Digestion

Question 1

What is the function of digestion?

Answer 1

To break down large, complex molecules into smaller, absorbable units.

Question 2

What are the two types of digestion?

Answer 2

Mechanical (e.g., chewing, churning) and chemical (enzymatic hydrolysis).

Question 3

What are the four basic processes of the digestive system?

Answer 3

Digestion, absorption, secretion, and motility.

Question 4

What role does the mucosa play?

Answer 4

Absorption and secretion; contains epithelial cells, lamina propria, and muscularis mucosae.

Question 5

What is the general structure of the gut wall?

Answer 5

Mucosa (with epithelium), submucosa, muscularis externa, and serosa.

Question 6

What is the enteric nervous system (ENS)?

Answer 6

A network of neurons in the GI tract that controls local reflexes.

Question 7

What are the two ENS plexuses?

Answer 7

Submucosal (Meissner’s) plexus and myenteric (Auerbach’s) plexus.

Question 8

What are the functions of the oral cavity in digestion?

Answer 8

Mechanical digestion (chewing) and chemical digestion (salivary enzymes).

Question 9

What enzyme begins starch digestion in the mouth?

Answer 9

Salivary amylase.

Question 10

What is the function of saliva?

Answer 10

Lubricates food, begins carbohydrate digestion, buffers pH, and contains antimicrobial compounds.

Question 11

What controls swallowing?

Answer 11

The swallowing reflex initiated by the medulla oblongata.

Question 12

What is peristalsis in the esophagus?

Answer 12

Wave-like muscle contractions that move the bolus to the stomach.

Question 13

What prevents food from entering the trachea?

Answer 13

The epiglottis.

Question 14

What are the three main functions of the stomach?

Answer 14

Storage, mechanical digestion, and chemical digestion (especially proteins).

Question 15

What enzyme is secreted by chief cells in the stomach?

Answer 15

Pepsinogen, which is activated to pepsin.

Question 16

What do parietal cells secrete?

Answer 16

Hydrochloric acid (HCl) and intrinsic factor.

Question 17

What does HCl do in the stomach?

Answer 17

Activates pepsin, denatures proteins, and kills microbes.

Question 18

What protects the stomach lining from HCl?

Answer 18

A mucus-bicarbonate barrier secreted by mucus cells.

Question 19

What is receptive relaxation?

Answer 19

The stomach relaxes to accommodate incoming food.

Question 20

What causes gastric emptying?

Answer 20

Peristaltic contractions moving chyme toward the pyloric sphincter.

Question 21

What slows gastric emptying?

Answer 21

Fats, high osmolarity, and low pH in the duodenum.

Question 22

What hormones regulate stomach activity?

Answer 22

Gastrin (stimulates acid), secretin (inhibits acid), CCK (inhibits motility).

Question 23

Where does most digestion and absorption occur?

Answer 23

In the small intestine (duodenum, jejunum, ileum).

Question 24

What controls small intestine secretions and motility?

Answer 24

The enteric nervous system and hormones (CCK, secretin).

Question 25

What does the exocrine pancreas secrete?

Answer 25

Water, bicarbonate (HCO₃⁻), and digestive enzymes (zymogens: trypsinogen, chymotrypsinogen, amylase, lipase, nuclease).

Question 26

What is the role of bicarbonate in pancreatic secretions?

Answer 26

It neutralizes the acidic chyme from the stomach.

Question 27

What activates pancreatic zymogens?

Answer 27

Enterokinase in the small intestine activates trypsinogen to trypsin, which activates other enzymes.

Question 28

What controls pancreatic secretion?

Answer 28

Parasympathetic nerves (ACh, VIP) and hormones (Secretin → HCO₃⁻; CCK → enzymes).

Question 29

What vessel delivers nutrient-rich blood from the gut to the liver?

Answer 29

The portal vein.

Question 30

Name two key metabolic functions of the liver.

Answer 30

Glycogen storage and gluconeogenesis (amino acids → glucose).

Question 31

What are Kupffer cells?

Answer 31

Liver immune cells that remove toxins and foreign materials from blood.

Question 32

What are liver lobules?

Answer 32

Structural units with central veins, portal triads, and bile canaliculi.

Question 33

What are the two functions of bile?

Answer 33

Digestive (emulsifies fats) and excretory (removes bilirubin).

Question 34

What stimulates gall bladder contraction?

Answer 34

Parasympathetic nerves (ACh) and cholecystokinin (CCK).

Question 35

What forms micelles and what is their role?

Answer 35

Fatty acids and bile salts; micelles transport lipids across the unstirred layer to enterocytes.

Question 36

Where does final digestion occur?

Answer 36

On the brush border of enterocytes via contact digestion.

Question 37

What are enterocytes?

Answer 37

Absorptive cells on villi that have microvilli and enzymes.

Question 38

What increases surface area in the small intestine?

Answer 38

Folds, villi, and microvilli (×600 increase in area).

Question 39

What structures produce new enterocytes?

Answer 39

Crypts of Lieberkuhn.

Question 40

What is peristalsis?

Answer 40

Propulsive wave-like muscle contractions moving contents along the gut.

Question 41

What is segmentation?

Answer 41

Rhythmic contractions mixing contents and promoting absorption

Question 42

What initiates peristalsis?

Answer 42

Stretching of the intestinal wall by digesta.

Question 43

What are the main functions of the colon?

Answer 43

Water and salt absorption, storage of faeces.

Question 44

What triggers mass movements in the colon?

Answer 44

The gastrocolic reflex (food entering the stomach).

Question 45

What controls defecation?

Answer 45

Internal sphincter (involuntary), external sphincter (voluntary).

Question 46

How much water is involved in daily digestion?

Answer 46

~9 L (2.5 L ingested + 6.5 L secreted).

Question 47

How much water is absorbed by the small intestine?

Answer 47

~8.5 L/day.

Question 48

How much water is excreted in faeces?

Answer 48

~0.1 L/day.

Question 49

How do emotions affect gastric motility?

Answer 49

Sadness/fear ↓ motility; anger/aggression ↑ motility.

Question 50

What causes vomiting?

Answer 50

Medulla-controlled reflex, triggered by stimuli like motion, pain, toxins, anxiety.

Question 51

What are causes of diarrhoea?

Answer 51

Infections, stress, osmotically active particles, toxins.

Question 52

What are causes of constipation?

Answer 52

Low fibre diet, ignoring urge, age, obstruction.