Digestion and Absorption

The digestive system includes the alimentary canal from mouth to anus and associated glands such as salivary glands, liver, and pancreas. The canal is organised for ingestion, propulsion, digestion, absorption, and egestion.

NEET often begins this chapter with organ-position questions: duodenum, caecum, pylorus, tongue papillae, and the sequence of food movement through the canal.

Digestion starts in the mouth where mastication increases surface area and salivary amylase begins starch breakdown. In the stomach, HCl creates an acidic medium and activates pepsinogen into pepsin. Mucus protects the gastric lining from self-digestion.

Remember the cell types: parietal cells for HCl, chief cells for pepsinogen. That pairing appears constantly in MCQs.

The liver produces bile, which emulsifies fats and does not itself contain digestive enzymes. The pancreas contributes trypsinogen, lipase, amylase, and bicarbonate-rich fluid. The intestinal mucosa secretes succus entericus, which completes digestion at the brush border.

The small intestine is the main site of absorption because of villi and microvilli. Monosaccharides and amino acids enter blood capillaries, while digested fats enter lymphatic lacteals. Many absorbed nutrients first travel to the liver through the hepatic portal system.

The large intestine mainly absorbs water and salts, not the bulk of digested nutrients. That contrast is another regular NEET test point.

Important disorders include jaundice, vomiting, diarrhoea, constipation, and various forms of gastric irritation or ulceration. The chapter also connects with practical health issues such as contaminated food, liver function, and intestinal infection.