Digestion is the process of breaking down the complex molecules into simpler molecules so that it gets absorbed easily by the action of the digestive enzymes.
How does the digestion occurs in the human body and what are the enzymes that help in the process of digestion?
First when we consume the food, it first enters the buccal cavity. Let us see the digestion process in the mouth cavity first.
Digestion in the Buccal Cavity:
The food we eat gets cut with the help of teeth and tongue and is chewed. The salivary glands present in the oral cavity secretes saliva. The chewed food gets mixed with the saliva. In a day 1 liter of saliva is secreted in humans.
This saliva consists of the digestive enzymes mucin and ptyalin.
Mucin is a sticky substance necessary for the easy movement of the food, where as ptyalin converts carbohydrates to maltose sugar.
The food which is chewed in the oral cavity is known as bolus. Digestion process does not occur in pharynx and oesophagus. The food then enters the stomach due to the peristaltic movements of the oesophagus and in this process the food gets mixed well with the enzymes.
Digestion in the stomach:
The food gets churned by the movements of the wall of the stomach. Stomach contains gastric glands that produces the gastric juice. The gastric juice contains mucin, pepsin and hydrochloric acid.
Mucin as seen in oral cavity helps in lubricating food.
Hydrochloric acids kills the bacteria that enters along with the food and activates the enzymes that helps in the process of digestion.
Pepsin converts proteins into peptones.
Then the food present gets converted to semiliquid state and is called as chyme.
Digestion in the duodenum:
The duodenum contains bile juice and pancreatic juice. Bile juice is secreted from the liver and pancreatic juice from the pancreas. Even though bile does not contain any enzymes, it helps in the emulsification of the fats. Pancreatic juice consists of the enzymes trypsin, amylopsin and lipase.
Trypsin converts peptones to amino acids.
Amylopsin converts carbohydrates into glucose and maltose.
Lipase converts fats into fatty acids and glycerol.
Digestion in the ileum:
Intestinal juice which is 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 amino acids. Maltase, sucrase and lactase 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.
After the digestion process gets completed, absorption, assimilation and elimination of the undigested food takes place.