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Physiology > Ch 23: Digestive System > Flashcards

Ch 23: Digestive System Flashcards

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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
What part of the stomach produce the most gastric juices?
Glands in fundus and body
26
What is secreted from the parietal cells?
1. HCl 2. Intrinsic factors
27
What is the purpose HCl in the stomach?
Low pH denatures proteins, activates pepsin, break down cell walls, kills bacteria
28
What is the purpose of intrinsic factor in the stomach?
Absorption of vitamin B12 in small intestine
29
What is secreted by the chief cell?
1. Pepsinogen 2. Lipases
30
What is pepsinogen?
Inactive enzyme that is activated by pepsin by HCl
31
What is lipases?
Digests lipids
32
What is secreted by enertoendocrine cells?
Secrete chemical messengers that act as paracrine (serotonin and histamine) or hormones (Somatostatin and gastrin)
33
What is the purpose of the mucosal barrier?
1. Protect thick layer of bicarbonate rich mucus 2. Protect tight junctions between epithelial cells (preventing leakage)
34
Describe the digestive process of the stomach?
1. Mechanical breakdown 2. Denaturation of proteins by HCl 3. Enzymatic digestion of protein by pepsin 4. Delivers chyme to small intestine
35
What happens to alcohol and aspirin in the stomach?
Absorbed in the blood
36
What is the purpose of intrinsic factor secretion?
1. Only stomach function essential to life 2. Required for Vitamin B12 absorption to mature RBCs
37
What occurs when the body lacks intrinsic factors?
Pernicious anemia
38
How much gastric juice is produced by the gastric mucosa per day?
3L
39
Describe the neural control of the ANS influencing gastric secretion?
1. Vagus nerve stimulation increase secretion 2. Sympathetic stimulation decreases secretion
40
What is the purpose of gastrin?
Increases enzyme and HCl secretion
41
Where are gastrin antagonists located?
Small intestine
42
What are 3 phases of gastric secretion?
1. Cephalic (reflex) phase 2. Gastric phase 3. Intestinal phase
43
What occurs during the cephalic phase?
Reflexes triggered by aroma, taste, sight, thought
44
What stimulates the gastric phase?
1. Distension 2. Peptides 3. Low acidity 4. Gastrin
45
What occurs during the gastric phase?
1. Lasts 3-4hrs 2. Enteroendocrine G cells stimulated by caffeine, peptides, rising pH increase gastrin release
46
What occurs during the intestinal phase?
Partially digested food enters small intestine causing a brief intestinal gastrin release
47
What are the inhibitory effects of the intestinal phase?
Chyme with H+, fats, peptides, and irritating substances
48
What is the purpose of gastrin?
1. Promotes enzyme and HCl release
49
What inhibits gastrin?
Low pH
50
What stimulates gastrin?
Buffering action of ingested proteins promoting the rise of pH
51
What are the 3 chemicals of the gastric phase and what they do?
ACh, histamine, gastrin Stimulate pariental cells through second-messenger systems
52
What stimulates maximum HCl secretion?
Activation of all 3 gastric phases chemicals
53
What is released in the intestinal phase?
Enterogastrones released by enteroendocrine cells
54
What are examples of enterogastrones?
1. Secretin 2. Cholecystokinin 3. Vasoactive intestinal peptide (VIP)
55
What is the purpose of enterogastrones?
Inhibit gastric secretion
56
What is dumping syndrome?
1. When small intestine pushed to accept more chyme 2. Nausea and vomiting 3. Common for weight loss
57
When does the Enterogastric Reflex occur?
Intestinal phase
58
What is affected by the Enterogastric Reflex?
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
What is the purpose of the enterogastric reflex?
When there is decreased gastric activity it protects small intestine from excessive acidity
60
What is HCl formation?
Parietal cells pup H+ from carbonic acid breakdown into lumen
61
What occurs during HCl formation?
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
What inhibits HCl formation?
