PHYStest3INTRANET Flashcards
1
Q
What is deglutition?
A
Swallowing.
2
Q
Where is the Auerbach’s/myenteric plexus found at and what is it for?
A
In the muscularis externa and it is the enteric nervous system used for movement.
3
Q
Where is the Meissner’s/submucous plexus at and what is it for?
A
In the Submucosa and it si the enteric nervous system used for secretion and blood flow.
4
Q
GI smooth muscle fibers are electrically connected via what?
A
Gap junctions.
5
Q
What is the purpose of the gap junctions in GI smooth muscle fibers?
A
allows ions to pass between muscles, allows muscle signals to move rapidly.
6
Q
With GI smooth muscle what direction will the action potential travel?
A
In all directions.
7
Q
How will most GI movement occur?
A
Rhythmically based on frequency of slow waves via pacemaker.
8
Q
What is the pacemaker of GI smooth muscle?
A
Interstitial cells of Cajal.
9
Q
Will the interstitial cells of Cajal have action potentials?
A
No, but they are slow undulating changes in resting membrane potential.
10
Q
The Rhythmically based patterns for GI smooth muscle movement slow wave sets what?
A
A basic electrical rhythm (BER) for each gut segment.
11
Q
Electrical slow waves only cause muscle contractions where?
A
In the stomach. Where action/spike potentials occur on top of slow wave= muscle contractions.
12
Q
True action potentials occurring on top of slow waves is stimulated by what?
A
Depolarization from stretch, Parasympathetic NS, Ach, Other GI hormones.
13
Q
The higher the slow wave potential is the more what?
A
Frequent the spike potentials can lead to tonic contractions.
14
Q
GI spike potentials last much longer than most others due to what?
A
Calcium-sodium channels are slow to open and close.
15
Q
What factors would lead to hyperpolarization of the spike potential?
A
Sympathetic stimulation, norepinephrine.
16
Q
What are the nervous systems involved with controling the gut?
A
- Enteric/intrinsic nervous system. 2. Extrinsic nervous system: SNS and PNS.
17
Q
Besides nervous control what is a controling mechanism of the gut?
A
Hormones.
18
Q
What is the brain of the GI tract?
A
The enteric nervous system.
19
Q
Can the enteric nervous system function on its own without SNS or PNS?
A
Yes, but it is greatly augmented by the SNS and PNS.
20
Q
How many nerve plexi make up the enteric nervous system?
A
two.
21
Q
How many neurons make up the enteric nervous system?
A
around 100 million.
22
Q
What will the enteric nervous system control?
A
GI movements and secretions.
23
Q
What will connect the enteric nervous system to the PNS and SNS?
A
Ganglia.
24
Q
The enteric nervous system ganglia receive information directly from where?
A
receptors in mucosa.
25
Enteric nervous system ganglia send what where?
Send motor fibers directly to smooth muscles or glands.
26
Most of the GI function is reflexive involving what?
receptors in mucosa (mechano and chemo), and interneurons relay between ganglia of the 2 plexi.
27
Where is the myenteric (auerbach's) plexus found at in the muscluaris externa?
Between the muscle layers.
28
Will the myenteric (auerbach's) plexus be excitatory or inhibitory?
Both.
29
Submucosal (meissner's) plexus primarily controls _____ activity.
Sensory.
30
What type of effect will the parasympathetic nervous system have on the GI tract?
Excitatory: increases motility and secretion.
31
Parasympathetic preganglionics stimulate the GI tract via what?
Ach.
32
Where are the parasympathetic postganglionic cell bodies that affect the GI tract found at?
in the enteric plexi.
33
The parasympathetic postganglionic stimulate the GI tract via what?
Ach or peptides like VIP or substance P.
34
What is the sympathetic nervous systems function with the GI tract?
Inhibitory: generally decreases motility and secretion.
35
Where will the sympathetic nervous system arise from that works with the GI tract?
From cord segments T5-L2.
36
How will the sympathetic preganglionics travel to the GI tract?
pass thru the sympathetic chain as splanchnic nerves and synapse in prevertebral ganglia.
37
The sympathetic preganglionics work with the GI tract via what?
Ach.
38
The sympathetic postganglionics work with the GI tract via what?
Adrenergic: norepinephron and small amounts of epinephrine.
39
What will sympathetic activity do to smooth muscle in blood vessels?
Vasoconstriction.
40
Sympathetic activity in sphincter muscles is usually what?
Excitatory.
41
True or False most sympathetic and parasympathetic fibers synapse with the enteric nervous system rather than directly on muscle and glands?
True.
42
What % of vagus fibers and sympathetic fibers are afferent?
Vagus-80%. Sympathetic-50%.
43
Why are visceral afferents needed?
For reflex activity in the GI tract.
44
What 3 levels are reflexes controlled or integrated at?
1. Locally. 2. Prevertebral ganglia. 3. CNS.
45
Local reflexes in the GI tract involves what?
Secretion, peristalsis, mixing.
46
Prevertebral reflexes of the GI tract involves what?
distance refelx for motility/ emptying of colon, ileum, and stomach.
47
What is the enterogastric reflex?
signals from colon and small intestines back to stomach to inhibit stomach motility and stomach secretions.
48
What is the colonoileal reflex?
Signals from colon back to ileum to inhibit emptying of ileum into colon.
49
CNS reflex to the GI tract travel how?
Transmit signals to brain stem or spinal cord and efferents via vagus or pelvic splanchnics.
50
CNS reflex to the GI tract is used for what?
Controlling stomach motor secretory activity, pain reflexes that inhibit the whole GI tract, and defecation reflex.
51
All blood from GI, pancreas, Spleen goes to the liver via what and leaves via what?
To liver via portal vein and leaves via hepatic veins to vena cava.
52
What will the liver do with non-fat, water-soluable nutrients?
Stores 1/2-3/4 of it for processing.
53
Will Fat go to the liver?
No it bypasses the liver.
54
How will fat bypass the liver?
Via intestinal lymphatic absorbtion to thoracic duct and general circulation.
55
GI hormones are released from what and into what?
From GI tract into portal circulation.
56
What are the targets of GI hormones?
GI tract or elsewhere.
57
How many definitive GI hormones are there?
4 of them.
58
Name the 4 GI hormones?
