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Physiology > Ch 23: Digestive System > Flashcards

Ch 23: Digestive System Flashcards

1
Q

What are 2 groups of organs in the digestive system?

A
  1. Alimentary canal
  2. Accessory digestive organs
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2
Q

What is the alimentary canal?

A
  1. Mouth to anus
  2. Digests food and absorbs fragments
  3. Mouth, pharynx, esophagus, stomach, small intestine, and large intestine
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3
Q

What are the accessory digestive organs?

A
  1. Teeth, tongue, gallbladder
  2. Digestive glands (liver, salivary, pancreas)
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4
Q

What are the 6 essential activities of the digestive processes?

A
  1. Ingestion
  2. Propulsion
  3. Mechanical breakdown
  4. Digestion
  5. Absorption
  6. Defacation
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5
Q

What are the tunics of the alimentary canal?

A
  1. Mucosa
  2. Submucosa
  3. Muscularis externa
  4. Serosa
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6
Q

What is the function of mucosa?

A
  1. Lines lumen
  2. Secretes mucus and digestive enzymes and hormones
  3. Absorbs end products of digestion
  4. Protects against infectious disease
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7
Q

What is muscularis externa?

A
  1. Responsible for segmentation and peristalsis
  2. Inner circular and outer longitudinal layers
  3. Circular layer thickens in area called sphincter
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8
Q

What is serosa?

A
  1. Visceral peritoneum
  2. External surface of most digestive organs
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9
Q

What is the composition of the enteric NS?

A
  1. Intrinsic nerve supply of alimentary canal
  2. Linked to CNS via afferent visceral fibers
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10
Q

What is the purpose of the long ANS fibers synapse with enteric plexuses?

A
  1. Sympathetic impulses inhibit digestive activities
  2. Parasympathetic impulses stimulate digestive activities
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11
Q

What is another term for chewing?

A

Mastication

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12
Q

What is another name for swallowing?

A

Deglutition

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13
Q

Where is the stomach located?

A

Upper left quadrant

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14
Q

What occurs in the stomach?

A

Digestion of bolus to chyme

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15
Q

What are structures of the stomach?

A
  1. Cardia
  2. Fundus
  3. Body
  4. Pyloric part
  5. Greater curvature
  6. Less curvature
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16
Q

What is the fundus?

A

Dome-shaped region beneath diaphragm

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17
Q

What is the mid portion of the stomach called?

A

Body

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18
Q

What is the route of food in the pyloric part?

A

Antrum → pyloric canal → pylorus → Pyloric valve (sphincter) → duodenum

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19
Q

What are modified mucosa and muscalaris of the stomach?

A
  1. Muscularis externa
  2. Mucosa
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20
Q

How many tunics are in the stomach?

A

4

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21
Q

What is the purpose of the muscularis externa?

A

Allows stomach to churn, mix, move, and break down food

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22
Q

What is the purpose of secreting 2-layer coat of alkaline mucus in the mucosa?

A

Surface layer traps bicarbonate rich fluid beneath it

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23
Q

What is found in the mucosa of the stomach?

A
  1. Mucous cells secrete two-layer coat of alkaline mucus
  2. Surface layer traps bicarbonate rich fluid beneath it
  3. Gastric glands producing gastric juice
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24
Q

What are gastric gland cell types?

A
  1. Mucous neck cells
  2. Parietal cells
  3. Chief cells
  4. Enteroendocrine cells
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25
Q

What part of the stomach produce the most gastric juices?

A

Glands in fundus and body

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26
Q

What is secreted from the parietal cells?

A
  1. HCl
  2. Intrinsic factors
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27
Q

What is the purpose HCl in the stomach?

A

Low pH denatures proteins, activates pepsin, break down cell walls, kills bacteria

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28
Q

What is the purpose of intrinsic factor in the stomach?

A

Absorption of vitamin B12 in small intestine

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29
Q

What is secreted by the chief cell?

A
  1. Pepsinogen
  2. Lipases
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30
Q

What is pepsinogen?

A

Inactive enzyme that is activated by pepsin by HCl

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31
Q

What is lipases?

A

Digests lipids

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32
Q

What is secreted by enertoendocrine cells?

A

Secrete chemical messengers that act as paracrine (serotonin and histamine) or hormones (Somatostatin and gastrin)

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33
Q

What is the purpose of the mucosal barrier?

A
  1. Protect thick layer of bicarbonate rich mucus
  2. Protect tight junctions between epithelial cells (preventing leakage)
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34
Q

Describe the digestive process of the stomach?

