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MCAT > Biology Ch 9. The Digestive System > Flashcards

Biology Ch 9. The Digestive System Flashcards

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MCAT flashcards
1
Q

Intracellular digestion

A

Involves the oxidation of glucose and fatty acids to make energy, part of metabolism

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2
Q

Extracellular digestion

A

Occurs in the lumen of the alimentary canal

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3
Q

Alimentary canal

A

Location where extracellular digestion occurs, runs from mouth to anus, occurs within lumen which is technically outside the body

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4
Q

Mechanical digestion

A

The physical breakdown of large food particles into smaller food particles

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5
Q

Chemical digestion

A

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

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6
Q

Digestive pathway

A

Oral cavity, pharynx, Soffa guess, stomach, small intestine, large intestine, rectum

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7
Q

Accessory organs of digestion

A

The salivary glands, pancreas, liver, and gallbladder, help to provide the enzymes and lubrication necessary to aid in the digestion of food

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8
Q

Enteric nervous system

A

In the walls of the alimentary canal and controls peristalsis, its activity is up regulated by the parasympathetic nervous system (increases secretion from exocrine valves and promotes peristalsis) and down regulated by the sympathetic nervous system

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9
Q

Oral cavity

A

Mouth, where alimentary canal starts, mastication and secretion of salivary amylase and lipase occur (both physical and chemical digestion), once food formed into a bolus, it is swallowed

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10
Q

Anus

A

Where alimentary canal ends

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11
Q

Sphincters

A

Circular smooth muscles around the alimentary canal that can contract to allow compartmentalization of function

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12
Q

Digestion

A

The breakdown of food into its constitute organic molecules: starches and other carbohydrates into monosaccharides, lipids into free fatty acids in glacier all, and proteins into amino acids

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13
Q

Absorption

A

Involves the transfer the products of digestion from the digestive tract into the circulatory system for distribution to the bodies tissues and cells

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14
Q

Pharynx

A

A shared pathway for both food entering the digestive system and air entering the respiratory system, connects the month and posterior nasal cavity to the esophagus, divided into nasopharynx, oropharynx, and laryngopharynx

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15
Q

Esophagus

A

Muscular tube that transports food from pharynx to stomach using peristalsis, lower esophageal (cardiac) sphincter at end, top third is skeletal muscle (somatic motor control), bottom third is smooth muscle (autonomic control), and middle third is both

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16
Q

Rectum

A

Location with feces are stored until an appropriate time of release

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17
Q

Peristalsis

A

Rhythmic contractions of the smooth muscle throughout the gut tube, in order to move materials through the digestive system

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18
Q

Hormones regulating feeding behavior

A

Antidiuretic hormone or vasopressin, aldosterone, glucagon and ghrelin, and leptin and cholecystokinin

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19
Q

Antidiuretic hormone and aldosterone feeding behavior

A

Promote thirst, encourage fluid consumption

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20
Q

Glucagon and ghrelin feeding behavior

A

Promote hunger, glucagon from pancreas and ghrelin from stomach

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21
Q

Leptin and cholecystokinin feeding behavior

A

Promote satiety

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22
Q

Mastication

A

Chewing, starts the mechanical digestion of food in the oral cavity, the breaking up of food using the teeth, lips, and tongue, increases SA to V ratio which allows for more enzymatic digestion, also reduces obstruction risk

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23
Q

Salivary amylase

A

Starts chemical digestion of food in the oral cavity, in saliva, aka ptyalin, capable of hydrolyzing starch into smaller sugars (maltose and dextrins)

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24
Q

Lipase

A

Starts chemical digestion of food in the oral cavity, catalyses the hydrolysis of lipids

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25
Q

Bolus

A

What food is formed into prior to it being swallowed

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26
Q

Lower esophageal (cardiac) sphincter

A

Where food from the esophagus enters the stomach, relaxes to allow the passage of food