1. Gastrin. 2. Cholecystokinin (CCK). 3. Secretin. 4. Gastric inhibitory peptide (GIP).
59
What will Gastrin do?
Stimulates gastric acid secretion and proliferation of gastric epithelium, decreased gastric emptying: peptides and amino acids in small intestine.
60
What will Cholecystokinin or CCK do?
Stimulates secretion of pancreatic enzymes and contraction/emptying of gall bladder, decreased gastric emptying: fatty/amino acids in small intestine.
61
What will Secretin do?
Stimulates secretion of water/bicarbonate from pancreas and bile ducts, decreases gastric emptying: acidic pH in small intestine.
62
What will gastric inhibitory peptide (GIP) do?
inhibits gastric secretion/motility: increases release of insulin from beta cells in response to elevated blood glucose: presence of fat/glucose in small intestine.
63
Other GI hormones that need to be mentioned are motilin and pancreatic polypeptide and what will they do?
Motilin- increases migrating motor complex to sweep undigested residual material through stomach/small intestine. Pancreatic polypeptide- A CCK antagonist. Suppresses pancreatic secretion.
64
When will motilin and pancreatic polypeptide be secreted?
Motilin- increased during fasting. Pancreatic polypeptide- decreased by somatostatin.
65
What will enteroglucagon or glucagon-like peptide do?
enhances release of insulin decreases release of glucagon.
66
What will glucagon do?
Lowers blood glucose.
67
When is glucagon secreted?
After ingestion of a meal containing carbohydrates or lipids.
68
Grehlin is a strong stimulant for what?
Appetite and feeding.
69
What will Grehlin do with fat?
It suppresses fat utilization.
70
Grehlin is a potent stimulator of what?
Growth hormone secretion.
71
From where will Grehlin be secreted?
From cells in antrum of stomach prior to feeding, and cells in the pancreas, and in the arcuate nucleus of the hypothalamus.
72
What is Prader-willi syndrome?
Plasma grehlin levels are very high in extreme obesity and uncontrollable appetite is present this might mean that obesity in this case might be due to other causes.
73
Ghrelin is the counterpart of what hormone?
Leptin.
74
Leptin is made where?
By adipose tissue.
75
What will ghrelin produced in the arcuate nucleus of the hypothalamus do?
Stimulates the secretion of growth hormone from the anterior pituitary gland.
76
Those suffering from anorexia nervosa suffer from high levels of what?
Ghrelin.
77
Ghrelin plays a role in what type of eating disorders?
Both anorexia and obesity.
78
What will Ghrelin secretion be like in thinner people?
Increases during the time of day from midnight to dawn.
79
Secretion of ghrelin in thin people from midnight to dawn suggests what?
A flaw in the circadian system of obese individuals.
80
Leptin plays a key role in regulating what?
Energy intake and energy expenditure, inculding appetite and metabolism.
81
What is one of the most important adipose derived hormones?
Leptin.
82
How will increased levels of leptin be associated with appetite?
Suppression.
83
What will obese peoples leptin levels be like?
Abnormally high and this suggests that obese individuals may be leptin resistant.
84
Short sleep duration may lead to obesity how?
through an increase of appetite via hormonal changes. Lack of sleep produces ghrelin which stimulates appetite and creates less leptin which amongst its many other effects suppresses appetite.
85
GI paracrines are secreted by what?
Endocrine cells in GI tract.
86
Where will GI paracrines act at?
They act locally on same tissue.
87
What are the 2 GI paracrines that we need to know?
Somatostatin, and histamine.
88
Majority of circulating somatostatin comes from where?
pancreas and GI.
89
What will somatostatins inhibit?
Inhibits secretion of GI hormones: gastrin, CCK, Secretin, GIP.
90
What will somatostatins suppress?
Suppresses secretion of gastric acid and pepsin, decreased gastric emptying, reduces smooth muscle contractions and GI blood flow.
91
What is the overall effect of somatostatins?
Decreasing rate of nutrient absorption.
92
Where is the GI paracrine Histamine secreted from?
Enterochromaffin-like cell of stomach.
93
What will the GI paracrine Hormone Histame do?
H2 receptors on parietal cells will bind histamine and increase H+ secretion in stomach.
94
GI neurocrines are peptides synthesized where?
In neurons of the GI tract.
95
GI neurocrines are released when?
Action potentials.
96
Where will GI neurocrines travel to act on target cells?
They travel across the synapse.
97
Give 2 examples of GI neurocrines?
1. Vasoactive intestinal peptide (VIP). 2. Gasrin-releasing peptide.
98
What will VIP do?
induce smooth muscle relaxation, stimulate secretion of water into pancreatic juice and bile, inhibit gastric acid secretion/absorption from intestinal lumen.
99
What will gastrin-releasing peptide do?
Increased gastrin secretions and this increases the HCL of the stomach.
100
Where will gastrin-releasing peptide be released at?
by postganglionic fibers of the vagus that innervate G cells of the stomach.
101
What are the 2 general types of contractions in the GI tract?
1. Phasic. 2. Tonic.
102
What are phasic contractions like?
Periodic contractions followed by relaxation.
103
Where will phasic contractions be found at?
Esophagus, stomach, and small intestines.
104
What are phasic contractions used for?
for mixing and propulsion.
105
What are the phasic contraction frequency based on?
on BER (basic electrical rhythm) of region
106
What are tonic contractions like?
constant contraction (tone) without relaxation.
107
Where are tonic contractions located at?
upper stomach, lower esophagus, and some sphincters.
108
Tonic contractions last how long?
Minutes to hours.
109
What causes tonic contractions?
Not BER, but repetitve spike potentials, hormones, calcium.
110
What are the 2 types of movement in the GI tract?
1. Propulsive. 2. Mixing.
111
What is the main propulsive movement of the gut?
Peristalsis.
112
What type of musclular contractions are done for propulsion?
Ring-like.
113
What stimulates ring-like contractions that produce propulsion in the GI tract?
distention, irritation, parasympathetic, hormones.
114
What enteric nervous system need to be functioning to have propulsion in the GI tract?
myenteric or auerbachs plexus.
115
What direction will peristalsis work in?
Both directions, but it dies out orally.
116
What happens to material that is distal to the constriction rings in peristalsis?
It moves forward.
117
As peristalsis moves contents of GI tract forward what happens to the muscle in the receiving segment?
