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

Chapter 9: The Digestive System Flashcards

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
What are the four anatomical divisions of the stomach? Do they contain mostly gastric or pyloric glands?
- Fundus (mostly gastric glands) - Body (mostly gastric glands) - Antrum (mostly pyloric glands) - Pylorus (mostly pyloric glands)
26
What is the internal curvature of the stomach known as? What about the external?
- Internal: lesser curvature | - External: greater curvature
27
The lining of the stomach is thrown into folds called _______.
rugae
28
The gastric glands respond to signals from what? Which is activated by what?
- 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
29
What are the three different cell types of gastric glands?
- Mucous cells - Chief cells - Parietal cells
30
What is the function of mucous cells?
Produce the bicarbonate-rich mucus that protects the muscular wall from the harshly acidic (pH 2) and proteolytic environment of the stomach
31
Gastric juice is a combination of what?
Of secretions from chief cells (pepsinogen) and parietal cells (HCl and intrinsic factor)
32
What activates pepsinogen to pepsin?
Hydrogen ions in the stomach, secreted by parietal cells as HCl, cleave pepsinogen to pepsin
33
What is the function of pepsin?
Digest proteins by cleaving peptide bonds near aromatic amino acids, resulting in short peptide fragments
34
What is the function of intrinsic factor?
This glycoprotein secreted by parietal cells is involved in the proper absorption of vitamin B12
35
What cells do pyloric glands contain?
G cells
36
What is the function of G cells?
Secrete gastrin
37
What is the function of gastrin?
Induces the parietal cells in the stomach to secrete more HCl and signals the stomach to contract, mixing its contents
38
The digestion of solid food in the stomach results in an acidic, semifluid mixture known as ______.
chyme
39
Food from the stomach passes into the duodenum through what?
The pyloric sphincter
40
What are the three segments of the small intestine?
- Duodenum (chemical digestion) - Jejunum (absorption) - Ileum (absorption)
41
What activates brush-border enzymes?
The presence of chyme in the duodenum
42
What is the function of enteropeptidase?
Activates trypsinogen to trypsin and procarboxypeptidases, initiating an activation cascade
43
What is the function of secretin?
- 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
What is the function of cholecystokinin?
Stimulates bile release from the gallbladder, release of pancreatic juices, and satiety
45
What are the consequences of a lack of a particular disaccharidase?
- 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
What are aminopeptidases?
Removes the N-terminal amino acid from a peptide
47
Can disaccharides be absorbed? Can dipeptides?
- Disaccharides: no, must be monosaccharides | - Dipeptides: yes
48
What is an enterogastrone? Give an example.
- A hormone that slows motility through the digestive tract | - Secretin
49
What is bile composed of?
- Bile salts (derived from cholesterol) - Pigments (especially bilirubin from the breakdown of hemoglobin) - Cholesterol
50
What is the function of bile salts in the small intestine?
Emulsification of fats and cholesterol into micelles, allowing them to be accessible to pancreatic lipase, which breaks their ester bonds
51
What is the ideal pH for the digestive enzymes in the small intestine?
8.5
52
What do acinar cells in the pancreas produce?
Pancreatic juices that contain bicarbonate, pancreatic amylase, pancreatic peptidases (trypsinogen, chymotrypsinogen, carboxypeptidases), and pancreatic lipase
53
Pancreatic juices are transferred to the duodenum via what?
The pancreatic duct that empties into the duodenum through the major and minor duodenal papillae
54
Where is the liver located?
In the upper right quadrant of the abdomen
55
What do bile ducts connect?
Connect the liver with both the gallbladder and small intestine
56
The liver receives blood from the abdominal portion of the GI tract through what?
The hepatic portal vein
57
What organ modifies ammonia to urea?
The liver
58
What are the major functions of the liver?
- Processing of nutrients - Production of urea - Detoxification of chemicals - Production of bile - Synthesis of albumin and clotting factors
59
What is the major pigment in bile?
Bilirubin, which is a by-product of the breakdown of hemoglobin
60
What happens if the liver is unable to process or excrete bilirubin?
Jaundice or yellowing of the skin may occur
61
What is the function of albumin? Where is it synthesized?
- 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
What is the function of the gallbladder?
Stores and concentrates bile
63
What happens upon release of CCK to the gallbladder?
It contracts and pushes bile out into the biliary tree
64
How do gallstones relate to solubility and Ksp?
Stone formation is the precipitation of a solid once its concentration has reached the Ksp of the compound
65
What is chymotrypsin activated by?
Trypsin
66
The accessory organs of digestion originate from which primary germ layer?
As outgrowths of the gut tube, the accessory organs of digestion arise from embryonic endoderm
67
What is the small intestine lined with?
Villi, which are small, fingerlike projections from the epithelial lining
68
What lies at the middle of each villus?
A capillary bed for the absorption of water-soluble nutrients and a lacteal, a lymphatic channel that takes up fat
69
How are simple sugars and amino acids absorbed into the epithelial cells lining the small intestine?
Secondary active transport and facilitated diffusion
70
How does the concentration of nutrients in the blood compare to the epithelial cells?
Epithelial cells have a higher concentration of nutrients, allowing them to diffuse into the capillaries
71
Where do lacteals enter the venous circulation?
Thoracic duct, which empties into the left subclavian vein
72
How are fat-soluble vitamins absorbed?
Dissolve directly into chylomicrons to enter the body
73
How are water-soluble vitamins absorbed?
Diffused directly across the endothelial cells of the small intestine
74
What are the three sections of the large intestine?
- Cecum - Colon - Rectum
75
What is the site of the appendix?
Cecum
76
What is the function of the cecum?
Accepts fluid exiting the small intestine through the ileocecal valve
77
What are the four sections of the colon?
- Ascending - Transverse - Descending - Sigmoid
78
What is the primary function of the colon?
Absorb water and salts from the undigested material left over from the small intestine, to form feces
79
What is the function of the rectum?
Serves as a storage site for feces
80
Differentiate the internal and external anal sphincters.
- External: voluntary control (somatic) | - Internal: involuntary control (automatic)
81
What vitamins do the gut bacteria produce?
- Vitamin K, which is essential for the production of clotting factors - Biotin (vitamin B7), which is a coenzyme for many metabolic enzymes
82
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?
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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