Introduction
Food is the intake of substances required for humans and animals to stay alive. It is eaten in two ways, cooked or uncooked.
Nutrition is the process by which nutrients are taken inside the body. It is essential for maintaining the body.
Diets are different kinds of food taken in by the human and animal body. It is also different eating habits like less consumption to reduce weight.
Carbohydrates
Carbohydrates are a class of chemical compound made up of a backbone of carbon, hydrogen and oxygen atoms and are a main source of energy.
The main aim is to have the appropriate intake of these essential nutrients. It also comprises fibre, a major nutritious factor, which plays a major role in the human body. Excess usage of carbohydrates poses serious problems, if we use more than the energy we require. The ration stands at: 1 gram of carbohydrates = 4 calories of energy. Carbohydrates exist in nature in two forms: Sugar and Starch.
Rice, nuts, potatoes, bread, cereal and biscuits are rich sources of starch. Sugar, honey, ice-cream, fruits and vegetables are rich sources of sugar. Deficiency of carbohydrates shows symptoms of metabolic acidosis and the excess of it has the symptoms of overweight and digestive tract irritation. Carbohydrates are built up by plants by a process called photosynthesis. Carbohydrates in the form of sugar and starch provide most of the energy for human diets.
Proteins
Proteins, also called amino acids, are structural materials required for growth and repair and replacement of damaged tissue.
The essential constituents of Proteins are hydrogen, oxygen, carbon and nitrogen. They also constitute amino acids which are essential throughout life. It is crucial for vital processes such as glandular secretions, enzymes and hormones. Excess proteins can be converted to glucose and used for the production of energy. 1 gm of protein = 4 calories; so their needs vary for different people, depending upon their physical activity and health conditions.
This is why moderate intake of proteins is essential. Infants especially need much more protein for their healthy growth. The convalescents, especially those with broken bones and burns require an adequate supply of proteins for a complete healing back to life. The most important function of proteins is tissue building. All meats, dairy, grains, plants, seeds, nuts and vegetables are rich sources of proteins. Grains are especially rich in proteins.
A diet consisting of a daily protein intake of 60-75gms for men and 40-60 for women is advised.
Fats
Fats are important source of energy and also aptly defined as lipids contain carbon, hydrogen and oxygen. One of the main functions of fat is that it slows down the emptying of the stomach and gives a sense of satisfaction and satiety after a meal, delaying the feeling of hunger. Fats help to insulate the body to protect against movement and torsion damages. Fats are required for the palatability of many foods. To achieve a palatable diet and to feed well, at least 20 – 25% of the total calories should come in the form of fat. Cholesterol is another type of fat that is found in food. It is needed for proper cell membrane maintenance and to synthesize some hormones.
It is very important for health and is synthesized in the liver. High fat diets are high in energy and except for the physically active people, it can lead to obesity. Sources of cholesterol are liver, kidney, brains, fish roe, cream, cheese and milk. Most of the essential fats come from butter, margarine and cooking oils and most others from protein foods like milk, cheese, meat bacons and fatty fish. Animal fats produce the invaluable Vitamin A and D.
Minerals
Minerals are inorganic chemical elements required for the body’s metabolism to control it, and the formation of the body’s structure. They play an important role in the health of teeth, bones, hair, blood, skin and connective tissue. They also have an important role in the body’s enzymes, vitamins and hormones. Each mineral in the body has specific functions. Minerals such as salt, potassium, calcium, magnesium, iron, phosphorus, sulphur and chlorine are termed as essential minerals for body. Recently it has been found out that copper, zinc, iodine, fluorine, chromium, manganese, selenium and cobalt are also essentials to good health. Too much of any minerals like pills or from environmental pollution can be toxic, resulting in death. A recommended daily intake of minerals is 320mgs for men and 270mgs for women. Important food sources are milk and milk products, leafy vegetables, egg yolk and fish.
Vitamins
Vitamins are organic substances that are essential for the energy in the body.
The diet supplies the different vitamins as the body is unable to make them. A daily intake of vitamins is absolutely essential. The different types of vitamins have their specific roles in the body. They are found in varying amount in different foods and most foods contain all vitamins. The most important vitamins are: vitamin A, D, E, K, B.complex and C. Of these, A, E and C are most essential to the body as they help in the most vital functions of the body as well as developing the body. Vitamin A helps in bone and teeth development, and integrity of the skin. It is found in liver, fish, milk, and vegetables. Taking in vitamin E can prevent heart disease and cancer and it can boost immunity in the elderly people.
