Digestive system

Question 1

What are the six major processes of digestion?

Answer 1

• Ingestion (taking in food by the mouth)
• Propulsion (swallowing, peristalsis)
• Mechanical digestion (chewing, churning, segmentation)
• Chemical digestion (enzymes)
• Absorption (Transport of digested end products into the blood and lymph vessels)
• Defecation

Question 2

Which macronutrient provides the most energy per gram?

Answer 2

Fat

Question 3

What is the basal metabolic rate of energy use in a resting person?

Answer 3

Approximately 1 kcal per minute

Question 4

What are the four histological layers of the GI tract?

Answer 4

• Mucosa
• Submucosa
• Muscularis externa
• Serosa

Question 5

What are the components of the mucosa layer?

Answer 5

Epithelium, Lamina propria, Muscularis mucosa

Question 6

What is the role of the submucosal plexus?

Answer 6

Controls secretion and blood flow in the gut

Question 7

What is the function of saliva?

Answer 7

• Protection
• taste
• lubrication
• digestion

Question 8

Which enzyme begins carbohydrate digestion in the mouth?

Answer 8

Salivary amylase

Question 9

What is the function of the oesophagus?

Answer 9

To transport the bolus to the stomach via peristalsis

Question 10

What cells produce hydrochloric acid (HCl)?

Answer 10

Parietal cells

Question 11

What cells secrete pepsinogen?

Answer 11

Chief cells

Question 12

What protects the stomach from self-digestion?

Answer 12

Mucus layers, bicarbonate, tight junctions, and rapid cell turnover

Question 13

What is intrinsic factor needed for?

Answer 13

Absorption of vitamin B12

Question 14

What condition is caused by a lack of vitamin B12?

Answer 14

Pernicious anemia

Question 15

What are the four stomach regions?

Answer 15

Cardia, Fundus, Body, Pyloric region

Question 16

What are the three phases of gastric secretion regulation?

Answer 16

• Cephalic phase
• Gastric phase
• Intestinal phase

Question 17

What hormone stimulates HCl and pepsinogen secretion in the stomach?

Answer 17

Gastrin

Question 18

Which cells does gastrin act on to stimulate HCl production?

Answer 18

Parietal cells (directly) and ECL cells (indirectly via histamine)

Question 19

What hormone inhibits gastric secretion when H+ concentration is high?

Answer 19

Somatostatin

Question 20

What are the three regions of the small intestine?

Answer 20

Duodenum, Jejunum, Ileum

Question 21

What is the primary site of digestion and absorption?

Answer 21

Small intestine

Question 22

What increases the surface area of the small intestine?

Answer 22

Plicae circulares, villi, microvilli

Question 23

What is segmentation in the small intestine?

Answer 23

Slow contractions that mix chyme and expose it to the mucosa

Question 24

Which gland secretes mucus-rich, bicarbonate fluid in the duodenum?

Answer 24

Brunner’s glands

Question 25

What hormone stimulates bicarbonate release from pancreas and liver?

Answer 25

Secretin

Question 26

What hormone stimulates enzyme release from the pancreas and gallbladder contraction?

Answer 26

Cholecystokinin (CCK)

Question 27

What are the two main functions of the pancreas?

Answer 27

Endocrine (insulin & glucagon), Exocrine (digestive enzymes & bicarbonate)

Question 28

What do acinar cells in the pancreas secrete?

Answer 28

Digestive enzymes and zymogens

Question 29

What do duct cells in the pancreas secrete?

Answer 29

Bicarbonate-rich fluid

Question 30

What is the pH of pancreatic juice?

Answer 30

Around pH 8 (alkaline)

Question 31

What are the three main components of bile?

Answer 31

Bile salts, cholesterol, bilirubin

Question 32

What are bile acids synthesized from?

Answer 32

Cholesterol

Question 33

Where are bile salts reabsorbed?

Answer 33

Small intestine (enterohepatic circulation)

Question 34

What is the primary cause of gallstones?

