Digestive system helps in the digestion and absorption of food that we eat. It starts from mouth and ends at anus.
The process of digestion begins in the mouth itself. The human mouth, rather the buccal cavity consists of salivary glands that secrete salivary amylase – an enzyme that digests starch. Thus, the food we chew/masticate starts to get digested in the mouth. Almost 30% of the starch gets digested in the mouth.
The food, now known as the bolus moves to stomach through a long muscular tube like structure called – the oesophagus. The oesophagus does not secrete any enzyme. It simply acts as the passage for the movement of food/bolus. The bolus moves through the oesophagus by peristalsis.
It reaches the stomach. The stomach is guarded by cardiac spinchter. The food is acted upon by various enzymes. The stomach consists of 3 parts – the upper cardiac region, the middle fundus region and the last pyloric region This food is still semi digested, and in a semi liquid state. The food, now known as chyme and it moves from the pyloric part of the stomach to the small intestine.
The small intestine is made of 3 parts- duodenum, jejunum and ileum. The walls of the small intestine consists of microvilli that helps in absorption of the food. The small intestine secretes a number of enzymes known as ‘succus entericus’. The enzymes released firstly digests the chyme and then the nutrients are being absorbed. The large intestine does not participate in digestion. It absorbs water and minerals and prepares the wastes, that is passed out from the body as faeces.
Other parts of the digestive system includes-
Gall bladder that forms bile that helps in the emulsification of fats, leading to its absorption.
Pancreas – it secretes most of the enzymes that help in the digestion.
The food gets digested and absorbed through a complex mechanism. Each nutrient gets broken into its simplest forms and then are absorbed. As for example- the carbohydrates gets broken into starch and then to its monomers that is glucose units. The entire process is a complex mechanism.