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The digestive system in humans

Digestion refers to the process whereby food substances are broken down into smaller particles for easy absorption. Digestion usually begins in the mouth and ends in the small intestines.

The Mouth
In the mouth, the food is chew and broken down into smaller particles. The salivary gland secretes an enzyme call salivary amylase to begin the digestion of carbohydrate into maltose; it also secretes saliva to softens the food and provide a pH which is slightly alkaline to enable salivary amylase to act properly.

Here the enzyme calls salivary amylase continuous the conversion of carbohydrate into maltose.

The stomach
In the stomach, digestion of protein begins here. The protease gland secretes enzymes call Pepsin and Renin and also hydrochloric acid which provides the suitable pH for Pepsin and Renin to act. The enzyme Pepsin breaks down protein into polypeptides and Renin coagulates and solidifies liquid protein for enzyme Pepsin to breakdown.

The duodenum
When the lives the stomach and on it way into the small intestine, the pancreas secretes the pancreatic juices which contain enzymes such as amylase to continue the conversion of carbohydrate, pepsin and renin to continue the conversion of protein into polypeptide and lipases to convert lipids into smaller droplets. The gallbladder also secretes the bile which is stored in the liver. The bile contains an enzyme call lipase which begins the conversion of fats and oil(lipids) into smaller droplets.

Small intestine
Digestion ends in the small intestine. The small intestine produces enzymes which complete the digestion of food substances. Examples include lactase to convert lactose to glucose and galactose. It also absorbs digested food substances into the body. The end product of carbohydrate is glucose, fructose and galactose; protein is amino acids and fats and oil(lipids) is fatty acids and glycerol.

Large intestine

This is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body. It absorbs water, potassium and some fat soluble vitamins.

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