The Digestive System Flashcards
1
Q
What is the purpose of saliva?
A
- Moist, lubricate materials in mouth
- Dissolve chemicals that stimulate taste buds and provide sensory information
- Digest carbs by salivary amylase
2
Q
What are the major functions of the stomach?
A
- Store ingested food
- Mechanical breakdown of ingested food: churning
- Chemical breakdown via acid and enzymes
- Produce intrinsic factor to absorb vitamin B12 in small intestine
- Nutrients NOT absorbed
3
Q
Describe the four cells of gastric glands
A
-
Parietal cells
- Secrete intrinsic factor and HCl
-
Chief cells
- Secrete pepsinogen
- Pepsinogen is converted by HCl to pepsin
-
G cells
- Found in pyloric glands
- an enteroendocrine that produces gastrin
-
D cells
- Found in pyloric glands
- an enteroendocrine that releases somatostatin (inhibits gastrin)
4
Q
What are the metabolic regulations of the liver?
A
- Composition of circulating blood
- Nutrient metabolism/storage
- Waste product removal
- Drug inactivation
5
Q
Describe the functions of bile
A
- Emulsification: break lipid droplets apart
- Increases SA exposed to enzymatic attack
- Creates tiny emulsion droplets coated with bile salts
6
Q
Describe the processes that occur in the digestive tract
A
- Ingestion: materials enter digestive tract via mouth
- Mechanical processing: crushing and shearing
- Digestion: chemical breakdown of food
- Secretion: release of water/acids/enzymes
- Absorption: movement of substrates into interstitial fluid of digestive tract
- Excretion: removal of waste products
7
Q
Describe the four layers of the digestive tract
A
-
Mucosa
- inner lining
- folded to increase SA
- mucous membrane
-
Submucosa
- dense irregular connective tissue
- large blood vessels and lymphatic vessels
- exocrine glands
-
Muscularis externa
- smooth muscle cells
- for mechanical processing, movement of materials
-
Serosa
- serous membrane (outer lining)
- protective
8
Q
How are digestive materials moved along the digestive tract?
A
- Peristalsis: waves of muscular contraction move a bolus forward
- Visceral smooth muscle tissue: cells undergo spontaneous depolarization to trigger waves of contraction
9
Q
What are the three factors that control the digestive functions?
A
-
Local
- chemicals released into interstitial fluid
- coordinate response to changing conditions eg pH
-
Neural
- moves materials along digestive tract
- Motor neurons: controls smooth muscle contractions and glandular secretion
-
Hormonal
- produced by enteroendocrine cells
- reach target organs after distribution in bloodstream
10
Q
Describe the functions of the gallbladder
A
- Stores bile
1. Duodenum releases cholecystokinin (CCK)
2. Hepatopancreatic sphincter dilates
3. Gallbladder contracts
4. Bile released into duodenum
11
Q
Describe the three phases of gastric secretion
A
-
Cephalic phase
- sight/smell/taste/thought of food
- directed by CNS (vagus nerve)
- increased gastric juice production (pepsinogen and HCl)
-
Gastric phase
- due to food presence in stomach
- Local: distention of gastric wall
- Hormonal: secretion of gastrin by G cells
-
Intestinal phase
- due to food presence in intestine
- continues small secretion of gastrin from stomach
12
Q
Describe the three segments of the small intestine
A
- 90% of nutrient absorption
-
Duodenum
- Receives chyme from stomach
- Neutralizes acids
-
Jejunum
- Chemical digestion
- Nutrient absorption
-
Ileum
- ends at ileocecal valve
- controls material flow into cecum of large intestine
13
Q
Describe the intestinal glands
A
-
Enteropeptidase
- Brush border enzyme
- Activates pancreatic pro enzyme trypsinogen
-
Enteroendocrine cells
- Produce intestinal hormones
- eg gastrin, cholecystokinin, secretin
14
Q
Describe the enzymes produced by the pancreas
A
-
Alpha-amylase
- Breaks down starch
-
Lipase
- Breaks down lipids
- Releases fatty acids and glycerol
-
Nucleases
- Breaks down nucleic acids
- Proteolytic enzymes
- Proteases: break down large protein complexes into polypeptides
- Peptidases: break down small peptides into amino acids
15
Q
What are the six major organs of the digestive tract and their functions?
A
-
Oral cavity (mouth)
- ingestion
- mechanical processing with teeth and tongue
- moisten and mix with salivary secretions
-
Pharynx
- muscular propulsion of materials into esophagus
-
Esophagus
- transport materials to stomach
-
Stomach
- chemical breakdown via acid and enzymes
- mechanical processing via muscular contractions
-
Small intestine
- enzymatic digestion
- absorption of water and nutrients
-
Large intestine
- dehydrates and compacts indigestible materials
- prepares for elimination
