Digestion and oral signs · Renal & GI
Digestive System MCQ
GI anatomy and physiology with the dental-relevant pieces emphasized: enzyme sites, intrinsic factor + B12, accessory organs, and oral signs of malabsorption (glossitis, enamel erosion, scurvy). 25 MCQs and 9 INBDE patient cases.
25 practice MCQsQuick-reference tableMnemonics + clinical pearlsFull distractor explanations
High-yield review
Concept summary and clinical relevance.
Quick-reference structure first, then detailed coverage. Mnemonics in amber, clinical pearls in blue.
Digestive physiology questions on the INBDE focus on which enzyme acts where, where each nutrient is absorbed, and the oral signs of GI disease. The mouth itself is the start of digestion (salivary amylase, lingual lipase), and many systemic GI conditions surface as oral findings (glossitis, enamel erosion, aphthous ulcers, gingival bleeding).
Digestive enzymes: site & substrate
| Enzyme | Source | Substrate |
|---|---|---|
| Salivary amylase | Salivary glands (mouth) | Starch (carbohydrate) |
| Lingual lipase | Lingual glands (mouth) | Triglycerides (fat) |
| Pepsin | Stomach chief cells (from pepsinogen) | Protein |
| Pancreatic amylase | Pancreas → small intestine | Starch |
| Pancreatic lipase | Pancreas → small intestine | Triglycerides |
| Trypsin / chymotrypsin | Pancreas → small intestine | Protein |
Stomach cells & secretions
| Cell | Secretes | Notes |
|---|---|---|
| Parietal | HCl + intrinsic factor | PPI side effect: ↓ B12 absorption |
| Chief | Pepsinogen (→ pepsin) | Protein digestion |
| Mucous | Mucus + bicarbonate | Protective barrier against HCl |
| G cells | Gastrin | Stimulates parietal cell HCl |
| Enterochromaffin-like (ECL) | Histamine | Stimulates HCl release |
Where each nutrient is absorbed
| Nutrient | Site | Dental relevance if deficient |
|---|---|---|
| Iron | Duodenum | Glossitis, angular cheilitis, anemia |
| Carbohydrates, proteins, most fats | Jejunum (main absorption) | Generalized malnutrition signs |
| Vitamin B12 (with IF) | Ileum | Glossitis, burning mouth, megaloblastic anemia |
| Bile salts | Ileum (recycled) | Fat malabsorption if resected |
| Fat-soluble vitamins (A, D, E, K) | Small intestine, requires bile | Bleeding (vit K), bone issues (vit D) |
| Water & electrolytes | Colon | - |
| Vitamin K (some) | Colon (synthesized by gut flora) | Antibiotics → bleeding tendency |
Clinical pearl, Oral signs of GI disease
Iron deficiency → atrophic glossitis, angular cheilitis. B12 deficiency (PPI users, gastrectomy, ileal resection, vegans) → smooth red tongue, burning mouth. Vitamin C deficiency (scurvy) → spongy bleeding gums, delayed wound healing. GERD → enamel erosion on palatal surfaces. Crohn's/celiac → recurrent aphthous ulcers, enamel hypoplasia. The mouth is often where systemic GI disease shows up first.
Clinical pearl, Vitamin K + dental bleeding risk
Vitamin K is needed for clotting factors II, VII, IX, X (and proteins C, S). Patients on long-term broad-spectrum antibiotics (which kill colonic flora that synthesize vitamin K) or with severe liver disease can have prolonged bleeding after extractions. Warfarin works by interfering with vitamin K, that's why warfarin patients need INR monitoring before surgical dental procedures.
Clinical pearl, Why intrinsic factor matters
Parietal cells make BOTH HCl and intrinsic factor (IF). Long-term proton pump inhibitor (PPI) use, autoimmune gastritis (pernicious anemia), gastrectomy, or ileal resection all impair B12 absorption: the IF–B12 complex needs the ileum. B12 deficiency causes glossitis and burning mouth before classic anemia is obvious; dentists sometimes flag it first.
Mnemonic, Stomach cells
“Parietal = Proton pump + IF. Chief = Cooks (Pepsinogen).” Parietal makes acid and intrinsic factor; chief makes pepsinogen for protein digestion.
Mnemonic, Fat-soluble vitamins
“ADEK require bile salts.” Vitamins A, D, E, K need bile-emulsified fat to absorb. Cholestasis or bile salt loss → deficiency risk.
