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MCAT: Biology > Chapter 9: The Digestive System > Flashcards

Chapter 9: The Digestive System Flashcards

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1
Q

What is intracellular digestion?

A

Involves the oxidation of glucose and fatty acids to make energy

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2
Q

What is extracellular digestion?

A

Occurs in the lumen of the alimentary canal

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3
Q

What is mechanical digestion?

A

The physical breakdown of large food particles into smaller food particles

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4
Q

What is chemical digestion?

A

The enzymatic cleavage of chemical bonds, such as peptide bonds of proteins or the glycosidic bonds of starches

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5
Q

Trace the path of food through the body, starting with ingestion and ending with excretion of feces.

A
  • Oral cavity (mouth)
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Rectum
  • Anus
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6
Q

What is the shared pathway for both food entering the digestive system and air entering the respiratory system?

A

Pharynx

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7
Q

Which organs help to provide the enzymes and lubrication necessary to aid the digestion of food?

A
  • Salivary glands
  • Pancreas
  • Liver
  • Gallbladder
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8
Q

What controls peristalsis? What is its activity upregulated and downregulated by?

A
  • The enteric nervous system
  • Upregulated by the parasympathetic nervous system
  • Downregulated by the sympathetic nervous system
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9
Q

What is the function of antidiuretic hormone (ADH) and aldosterone in feeding behaviour?

A

Trigger the sensation of thirst

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10
Q

What is the function of glucagon and ghrelin in feeding behaviour? What are they secreted by?

A
  • Stimulate feelings of hunger
  • Glucagon is secreted by the pancreas
  • Ghrelin is secreted by the stomach and pancreas
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11
Q

What is the function of leptin and cholecystokinin (CKK) in feeding behaviour?

A

Stimulate feelings of satiety

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12
Q

What starts the mechanical digestion of food in the oral cavity?

A

Mastication

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13
Q

What starts the chemical digestion of food in the oral cavity?

A
  • Salivary amylase, which hydrolyzes starch into smaller sugars (maltose and dextrins)
  • Salivary lipase, which hydrolyzes lipids
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14
Q

The food that enters the pharynx and is swallowed is called the ______.

A

bolus

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15
Q

How many salivary glands do we possess? What are they activated by?

A
  • 3

- Activated by the parasympathetic nervous system

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16
Q

What does the pharynx connect?

A

Leads from the mouth and posterior nasal cavity to the esophagus and to the larynx

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17
Q

What are the three parts of the pharynx?

A
  • Nasopharynx (behind the nasal cavity)
  • Oropharynx (at the back of the mouth)
  • Laryngopharynx (above the vocal cords)
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18
Q

How is food prevented from entering the larynx during swallowing?

A

By the epiglottis

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19
Q

How does the muscle of the top of the esophagus differ from the bottom?

A
  • Top: skeletal muscle
  • Middle: skeletal and smooth muscle
  • Bottom: smooth muscle
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20
Q

How does the skeletal muscle top of the esophagus differ from the smooth muscle bottom?

A
  • Top (skeletal): under somatic (voluntary) motor control

- Bottom (smooth): under automatic (involuntary) control

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21
Q

From the esophagus, how does food enter the stomach?

A

Through the lower esophageal (cardiac) sphincter

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22
Q

The reversal of peristalsis in the esophagus leads to what?

A

Emesis (vomiting)

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23
Q

Swallowing is initiated in the muscles of what the _________’ which constitute the ______ __________ sphincter.

A

oropharynx

upper esophageal

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24
Q

Where is the stomach located?

A

In the upper left quadrant of the abdominal cavity, under the diaphragm

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25
Q

What are the four anatomical divisions of the stomach? Do they contain mostly gastric or pyloric glands?

A
  • Fundus (mostly gastric glands)
  • Body (mostly gastric glands)
  • Antrum (mostly pyloric glands)
  • Pylorus (mostly pyloric glands)
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26
Q

What is the internal curvature of the stomach known as? What about the external?

A
  • Internal: lesser curvature

- External: greater curvature

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27
Q

The lining of the stomach is thrown into folds called _______.

A

rugae

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28
Q

The gastric glands respond to signals from what? Which is activated by what?

A
  • Respond to signals from the vagus nerve of the parasympathetic nervous system
  • Activated by the brain in response to the sight, taste, and smell of food
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29
Q

What are the three different cell types of gastric glands?

A
  • Mucous cells
  • Chief cells
  • Parietal cells
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30
Q

What is the function of mucous cells?

A

Produce the bicarbonate-rich mucus that protects the muscular wall from the harshly acidic (pH 2) and proteolytic environment of the stomach

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31
Q

Gastric juice is a combination of what?

A

Of secretions from chief cells (pepsinogen) and parietal cells (HCl and intrinsic factor)

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32
Q

What activates pepsinogen to pepsin?

A

Hydrogen ions in the stomach, secreted by parietal cells as HCl, cleave pepsinogen to pepsin

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33
Q

What is the function of pepsin?

A

Digest proteins by cleaving peptide bonds near aromatic amino acids, resulting in short peptide fragments

34
Q

What is the function of intrinsic factor?

A

This glycoprotein secreted by parietal cells is involved in the proper absorption of vitamin B12

35
Q

What cells do pyloric glands contain?

A

G cells

36
Q

What is the function of G cells?

A

Secrete gastrin

37
Q

What is the function of gastrin?

A

Induces the parietal cells in the stomach to secrete more HCl and signals the stomach to contract, mixing its contents

38
Q

The digestion of solid food in the stomach results in an acidic, semifluid mixture known as ______.

A

chyme

39
Q

Food from the stomach passes into the duodenum through what?

A

The pyloric sphincter

40
Q

What are the three segments of the small intestine?

