Attribution: National Cancer Institute (NCI), Public Domain, via Wikimedia Commons
| Recall Cue (Left Column) | Notes (Right Column) |
|---|---|
| What is the first enzyme in digestion? | Salivary amylase (ptyalin) — secreted by parotid, sublingual, submandibular glands; acts on starch → maltose + limit dextrins; optimal pH 6.8 |
| What is chyme? | Semi-fluid, acidic mass produced in stomach after mechanical churning + chemical digestion; passes through pyloric sphincter to duodenum |
| 3 functions of HCl? | (1) Kills ingested bacteria (2) Activates pepsinogen → pepsin (3) Maintains pH 1.5–2.0 for pepsin activity |
| What activates trypsinogen? | Enterokinase (from duodenal mucosa) → trypsinogen → trypsin; trypsin then activates chymotrypsinogen, proelastase, procarboxypeptidase |
| Bile's role? | Produced by liver, stored in gallbladder; bile SALTS emulsify fats (NO enzymes); increases surface area for pancreatic lipase |
| What do villi + microvilli do? | Amplify absorptive surface area ~600-fold; brush border contains maltase, sucrase, lactase, aminopeptidase, dipeptidases |
| Glucose absorption route? | Active transport (SGLT) → blood capillaries → portal vein → liver |
| Fat absorption route? | Fatty acids + glycerol → chylomicrons → lacteals → thoracic duct → left subclavian vein (bypasses liver) |
| Large intestine function? | Absorbs water (osmosis) + minerals; bacteria synthesize vitamins B and K; compacts faeces |
| 4 GI hormones? | Gastrin (G-cells, HCl + pepsinogen), Secretin (S-cells, bicarbonate), CCK (I-cells, bile + enzymes), GIP (K-cells, inhibit acid + insulin) |
| Kwashiorkor vs Marasmus? | Kwashiorkor = protein deficiency + oedema; Marasmus = total calorie + protein deficiency + wasting + NO oedema |
| Most tested NEET fact? | Bile contains NO digestive enzymes — emulsification only (not enzymatic fat digestion) |
Bottom Summary: The digestive system operates as a precisely coordinated production line. Starch digestion begins in the mouth (salivary amylase, pH 6.8). The stomach uses HCl and pepsin for protein digestion, while protecting itself with mucus. The small intestine is the central hub — receiving pancreatic juice (enzymes) and bile (emulsification), completing all digestion at the brush border, and absorbing nutrients via two routes: blood capillaries (glucose, amino acids) or lacteals (fats → lymph). The large intestine conserves water and hosts vitamin-synthesizing bacteria. Four hormones (gastrin, secretin, CCK, GIP) coordinate this entire process. The critical NEET distinction: bile emulsifies but does NOT enzymatically digest fats.