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MCAT > Biology Ch 9. The Digestive System > Flashcards

Biology Ch 9. The Digestive System Flashcards

(120 cards)

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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
Bolus
What food is formed into prior to it being swallowed
26
Lower esophageal (cardiac) sphincter
Where food from the esophagus enters the stomach, relaxes to allow the passage of food
27
Stomach parts
Fundus, body, antrum, and pylorus
28
Less curvature
Internal curvature of the stomach
29
Greater curvature
External curvature of the stomach
30
Rugae
Folds of the stomach
31
Stomach
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
32
Mucous cells
Produce bicarbonate rich mucus to protect the stomach from harshly acidic and proteolytic environment
33
Chief cells
Secrete pepsinogen, a protease activated in the acidic environment of the stomach
34
Pepsinogen
A protease activated by the acidic environment of the stomach, inactive, zymogen form of pepsin
35
Parietal cells
Secrete hydrochloric acid and intrinsic factor, which is needed for vitamin B 12 absorption, hydrogen ions released cleave pepsinogen to pepsin
36
Intrinsic factor
Secreted by the parietal cells in the stomach, needed for vitamin B 12 absorption
37
G cells
Secrete gastrin
38
Gastrin
Peptide hormone that increases hydrochloric acid secretion and gastric motility, induces parietal cells and the stomach to contract, mixing contents
39
Chyme
Food particles that have undergone mechanical and chemical digestion in the stomach, semifluid mixture
40
Pyloric sphincter
Where food leaves the stomach and enters the duodenum
41
Duodenum
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
42
Disaccharidases
Brush-border enzymes that break down maltose (maltase), isomaltose (isomaltase), lactose (lactase), and sucrose (sucrase) into monosaccharides
43
Brush-border enzymes
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
44
Enteropeptidase
Activates trypsinogen and procarboxypeptidases A and B, initiating an activation cascade of other accessory organs of digestion
45
Secretin
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
46
Cholecystokinin
CCK - Peptide hormone that stimulates bile release from the gallbladder, release of pancreatic juices, and promotes satiety in the brain
47
Salivary glands
Three pairs of them produce saliva in the oral cavity
48
Saliva
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
49
Nasopharynx
Division of the pharynx behind the nasal cavity
50
Oropharynx
Division of the pharynx at the back of the mouth
51
Laryngopharynx
Division of the pharynx above the vocal cords
52
Epiglottis
A cartilaginous structure that folds down to cover the laryngeal inlet during swallowing to prevent food from entering larynx
53
Emesis
aka vomiting, reversal of peristalsis in response to chemicals, infectious agents, physical stimulation of the posterior pharynx, or cognitive stimulation
54
Upper esophageal sphincter
Where swallowing in initials in the muscles of the oropharynx
55
Fundus
Part of the stomach, contains mostly gastric glands
56
Body
Part of the stomach, contains mostly gastric glands
57
Antrum
Part of the stomach, contains mostly pyloric glands
58
Pylorus
Part of the stomach, contains mostly pyloric glands
59
Gastric glands
Respond to signals from the vagus nerve of the PNS, have three different cell types: mucous cells, chief cells, and parietal cells
60
Gastric juice
Combination of secretions from chief cells and parietal cells
61
Pepsin
Digests proteins by cleaving peptide bonds near aromatic amino acids, resulting in short peptide fragments
62
Stomach hydrochloric acid
Hydrogen ions cleave pepsinogen into pepsin, kills most harmful bacteria, and helps to denature proteins
63
Pyloric glands
Contain G cells
64
Stomach absorption
Mainly digestion, only a few substances such as alcohol and aspirin that are absorbed directly from the stomach
65
Small intestine
Divided into three segments,
66
Small intestine segments
Duodenum, jejunum, and ileum
67
Lacking a particular disaccharidase
Bacteria in intenstines hydrolyze disaccharide producing methanols gas, osmotic effect pulling water into stool and causing diarrhea
68
Peptidases
Breaks down proteins
69
Aminopeptidase
Peptidase secreted by glands in the duodenum that remove the N terminal animal acid from a peptde
70
Dipeptidases
Cleaves the peptide bonds of dipeptides to release free animo acids
71
Trypsinogen
A pancreatic protease which is activated by enteropeptidase into trypsin
72
Trypsin
Initiates an activation cascade
73
Enterogastrone
