When we talk about food it is necessary to know a little about what happens to the food that we consume. Here is a very brief account of our digestive process.
The largest structure of the digestive system is the gastrointestinal tract (GI). This starts at the mouth and stretches all the way to the anus. It covers a distance of about nine metres. Colon is the largest component of the GI tract. The other components of the digestive system are the mouth, teeth and epiglottis, and the accessory digestive glands (liver, gall bladder and pancreas).
Digestion begins in the mouth where the food is broken down into smaller particles and mixed with saliva. The small particles mixed with saliva are known as bolus. Amylase found in the saliva called ptyalin will convert large insoluble starch molecules into soluble starches (such as amylodextrin, erythrodextrin, and achrodextrin). The smaller starches are finally converted into maltose. Lipase is also an enzyme found in the saliva. Lipase begins to break down the fats. This broken down compound is called bolus which is in a condition that is conducive to swallowing easily. Bolus is slightly alkaline because of the alkalinity of saliva. We can say that roughly 30% of the digestion takes place in the mouth. That is why it is important to take longer time chew the food well in the mouth before swallowing it.
Saliva also supplies antibodies like immunoglobulin A which supports the immune system in preventing infections of the salivary glands. Saliva also contains a glycoprotein which binds to vitamin B12 in order to carry it safely through the acidic content of the stomach. When the mixture of glycoprotein and the vitamin B12 reach the duodenum, pancreatic enzymes break down the glycoprotein and free the vitamin which then binds with intrinsic factor. Intrinsic factor is a glycoprotein produced by the stomach. It is necessary for the absorption of vitamin B12 later on in the small intestine.
At the end of the mouth you find the larynx through which air is transported to the lungs and pharynx through which food is transported to the oesophagus and then to the stomach.
A flap called epiglottis is attached to the entrance of the larynx. It is visible through the mouth. It is made of elastic cartilage. It is covered with a mucous membrane. Taste buds are on its lingual surface which faces into the mouth. The other side faces the larynx. Its function is to guard the opening between the vocal folds. During breathing it is pointed upwards and its underside becomes a part of pharynx covering it fully. During swallowing it folds down to a horizontal position with its upper side covering the pharynx. In other words it acts as a trap door to prevent the food from entering the wind pipe which leads to the lungs. But for some reason if particles of ingested food escapes into the larynx, you will get a strong cough to expel these particles and to prevent the lungs from damage.
The food goes down the oesophagus with the help of peristalsis of the oesophagus. Peristalsis is the contraction and relaxation of muscles in successive wave form which pushes the food along its path. Peristalsis is found in the entire digestive tract.
When the food reaches the stomach, salivary amylase is inactivated by gastric juice which is produced in the stomach. Gastric juice mainly contains hydrochloric acid and pepsin. These two chemicals may damage the stomach wall, and therefore stomach produces mucus, providing a slimy layer that acts as a shield against the damaging effects of the chemicals.
The gastric acid and the mucus produced in the stomach coverts bolus into chime which is a semi-fluid mass of partially digested food that is moved from the stomach into the duodenum. Chime enters the duodenum where it mixes with the enzymes produced by the pancreas. After that the chime enters the small intestine where it is fully broken down and absorbed into the blood stream. Most of the remaining digestive process takes place in the small intestines.
From the small intestine the food is pushed into the large intestine. Colon is a part of the large intestine. Colon has bacteria that can break down the food further. It is shorter than the small intestine but larger in diameter. Water, salt and some minerals are reabsorbed into the blood in the colon. The pH level in the large intestine is about 5.6 ~ 6.9. Unless the waste is eliminated in a timely manner the large intestine may end up absorbing some toxins such as heavy metals such as mercury and lead and arsenic.
The waste products of digestion are eliminated from the anus through the rectum.
The largest structure of the digestive system is the gastrointestinal tract (GI). This starts at the mouth and stretches all the way to the anus. It covers a distance of about nine metres. Colon is the largest component of the GI tract. The other components of the digestive system are the mouth, teeth and epiglottis, and the accessory digestive glands (liver, gall bladder and pancreas).
Digestion begins in the mouth where the food is broken down into smaller particles and mixed with saliva. The small particles mixed with saliva are known as bolus. Amylase found in the saliva called ptyalin will convert large insoluble starch molecules into soluble starches (such as amylodextrin, erythrodextrin, and achrodextrin). The smaller starches are finally converted into maltose. Lipase is also an enzyme found in the saliva. Lipase begins to break down the fats. This broken down compound is called bolus which is in a condition that is conducive to swallowing easily. Bolus is slightly alkaline because of the alkalinity of saliva. We can say that roughly 30% of the digestion takes place in the mouth. That is why it is important to take longer time chew the food well in the mouth before swallowing it.
Saliva also supplies antibodies like immunoglobulin A which supports the immune system in preventing infections of the salivary glands. Saliva also contains a glycoprotein which binds to vitamin B12 in order to carry it safely through the acidic content of the stomach. When the mixture of glycoprotein and the vitamin B12 reach the duodenum, pancreatic enzymes break down the glycoprotein and free the vitamin which then binds with intrinsic factor. Intrinsic factor is a glycoprotein produced by the stomach. It is necessary for the absorption of vitamin B12 later on in the small intestine.
At the end of the mouth you find the larynx through which air is transported to the lungs and pharynx through which food is transported to the oesophagus and then to the stomach.
 |
| Epiglottis |
A flap called epiglottis is attached to the entrance of the larynx. It is visible through the mouth. It is made of elastic cartilage. It is covered with a mucous membrane. Taste buds are on its lingual surface which faces into the mouth. The other side faces the larynx. Its function is to guard the opening between the vocal folds. During breathing it is pointed upwards and its underside becomes a part of pharynx covering it fully. During swallowing it folds down to a horizontal position with its upper side covering the pharynx. In other words it acts as a trap door to prevent the food from entering the wind pipe which leads to the lungs. But for some reason if particles of ingested food escapes into the larynx, you will get a strong cough to expel these particles and to prevent the lungs from damage.
 |
| Head and neck |
The food goes down the oesophagus with the help of peristalsis of the oesophagus. Peristalsis is the contraction and relaxation of muscles in successive wave form which pushes the food along its path. Peristalsis is found in the entire digestive tract.
 |
| Epiglottis |
When the food reaches the stomach, salivary amylase is inactivated by gastric juice which is produced in the stomach. Gastric juice mainly contains hydrochloric acid and pepsin. These two chemicals may damage the stomach wall, and therefore stomach produces mucus, providing a slimy layer that acts as a shield against the damaging effects of the chemicals.
The gastric acid and the mucus produced in the stomach coverts bolus into chime which is a semi-fluid mass of partially digested food that is moved from the stomach into the duodenum. Chime enters the duodenum where it mixes with the enzymes produced by the pancreas. After that the chime enters the small intestine where it is fully broken down and absorbed into the blood stream. Most of the remaining digestive process takes place in the small intestines.
From the small intestine the food is pushed into the large intestine. Colon is a part of the large intestine. Colon has bacteria that can break down the food further. It is shorter than the small intestine but larger in diameter. Water, salt and some minerals are reabsorbed into the blood in the colon. The pH level in the large intestine is about 5.6 ~ 6.9. Unless the waste is eliminated in a timely manner the large intestine may end up absorbing some toxins such as heavy metals such as mercury and lead and arsenic.
The waste products of digestion are eliminated from the anus through the rectum.
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