6. Digestive System

Question 1

What are the two groups of the digestive system?

Answer 1

1. Gastrointestinal (GI) tract: mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus
2. Accessory digestive organs: teeth, tongue, salivary glands, liver, gall bladder, pancreas

Question 2

What are the five processes of digestion?

Answer 2

1. Ingestion – Taking food into the mouth.
2. Propulsion – Swallowing & peristalsis (moving food through the tract).
3. Digestion –
   • Mechanical: Physical breakdown (chewing, churning).
   • Chemical: Enzyme breakdown (e.g., amylase, pepsin).
4. Absorption – Nutrient transfer to blood/lymph.
5. Defecation – Elimination of waste as feces.

Question 3

What are the four layers of the GI tract?

Answer 3

• Mucosa (innermost)
• Submucosa
• Muscularis (for movement)
• Serosa (outer layer)

Question 4

What type of epithelium is found in different parts of the GI tract?

Answer 4

• Mouth, esophagus, anus → Stratified squamous
• Stomach, intestines → Simple columnar

Question 5

What is the function of saliva?

Answer 5

1. Dissolves and lubricates food to form a bolus
2. Starts digestion of starch (salivary amylase)

Question 6

What are the three major salivary glands?

Answer 6

• Parotid (largest, near ear)
• Submandibular (under jaw)
• Sublingual (under tongue)

Question 7

What are the mechanical and chemical digestive processes in the mouth?

Answer 7

• Mechanical: chewing by teeth
Chemical:
• Salivary amylase: breaks starch into maltose
• Lingual lipase: produced but inactive in mouth

Question 8

What are the three phases of swallowing?

Answer 8

• Voluntary phase: tongue pushes bolus into pharynx
• Pharyngeal phase: involuntary, soft palate closes nasopharynx, epiglottis closes trachea
• Esophageal phase: peristalsis moves bolus down esophagus

Question 9

What prevents food from entering the airway during swallowing?

Answer 9

The epiglottis covers the trachea

Breathing will halt

Question 10

What is the function of the esophagus?

Answer 10

Transports food to the stomach via peristalsis

Question 11

What is peristalsis?

Answer 11

Alternating contractions of circular and longitudinal muscles to move food through GI tract

Question 12

What are the two esophageal sphincters?

Answer 12

• Upper esophageal sphincter: regulates entry
• Lower esophageal sphincter (LES): prevents reflux

Question 13

What are the functions of the stomach?

Answer 13

• Holds food
• Churns food into chyme
• Secretes gastric juice
• Begins protein digestion

Question 14

What are the components of gastric juice?

Answer 14

• Hydrochloric acid (HCl): activates enzymes, kills microbes
• Pepsinogen (inactive) → Pepsin (active, digests proteins)
• Intrinsic factor: necessary for vitamin B12 absorption
• Mucus: protects stomach lining

Question 15

What are the specialized stomach cells?

Answer 15

• Parietal cells → HCl, intrinsic factor
• Chief cells → Pepsinogen
• G cells → Gastrin (hormone)
• mucus cells → produces protective mucus

Question 16

How does the stomach protect itself from digestion?

Answer 16

1. Pepsinogen is secreted inactive
2. Thick mucous barrier with bicarbonate

Question 17

What is gastroesophageal reflux disease (GERD)?

Answer 17

When the lower esophageal sphincter (LES) fails to close properly, causing acid reflux

Question 18

What are the functions of the liver?

Answer 18

• Produces bile
• Regulates blood glucose
• Protein metabolism (deamination, plasma proteins)
• Stores vitamins (A, D, E, K, B12) and minerals (Fe, Cu)
• Detoxifies alcohol and drugs
• breakdown of hemoglobin

Question 19

What is the function of bile?

Answer 19

Emulsifies fats (breaks down fat globules for digestion)

Question 20

What is the function of the gall bladder?

Answer 20

Stores and concentrates bile

Question 21

What is the function of the pancreas?

Answer 21

• Produces pancreatic juice, containing:
Sodium bicarbonate (neutralizes stomach acid)
• Enzymes for digestion:
• Pancreatic amylase (carbs)
• Pancreatic lipase (lipids)
• Proteases (inactive form): trypsinogen, chymotrypsinogen, procarboxypeptidase

Question 22

How are pancreatic enzymes activated?

Answer 22

• Enterokinase (in the small intestine) activates trypsinogen → trypsin
• Trypsin then activates other enzymes (chymotrypsinogen, procarboxypeptidase, proelatase

Question 23

What are the functions of the small intestine?

Answer 23

• Completes digestion (via brush border enzymes)
• Absorbs nutrients (90%)
• Releases hormones (secretin, cholecystokinin)

Question 24

What increases surface area in the small intestine?

Answer 24

Villi and microvilli

Question 25

What hormones regulate digestion in the small intestine?

Answer 25

• Secretin: stimulates pancreas to release bicarbonate • Cholecystokinin (CCK): stimulates release of bile and digestive enzymes

Question 26

How are carbohydrates absorbed?

Answer 26

• Glucose & galactose: active transport • Fructose: facilitated diffusion • both leave interstitial cell by facilitated diffusion • Transported to bloodstream → liver

Question 27

How are proteins absorbed?

Answer 27

• Amino acids: active transport • leaves interstitial cell through facilitated diffusion • Transported to bloodstream → liver

Question 28

How are lipids absorbed?

Answer 28

• Short-chain fatty acids: simple diffusion → bloodstream • Long-chain fatty acids: form chylomicrons → lymphatic system → blood

Question 29

What are the functions of the large intestine?

Answer 29

• Absorbs water, vitamins, minerals • Forms and stores feces • Hosts gut bacteria (produce Vitamin K & biotin)

Question 30

What is the defecation reflex

Answer 30

• Feces stretches rectum → spinal reflex • Internal anal sphincter (involuntary) relaxes • External anal sphincter (voluntary) contracts until defecation is appropriate

Question 31

Why is bile important for lipid digestion

Answer 31

bile emulsifies fats, breaking large fat globules into smaller droplets, increasing the surface area allowing for efficient lipid digestion

Question 32

Name the brush border enzymes found in the small intestine

Answer 32

1. Sucrase- glucose + fructose 2. Lactase- glucose + galactose 3. Maltase- glucose + glucose 4. Aminopeptidase- amino acids 5. Dipeptidase- amino acids