Rich sources are nuts and seeds, grains and leafy vegetables. Vitamin K is essential for blood clotting and liver proteins production. It is found in pork liver and beef liver and vegetables. Vitamin C keeps the immune system healthy. It helps in diabetes, high blood pressure, high cholesterol; helps in cancer prevention and heart diseases. It also helps prevent vision loss and premature birth. Eating adequate amount of fish, meat, dairy products, plenty of fruits and vegetables (especially green) and livers keeps the body fit, healthy and helps in long run to life.
Oesophagus
The oesophagus is a thick muscular tube connecting the mouth to the stomach. It passes through the chest and the abdomen. Its function is to push the food down through the tube and into the stomach.
Liver
In the human body, the liver is the biggest and gland having the highest weight. This lies just below the oesophagus and is a covering above the gall bladder. The primary function of the liver is to make and eject bile which is needed in disintegrating fat in foods.
Stomach
The stomach is a bag, the walls of which are made of involuntary muscle. It lies just below the liver. The stomach takes in the food via the oesophagus and once the food has been processed, it passes out of the stomach into the small intestine.
Gall Bladder
The gall bladder is a small sac 10cm long. It is located below the liver. Its main function is to store bile, concentrate it and then release it when needed during digestion.
Pancreas
The stomach is just above the pancreatic gland. The latter dumps its contents into the duodenum, which is also termed as a small intestine.
Duodenum
The duodenum is the part of the digestive system that accepts the food as it leaves the stomach. This C curved organ is the smallest part of the small intestine, and beginning of digestive process takes place here.
Ascending Colon
The ascending colon is the portion that rises on body’s right flank and extends to the depth of the liver. It lies below the stomach. Its function is absorption of water and salts. It is very important that humans have access to plenty of fresh, clean water, so that it can replace lost fluid.
Caecum
The caecum is a pouch, 6cm long with a closed end and it is just above the appendix. Its function is mainly to absorb fluids and salts and mix them with the waste products it receives.
Appendix
Appendix is a small coiled tube 3-4 inches and it is attached to the caecum. Its function is supplying the intestines with blood vessels, nerves and lymphatics
Transverse Colon
Transverse colon is a part of the colon and is situated just above the descending colon and it runs from right to left side of the body horizontally. Its function is absorption of water and salts. As this occurs the waste becomes more solid and firm.
Descending Colon
This, also a part of the main colon descends on the left side of the body to the point of iliac crest, after which is the Sigmoid colon. This also serves to move the part received from the small intestine into the rectum ready for elimination.
Ileum
The ileum, constituting the lowest part of is the lowest section of the small intestine, is 3.6mtrs in length. It is specially designed for the absorption of water, fats, bile and bile salts. It further leads into the large intestine.
Sigmoid Colon
The Sigmoid colon is part of the large intestine. It is situated near the left side of the iliac crest and runs along the middle of the body, ending at the rectum. The special function of this is to produce high pressure so as to force the solid waste products into the rectum.
Rectum
The rectum is wide elongated tube like structure, 10cms long, which leads to the anal cavity, forms the final section of the alimentary canal. Its function in the system is to store the solid waste until it is eliminated from the body, involving a process called defecation.
Duodenum
Hormones are secreted in the duodenum and they control the release of enzymes and bile. The food released from the stomach is vigorously mixed here. The critical digestive process is conducted here.
Salivary Glands
Saliva is excreted in the mouth continuously. When a person eats, saliva increases. The salivary glands are located within the mouth. The composition of three pairs of saliva glands – the parotid, mandibular and sub lingual glands are very helpful in digestion as it contains a unique enzyme called ptyalin.
Liver
Liver is the largest and heaviest gland in the body. It’s one and only main digestive function is to produce and secrete bile. The bile smoothens the fat, making the enzymatic breakdown of fats more efficient.
Gall Bladder
It is a bag of about 10cms long, located below the liver. It stores bile, concentrates it and then releases it during digestion.
Mucosa
It is the layer lying directly inside the digestive tract. It has a major role to play as the mucosa is in direct contact with the food moving through the canal. It helps in digestion and also to absorb nutrients.
Submucosa
It is connective tissue and it helps to join the mucosa and muscularis layer together. It helps in the digestion process as it is nearest to the food moving along the canal.
Muscularis
This is basically a muscle tissue, between the submucosa and the serosa. This skeletal muscle helps in swallowing food. It is also a skeletal muscle causing voluntary excretion from the anus. Both the processes are automatically controlled by the muscles.
Serosa
This is the exterior part of the stomach and most distant from food and alimentary canal. It consists of a connective tissue called serous membrane and it encloses all body cavities. It secures the digestive part from injury or damages.
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