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MCAT Biology > Ch 9 - The Digestive System > Flashcards

Ch 9 - The Digestive System Flashcards

1
Q

What is the difference between intracellular and extracellular digestion?

A
  • intra: involves the oxidation of glucose and fatty acids to make energy
  • extra: occurs in the lumen of the alimentary canal
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2
Q

What is the difference between mechanical and chemical digestion?

A
  • mechanical: physical breakdown of large food particles into smaller food particles
  • chemical: the enzymatic cleavage of chemical bonds, such as the peptide bonds of proteins or the glycosidic bonds of starches
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3
Q

What is the pathway of the digestive tract?

A

oral cavity > pharynx > esophagus > stomach > small intestine > large intensive > rectum

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4
Q

What are the accessory organs of digestion?

A

the salivary glands, pancreas, liver, and glallbladder

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5
Q

What is the enteric nervous system?

A
  • in the wall of the alimentary canal and controls peristalsis
  • its activity is upregulated by the parasympathetic nervous system and downregulated by the sympathetic nervous system
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6
Q

Which hormones regulate feeding behavior?

A
  • ADH or vasopressin and aldosterone promote thirst
  • glucagon and ghrelin promote hunger
  • leptin and cholecystokinin promote satiety
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7
Q

What starts the mechanical and chemical digestion?

A
  • in the oral cavity, mastication starts the mechanical digestion of food, while salivary amylase and lipase start the chemical digestion of food
  • food is formed into a bolus and swallowed
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8
Q

What does the pharynx connect?

A

the mouth and the posterior nasal cavity to the esophagus

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9
Q

What does the esophagus do?

A
  • propels food to the stomach using peristalsis
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10
Q

How does food enter the stomach?

A

through the lower esophageal (cardiac) sphincter

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11
Q

What are the parts of the stomach?

A
  • 4 parts; fundus, body, antrum, and pylorus
  • a lesser and greater curvature and is thrown into folds called rugae
  • numerous secretory cells line the stomach
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12
Q

What do mucous cells do in the stomach?

A

produce bicarbonate-rich mucus to protect the stomach

- increase pH

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13
Q

What do chief cells do in the stomach?

A

secrete pepsinogen, a protease activated by the acidic environment of the stomach
- digest proteins, activated by H+

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14
Q

What do parietal cells do in the stomach?

A

secrete hydrochloric acid and intrinsic factor, which is needed for vitamin B12 absorption

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15
Q

What do G cells do in the stomach?

A

secrete gastrin, a peptide hormone that increases HCl secretion and gastric motility

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16
Q

What happens after mechanical and chemical digestion in the stomach?

A

the food particles are now called chyme and food passes into the duodenum through the pyloric sphincter

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17
Q

What is the duodenum?

A

the first part of the small intestine and is primarily involved in chemical digestion

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18
Q

What do disaccharides do in the duodenum?

A

are brush-border enzymes that break down maltose, isomaltose, lactose, and sucrose into monosaccharides

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19
Q

What are 2 types of brush-border peptidases?

A

aminopeptidase and dipeptidase

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20
Q

What do enteropeptidase do in the duodenum?

A

activates trypsinogen and procarboxypeptidase, initiating an activation cascade

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21
Q

What does secretin do in the duodenum?

A

stimulates the release of pancreatic juices into the digestive tract and slows motility

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22
Q

What does cholecystokinin do in the duodenum?

A

stimulates bile release from the gallbladder, release of pancreatic juices, and satiety

23
Q

Where are acinar cells and what do they do?

A
  • in the pancreas produce pancreatic juices that contain bicarbonate, pancreatic amylase, pancreatic peptidases (trypsinogen, chymotrypsinogen, carboxypeptidases A and B), and pancreatic lipase
24
Q

What role does liver play in digestion?

A
  • synthesizes bile, which can be stored in the gallbladder or secreted into the duodenum directly
  • process nutrients (through glycogenesis and glycogenolysis, storage and mobilization of fats, and gluconeogenesis)
  • produces urea
  • detoxifies chemicals
  • activates or inactivates medications
  • produces bile
  • synthesizes albumin and clotting factors
25
Q

What are the main components of bile and what does it do?

A
  • emulsifies fats, making them soluble and increasing their surface area
  • main components are bile salts, pigments (especially bilirubin from the breakdown of hgb) and cholesterol
26
Q

What role does the gallbladder play in digestion?

A

stores and concentrates bile

27
Q

What is the jejunum and ileum?

A

the small intestine and primarily involved in absorption

28
Q

What is the small intestine lined with?