It relaxes and longitudinal muscle contracts to expand its diameter.
118
What is the Law of the Gut?
combination of myenteric with relaxation of distal segment and movement from oral to anal.
119
Peristalsis can also cause mixing especially if what happens?
if food is propelled against a closed sphincter.
120
Can peristalsis occur in bile and gland ducts and ureters?
yes.
121
Absorption of food happens via contact with what?
Mucosa.
122
What are the 2 functions of the secretory glands in the GI tract?
1. Digestion. 2. Lubrication/protection.
123
Most GI secretions are formed in response to what?
Presence of food.
124
What is secreted for lubrication/protection?
Mucus.
125
What is secreted for digestion?
Enzymes.
126
Why are hormones secreted?
Regulation.
127
What are secretory cells like of the GI tract that are in the epithelium region?
Single cells on the epithelium and pits/crypts that are invaginations of epithelium.
128
These single cell secretory cells in the on the epithelium secrete in response to what?
Local irritation.
129
Tubular glands of the GI tract are found where?
in stomach, and upper duodenum.
130
What will tubular glands secrete?
acid and pepsiongen.
131
What are the complex GI tract glands that are outside the GI tract?
salivary, pancreas, liver, gall bladder.
132
These complex glands of the GI tract are for what?
Digestion/emulsification of food.
133
What are the mechanical stiumi for secretion?
tactile, chemical, stretch.
134
How will para- and sympa- thetic nervous systems effect GI secretion?
Para-increase rate of secretion. Sympa- reduces rate of secretion.
135
What part of GI secretion will the hormones regulate?
Volume and character of secretions.
136
Hormones of the GI tract are released from where and because of what?
from mucosa in response to food.
137
what is mucus (thick secretion) composed of?
Water, electrolytes, polysaccharides, protein.
138
Will mucus be the same at all parts of the GI tract?
No it varies between different parts.
139
What will mucus do to fecal particles?
Help them bind together.
140
Will mucus breakdown from enzymatic activity?
No it is resistant to breakdown by digestive enzymes.
141
What is the role of mucus in pH?
It is a buffering agent.
142
What do digestive enzymes need to be more effective at digestion?
Increased surface area provided by mastication.
143
What type of food really needs good mastication and why?
Raw fruits and vegetables to remove the cellulose surrounding the nutrients.
144
The mouth prevents what from happening to the GI tract?
Excoration (Strip off or remove skin).
145
Is chewing volunatry or involuntary?
Both.
146
How much saliva is produced a day?
1-1.5 liters.
147
What is the pH of saliva?
6-7.0.
148
What 2 things will saliva contain?
1. serous secretion-ptyalin. 2. Mucus secretions- mucin.
149
What are the 3 sets of salivary glands?
1. Submandibular. 2. Parotid. 3. Sublingual.
150
What are submandibular secretions like?
mixed serous and mucus. Amylase and mucus.
151
What are the partoid glands secretions like?
mostly serous. Salivary amylase.
152
What are the sublingual glands secretions like?
mixed serous and mucus.
153
Buccal glands secrete what?
Only mucus.
154
Saliva is a solvent for what?
molecules that stimulate taste buds.
155
Saliva initiates digestion of what via amylase?
Carbohydrates.
156
How is saliva an antibacterial agent?
Washes away and attacks pathogenic bacteria and food particles to decrease tooth decay.
157
Saliva functions to help reabsorbe what?
Na+ and Cl-.
158
Saliva's initial secretion by acinar cells is what?
Isotonic. (same salt content as blood).
159
What will modify the composition of the isotonic saliva?
Ductal cells.
160
What will ductal cells do to saliva?
Na+ is reabsorbed, and K+ os actively secreted.
161
Excess Na+ reabsorption caused ________ Cl- reabsorption.
Passive.
162
In the formation of saliva what will actively be secreted and exchanged for Cl-?
Bicarbonate.
163
Normaly water would follow bicarbonate in saliva formation, but ductal cells are not permeable to water so final saliva is like what?
Hypotonic.
164
What will saliva be like during maximal salivation?
More closely resembles plasma.
165
How will para- and sympa- thetic nervous systems effect regulation of saliva?
They both increase, but mostly para- will increase the saliva.
166
Reflex for saliva production from para- and sympa comes from a reflex found in what nuclei?
Through superior and inferior salivatory nuclei in brainstem.
167
Parasympathetic stimulation will be via what and to what to increase saliva?
Via Ach and to muscarinic receptors on acinar and ductal cells of saliva glands.
168
Parasympathetic stimulation of Ach to muscarinic receptors on acinar and ductal glands increases saliva how?
By increasing blood flow to glands.
169
What Spinal cord levels will sympathetic output to salivary glands come from?
T1-T3.
170
Sympathetic stimulation to saliva glands works via what and to what?
Norepinephrine wth beta receptors.
171
Norephinephrine to beta receptors of saliva glands will do what?
Decreases blood flow and so there is less saliva.
172
What part of the brain regulates the food likes and dislikes?
appetite area of the brain.
173
Where is the appetite area of the brain at?
Located close to parasympathetic centers in anterior hypothalamus.
174
The appetite area of the brain functions in response to what?
taste and smell areas of cerebral cortex and amygdala.
175
Reflex for saliva production originating in the stomach and proximal small intestine are due to what?
Irritating foods or nausea.
176
How is the oral deglutition stage done?
Voluntaraly food is formed into a bolus and propelled backwards to pharynx by tongue.
177
How is the pharyngeal and esophageal stages of deglutition done?
Involuntary and controlled by the swallowing center in the medulla.
178
The pharyngeal stage of deglutition is done via what nerves?
Trigeminal and glosso-pharyngeal.
179
What are the mechanics of the first 2 parts of the pharyngeal stage of deglutition?
soft palate is pulled upward to prevent food from entering nasopharynx, and palatopharyngeal folds approximate allowing only small pieces to enter.
180
What are the 3-5 parts of the pharyngeal stage deglutition?
3. Vocal folds approximated and larynx pulled upward against epiglottis to keep food out of larynx and trachea. 4. Upward movement of larynex pulls and enlarges openings to esophagus and upper esophageal sphincter relaxes. 5. Contraction of pharynx via peristalsis moves food to esophagus.