A
  1. Mechanical breakdown
  2. Denaturation of proteins by HCl
  3. Enzymatic digestion of protein by pepsin
  4. Delivers chyme to small intestine
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35
Q

What happens to alcohol and aspirin in the stomach?

A

Absorbed in the blood

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36
Q

What is the purpose of intrinsic factor secretion?

A
  1. Only stomach function essential to life
  2. Required for Vitamin B12 absorption to mature RBCs
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37
Q

What occurs when the body lacks intrinsic factors?

A

Pernicious anemia

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38
Q

How much gastric juice is produced by the gastric mucosa per day?

A

3L

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39
Q

Describe the neural control of the ANS influencing gastric secretion?

A
  1. Vagus nerve stimulation increase secretion
  2. Sympathetic stimulation decreases secretion
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40
Q

What is the purpose of gastrin?

A

Increases enzyme and HCl secretion

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41
Q

Where are gastrin antagonists located?

A

Small intestine

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42
Q

What are 3 phases of gastric secretion?

A
  1. Cephalic (reflex) phase
  2. Gastric phase
  3. Intestinal phase
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43
Q

What occurs during the cephalic phase?

A

Reflexes triggered by aroma, taste, sight, thought

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44
Q

What stimulates the gastric phase?

A
  1. Distension
  2. Peptides
  3. Low acidity
  4. Gastrin
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45
Q

What occurs during the gastric phase?

A
  1. Lasts 3-4hrs
  2. Enteroendocrine G cells stimulated by caffeine, peptides, rising pH increase gastrin release
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46
Q

What occurs during the intestinal phase?

A

Partially digested food enters small intestine causing a brief intestinal gastrin release

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47
Q

What are the inhibitory effects of the intestinal phase?

A

Chyme with H+, fats, peptides, and irritating substances

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48
Q

What is the purpose of gastrin?

A
  1. Promotes enzyme and HCl release
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49
Q

What inhibits gastrin?

A

Low pH

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50
Q

What stimulates gastrin?

A

Buffering action of ingested proteins promoting the rise of pH

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51
Q

What are the 3 chemicals of the gastric phase and what they do?

A

ACh, histamine, gastrin

Stimulate pariental cells through second-messenger systems

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52
Q

What stimulates maximum HCl secretion?

A

Activation of all 3 gastric phases chemicals

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53
Q

What is released in the intestinal phase?

A

Enterogastrones released by enteroendocrine cells

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54
Q

What are examples of enterogastrones?

A
  1. Secretin
  2. Cholecystokinin
  3. Vasoactive intestinal peptide (VIP)
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55
Q

What is the purpose of enterogastrones?

A

Inhibit gastric secretion

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56
Q

What is dumping syndrome?

A
  1. When small intestine pushed to accept more chyme
  2. Nausea and vomiting
  3. Common for weight loss
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57
Q

When does the Enterogastric Reflex occur?

A

Intestinal phase

58
Q

What is affected by the Enterogastric Reflex?

A
  1. Inhibit vagal nuclei in medulla
  2. Inhibit local reflexes
  3. Activate sympathetic fibers causing tightening of the pyloric sphincter and no more food entry to small intestine
59
Q

What is the purpose of the enterogastric reflex?

A

When there is decreased gastric activity it protects small intestine from excessive acidity

60
Q

What is HCl formation?

A

Parietal cells pup H+ from carbonic acid breakdown into lumen

61
Q

What occurs during HCl formation?

A
  1. K+ enters cells to balance charge
  2. HCO3- from carbonic acid breakdown from blood that leaves the stomach creating an alkaline tide
  3. Cl- follows H+ to form HCl
62
Q

What inhibits HCl formation?

A

Proton pump inhibitors like omeprazole (Prilosec)

63
Q

How does the stomach respond to filling?

A

Stretche to accommodate incoming food

64
Q

What instigates stretching of the stomach?

A
  1. Pressure constant until 1.5L of food ingestion
  2. Gastric accomidation
65
Q

What is receptive relaxation?

A

Coordinated by swallowing center of brain stem

66
Q

What is gastric accommodation?

A

Plasticity of smooth muscle

67
Q

What increases the force of contraction?

A

Distension and gastrin

68
Q

What is the rate of peristaltic waves

A

3 waves per minute

69
Q

What is a peristaltic wave?

A
  1. Basic electrical rhythm (BER) set by enteric pacemaker cells
  2. Pacemaker cells linked by gap junctions  entire muscularis contracts
70
Q

What happens to chyme during a peristaltic wave?

A
  1. Delivered in 3mL spurts to duodenum
  2. Forced backward into stomach
71
Q

Describe the gastric contractile activity?