A
  • villi, which are covered with microvilli, increasing the surface are available for absorption
  • villi contain a capillary bed and a lacteal, a vessel of the lymphatic system
29
Q

What compounds enter the capillary bed v the lacteal of the villi?

A
  • capillary: water soluble compounds such as monosaccharides, amino acids, water soluble vitamins, small fatty acids, and water
  • lacteal: fat soluble compounds such as fat, cholesterol, and fat soluble vitamins
30
Q

What role does the large intestine play in digestion?

A

absorbs water and salts, forming a semisolid feces

31
Q

What role does the cecum play in digestion?

A

an outpocketing that accepts fluid from the small intestine through the ileocecal valve and is the site of attachment of the appendix

32
Q

How is the colon divided?

A

into ascending, transverse, descending, and sigmoid

33
Q

What role does the rectum play in digestion?

A

stores feces, which are then excreted through the anus

34
Q

What does gut bacteria produce?

A

vitamin K and biotin (vitamin B7)

35
Q

Which glands are innervated by the parasympathetic nervous system?

A

all except sweat glands

36
Q

What effect does the parasympathetic and sympathetic nervous system have on the digestive system?

A
  • para increases secretions from all the glands and promotes peristalsis
  • sympa lows peristalsis
37
Q

Where are the 2 places chemical digestion of carbohydrates occurs and what amylases are used?

A
  • salivary amylase (active in the mouth) has a higher specificity for rapidly-soluble starches
  • pancreatic amylase (small intestine) has a higher specificity for less soluble, more nonpolar starches
38
Q

What are the 6 products the stomach secretes?

A
  • HCl (kills microbes, denatures proteins, and converts pepsinogen into pepsin)
  • pepsinogen (cleaved in the stomach to pepsin; enzyme that partially digests proteins)
  • mucus (protects mucosa)
  • bicarbonate (protects mucosa)
  • water (dissolves and dilutes ingested materials)
  • intrinsic factor (required for normal absorption of vitamin B12)
39
Q

What 2 main enzymes are found in saliva and what do they do?

A

saliva contains salivary amylase (ptyalin) which digests starch into smaller sugars (maltose and dextrin) and lipase which digests fats

40
Q

Is sucrase an enzyme or hormone and what does it do?

A
  • enzyme

- brush-border enzyme that breaks down sucrose into monosaccharides

41
Q

Is secretin an enzyme or hormone and what does it do?

A
  • hormone

- increases pancreatic secretions, especially bicarbonate; reduces HCl secretion; decreases motility

42
Q

Is dipeptidase an enzyme or hormone and what does it do?

A
  • enzyme

- brush border enzyme that breaks down dipeptides into free amino acids

43
Q

Is cholecystokinin an enzyme or hormone and what does it do?

A
  • hormone

- recruits secretions from gallbladder and pancreas; promotes satiety

44
Q

Is enteropeptidase an enzyme or hormone and what does it do?

A
  • enzyme

- activates trypsinogen, which initiates an activation cascade

45
Q

How does bile and pancreatic lipase work together to digest fats?

A
  • bile accomplishes mechanical digestion of fats, emulsifying them and increasing their surface area
  • pancreatic lipase accomplishes chemical digestion of fats, breaking their ester bonds
46
Q

What are the pancreatic enzymes that digest carbohydrates? Proteins? Fats?

A
  • carb: pancreatic amylase
  • proteins: trypsin, chymotrypsin, carboxypeptidases A and B
  • fats: pancreatic lipase
47
Q

Where is bile synthesized, where is it stored, and where does it carry out its digestive function?

A
  • synthesized in liver
  • stored in gallbladder
  • perform in duodenum
48
Q

What accessory organs of digestion originate from which primary germ layer?

A

embryonic endoderm

49
Q

What are the 4 fat soluble vitamins?

A

A, D, E, K

50
Q

Which organs are where proteins are digested?

A

starts in stomach and then to small intestine

51
Q

Which biomolecules do not drain into the liver before arriving at the right side of the heart?

A
  • while the capillaries from the intestine come together to form the portal vein, which drains to the liver, the lacteals come together to form the thoracic duct, which drains directly into the left subclavian vein
  • fat soluble compounds do not pass through the liver before reaching the right heart
52
Q

What enzymes hydrolyze starch into maltose?

A

enzymes from the salivary glands and pancreas

53
Q

Where are amino acids, fat soluble vitamins, and cholesterol absored?

A

small intestine

MCAT Biology (12 decks)

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