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27
Q

Stomach parts

A

Fundus, body, antrum, and pylorus

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28
Q

Less curvature

A

Internal curvature of the stomach

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29
Q

Greater curvature

A

External curvature of the stomach

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30
Q

Rugae

A

Folds of the stomach

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31
Q

Stomach

A

Has four parts, has lesser and greater curvature, is thrown into rugae, lined with numerous secretory cells, ends with pyloric sphincter, capacity of 2 L, located in the upper left quadrant of the abdominal cavity underneath the diaphragm , uses HCl and enzymes to digest food

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32
Q

Mucous cells

A

Produce bicarbonate rich mucus to protect the stomach from harshly acidic and proteolytic environment

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33
Q

Chief cells

A

Secrete pepsinogen, a protease activated in the acidic environment of the stomach

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34
Q

Pepsinogen

A

A protease activated by the acidic environment of the stomach, inactive, zymogen form of pepsin

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35
Q

Parietal cells

A

Secrete hydrochloric acid and intrinsic factor, which is needed for vitamin B 12 absorption, hydrogen ions released cleave pepsinogen to pepsin

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36
Q

Intrinsic factor

A

Secreted by the parietal cells in the stomach, needed for vitamin B 12 absorption

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37
Q

G cells

A

Secrete gastrin

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38
Q

Gastrin

A

Peptide hormone that increases hydrochloric acid secretion and gastric motility, induces parietal cells and the stomach to contract, mixing contents

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39
Q

Chyme

A

Food particles that have undergone mechanical and chemical digestion in the stomach, semifluid mixture

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40
Q

Pyloric sphincter

A

Where food leaves the stomach and enters the duodenum

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41
Q

Duodenum

A

First part of the small intestine and is primarily involved in chemical digestion, presence of chyme causes release of brush based enzymes, enteropeptidase, secretin, and CCK

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42
Q

Disaccharidases

A

Brush-border enzymes that break down maltose (maltase), isomaltose (isomaltase), lactose (lactase), and sucrose (sucrase) into monosaccharides

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43
Q

Brush-border enzymes

A

Present on the luminal surface of cells lining the duodenum and break down dimers and trimers of biomolecules into absorbable monomers, Includes dissacharidases, amino peptidase, and dipeptidases

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44
Q

Enteropeptidase

A

Activates trypsinogen and procarboxypeptidases A and B, initiating an activation cascade of other accessory organs of digestion

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45
Q

Secretin

A

Peptide hormone that stimulates the release of pancreatic juices into the digestive tract, regulates pH by reducing HCl secretion from parietal cells, can increase bicarbonate secretion from the pancreas, and is a type of enterogastrone

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46
Q

Cholecystokinin

A

CCK - Peptide hormone that stimulates bile release from the gallbladder, release of pancreatic juices, and promotes satiety in the brain

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47
Q

Salivary glands

A

Three pairs of them produce saliva in the oral cavity

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48
Q

Saliva

A

Produced by three pairs of salivary glands in oral cavity, aids in mechanical digestion by moistening and lubricating food, innervated by the parasympathetic nervous system by presence of food, contains salivary amylase and lipase

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49
Q

Nasopharynx

A

Division of the pharynx behind the nasal cavity

50
Q

Oropharynx

A

Division of the pharynx at the back of the mouth

51
Q

Laryngopharynx

A

Division of the pharynx above the vocal cords

52
Q

Epiglottis

A

A cartilaginous structure that folds down to cover the laryngeal inlet during swallowing to prevent food from entering larynx

53
Q

Emesis

A

aka vomiting, reversal of peristalsis in response to chemicals, infectious agents, physical stimulation of the posterior pharynx, or cognitive stimulation

54
Q

Upper esophageal sphincter

A

Where swallowing in initials in the muscles of the oropharynx

55
Q

Fundus

A

Part of the stomach, contains mostly gastric glands

56
Q

Body

A

Part of the stomach, contains mostly gastric glands

57
Q

Antrum

A

Part of the stomach, contains mostly pyloric glands

58
Q

Pylorus

A

Part of the stomach, contains mostly pyloric glands

59
Q

Gastric glands

A

Respond to signals from the vagus nerve of the PNS, have three different cell types: mucous cells, chief cells, and parietal cells

