Published On: Tue, Sep 11th, 2012

Digestion Process in Human Body

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Process of Digestion in Human Body

Food is passed into the alimentary canal and is distributed to various cells of the body. The complex substances cannot pass through the wall of the alimentary canal and so they are changed to simpler substances by a process called as digestion. The process of digestion is carried out by chemical substances called as digestive .

Definition of Digestion:

The process of digestion is the breaking down of complex substances into simpler substances with the help of digestive enzymes.

Parts and Accessory organs of the gastro-intestinal Tract:

The gastrointestinal tract comprises of the oral cavity, esophagus, stomach, small intestine and the large intestine. The parts present in the small intestine are duodenum, jejunum and ileum and that of large intestine are colon and rectum. Accessory organs are also present like pancreas, liver and gall bladder. These accessory organs helps in the process of digestion.

Overview of the Process of Digestion:

The process of digestion begins in the mouth, where the teeth starts grinding the food mechanically. Salivary glands are present in the mouth which secretes saliva into the oral cavity. This saliva lubricates the food and it also contains an enzyme, amylase which digests the starches. The mixed food or chewed food is now known as chyme. This chyme now enters into the esophagus and reaches the stomach. The stomach lining produces highly acidic gastric juice which further breaks down the chyme. The enzyme present in the gastric juice begins the digestion of the proteins. Muscular contractions of the stomach further grinds the food (chyme) into a smooth liquid. Due to further contractions of the stomach, the chyme is driven into the small intestine.

Further digestion of the proteins, sugars and nucleotides/nucleosides takes place in the small intestine by the action of pancreatic and intestinal enzymes. Majority of the essential nutrients are absorbed in the small intestine. The chyme when enters into the small intestine it is known as chyle. By the time the chyle reaches the large intestine, majority of the nutrients will be absorbed and the large intestine’s function is mainly the absorption of the water and to synthesize vitamin K and some B .

The disorders of the gastrointestinal tract may be localized to a particular structure or organ. It may also be generalized throughout the tract. Most of the disorders of the gastrointestinal tract have some common symptoms.

Process of Digestion in Detail

1. Digestion in the mouth cavity:

Food is chewed in the mouth cavity with the help of teeth and tongue. The salivary glands present in the mouth cavity secrete saliva. One litre of saliva is secreted in a day in humans.

Saliva contains the digestive enzymes mucin and ptyalin. Mucin is a sticky substance and provides an easy movement for food. Ptyalin converts the carbohydrates to maltose . The food chewed in the oral cavity is called as bolus.

The process of digestion does not take place in pharyx and oesophagus and food enters the stomach by passing through them due to the peristalitic movements of the oesophagus and food gets mixed well with the enzymes.

2. Digestion in the stomach:

In the stomach, the food gets churned by the movements of the wall of the stomach. Gastric glands secrete gastric juice that contains mucin, pepsin andhydrochloric acid.

Mucin help in lubricating the food. Hydrochloric acid activates the enzymes to digest the food and kills any which may have entered along with the food. Pepsin converts proteins into peptones. Then the food gets converted to semiliquid state and is called as chyme.

3. Digestion in the duodenum:

The duodenum receives the bile juice from the liver and pancreatic juice from the pancreas. Bile does not contain any enzymes but helps in the emulsification of the fats. Pancreatic juice consists of the enzymes trypsin, amylopsin and .

Trypsin converts peptones to aminoacids. Amylopsin converts carbohydrates into glucose and maltose. Lipase converts fats into fattyacids and glycerol.

4. Digestion in the ileum:

Intestinal juice called as succus entericus is produced by the intestinal glands. Succus entericus consists of five enzymes namely erepsin, maltase, sucrase, lactase and lipase.

Erepsin helps in converting peptones into aminoacids. Maltase, sucrase andlactase convert sugars into glucose. Lipase converts fats into fatty acids and glycerol.

At the end, carbohydrates gets converted to glucose, proteins into amino acids and fats into fatty acids and glycerol.

Absorption

The digested food is now absorbed by the numerous finger like folds known as villi in the small intestine. From the villi the food gets absorbed into the blood. Most of the absorption is carried out in the small intestine.

Assimilation

The digested food from the blood enters into the various cells of the body and provides energy. This is known as assimilation.

Elimination of the undigested food

The undigested food passes into the large intestine. It absorbs water from the digested food. The semisolid mass of undigested food is called as faeces and is eliminated through anus.

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