Parts of the digestive system and the functions
Mouth
Physical and chemical digestions take place in the mouth. The teeth break down food into smaller pieces to increase the surface area of the food exposed to enzymes. Saliva is produced by the salivary glands. Saliva contains the digestive enzyme,amylase, which breaks down starch in the food into maltose, a type of sugar. The tongue helps to mix the food with the saliva and rolls the partially digested food into a small ball(bolus) which is then swallowed into the oesophagus(gullet).
Oesophagus(gullet)
The oesophagus(gullet) is a long narrow tube joining the mouth and the stomach.When is food is swallowed, it does not 'drop' into the stomach as one might have imagined because of the force of gravity.In fact, the oesophagus has strong muscles in its walls.These muscles help to push the food down into the stomach by contracting and relaxing.
Stomach
The stomach is a muscular bag.The muscles contract and churn the food to mix it with a digestive juice called gastric juice.The proteases in the gastric juice digest the proteins in the food and the remaining food would turn into a thick mass of semi-liquid also known as chyme.The chyme would then move to the small intestine after a few hours.
Small Intestine
The small intestine is where most of the digestion and absorption of food takes place.The pancreas produces pancreatic juices and the small intestine,intestinal juices.Amylase from the pancreas breaks down starch into maltose.Maltese from the walls of the small intestine further breaks it down into glucose.The large surface area enables small food molecules from the digested food to be absorbed quickly.
Large Intestine
The undigested food moves from the small intestine to the large intestine through peristalsis.There are different types of bacteria living in the large intestine but most are harmless.Some are beneficial as they make vitamins required by the body.Cells linig the large intestine absorb these vitamins as well as mineral salts and excess water.A mixture of undigested food and dead bacteria are known as faeces and is temporarily stored in the rectum.Mostly the muscles of the rectum are contracted.Only when the muscles between the rectum and anus relax,will the faeces then be passed out of the body.This is know as defaecation.
Oesophagus(gullet)
The oesophagus(gullet) is a long narrow tube joining the mouth and the stomach.When is food is swallowed, it does not 'drop' into the stomach as one might have imagined because of the force of gravity.In fact, the oesophagus has strong muscles in its walls.These muscles help to push the food down into the stomach by contracting and relaxing.
Stomach
The stomach is a muscular bag.The muscles contract and churn the food to mix it with a digestive juice called gastric juice.The proteases in the gastric juice digest the proteins in the food and the remaining food would turn into a thick mass of semi-liquid also known as chyme.The chyme would then move to the small intestine after a few hours.
Small Intestine
The small intestine is where most of the digestion and absorption of food takes place.The pancreas produces pancreatic juices and the small intestine,intestinal juices.Amylase from the pancreas breaks down starch into maltose.Maltese from the walls of the small intestine further breaks it down into glucose.The large surface area enables small food molecules from the digested food to be absorbed quickly.
Large Intestine
The undigested food moves from the small intestine to the large intestine through peristalsis.There are different types of bacteria living in the large intestine but most are harmless.Some are beneficial as they make vitamins required by the body.Cells linig the large intestine absorb these vitamins as well as mineral salts and excess water.A mixture of undigested food and dead bacteria are known as faeces and is temporarily stored in the rectum.Mostly the muscles of the rectum are contracted.Only when the muscles between the rectum and anus relax,will the faeces then be passed out of the body.This is know as defaecation.
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