60
Q

Gastric juice

A

Combination of secretions from chief cells and parietal cells

61
Q

Pepsin

A

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

62
Q

Stomach hydrochloric acid

A

Hydrogen ions cleave pepsinogen into pepsin, kills most harmful bacteria, and helps to denature proteins

63
Q

Pyloric glands

A

Contain G cells

64
Q

Stomach absorption

A

Mainly digestion, only a few substances such as alcohol and aspirin that are absorbed directly from the stomach

65
Q

Small intestine

A

Divided into three segments,

66
Q

Small intestine segments

A

Duodenum, jejunum, and ileum

67
Q

Lacking a particular disaccharidase

A

Bacteria in intenstines hydrolyze disaccharide producing methanols gas, osmotic effect pulling water into stool and causing diarrhea

68
Q

Peptidases

A

Breaks down proteins

69
Q

Aminopeptidase

A

Peptidase secreted by glands in the duodenum that remove the N terminal animal acid from a peptde

70
Q

Dipeptidases

A

Cleaves the peptide bonds of dipeptides to release free animo acids

71
Q

Trypsinogen

A

A pancreatic protease which is activated by enteropeptidase into trypsin

72
Q

Trypsin

A

Initiates an activation cascade

73
Q

Enterogastrone

A

A hormone that slows motility through the digestive tract, allows increased time for digestive enzymes (especially needed for fats)

74
Q

Bile

A

Complex fluid composed of bile salts, pigments, and cholesterol

75
Q

Bile salts

A

Derived from cholesterol, do not directly perform chemical digestion (they are not enzymes) but serve important role in the mechanical digestion of fats and chemical digestion of lipids

76
Q

Bile salts emulsification

A

Emulsify fats and cholesterol into micelles using hydrophilic and hydrophobic regions, necessary so that fats dont separate out of mixture because pancreatic lipase is water-soluble, also increase surface area so lipase can act faster

77
Q

Pancreatic juices

A

Complex mixture of sever enzymes in a bicarbonate-rich alkaline solution, helps to neutralize acidic chyme to pH where enzymes are the most active (around pH 8.5), travels to duodenum via duct system ad enter via the major and minor duodenal papillae

78
Q

Acinar cells

A

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

79
Q

Liver digestion

A

Located in upper right quadrant of the abdomen, synthesizes bile which is either then stored in the gallbladder or released immediately, also processes nutrients from blood draining from abdominal portion of the digestive tract through the hepatic portal vein and then sends blood to IVC, produces urea, detoxifies chemicals, activates or inactivates medications, and synthesizes albumin and clotting factors

80
Q

Bile pigments

A

Most important bilirubin from the breakdown of hemoglobin)

81
Q

Gallbladder

A

Stores and concentrates bile, located just beneath the liver, contracts and releases bile into binary tree upon release of CCK, common site of cholesterol or bilirubin stone formation

82
Q

Accessory organs of digestion

A

The pancreas, liver, and gallbladder

83
Q

Pancreatic amylase

A

Breaks down large polysaccharides into small disaccharides, responsible for carbohydrate digestion

84
Q

Pancreatic peptidases

A

Include trypsinogen, chymotrypsinogen, and carboxypeptidases A and B, all released in zymogen form but are activated by enteropeptidase

85
Q

Pancreatic lipase

A

Capable of breaking down fats into fatty acids and glycerol

86
Q

Major and minor duodenal papillae

A

Where bile ducts empty pancreatic juices into the duodenum

87
Q

Bile ducts

A

Connects the liver with both the gallbladder and small intestine

88
Q

Liver glucose

A

Liver takes up excess sugar to create glycogen, can produce glucose using glycogenolysis and gluconeogenesis

89
Q

Glycogen

A

Storage form of glucose

90
Q

Bilirubin

A

A byproduct of the breakdown of hemoglobin, conjugated in the liver and secreted into the bile for excretion, if the body is unable to process or excrete bilirubin, jaundice may occur