A hormone that slows motility through the digestive tract, allows increased time for digestive enzymes (especially needed for fats)
74
Bile
Complex fluid composed of bile salts, pigments, and cholesterol
75
Bile salts
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
Bile salts emulsification
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
Pancreatic juices
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
Acinar cells
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
Liver digestion
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
Bile pigments
Most important bilirubin from the breakdown of hemoglobin)
81
Gallbladder
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
Accessory organs of digestion
The pancreas, liver, and gallbladder
83
Pancreatic amylase
Breaks down large polysaccharides into small disaccharides, responsible for carbohydrate digestion
84
Pancreatic peptidases
Include trypsinogen, chymotrypsinogen, and carboxypeptidases A and B, all released in zymogen form but are activated by enteropeptidase
85
Pancreatic lipase
Capable of breaking down fats into fatty acids and glycerol
86
Major and minor duodenal papillae
Where bile ducts empty pancreatic juices into the duodenum
87
Bile ducts
Connects the liver with both the gallbladder and small intestine
88
Liver glucose
Liver takes up excess sugar to create glycogen, can produce glucose using glycogenolysis and gluconeogenesis
89
Glycogen
Storage form of glucose
90
Bilirubin
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
Jaundice
Yellowing of the skin because the body is unable to process or excrete bilirubin
92
Albumin
Protein that maintains plasma oncotic pressure and serves as a carrier for many drugs and hormones, synthesized by the liver
93
Clotting factors
Synthesized by the liver, used during blood coagulation
94
Biliary tree
Connects gallbladder to duodenum, merges with pancreatic duct
95
Triacylglyercols digestive pathway
Lipase in oral cavity, lipase from pancreas, bile micelles from gallbladder
96
Carbohydrates digestive pathway
Amylase in oral cavity, amylase from pancreas, sucrase, lactase, maltase, and isomaltase from the small intestine (brush border)
97
Protein digestive pathway
Pepsin from stomach, typsin, chymotrypsin, carboxypeptidases A and B in the pancreas, dipeptidases and aminopeptidase from the small intestine (brush border)
98
Jejunum
Primarily involved in absorption, lined with villi
99
Ileum
Primarily involved in absorption, lined with villi
100
Villi
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
Lacteal
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
Microvilli
Cover villi to increase SA for absorption
103
Large intestine
Absorbs water and salts, forms semisolid feces, divided into the cecum, the colon, and the rectum
104
Cecum
An out pocketing that accepts fluid from the small intestine through the ileocecal valve and is the site of attachment of the appendix
105
Ilocecal valve
Transfers fluid from the small intestine to the cecum
106
Colon
Divided into ascending, transverse, descending, and sigmoid portions, main function to absorb water and salts
107
Rectum
Stores feces which contains indigestible material, water, bacteria, and certain digestive secretions that are not reabsorbed (enzymes and some bile)
108
Gut bacteria
Produce Vitamin K and biotin
109
Simple sugars and amino acid absorption
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
Short chain fatty acid absorption
Same process as carbohydrates and amino acids by diffusing directly into intestinal capillaries, are nonpolar so they can traverse across cell membrane
111
Larger fats, glycerol, and cholesterol absorption
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
Thoracic duct
Where laterals converge and enter the venous circulation and them empty into the left subclavian vein
113
Chylomicrons
Packaged triglycerides and esterified cholesterol that enters the lymphatic circulation through lacteals
114
Fat soluble vitamins
A, D, E, K, dissolve directly into chylomicrons to enter the lymphatic system
115
Water soluble vitamins
B complex and C, taken up across endothelial cells passing directly into plasma
116
Transcellular passing
Across the cell membrane, water uses this method to reach blood along with paracellular passing
117
Paracellular passing
Squeezing between cells, water uses this method to reach blood along with transcellular passing
118
Appendix
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
Internal anal sphincter
Under involuntary/autonomic control
120
External anal sphincter
Under voluntary/somatic control

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