A
  • Duodenum (chemical digestion)
  • Jejunum (absorption)
  • Ileum (absorption)
41
Q

What activates brush-border enzymes?

A

The presence of chyme in the duodenum

42
Q

What is the function of enteropeptidase?

A

Activates trypsinogen to trypsin and procarboxypeptidases, initiating an activation cascade

43
Q

What is the function of secretin?

A
  • Stimulates the release of pancreatic juices into the digestive tract and slows motility
  • Regulates the pH of the GI by reducing HCl secretion from parietal cells, and increasing bicarbonate secretion from the pancreas
44
Q

What is the function of cholecystokinin?

A

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

45
Q

What are the consequences of a lack of a particular disaccharidase?

A
  • Bacteria in the intestines are able to hydrolyze the disaccharide, producing methane gas as a by-product
  • Osmotic effect, which pulls water into the stool and causes diarrhea
46
Q

What are aminopeptidases?

A

Removes the N-terminal amino acid from a peptide

47
Q

Can disaccharides be absorbed? Can dipeptides?

A
  • Disaccharides: no, must be monosaccharides

- Dipeptides: yes

48
Q

What is an enterogastrone? Give an example.

A
  • A hormone that slows motility through the digestive tract

- Secretin

49
Q

What is bile composed of?

A
  • Bile salts (derived from cholesterol)
  • Pigments (especially bilirubin from the breakdown of hemoglobin)
  • Cholesterol
50
Q

What is the function of bile salts in the small intestine?

A

Emulsification of fats and cholesterol into micelles, allowing them to be accessible to pancreatic lipase, which breaks their ester bonds

51
Q

What is the ideal pH for the digestive enzymes in the small intestine?

A

8.5

52
Q

What do acinar cells in the pancreas produce?

A

Pancreatic juices that contain bicarbonate, pancreatic amylase, pancreatic peptidases (trypsinogen, chymotrypsinogen, carboxypeptidases), and pancreatic lipase

53
Q

Pancreatic juices are transferred to the duodenum via what?

A

The pancreatic duct that empties into the duodenum through the major and minor duodenal papillae

54
Q

Where is the liver located?

A

In the upper right quadrant of the abdomen

55
Q

What do bile ducts connect?

A

Connect the liver with both the gallbladder and small intestine

56
Q

The liver receives blood from the abdominal portion of the GI tract through what?

A

The hepatic portal vein

57
Q

What organ modifies ammonia to urea?

A

The liver

58
Q

What are the major functions of the liver?

A
  • Processing of nutrients
  • Production of urea
  • Detoxification of chemicals
  • Production of bile
  • Synthesis of albumin and clotting factors
59
Q

What is the major pigment in bile?

A

Bilirubin, which is a by-product of the breakdown of hemoglobin

60
Q

What happens if the liver is unable to process or excrete bilirubin?

A

Jaundice or yellowing of the skin may occur

61
Q

What is the function of albumin? Where is it synthesized?

A
  • Liver
  • Maintains plasma oncotic pressure and serves as a carrier for many drugs and hormones, as well as clotting factors used during blood coagulation
62
Q

What is the function of the gallbladder?

A

Stores and concentrates bile

63
Q

What happens upon release of CCK to the gallbladder?

A

It contracts and pushes bile out into the biliary tree

64
Q

How do gallstones relate to solubility and Ksp?

A

Stone formation is the precipitation of a solid once its concentration has reached the Ksp of the compound

65
Q

What is chymotrypsin activated by?

A

Trypsin

66
Q

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

A

As outgrowths of the gut tube, the accessory organs of digestion arise from embryonic endoderm

67
Q

What is the small intestine lined with?

A

Villi, which are small, fingerlike projections from the epithelial lining

68
Q

What lies at the middle of each villus?

A

A capillary bed for the absorption of water-soluble nutrients and a lacteal, a lymphatic channel that takes up fat

69
Q

How are simple sugars and amino acids absorbed into the epithelial cells lining the small intestine?

A

Secondary active transport and facilitated diffusion

70
Q

How does the concentration of nutrients in the blood compare to the epithelial cells?

A

Epithelial cells have a higher concentration of nutrients, allowing them to diffuse into the capillaries

71
Q

Where do lacteals enter the venous circulation?

A

Thoracic duct, which empties into the left subclavian vein

72
Q

How are fat-soluble vitamins absorbed?

A

Dissolve directly into chylomicrons to enter the body

73
Q

How are water-soluble vitamins absorbed?

A

Diffused directly across the endothelial cells of the small intestine

74
Q

What are the three sections of the large intestine?

A
  • Cecum
  • Colon
  • Rectum
75
Q

What is the site of the appendix?

A

Cecum

76
Q

What is the function of the cecum?

A

Accepts fluid exiting the small intestine through the ileocecal valve

77
Q

What are the four sections of the colon?

A
  • Ascending
  • Transverse
  • Descending
  • Sigmoid
78
Q

What is the primary function of the colon?

A

Absorb water and salts from the undigested material left over from the small intestine, to form feces

79
Q

What is the function of the rectum?

A

Serves as a storage site for feces

80
Q

Differentiate the internal and external anal sphincters.

A
  • External: voluntary control (somatic)

- Internal: involuntary control (automatic)

81
Q

What vitamins do the gut bacteria produce?

A
  • Vitamin K, which is essential for the production of clotting factors
  • Biotin (vitamin B7), which is a coenzyme for many metabolic enzymes
82
Q

Vibrio cholera causes a severe infection in the intestines, leading to massive volumes of watery diarrhea - up to 20 liters per day. Given these symptoms, does cholera likely impact the small intestine or the large intestine?

A

While the large intestine’s main function is to absorb water, the small intestine actually absorbs a much larger volume of water.

MCAT: Biology (12 decks)

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