91
Q

Jaundice

A

Yellowing of the skin because the body is unable to process or excrete bilirubin

92
Q

Albumin

A

Protein that maintains plasma oncotic pressure and serves as a carrier for many drugs and hormones, synthesized by the liver

93
Q

Clotting factors

A

Synthesized by the liver, used during blood coagulation

94
Q

Biliary tree

A

Connects gallbladder to duodenum, merges with pancreatic duct

95
Q

Triacylglyercols digestive pathway

A

Lipase in oral cavity, lipase from pancreas, bile micelles from gallbladder

96
Q

Carbohydrates digestive pathway

A

Amylase in oral cavity, amylase from pancreas, sucrase, lactase, maltase, and isomaltase from the small intestine (brush border)

97
Q

Protein digestive pathway

A

Pepsin from stomach, typsin, chymotrypsin, carboxypeptidases A and B in the pancreas, dipeptidases and aminopeptidase from the small intestine (brush border)

98
Q

Jejunum

A

Primarily involved in absorption, lined with villi

99
Q

Ileum

A

Primarily involved in absorption, lined with villi

100
Q

Villi

A

Lines small intestine, small fingerling projections from the epithelial lining covered in microvilli which furtherer increase the surface area for absorption, contain a capillary bed (for water soluble compounds such as monosaccharides, amino acids, water soluble vitamins, small fatty acids etc) and a lacteal (for fat soluble compounds such as cholesterol, fat soluble vitamins)

101
Q

Lacteal

A

A vessel of the lymphatic system, transports fat soluble compounds from the small intestine, form the beginning of the lymphatic system, converge and enter the venous circulation at the thoracic duct which empties into the left subclavian vein

102
Q

Microvilli

A

Cover villi to increase SA for absorption

103
Q

Large intestine

A

Absorbs water and salts, forms semisolid feces, divided into the cecum, the colon, and the rectum

104
Q

Cecum

A

An out pocketing that accepts fluid from the small intestine through the ileocecal valve and is the site of attachment of the appendix

105
Q

Ilocecal valve

A

Transfers fluid from the small intestine to the cecum

106
Q

Colon

A

Divided into ascending, transverse, descending, and sigmoid portions, main function to absorb water and salts

107
Q

Rectum

A

Stores feces which contains indigestible material, water, bacteria, and certain digestive secretions that are not reabsorbed (enzymes and some bile)

108
Q

Gut bacteria

A

Produce Vitamin K and biotin

109
Q

Simple sugars and amino acid absorption

A

Absorbed by secondary active transport and facilitated diffusion, diffuse across epithelial cell membrane into the intestinal capillaries, because blood constantly flowing, there is always a concentration gradient, absorbed molecules head to liver via hepatic portal circulation

110
Q

Short chain fatty acid absorption

A

Same process as carbohydrates and amino acids by diffusing directly into intestinal capillaries, are nonpolar so they can traverse across cell membrane

111
Q

Larger fats, glycerol, and cholesterol absorption

A

Move separately into intestinal cells and then reform into triglycerides, triglycerides and cholesterol are then packaged into chylomicrons which enter the lymphatic system via lacteals

112
Q

Thoracic duct

A

Where laterals converge and enter the venous circulation and them empty into the left subclavian vein

113
Q

Chylomicrons

A

Packaged triglycerides and esterified cholesterol that enters the lymphatic circulation through lacteals

114
Q

Fat soluble vitamins

A

A, D, E, K, dissolve directly into chylomicrons to enter the lymphatic system

115
Q

Water soluble vitamins

A

B complex and C, taken up across endothelial cells passing directly into plasma

116
Q

Transcellular passing

A

Across the cell membrane, water uses this method to reach blood along with paracellular passing

117
Q

Paracellular passing

A

Squeezing between cells, water uses this method to reach blood along with transcellular passing

118
Q

Appendix

A

A small fingerlike projection that was once thought to be vestigial but may play a role in warding off some bacteria infections and repopulating the large intestine with normal flora after episodes of diarrhea

119
Q

Internal anal sphincter

A

Under involuntary/autonomic control

120
Q

External anal sphincter

A

Under voluntary/somatic control

MCAT (67 decks)

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