Answer 34

Excess cholesterol not emulsified into micelles

Question 35

What organ stores and concentrates bile?

Answer 35

Gallbladder

Question 36

What is bilirubin derived from?

Answer 36

Breakdown of haem from red blood cells

Question 37

What condition results from excess bilirubin in the blood?

Answer 37

Jaundice

Question 38

What are the types of jaundice?

Answer 38

Hemolytic, Hepatic, Obstructive

Question 39

What is the detoxification cycle for ammonia in the liver called?

Answer 39

Urea cycle (Ornithine cycle)

Question 40

What enzyme family is involved in Phase I drug metabolism?

Answer 40

Cytochrome P450

Question 41

What is the primary enzyme system for alcohol metabolism in the liver?

Answer 41

Alcohol dehydrogenase (ADH)

Question 42

What causes Asian flush syndrome?

Answer 42

Deficiency in ALDH enzyme leading to acetaldehyde buildup

Question 43

What liver function tests indicate injury?

Answer 43

ALT, AST, bilirubin, GGT, prothrombin time

Question 44

What are the main sites of digestion in the small intestine?

Answer 44

Lumen (pancreatic enzymes), brush border membrane (brush border enzymes), and cytosol (cytosolic digestion)

Question 45

What is the role of bacterial enzymes in digestion?

Answer 45

They contribute to digestion in the large intestine and are absorbed in the colon

Question 46

What type of enzymes are involved in protein digestion in the stomach and small intestine?

Answer 46

Gastric and pancreatic protease enzymes

Question 47

What are endopeptidases and exopeptidases?

Answer 47

Endopeptidases cleave internal peptide bonds; exopeptidases cleave amino acids from the terminal ends

Question 48

Where are most amino acids absorbed?

Answer 48

In the duodenum (first part of the small intestine)

Question 49

How are absorbed amino acids transported?

Answer 49

Via the portal vein to the liver

Question 50

What enzyme initiates the luminal digestion of starch?

Answer 50

Amylase

Question 51

What transporter is responsible for glucose and galactose absorption into enterocytes?

Answer 51

SGLT1 (sodium-glucose linked transporter 1)

Question 52

What transporter exports glucose and galactose from enterocytes into blood?

Answer 52

GLUT2

Question 53

How is fructose absorbed?

Answer 53

By facilitated diffusion via GLUT5 on the apical membrane and GLUT2 on the basolateral membrane

Question 54

What are the main enzymes responsible for lipid digestion?

Answer 54

Lipases

Question 55

Where does most lipid digestion occur?

Answer 55

In the small intestine

Question 56

What role does bile play in lipid digestion?

Answer 56

It emulsifies fats, aiding in digestion and absorption

Question 57

What structures help transport lipids in the intestine?

Answer 57

Micelles and chylomicrons

Question 58

What are the main functions of the large intestine?

Answer 58

Water and salt absorption, storage and concentration of feces, and expulsion of feces

Question 59

What vitamins are produced by bacteria in the large intestine?

Answer 59

Vitamin K and some B vitamins

Question 60

Name the anatomical regions of the large intestine

Answer 60

Caecum, appendix, colon (ascending, transverse, descending, sigmoid), rectum, and anal canal

Question 61

What are taeniae coli?

Answer 61

Thickened bands of longitudinal muscle in the large intestine

Question 62

What are haustra?

Answer 62

Pouches formed by segmental contractions of circular muscle in the large intestine

Question 63

What is the role of bacterial flora in the colon?

Answer 63

Fermentation of indigestible carbs/lipids, gas production, vitamin synthesis, and immune support

Question 64

What is the typical daily volume of gas produced in the colon?

Answer 64

400–700 ml/day

Question 65

What triggers the defecation reflex?

Answer 65

Distension of the rectal wall

Question 66

What muscular actions are involved in defecation?

Answer 66

Relaxation of the internal anal sphincter, contraction of the external anal sphincter, and rectal peristalsis