A
  1. Propulsion: peristaltic waves move from the fundus toward the pylorus
  2. Grinding: mixing, pyloric end of the stomach act as a pump that delivers small amounts of chyme into duodenum
  3. Retropulsion: wave closes valve, forcing contents of the pylorus moves backwards
72
Q

What occurs when the chyme enters duodenum?

A
  1. Receptors respond to stretch and chemical signals
  2. Enterogastric reflex and enterogastrones inhibit gastric secretion and duodenal filling
73
Q

What is the difference between carbohydrate-rich and fatty chyme?

A

Carb: moves quickly through the duodenum (3-6 hrs)
Fatty: remains in duodenum (6+ hrs)

74
Q

What is the major organ of digestion and absorption?

A

Small intestine

75
Q

What are the subdivisions of the small intestine?

A
  1. Duodenum
  2. Jejunum
  3. Ileum
76
Q

Describe the structure of the duodenum?

A
  1. Curves arougn pancreas
  2. Connected to bile and pancreatic duct that is controlled by the hepatopancreatic sphincter
77
Q

What in the jejunum?

A

Extends from duodenum to ileum

78
Q

What is the ileum?

A

Joins large intestine to small

79
Q

What increases the surface area for nutrient absorption in the small intestine ?

A
  1. Circular folds (plicae circulares)
  2. Villi
  3. Microvilli (brush border)
80
Q

What are circular folds?

A

Permanent folds that force chyme to slowly spiral through lumen

81
Q

What is the purpose for villi?

A

Extensions of mucosa with capillary bed and lacteal for absorption

82
Q

What is the purpose of microvilli?

A

Contain enzymes for carbohydrate and protein digestion

83
Q

How much of intestinal juice is delivered daily?

A

1-2L

84
Q

Describe the properties of intestinal juice?

A
  1. Slightly alkaline
  2. Largely water
  3. Facilitates transport and absorption of nutrients
85
Q

What is a fat emulsifier?

A

Bile

86
Q

What is purpose of the liver in the digestive system?

A

Bile production

87
Q

What is the purpose of the gallbladder in the digestive system?

A

Bile storage

88
Q

What connects the liver to gall bladder?

A

Bile duct

89
Q

What is the largest gland in the body?

A

Liver

90
Q

What is regenerative capacity?

A

Restores full size in 6-12 months after 80% removal

91
Q

What is Kupffer cells?

A

Remove old RBCs

92
Q

What is the function of hepatocytes?

A
  1. Filter and process bloodbourne nutrients
  2. Store fat soluble vitamins
  3. Perform detox
  4. Produce 900mL bile per day
93
Q

What is bile?

A

Yellow-green, alkaline solution

94
Q

What are the components of bile?

A
  1. Bile salts
  2. Bilirubin
  3. Cholesterol, triglycerides, phospholipids, and electrolytes
95
Q

What is bile salts?

A

cholesterol derivatives that function in fat emulsification and absorption

96
Q

What is bilirubin?

A

pigment formed from heme

97
Q

How is feces colored from bilirubin?

A

Bacteria break down in intestine to stercobilin → brown color of feces

98
Q

What release bile from the gallbladder?

A

Muscular contractions

99
Q

What occurs from high cholesterol and not enough bile salts?

A

Gallstones

100
Q

What is obstructive jaundice?

A

Obstruct flow of bile from gallbladder

101
Q

What is the treatment for gallstones?

A

Treated with drugs, ultrasound vibrations (lithotripsy), laser vaporization, surgery

102
Q

What is the endocrine function of the pancreas?

A

Pancreatic islets secrete insulin and glucagon

103
Q

What is the exocrine function of the pancreas?

A

Acini (clusters of secretory cells) secrete pancreatic juice

104
Q

Where does the pancreatic juice flow to?

A
  1. Duodenum by pancreatic duct
  2. Contain proenzymes
105
Q

Describe the properties of pancreatic juices?

A
  1. Watery alkaline solution
  2. Electrolytes
106
Q

What pancreatic enzymes are secreted in active form but require ions or bile for optimal activity?

A

Amylase, lipases, nucleases

107
Q

How is protease activated in the duodenum?

A
  1. Trypsinogen activated by trypsin by brush border enzyme enteropeptidase
  2. Procarboxypeptidase and chymotrypsinogen activated by trypsin
108
Q

Describe the mechanism of promoting the secretion and release of bile and pancreatic juices?