Proton pump inhibitors like omeprazole (Prilosec)
63
How does the stomach respond to filling?
Stretche to accommodate incoming food
64
What instigates stretching of the stomach?
1. Pressure constant until 1.5L of food ingestion 2. Gastric accomidation
65
What is receptive relaxation?
Coordinated by swallowing center of brain stem
66
What is gastric accommodation?
Plasticity of smooth muscle
67
What increases the force of contraction?
Distension and gastrin
68
What is the rate of peristaltic waves
3 waves per minute
69
What is a peristaltic wave?
1. Basic electrical rhythm (BER) set by enteric pacemaker cells 2. Pacemaker cells linked by gap junctions  entire muscularis contracts
70
What happens to chyme during a peristaltic wave?
1. Delivered in 3mL spurts to duodenum 2. Forced backward into stomach
71
Describe the gastric contractile activity?
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
What occurs when the chyme enters duodenum?
1. Receptors respond to stretch and chemical signals 2. Enterogastric reflex and enterogastrones inhibit gastric secretion and duodenal filling
73
What is the difference between carbohydrate-rich and fatty chyme?
Carb: moves quickly through the duodenum (3-6 hrs) Fatty: remains in duodenum (6+ hrs)
74
What is the major organ of digestion and absorption?
Small intestine
75
What are the subdivisions of the small intestine?
1. Duodenum 2. Jejunum 3. Ileum
76
Describe the structure of the duodenum?
1. Curves arougn pancreas 2. Connected to bile and pancreatic duct that is controlled by the hepatopancreatic sphincter
77
What in the jejunum?
Extends from duodenum to ileum
78
What is the ileum?
Joins large intestine to small
79
What increases the surface area for nutrient absorption in the small intestine ?
1. Circular folds (plicae circulares) 2. Villi 3. Microvilli (brush border)
80
What are circular folds?
Permanent folds that force chyme to slowly spiral through lumen
81
What is the purpose for villi?
Extensions of mucosa with capillary bed and lacteal for absorption
82
What is the purpose of microvilli?
Contain enzymes for carbohydrate and protein digestion
83
How much of intestinal juice is delivered daily?
1-2L
84
Describe the properties of intestinal juice?
1. Slightly alkaline 2. Largely water 3. Facilitates transport and absorption of nutrients
85
What is a fat emulsifier?
Bile
86
What is purpose of the liver in the digestive system?
Bile production
87
What is the purpose of the gallbladder in the digestive system?
Bile storage
88
What connects the liver to gall bladder?
Bile duct
89
What is the largest gland in the body?
Liver
90
What is regenerative capacity?
Restores full size in 6-12 months after 80% removal
91
What is Kupffer cells?
Remove old RBCs
92
What is the function of hepatocytes?
1. Filter and process bloodbourne nutrients 2. Store fat soluble vitamins 3. Perform detox 4. Produce 900mL bile per day
93
What is bile?
Yellow-green, alkaline solution
94
What are the components of bile?
1. Bile salts 2. Bilirubin 3. Cholesterol, triglycerides, phospholipids, and electrolytes
95
What is bile salts?
cholesterol derivatives that function in fat emulsification and absorption
96
What is bilirubin?
pigment formed from heme
97
How is feces colored from bilirubin?
Bacteria break down in intestine to stercobilin → brown color of feces
98
What release bile from the gallbladder?
Muscular contractions
99
What occurs from high cholesterol and not enough bile salts?
Gallstones
100
What is obstructive jaundice?
Obstruct flow of bile from gallbladder
101
What is the treatment for gallstones?
Treated with drugs, ultrasound vibrations (lithotripsy), laser vaporization, surgery
102
What is the endocrine function of the pancreas?
Pancreatic islets secrete insulin and glucagon
103
What is the exocrine function of the pancreas?
Acini (clusters of secretory cells) secrete pancreatic juice
104
Where does the pancreatic juice flow to?
