Most of us know that the human body needs to eat to replenish energy, and that eating the wrong foods can cause health problems and even indigestion.
"Learn to chew and spend more time masticating your food"
We are knowledgeable about carbohydrates, fats and proteins, but they should also understand what happens to food after it has entered their digestive system. Because the vast majority of foods are too large to be absorbed across the plasma membranes of the cells, the food must be broken down first, both chemically and mechanically. This process is called digestion.
What follows is a very technical discussion of digestion and metabolism. Outside of a biology or medical textbook one would not normally encounter such detail. My logic for adopting this approach was to ensure that you, would be fully informed as to how your digestive system works. Understanding this process empowers you to make better decisions regarding diet and the use, or non use, of supplements.
Mechanical digestion consists of various movements that aid chemical digestion. Food must be broken down by the teeth before it can be swallowed. The smooth muscles of the stomach and small intestine then churn the food so it is thoroughly mixed with the enzymes (a substance produced by a living organism) that catalyze the reactions.
Chemical digestion is a series of catabolic (decomposition) reactions that break down the large carbohydrate, lipid and protein molecules of food into smaller molecules. These products of digestion are small enough to pass through the walls of the digestive organs, into the blood and lymph capillaries, and finally into the body’s cells.
The digestive system is divided into two main sections: the gastrointestinal tract (GI), also referred to as the alimentary canal, and the accessory organs. The GI is made up of the mouth , esophagus, stomach, small intestine and large intestine. The GI tract holds the food from the time it is eaten until it is prepared for excretion. Muscular contractions in the walls of the GI tract break down the food physically by churning it. Secretions produced by cells along the GI tract break down the food chemically.
Digestion -By Role Of Organs
The Mouth
The most part digestion in the mouth is done by the salivary glands, teeth and tongue. We must chew the food proper before gulp it. Saliva is a fluid continuously secreted by glands in or near the mouth. Saliva is secreted to keep the mucous membranes of the mouth moist. When food enters the mouth, secretion increases so saliva can lubricate, dissolve and chemically
break down the food. Through chewing, the teeth tear the food apart and mix it with saliva.
Saliva is 99.5 percent water and 0.5 percent solutes.
The Stomach
After food enters the stomach, peristaltic movements ripple across the stomach every 15 to 25 seconds except for in a part of the stomach called the fundus, which acts as a storage area. Here foods may sit for an hour or more with only salivary digestion(moistening food) continuing. In the rest of the stomach the movements, or mixing waves, churn the food with the gastric secretions, producing a thin liquid called chyme.
The main chemical activity of the stomach is to begin the breakdown of proteins. This is accomplished by the gastric juice, which is made up by the enzymes pepsin and rennin, and hydrochloric acid (HCI). Pepsin breaks certain peptide bonds between the amino acids that make up proteins. Hence a protein chain of many amino acids is broken down into fragments of amino acids. Long fragments are called proteoses and short fragments are called peptones.
Rennin helps solidify casein, a milk protein. Thus it can be held in the stomach long enough for pepsin to break it down. Pepsin is most effective in the acidic environment of the stomach (pH of 1). The HCI in the gastric juice ensures an acidic medium.
Food rich in carbohydrates leaves the stomach in a short period of time. Protein-rich foods are slower, and fatty foods are the slowest of all to be emptied out. The stomach is impermeable to the passage of most materials into the blood (with the exception of some water, salts, certain drugs and alcohol), so most substances are not absorbed until they reach the small intestine.
The Small Intestine
Chemical digestion in the small intestine depends not only on its own secretions but also on the activities of three organs outside the GI tract: the liver, gallbladder and pancreas.
Mechanical digestion consists of three distinct peristaltic movements, which serve to mix the chyme with the digestive juices and move the entire mixture further down the GI tract.
The Large Intestine
Digestion is almost complete by the time the chyme reaches the large intestine. Bacterial action results in the synthesis of vitamin K and some of the B vitamins. Any remaining proteins and amino acids are broken down by bacteria into simpler substances: fatty acids, hydrogen sulfide, skatole and indole. Together with intestinal water, some of it is absorbed. What is left is passed out of the body.
METABOLISM
The whole range of biochemical processes that occur within a living organism. Metabolism consists of anabolism (the buildup of substances) and catabolism (the breakdown of substances). The term metabolism is commonly used to refer specifically to the breakdown of food and its transformation into energy.
"That's All About Digestion And Metabolism.Hope This Information Clear Your Doubts"
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