Table 46.1 — Hormones of digestion
4 rows| Hormone | Source | Stimulus | Action |
|---|---|---|---|
| Gastrin | Pyloric stomach | Food (protein) entering stomach | Stimulates HCl and pepsinogen secretion — acts on the organ that secreted it |
| CCK | Duodenum | Fatty chyme | Gallbladder contraction + pancreatic enzyme secretion. Structurally like gastrin |
| GIP | Duodenum | Fatty chyme | Inhibits stomach emptying. Also stimulates insulin secretion |
| Secretin | Duodenum | Acidic chyme | Stimulates pancreatic bicarbonate. The first hormone ever discovered (1902) |
Table 46.1 — Enzymes of digestion
8 rows| Location | Enzyme | Substrate | Product |
|---|---|---|---|
| Salivary glands | Amylase | Starch, glycogen | Disaccharides |
| Stomach | Pepsin | Proteins | Short peptides |
| Pancreas | Lipase | Triglycerides | Fatty acids, monoglycerides |
| Pancreas | Trypsin, chymotrypsin | Proteins | Peptides |
| Pancreas | DNase / RNase | DNA / RNA | Nucleotides |
| Small intestine (brush border) | Peptidases | Short peptides | Amino acids |
| Small intestine (brush border) | Nucleases | DNA, RNA | Sugars and nucleic acid bases |
| Small intestine (brush border) | Lactase, maltase, sucrase | Disaccharides | Monosaccharides |
Table 46.2 — Vitamins: function and deficiency
13 rows| Vitamin | Function | Deficiency |
|---|---|---|
| A (retinol) | Visual pigments; maintains epithelial tissue | Night blindness, flaky skin |
| B1 | Coenzyme in CO₂ removal in cellular respiration | Beriberi, weakened heart, edema |
| B2 (riboflavin) | Part of FAD and FMN | Skin inflammation and breakdown, eye irritation |
| B3 (niacin) | Part of NAD⁺ and NADP⁺ | Pellagra, nerve inflammation, mental disorders |
| B5 (pantothenic acid) | Part of coenzyme A | Rare: fatigue, loss of coordination |
| B6 (pyridoxine) | Coenzyme in amino acid metabolism | Anemia, convulsions, irritability |
| B12 (cyanocobalamin) | Coenzyme in nucleic acid production | Pernicious anemia |
| Biotin | Coenzyme in fat synthesis and amino acid metabolism | Rare: depression, nausea |
| Folic acid | Coenzyme in amino acid and nucleic acid metabolism | Anemia, diarrhea |
| C | Forms collagen, connective tissue of blood vessels | Scurvy, breakdown of skin and vessels |
| D (calciferol) | Increases calcium absorption, promotes bone formation | Rickets, bone deformities |
| E (tocopherol) | Protects fatty acids and membranes from oxidation | Rare |
| K | Essential to blood clotting | Severe bleeding |
Digestive tract shape by diet
4 rows| Diet | Example | Tract features |
|---|---|---|
| Nonruminant herbivore | Rabbit | Simple stomach, very large cecum, coprophagy |
| Ruminant herbivore | Deer, cow | Four-chambered stomach with large rumen; long intestines |
| Insectivore | Mole | Short intestine, no cecum |
| Carnivore | Fox | Short intestine and colon, small cecum |
Exam traps
11 pairsQuestions get built out of near-misses. If you can state each difference in one sentence, you will not lose those points.
CCK and GIPvsSecretin
CCK and GIP answer to fat. Secretin answers to acid. All three slow the stomach, but only secretin calls for bicarbonate and only CCK squeezes the gallbladder.
GastrinvsEnterogastrones
Gastrin comes from the stomach and turns secretion ON. Enterogastrones come from the duodenum and turn stomach activity OFF.
Sugars and amino acidsvsFats
Sugars and amino acids → blood → hepatic portal vein → liver first. Fats → chylomicrons → lymphatic system, skipping the liver.
PepsinogenvsPepsin
Pepsinogen is the inactive form with 44 blocking amino acids. HCl strips them off to make active pepsin. Same logic as trypsinogen → trypsin.
Chief cellsvsParietal cells
CHief cells → pepsinogen (both start with "ch" for chief/chyme-protein). Parietal cells → HCl and intrinsic factor.
InsulinvsGlucagon
Insulin (β cells) puts glucose IN storage — lowers blood glucose. Glucagon (α cells) calls glucose OUT — raises blood glucose.
RumenvsAbomasum
Rumen = the fermentation vat, first chamber, contents can be regurgitated. Abomasum = the true stomach, last chamber, the only one making gastric juice.
Ruminant (foregut)vsRabbit/horse (hindgut)
Foregut fermenters can regurgitate and rechew. Cecal fermenters cannot, because the cecum is past the stomach — hence coprophagy in rabbits and rodents.
Leptin in micevsLeptin in obese humans
ob/ob mice are obese because they make NO leptin. Obese humans have HIGH leptin — the failure is reduced sensitivity, not reduced production.
GhrelinvsLeptin
Ghrelin says "eat" and rises before meals. Leptin says "stop" and tracks how much fat you carry.
Large intestinevsSmall intestine
"Large" refers to diameter, not length — the small intestine is far longer. Large intestine has no villi and does no digestion.