181
How long will the pharyngeal stage of deglutition last?
It is rapid lasting only 2-3 seconds.
182
What happens to breathing during the pharyngeal stage of deglutition?
It is inhibited via swallowing center inhibition on respiration center.
183
What is the esophageal stage of deglutition like?
Involuntary via swallowing reflex and enteric nervous system.
184
What are the 2 phases of peristalsis exhibited by the esophagus during deglutition?
Primary and secondary waves.
185
What is the primary wave of esophagus deglutition?
Continuation of pharyngeal peristaltic waves, from pharynx to stomach in 8-10 seconds.
186
How long will the primary wave phase last if aided by gravity?
5-8 seconds.
187
What is the secondary wave phase of the esophagus deglutition like?
due to distention from food not moved by primary. The second wave continues until esophagus is clear.
188
The secondary wave phase happens via what reflex?
Pharyngeal reflex.
189
Whatpathways will the pharyngeal reflex use?
vagus---> medulla-----> vagus and glossopharyngeal.
190
The final stage of deglutition requires what?
Relaxation of stomach.
191
Gastric relaxation happens via what?
Myenteric inhibitory neurons.
192
Relaxation of entire stomach and proximal duodenum =?
Prepared to receive food.
193
Where is the lower esophageal sphincter at?
The final 3 cm of the distal esophagus.
194
What is the lower esohpageal sphincter normally like?
Tonically constricted.
195
What will cause the lower esophageal sphincter to relax?
Receptive relaxation with peristaltic waves.
196
Paralysis of the swallowing mechanism is due to damage to what crainial nerves?
V, VII, IX, X.
197
What diseases cause swallowing disorders?
Those that damage the swallowing center in the brain.
198
What happens during swallowing with a failure of the glottis to close?
Food passes into lungs instead of the esophagus.
199
What happens to swallowing under anesthesia?
Vomit materials into pharynx then instead of swallowing simply sucked into trachea because refelx mechanism is blocked.
200
What is achalasia?
Lower esophageal sphincter fails to relax during swallowing so food fails to pass from esophagus to stomach.
201
Achalasia is due to what?
Damage of myenteric plexus, secondary to chronic reflux.
202
What is the treatment for Achalasia?
Stretching via balloon or antispasmotic drugs.
203
What are the 2 esophageal sphincters?
upper and lower.
204
The upper and lower esophageal sphincters are aka?
Upper- Criropharyngeal muscle. Lower- cardiac sphincter.
205
What will the upper esophageal sphincter do?
Prevents air from entering the esophagus.
206
What will the lower esophageal sphincter do?
Prevents reflux of stomach contents.
207
When are both esophageal sphincters closed?
They are both closed except during swallowing.
208
What is the esophageal secretions like?
Entirely mucus for lubrication.
209
What kind of glands will the esophagus be lined with?
Simple mucous glands.
210
The Proximal and distal portion of the esophagus have mucous glands to prevent what?
Excoriation from newly swallowed food and digestion by refluxed gastric juices.
211
How long will it take food to pass through the esophagus?
about 10 seconds.
212
What are the 2 types of esophageal peristalsis?
primary and secondary.
213
How are the primary and secondary esophageal peristalsis initiated?
Primary- by swallowing. Secondary- initiated by digestion if primary wave does not move all food through.
214
The gastroesophageal reflux disorder is aka?
Heartburn.
215
What are the symptoms of the gastroesophageal reflux disorder?
Chronic cough, ENT complaints, asthma, hoarseness, anemia.
216
What are the causes of gastroesophageal reflux disorder (GERD)?
inapproptiate relaxation of Lower esophageal sphincter.
217
What complications can come with GERD?
Risk of barrett's esophagus and cancer.
218
What are the treatments of GERD?
Diet/lifestyle modifications, medications (H2 receptor blockers).
219
What are the 3 functions of the stomach?
1. Storage until processing can occur. 2. Mixing with gastric secretions to form chyme. 3. Controlled emptying of chyme.
220
How will chyme be released from the stomach?
Slowly to facilitate proper digestion and absorption by small intestines.
221
What are the 2 major parts of the stomach?
body and antrum.
222
What will increasd food volume do to the stomach?
Stretching activates local myenteric plexus and increases stomach emptying.
223
Gastrin will do what to the stomach?
Increases; secretion of gastric juices, motor activity, and opens the pyloric quicker.
224
What reflex will decrease the stomach emptying?
Enterogastric reflex.
225
The enterogastric reflex is from where?
Duodenum to stomach.
226
How will the enterogastric reflex travel?
extrinsic nerves to prevertebral sympathetic ganglia then back to stomach. (vagus to brian and vagus to stomach).
227
What will presence of fatty or acidic chyme in the stomach do?
Increase hormones. Mainly Cholecystokinine, also secretin and gastrin inhibiting peptide.
228
What is the largest factor controlling gastric emptying?
Duodenum.
229
How will the duodenum control gastric emptying?
It limits the amount of chyme to only what small intestines can process.
230
The Enterogastric reflex is initated by what?
Distention of duodenum, irritation of duodenum, acidity of duodenal chyme, and breakdown products of protein and fat.
231
Gastric secretions include what?
Mucus, HCL, Pepsinogen, intrinsic factor, gastrin, salts, water, and bicarbonate.
232
What is the role of mucus in the stomach?
Protection from corrosion by HCL.
233
What is HCl's role in the stomach?
Acidification to optimal pH for enzymes to function.
234
What is the role of pepsiongen in the stomach?
Precursor of enzyme for protein digestion.
235
What will intrinsic factor's role be in the stomach?
Absorption of vitamin B12 in colon.
236
What will gastrin's role be in the stomach?
Regulates H+ secretion.
237
How much mucus will line the entire surface of the stomach?
Very viscous alkaline mucus will line the stomach nearly 1 cm thick.
238
What type of cells will secrete mucus in the stomach?
Mucous neck cells.
239
What type of cells secrete pepsinogen in the stomach (give both names)?
Peptic or chief cells.
240
What type of cells secrete HCL and Intrinsic factor in the stomach (give both names)?
Parietal (oxyntic).
241
What is the group of glands called that have cells that secrete HCL, Pepsinogenm intrinsic factor, and mucus?
Oxyntic or gastric glands.
242
What are pyloric glands?