Mnemonic, Small bowel division
“Duodenum: digestion + iron. Jejunum: juicy nutrients (most absorption). Ileum: intrinsic factor + B12 + bile salts.”
Mouth & esophagus
- Salivary amylase begins starch digestion; lingual lipase starts fat digestion (more important in infants).
- Esophagus moves the bolus by peristalsis; the lower esophageal sphincter (LES) prevents reflux.
- GERD erodes enamel: characteristically on palatal surfaces of upper anteriors.
Stomach
- Parietal cells: HCl + intrinsic factor.
- Chief cells: pepsinogen, activated to pepsin in acid.
- Mucous cells: mucus + bicarbonate barrier protecting the gastric lining.
- G cells: gastrin (stimulates HCl).
Small intestine
- Duodenum: digestion (pancreatic enzymes + bile salts) and iron absorption.
- Jejunum: main site of nutrient absorption: carbs, proteins, fats.
- Ileum: bile salt recycling and vitamin B12 absorption (with intrinsic factor).
Large intestine & accessory organs
- Colon: absorbs water, electrolytes; gut flora synthesize some vitamin K.
- Liver: produces bile, synthesizes clotting factors, clears many drugs.
- Gallbladder: stores and releases bile.
- Pancreas: exocrine (digestive enzymes) + endocrine (insulin, glucagon).
Core Recall Check
25 board-style MCQs.
Active recall is the highest-yield study method. Pick an answer, check it, and read why every distractor is wrong.
0 of 25 answered · 0 correct
Keys: A-E or 1-5, Enter to check
- Question 1EasyWhich enzyme begins carbohydrate digestion in the mouth?
- Question 2EasyWhat is the primary function of the esophagus?
- Question 3EasyWhich stomach cell produces hydrochloric acid and intrinsic factor?
- Question 4EasyWhich substance is necessary for vitamin B12 absorption in the ileum?
- Question 5EasyWhere does most digestion and absorption of nutrients occur?
- Question 6ModerateWhich intestinal section is the main site of vitamin B12 absorption?
- Question 7EasyWhich organ produces bile?
- Question 8EasyWhat is the main function of bile salts?
- Question 9EasyWhich vitamin is partly synthesized by colonic bacteria?
- Question 10EasyWhich dental finding is most characteristic of chronic vomiting or gastroesophageal reflux?
- Question 11EasyWhich vitamin deficiency develops if intrinsic factor is absent (e.g., long-term PPI use, gastrectomy, autoimmune gastritis)?
- Question 12EasyChief cells of the stomach secrete:
- Question 13ModerateThe exocrine pancreas aids digestion by secreting enzymes for all three macronutrients plus:
- Question 14ModeratePancreatic trypsinogen is activated to trypsin in the small intestine by:
- Question 15ModerateAfter absorption, long-chain dietary fats enter the circulation as chylomicrons that first travel through:
- Question 16ModerateAdvanced liver disease can increase surgical bleeding risk because the liver produces most:
- Question 17ModerateJaundice results from accumulation of bilirubin, which is produced mainly from breakdown of:
- Question 18ModerateBile salts are reabsorbed in the terminal ileum and returned to the liver, a process called:
- Question 19EasyThe gallbladder's main role is to:
- Question 20EasyLactose intolerance is caused by deficiency of:
- Question 21ModerateCeliac disease causes malabsorption by triggering immune-mediated destruction of:
- Question 22ModerateWhich inflammatory bowel disease can affect any part of the GI tract and produce oral cobblestone mucosa and aphthous-like ulcers?
- Question 23EasyThe primary function of the colon is to:
- Question 24ModerateAn oral drug absorbed from the gut reaches the liver before the rest of the body through the portal vein, a process called:
- Question 25ModerateIron deficiency anemia commonly produces which oral findings?
Clinical Reasoning Cases
INBDE patient cases.
9 ADA INBDE-format patient cases on digestive system. Each case is a shared patient box plus linked questions with full distractor explanations.
INBDE Patient Cases
Digestive System INBDE Patient Cases →
9 patient cases · 45 linked questions
Open cases →
Author
Dr. Isaac Sun, DDS
Founder, KYT Dental Services. These MCQs are reviewed by a practicing clinician and offered as an educational reference for dental students.
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