1. Duodenum by pancreatic duct 2. Contain proenzymes
105
Describe the properties of pancreatic juices?
1. Watery alkaline solution 2. Electrolytes
106
What pancreatic enzymes are secreted in active form but require ions or bile for optimal activity?
Amylase, lipases, nucleases
107
How is protease activated in the duodenum?
1. Trypsinogen activated by trypsin by brush border enzyme enteropeptidase 2. Procarboxypeptidase and chymotrypsinogen activated by trypsin
108
Describe the mechanism of promoting the secretion and release of bile and pancreatic juices?
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
What is in chyme?
1. Partially digested carb and proteins 2. Undigested fats
110
What does the chyme do in the small intestine?
1. Most water and all nutrients absorbed
111
What is required for digestion and absorption in the small intestine?
1. Slow delivery of acidic, hypertonic chyme 2. Delivery of bile, enzymes, and bicarbonate ions from liver and pancreas 3. Mixing
112
What is the most common motion of small intestine?
Segmentation
113
What initiates segmentation?
Intrinsic pacemaker cells
114
What affects segmentation?
1. Intensity altered by long & short reflexes; hormones 2. Parasympathetic Increase ; sympathetic Decrease 3. Wanes in late intestinal (fasting) phase
115
What is peristalsis?
1. Initiated by rise in hormone motion in late intestinal phase 2. Each wave starts distal to previous 3. Movement to large intestine
116
What are the regions of the large intestine?
1. Cecum 2. Appendix 3. Colon 4. Rectum 5. Anal canal
117
What is the first part of the large intestine?
Cecum
118
What is the mass of lymphoid tissue?
Appendix
119
What is the purpose of the appendix?
1. Part of the MALT immune system 2. Bacterial storehouse that recolonizes gut 3. Twisted causes enteric bacteria accumulate and multiply
120
Where is the colon located?
Retroperitoneal except for transverse and sigmoid regions
121
What are the regions of the colon?
1. Ascending colon 2. Transverse colon 3. Descending colon 4. Sigmoid colon in pelvis to rectum
122
What is the composition of the rectum?
3 rectal valves that stop feces from being passed with gas
123
What is the anal canal?
Last segment of the large intestine
124
What is the opening of the large intestine?
Anus
125
What is the difference between the internal and anal sphincter?
I: smooth muscles E: skeletal muscle
126
What occurs in the large intestine?
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
What is the Haustral contraction?
Slow segmenting movements of the large intestine
128
What is the gastrocolic reflex?
Initiated by presence of food in stomach
129
What is mass movement?
Three to four slow powerful peristaltic waves per day in colon
130
What is defecation?
Mass movements force feces toward rectum
131
What is the valsalva's maneuver?
Closing of glottis, contraction of diaphragm and abdominal wall muscles → increased intra-abdominal pressure
132
What is initiated at distension?
Spinal defecation reflex
133
What reaction occur from digestion?
1. Catabolic 2. Enzymes: intrinsic and accessory gland enzymes that breakdown food 3. Hydrolysis
134
What reactions occur at absorption?
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
What is the path of carb digestion?
1. Mouth (saliva) 2. Pancreas (amylase) 3. Small intestine (brush border enzymes)
136
What is the path of protein digestion?
1. Stomach (pepsin) 2. Pancreatic enzymes 3. Small intestine (brush border enzymes)
137
What is the path of nucleic acid?
1. Pancreatic ribonuclease and deoxyribonuclease 2. Brush border enzymes
138
What is the path of fat digestion?
1. Mouth: lingual lipase 2. Stomach: gastric lipase 3. Liver: emulsification by bile salts 4. Pancreatic lipases
139
What enzyme break down proteins?
Protease
140
What enzyme break down fats?
Lipase
141
What enzyme break down carbs?
Amylase
142
What enzyme break down nucleic acids?
Nucleases

Physiology (22 decks)

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