Glands that secrete gastrin, mucus and small amounts of pepsinogen.
243
What are the different type of pyloric glands?
Mucous cells, few peptic cells and no parietal cells.
244
What is achlorhydria?
Lack of stomach acid.
245
What will a lack of stomach acid lead to?
A B12 deficiency.
246
What will a B12 deficiency lead to?
Pernicious anemia due to Failure of RBC maturation.
247
What is needed to convert pepsinogen to pepsin?
HCL.
248
Parietal cells are closely associated with what?
Enterochromafin-like cells.
249
Enterochromafin-like cells = what?
Histamine.
250
HCL secretion is directly related what?
The amount of histamine.
251
What are 3 primary stimuli for H+ secretion?
1. Ach. 2. Histamine. 3. Gastrin.
252
What are the 3 phases of HCL secretion and they make up what % of HCL secretion?
1. Cephalic-30%. 2. Gastric- 60%. 3. Intestinal-10%.
253
In general how will the cephalic phase of HCL secretion work?
Before a meal via Ach gastrin is released and this leads to H+ secretion.
254
How will the gastric phase of HCL secretion work?
After a meal vagus nerve stimulates gastrin and stomach distention and amino acid and small peptides also help with HCL secretion.
255
How will the intestinal phase of HCL secretion work?
Receptors in small intestine and distention and amino acid triggers local neural reflex and gastrin.
256
Once HCL is no longer needed what will inhibit the secretion of HCL?
Decreased pH is major control, but also somatostatin and gastric inhibitory peptide (GIP) will inhibit gastrin secretion.
257
Lower pH inhibits secretion of what?
Gastrin and therefore HCL.
258
What will bicarbonate do in the stomach and where is it released from?
Released from surface cells and it is trapped in the mucus to increase the pH to around 7.
259
What will stimulate the secretion of mucus?
Ach from parasympathetic NS and eating food.
260
What are the causes of gastritis?
Bacterial infection and ingested irritants.
261
What will chronic gastritis lead to?
atrophy--> little to no secretion---> achlorhydria and pernicious anemia due to loss of HCL and Intrinsic factor.
262
What are the most frequent sites for peptic ulcers?
Within centemeters of pylorus, along lesser curvature of stomach or distal esophagus.
263
What is the Etiology (study of cause of disease) of peptic ulcers?
Imbalance between rate of secretion of HCL and pepsinogen vs. integrity of gastroduodenal mucosa.
264
What type of bacteria will destroy mucosal barrier and increases gastric acid secretion?
Helicobacter pylori.
265
What are other factors that lead to peptic ulcers?
Smoking, alcohol, asprin.
266
What is a type of effective treatment of peptic ulcers?
Antibiotics and acid-suppressant drugs.
267
How will acid-suppressant drugs work?
antihistamine---> reducing gastric acid secretion by 70-80%.
268
The pancreas is made of compound glands similar to what glands?
Salivary glands.
269
What 2 things will the pancreas secrete?
Digestive enzymes and sodium bicarbonate.
270
The pancreas will secrete digestive enzymes and sodium bicarbonate from where?
Digestive enzymes from acini. Sodium bicarbonate from ductule/duct of acini.
271
What is the purpose of sodium bicarbonate secreted from the pancreas?
TO Neutralize acidity of chyme.
272
What will stimulate the secretions of the pancreas?
Chyme in upper small intestine and the characteristics of pancreatic secretions will be dependent on content of chyme.
273
The pancreatic duct joins what?
Hepatic duct.
274
Pancreatic secretions go through what sphincter?
Sphincter of oddi.
275
What form will pancreatic enzymes be synthesized as?
Inactive form.
276
Name the 3 digestive enzymes synthesized in the pancreas?
Trypsinogen, chymotrypsinogen and procarboxyypolypeptidase.
277
What is the total amount of pancreatic secretions of enzymes per day?
1 liter.
278
When will the proteolytic (inactive) pancreatic enzymes become active?
Not until the duodenum.
279
What will keep trypsin from becoming active and where will this be secreted from?
Trypsin inhibitor and it is secreted the same cells that secrete trypsin.
280
How will trypsin inhibitor effect other enzymes?
Trypsin activates other enzymes and so trypsin inhibitor prevents activation of all.
281
What happens to pancreatic enzymes when the duct is blocked or damaged?
Secretions pool and trypsin inhibitor is overwhelmed and pancreatic enzymes are activated and it can digest the pancreas within hours.
282
What will it be called when the pancreatic enzymes digest the pancreas?
Acute pancreatitis.
283
What will Acetylcholine do to the pancreas?
Stimulates acini to secrete enzymes.
284
What will cholecystokinin do to the pancreas?
Stimulates acini to secrete enzymes.
285
What will secretin do to the pancreas?
Stimulates duct for more water and solution of sodium bicarbonate.
286
Cholecystokinin is secreted by what and when?
By duodenum and jejunum when food enters the small intestine.
287
Where will Ach come from that goes to the Pancreas?
From parasympathetic ns via vagus and cholinergic nerves in enteric NS.
288
Secretin is secreted by what and when?
By duodenum and jejunum when food enters the small intestine.
289
What does it mean that the pancreas stimuli potentiate each other?
That the total secretion is greater than the sum of the individual secretions.
290
What are the pancreatic enzymes for digesting proteins?
Trypsin chymotrypsin and carboxypolypeptidase.
291
How will trypsin and chymotrypsin digest proteins?
Digests them into peptides but doesn't release indivual amino acids.
292
How will carboxypolypeptidase digest proteins?
Splits some peptides into individual amino acids.
293
What is the pancreatic enzyme for carbohydrate digestion?
Pancreatic amylase.
294
How will pancreatic amylase work?
Hydrolizes starches, glycogen and other CHO into disaccharides and trisaccharides.
295
What are the 3 pancreatic enzymes for fat digestion?
1. Lipase. 2. Cholesterol esterase. 3. Phospholipase.
296
How will lipase digest fat?
takes neutral fat into fatty acids and monoglycerides.
297
How will Cholesterol esterase digest fat?
hydrolizes cholesterol esters.
298
How will phospholipases digest fat?
Phospholipids into fatty acids.
299
Bicarbonate and ions and water are mainly secreted by what part of the pancreas?
By epithelial cells of the ductules and ducts that lead from the acini.