A
  1. Chyme enters duodenum causing duodenal enteroendocrine to release CCK and secretin
  2. CCK and secretin enter the bloodstream
  3. CCK induces secretion of enzyme-rich
    pancreatic juice
  4. Bile salts and, to a lesser extent, secretin
    transported via bloodstream stimulate Liver to produce bile more rapidly.
  5. CCK (via blood stream) causes gallbladder to contract and Hepatopancreatic Sphincter to relax. Bile Enters duodenum.
  6. During cephalic and gastric phases, vagal Nerve stimulates gallbladder to
    contract weakly.
109
Q

What is in chyme?

A
  1. Partially digested carb and proteins
  2. Undigested fats
110
Q

What does the chyme do in the small intestine?

A
  1. Most water and all nutrients absorbed
111
Q

What is required for digestion and absorption in the small intestine?

A
  1. Slow delivery of acidic, hypertonic chyme
  2. Delivery of bile, enzymes, and bicarbonate ions from liver and pancreas
  3. Mixing
112
Q

What is the most common motion of small intestine?

A

Segmentation

113
Q

What initiates segmentation?

A

Intrinsic pacemaker cells

114
Q

What affects segmentation?

A
  1. Intensity altered by long & short reflexes; hormones
  2. Parasympathetic Increase ; sympathetic Decrease
  3. Wanes in late intestinal (fasting) phase
115
Q

What is peristalsis?

A
  1. Initiated by rise in hormone motion in late intestinal phase
  2. Each wave starts distal to previous
  3. Movement to large intestine
116
Q

What are the regions of the large intestine?

A
  1. Cecum
  2. Appendix
  3. Colon
  4. Rectum
  5. Anal canal
117
Q

What is the first part of the large intestine?

A

Cecum

118
Q

What is the mass of lymphoid tissue?

A

Appendix

119
Q

What is the purpose of the appendix?

A
  1. Part of the MALT immune system
  2. Bacterial storehouse that recolonizes gut
  3. Twisted causes enteric bacteria accumulate and multiply
120
Q

Where is the colon located?

A

Retroperitoneal except for transverse and sigmoid regions

121
Q

What are the regions of the colon?

A
  1. Ascending colon
  2. Transverse colon
  3. Descending colon
  4. Sigmoid colon in pelvis to rectum
122
Q

What is the composition of the rectum?

A

3 rectal valves that stop feces from being passed with gas

123
Q

What is the anal canal?

A

Last segment of the large intestine

124
Q

What is the opening of the large intestine?

A

Anus

125
Q

What is the difference between the internal and anal sphincter?

A

I: smooth muscles
E: skeletal muscle

126
Q

What occurs in the large intestine?

A
  1. Vitamins, water, and electrolytes reclaimed
  2. No circular folds, villi, or digestive secretions
  3. No food breakdown except by enteric bacteria
  4. Propulsion of feces to anus; defecation
127
Q

What is the Haustral contraction?

A

Slow segmenting movements of the large intestine

128
Q

What is the gastrocolic reflex?

A

Initiated by presence of food in stomach

129
Q

What is mass movement?

A

Three to four slow powerful peristaltic waves per day in colon

130
Q

What is defecation?

A

Mass movements force feces toward rectum

131
Q

What is the valsalva’s maneuver?

A

Closing of glottis, contraction of diaphragm and abdominal wall muscles → increased intra-abdominal pressure

132
Q

What is initiated at distension?

A

Spinal defecation reflex

133
Q

What reaction occur from digestion?

A
  1. Catabolic
  2. Enzymes: intrinsic and accessory gland enzymes that breakdown food
  3. Hydrolysis
134
Q

What reactions occur at absorption?

A
  1. Most water is absorbed in the small intestine
  2. Ileum reclaims bile salts
  3. Absorption of nutrients is actively transported to blood except lipids
135
Q

What is the path of carb digestion?

A
  1. Mouth (saliva)
  2. Pancreas (amylase)
  3. Small intestine (brush border enzymes)
136
Q

What is the path of protein digestion?

A
  1. Stomach (pepsin)
  2. Pancreatic enzymes
  3. Small intestine (brush border enzymes)
137
Q

What is the path of nucleic acid?

A
  1. Pancreatic ribonuclease and deoxyribonuclease
  2. Brush border enzymes
138
Q

What is the path of fat digestion?

A
  1. Mouth: lingual lipase
  2. Stomach: gastric lipase
  3. Liver: emulsification by bile salts
  4. Pancreatic lipases
139
Q

What enzyme break down proteins?

A

Protease

140
Q

What enzyme break down fats?

A

Lipase

141
Q

What enzyme break down carbs?

A

Amylase

142
Q

What enzyme break down nucleic acids?

A

Nucleases

Physiology (22 decks)

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