Question

Explain the digestion of food in human alimentary canal

Answer 1

Digestion starts from mouth where food is broken down into pieces through mastication by teeth and mixed with saliva. Saliva contain salivary amylase which starts the digestion of starch. Food become a slurry of mass in mouth which then passes to stomach where gastric juice is secreted. Gastric juice contain HCl, mucus and pepsin. HCl kills microorganisms present in food and make the medium acidic. Mucus protects the inner lining of stomach from the damaging effect of HCl and digestion of stomach wall by pepsin. Pepsin starts the digestion of protein. The thick liquid formed in stomach called as chyme, passes to small intestine. In the deudenum of small intestine, bile and pancreatic juice are secreted. Bile emulsify the fats and allow their absorption. Pancreatic juice contain trypsin, chymotrypsin, enteropeptidase which break down proteins and maltase, sucrase, lactase which break down carbohydrates. Inner lining of small intestine contain small finger-like projections called villi and microvilli which absorb nutrients from broken down foods. Remaining food enters large intestine where gut bacteria digest the unbroken food particles and the digestion by enzymes continue to take place. Nutrients and water are absorbed in colon of large intestine and undigested food become concentrated which is called faeces. Faeces are temporarily stored in rectum and finally egested from the body through anus.