300
Bicarbonate concentration from pancreas is how much more concentrated that bicarbonate ions found in the plasma?
5 times.
301
What is the purpose of pancreatic secretion of bicarbonate ions?
To neutralize HCL that is empted into duodenum from stomach.
302
What are the 3 phases of pancreatic secretion?
The same as the stomach cephalic, gastric, and intestinal phases.
303
What will the cephalic and gastric phase of pancreatic secretion be like?
Nervous system singals the secretion in the stomach also causes Vagal Ach release in the pancreas.
304
What is the major phase of pancreatic secretion?
The intestinal phase.
305
What is the intestinal phase of pancreatic secretion like?
After chyme enters the small intestines then pancreatic secretions become great due to secretin.
306
What will secretin do?
Stimulates secretion of large amounts of bicarbonate ions.
307
The inactive form of secretin is a prosecretin and it comes from where?
S cells of duodenum and jejunum.
308
When will secretin be released?
When acidic chyme enters the duodenum from the stomach.
309
How will secretn effect the digestive actvity in the duodenum?
It will decrease the digestive activity by gastric juices in duodenum.
310
What are the 2 functions of secretin?
1. Protective mechanism to prevent duodenal ulcers. 2. Provides appropriate pH (7-8) for pancreatic enzymes.
311
What is the most common cause of pancreatitis?
Drinking excess alcohol.
312
What is the second most common cause of pancreatitis?
blockage of the papilla of vater by a gallstone.
313
Without pancreatic enzymes how will fat, carbohydrate and protein digestion be affected?
60% of fat and 1/3-1/2 of proteins and carbohydrates entering small intestines may be unabsorbed.
314
How much bile is secreted by the liver a day?
600-1000 ml.
315
Bile is made from what precursor?
Cholesterol from diet or synthesized.
316
What is the composition of Bile?
Mostly bile salts, bilirubin, cholesterol, lecithin and electrolytes of plasma.
317
What are the 2 important functions of bile?
1. Fat digestion and absorption. 2. Excretion of waste from blood (bilirubin and excess excess cholesterol).
318
How will bile help with fat digestion and absorption?
Emulsify large fat particles into smaller particles which can be attacked by lipase enzymes of pancreatic juices, and aid in absorption fo digested fat end products through intestinal mucosal membrane.
319
Without bile salts what happens to ingested fats?
40% are lost in feces and we develop a metabolic deficit.
320
Hepatocytes secrete bile into what?
Canalliculi.
321
What is the initial and secondary stages of bile?
Initial- bile acids, and cholesterol. Secondary- sodium and bicarbonate.
322
When will bile be secreted from liver cells?
Continually.
323
What is the maximun volume of the gall bladder?
30-60 ml.
324
How many hours of bile secretion can be stored in gall bladder?
12 hours because water, sodium, chloride and other electrolytes are continually absorbed through the gallbladder mucosa.
325
What will the gall bladder do with bile?
Make it more concentrated.
326
What will make the gall bladder empty?
Digestion in the small intestine will cause release of CCK which will cause emptying of the gall bladder.
327
How will the gall bladder empty?
Rhythmic contractions and relaxation of sphincter of oddi.
328
Besides CCK what will cause the gall bladder to empty?
Ach from the vagus and enteric nervous system.
329
With significant quantities of fat present how long will it take for the gall bladder to empty?
about 1 hour.
330
What happens to the bile salts that are secreted?
90% are reabsorbed into blood from small intestines.
331
How many times can bile salts be reabsorbed before they are carried out in the feces?
17 times.
332
How much cholesterol is removed from blood a day and secreted into bile?
1-2 grams.
333
Cholesterol is insoluable in pure water so how will it become soluable?
Mixes with bile salt and lecithin and becomes soluable.
334
What causes gall stones?
Cholesterol may precipitate in gall bladder.
335
What type of movements will the small intestines have?
Mixing or segmentation contractions.
336
Small intestine has segments that are like what and caused by what?
Sausage-like segments via basic electrical rhythms.
337
Slow wave is not effective in the small intestines without what?
added stimulation from myenteric plexus.
338
The small intestines chop chyme how many times per mintue?
2-3 times.
339
Mixing or segmentation contractions can be propulsive but less than what?
Peristaltic waves.
340
Propulsive movements = what?
Peristalsis.
341
Chyme travels from pylorus through the entire small intestines to the ileocecal valve in how long?
3-5 hours.
342
Spreading chyme along the small intestine walls helps with what?
digestion/absorption.
343
What hormones will increase the movements of chyme in the small intestines?
Gastrin, CCK, insulin, motilin and serotonin.
344
What hormones will decrease the movements of chyme in the small intestines?
Secretin and glucagon.
345
What reflex will open the ileocecal valve and let chyme pass from small intestines and become feces in the large intestines?
The gastroileal reflex.
346
What is peristaltic rush?
An intense irritation of Small intestine mucosa.
347
Peristaltic rush creats what?
Powerful and rapid peristalsis.
348
Peristaltic rush is mediated by what?
Relfexes in autonomic nervous system and brainstem and intrinsic stimulation of myenteric plexus.
349
Peristaltic rush relieves the small intestine of what?
Irritating substances in chyme and excessive distention.
350
Food in duodenum will increase secretion of CCK from what type of cells?
I cells in duodenum and upper jejunum.
351
What will secretin of CCK in duodenum and upper jejunum do?
increases the secretion of more pancreatic digestive enzymes by acinar cells.
352
When will 70-80% of pancreatic enzymes be secreted?
After a meal.
353
What will increase the secretn of CCK from I cells in duodenum and upper jejunum?
Products of partial protein digestion and long-chain fatty acids in chyme coming from stomach.
354
What do brunner's glands in the duodenum secrete?
Mucus.
355
Brunner's glands in the duodenum secrete mucus in response to what?
Tactile, vagal stimulation and secretin
356
What is the function of mucus in the duodenum?
Protection from acidic juices and neutralizing HCL.
357
What will inhibit the secretion of mucus in the small intestines?
Sympathetic nervous system.
358
What happens to duodenum with too much sympathetic stimulation?
Can leave the duodenum unprotected causing peptic ulcers.
359
What cells make up the crypts and villi of the small intestines?
goblet cells and enterocytes.
360
What will goblet cells secrete?
