 chromosomes (genetic material). After birth, spermatogonia continue to divide during mitosis. This cell division process produces two daughter cells with the same chromosome number (46) as the parent.
At puberty onset, some spermatozoa grow to become primary spermatocytes. These cells undergo meiosis, the cell division process that cuts back the number of chromosomes from 46 to 23. Each primary spermatocyte undergoes the first meiotic division to produce two secondary spermatocytes. Each secondary spermatocyte undergoes the second meiotic division to produce two spermatids. Each spermatid develops into a mature spermatozoon (sperm cell). In this way, meiosis produces millions of sperm every day.
Oogenesis is the formation of the ovum (female sex cells), which begin as hundreds of thousands of oogonia (stem cells) in the fetal ovaries. During prenatal development, the oogonia grow to become primary oocytes that contain 46 chromosomes. Each oocyte undergoes meiosis; at birth, oocytes are in prophase. During this first meiotic division, oocytes enter a resting phase that lasts until the oocyte resumes development during the ovarian cycle (puberty). The female is born with all the oocytes she will ever have.