Mucus to lubricate and protect.
361
What will enterocytes secrete?
water and electrolytes.
362
Secretin is secreted by what and when?
1800 ml/day.
363
What will the secretion of chloride and bicarbonate in the small intestines do?
Osmotic movement of water.
364
The enzyme peptidase does what in the small intestine?
splits peptides into amino acids.
365
What will these enzymes do in the small intestines sucrase, maltase, isomaltase and lactase?
Split disaccharides into monsaccharides.
366
What will lipase do in the small intestine?
Split neural fat into glycerol and fatty acids.
367
What is the life cycle of epithelial cells in the small intestines?
5 days.
368
What does sprue mean?
Pathological malabsorption.
369
What are the major foods on which the body lives on?
Carbs, fats, and proteins.
370
Hydrolysis is done on all 3 types of major food to break them down, but how will hydrolysis differ between these 3 types of food?
Type of enzymes required for hydolysis.
371
Almost all carbs are digested as what?
Monosaccharides.
372
How will the body get monosaccharides?
Polysaccharides or disaccharides that are bound by condensation.
373
What is fat?
Triglycerides.
374
How will fats be digested?
The triglycerides are a combination of 3 fatty acids condensed with a single glycerol and they are digested as fatty acids.
375
How will proteins be digested?
As amino acids.
376
How will amino acids make proteins?
Amino acids bound by peptide linkages.
377
What are the 3 major sources of carbs?
sucrose, lactose, starches.
378
What is sucrose?
Disaccharide in cane sugar.
379
What is lactose?
Disaccharide in milk.
380
What are starches?
Large polysaccharides present in almost all nonanimal foods.
381
Can cellulose be digested by humans?
No.
382
What will chewing and saliva do to starch?
hydrolyzes it to disaccharide maltose and glucose molecules.
383
What % of starches are hydrolyzed by the time food is swallowed?
5%.
384
Starch digestion continues in proximal stomach up to when?
1 hour before mixing with secretions.
385
Digestion of carbs is done in 15-30 minutes after chyme emptys stomach by what?
Pancreatic amylase.
386
Carbs that are digested are converted into what?
Maltose and or other very small glucose polymers.
387
What cells contain lactase, sucrase, maltase, and alpha-dextrinase and what will the enzymes do?
Enterocytes. They split the disaccharides lactaose, sucrose, maltose and small glucose polymers into monsaccharides.
388
Monosaccharides are the final product of carbs and they are absorbed how?
They are water soluable and are absorbed into the portal blood.
389
What will happen to lactose?
Split into galactose and glucose.
390
What will happen to sucrose?
Spilts into fructose and glucose.
391
What happens to maltose and small glucose polymers?
Split into glucose.
392
What will make up more than 80% of final products of carbs?
Glucose.
393
What % of carbs will be galactose and fructose for final products?
10%.
394
What will digest proteins in the acidic stomach?
Pepsin.
395
HCL when secreted by parietal cells has a pH of what?
0.8 when secreted.
396
Once HCL mixes with other stomach contents what will the pH be?
2-3 when mixed.
397
Why will it be important for the stomach pH to be between 2 and 3?
This is the pH for pepsin to function best.
398
Pepsin will do what to proteins?
Digests collagen.
399
Why will collagen need to be digested in proteins?
This allows other enzymes to penetrate meat and digest other meat proteins.
400
Pepsin provides what % of total protein digestion?
10-20%.
401
Pepsin converts protein into what?
Proteoses, peptones, and a few polypeptides.
402
Where will most protein digestion occur at?
The duodenum and jejunum.
403
Protein digestion happens in the duodenum and jejunum via what?
Pancreatic proteolytic enzymes.
404
Trypsin and chymotrypsin are pancreatic proteolytic enzymes that do what?
Turn protein molecules into polypeptides.
405
Carboxypolypeptidase is a proteolytic enzyme that does what?
Cleaves amino acids from polypeptides.
406
What is the active form of proelastase and what will it do?
Elastase and it digests elastin fibers of meat.
407
After pancreatic enzyme activity of proteins what remains?
Dipeptides and tripeptides.
408
How will the dipeptides and tripeptides be digested?
Peptidases.
409
What is the last stage of protein digestion?
Digestion of peptidases.
410
What is the final 99% of proteins products absorbed?
Individual amino acids.
411
What is the most abundant dietary fat?
Triglycerides.
412
What are some other dietary forms of fat besides trigylcerides?
Phospholipids, cholesterol and cholesterol esters.
413
What % of triglycerides are digested in the stomach by lipases?
less than 10%.
414
Essentially all fat digestion occurs where?
In the small intestines.
415
Most fat emulsifaction occurs where via what?
In duodenum via bile.
416
What is the most important enzyme for digestion of triglycerides?
Pancreatic lipase.
417
Is the lipase from enterocytes of the small intestine important in digestion of triglycerides?
It is not usually needed.
418
When will lipase attack fat?
After emulsification.
419
What will pancreatic lipases do to triglycerides?
Split into Free fatty acids and 2-monoglycerides.
420
What will Bile salt do to the Free fatty acids and the monoglycerides?
Removes them.
421
What will transport the monoglycerides and free fatty acids to the brush border to be absorbed into the blood?
Bile salts that form micelles.
422
What is the total fluid absorbed in the GI each day by the intestines?
1.5 liters.
423
How much fluid is secreted by the GI tract each day?
7 liters
424
So total how much fluid will the GI tract absorbe each day?
8-9 liters.
425
Of the 8-9 liters abosrbed each day how much happens in the small intestine?
7-7.5
426
How much fluid that will be absorbed will pass through the ilieocecal valve into the colon?
1.5 liters.
427
How effective is the stomach at absorbing things?
Bad.
428
Why will the stomach be a poor absorber?
Lacks villus type of absorptive membrane and tight junctions between epithelial cells.
429
What type of substances can be absorbed in the stomach?
Only a few highly lipid-soluable substanace like alcohol and some drugs like asprin.
430
What is the absorptive surface of the small intestines?
Folds of kerckring.
431
Folds of kerckring increase absorptive surface area of the small intestines how much?
3 times.
432
What is on the surface of the small intestine epithelium to help increase surface area?
Micro villi.
433
How much surface area will the micro villi increase of the small intestines?
10 times.
434
What is on the micro villi and how much will it increase surface area?
Brush border and increases surface area another 20 times.
435
How much total area for absorption will there be in the small intestines?
more than 250 square meters which is equal to the area of a tennis court surface.
436
How much fat, amino acids, ions and water are absorbed through the intestines a day?
fat- less than 100 g. Amino acids- 50-100g. Ions- 50-100g. Water- 7-8 liters.
437
Will the intestines be working close to their absorptive capacity usually?
No.
438
What will the large intestines absorbe?
Water ions and very few nutrients.
439
How will water and ions be transported through the intestinal membrane?
Entirely by diffusion via usual laws of osmosis.
440
Intestines must absorb 25-30 g of sodium to prevent what?
Net loss of water.
441
What will aldosterone do in the intestines?
Greatly enhances na+ absorption and water retention.
442
Essentially all Carbs are absorbed as what?
Glucose 80% and some other monosaccharides.
443
Glucose is transported across the intestinal membrane how?
Via sodium co-transport mechanism.
444
What must be transported to have glucose absorbed?
Without Na+ transport virtually no glucose can be absorbed.
445
How will galactose be absorbed?
Same mechanism as glucose.
446
How will fructose be absorbed?
Via diffusion through intestineal epithelium, but not coupled with sodium transport.
447
What is the rate of fructose absorption like?
1/2 that of glucose or galactose.
448
After digestion how will most proteins be absorbed?
Dipeptides, tripeptides, and a few free amino acids.
449
How will the dipeptides and tripeptides be transported across the intestinal membrane?
Via sodium co-transport mechanism like glucose.
450
In the presence of ____ _____ 97% of fat is absorbed.
Bile micelles.
451
IN absence of Bile micelles how much fat is absorbed?
40-50%.
452
What is the purpose of the ileocecal valve?
To prevent backflow of feces.
453
The ileocecal sphincter in ileum proximal to valve constricted and slows emptying of ileal contents into cecum until when?
Gastroileal reflex after a meal.
454
What will delaying release of chyme into colon do?
Increases absorption of nutrients.
455
What will increase and decrease the contraction of the ileocecal sphincter?
Increase- with distention or irritationof cecum. Decreased- with distention, irritation, chyme in ileum.
456
Will the large intestines have cyrpts of leiberkuhn and villi?
Crypts of leiberkuhn yes, but no villi.
457
What will large intestine cells secrete?
No enzymes, but lots of mucus.
458
The proximal 1/2 of the colon is known as what?
absorbing colon.
459
The distal 1/2 of the colon is known as what?
Storage colon.
460
What is the difference between the epithelial cells of the large intestines and the small intestines?
Large has tight juncitons between epithelial cells.
461
What is the purpose of tight junctions?
prevents backflow of ions for more complete absorption than small intestines.
462
Mucosa of the large intestine secretes bicarbonate ions while simultaneously doing what?
absorbing an equal amount of chloride ions.
463
When mucosa absorbes chloride ions what will this do?
Create an osmotic gradient which causes absorption of water.
464
What is the maximun amount of fluid the large intestines can absore a day?
5-8 liters.
465
What vitamins form in the large intestines?
K, B12, B1, B2.
466
What is haustral mixing like and where is it done at?
Like segmentation but found in the large intestine.
467
What will haustral mixing involve?
Contraction of circular muscle and taenia coli.
468
What will haustral mixing cause?
Unstimulated parts to bulge----> Haustrations.
469
Haustral mixing digs deeply into fecal material and this does what?
Exposes it to colonic mucosa for absorption of fluid.
470
What are the contractions like for haustral mixing?
Reach peak intensity then disappear and reoccur in 1-3 minutes in nearby regions as they slowly move towards the anus.
471
A series of mass movement of the colon happens how many times a day?
1-3 times a day.
472
When feces are forced into rectum they set off what?
Intrinsic reflex.
473
What is the intrinsic reflex like?
Too weak to cause defecation and must be fortified by a second reflex.
474
What are the 2 anal sphincters?
internal and external.
475
Which anal sphincter is under voluntary control and controlled by what nerve?
External and controled by the pudendal nerve
476
Most of the time the rectum is what?
Empty.
477
Stretch signals for the defecation reflex synapse at what levels?
S-2,3,4
478
The signals from S2-4 intensify what?
Peristaltic activity and relax the anal sphincter.
479
If convenient defication is completed by what?
Voluntary relaxing the external anal sphincter.
480
If defecation is delayed what happens?
The urge is temporarily reduced due to ability of rectum adaptation to distention.
481
Feces is composed of what?
3/4 water and 1/4 solid matter.
482
What is the solid matter of feces made of?
30% dead bacteria, 10-20% fat, 10-20% inorganic material, 2-3% protein, 30% undigested roughage from food and dried constituents of digestive jucies.
483
Brown color of feces comes from what?
Stercobilin and urobilin.
484
Stercobilin and urobilin are derivatives of what?
Bilirubin.
485
What causes the odor of feces?
Product of bacterial action.
486
What will large intestine irritation (bacterial infection= enteritis) lead to?
Secretion of extra large quantities of water and electrolytes in addition to mucosa and this is diarrhea.
487
How much energy is liberated from carbs?
4C.
488
How much energy is liberated from fat?
9C.
489
How much energy is liberated from proteins?
4C.
490
What is the average USA diet?
15%-Protein, 40%-fat, 45%- carbs.
491
What is a non-western diet like?
Perdominantly CHO 80%.
492
What is the daily requirement of Protein?
30-50g. Athletes 2.2 g/kg.
493
What type of proein is more complete animal or vegetable/grain?
Animal.
494
Nitrogen excretion equals what?
Protein metabolism.
495
How will nitrogen be excreted?
90% in urine and 10% in feces.
496
What will a negative nitrogen balance mean?
Daily stores of protein are decreasing due to consumption for energy.
497
Respiratory quotient equals what?
FAT, CHO, PRO metabolism.
498
What is the Co2 to O2 ratio for carb, fat, and protein metabolism?
Carbs 1:1, Fat 70:100, Pro 80:100
499
What % of energy ingested reaches cells and where will the rest go?
27% the rest is converted to heat.
500
What is the expenditure of energy in sedentary vs laborers?
Sedentary- 2000C/d laborere/athletes- 7000C/d
