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PHGY 210 > Digestion > Flashcards

Digestion Flashcards

1
Q

What are the four accessory digestive organs?

A

Mouth
Pancreas
Liver
Gallbladder

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2
Q

What are the 6 activities of the GIT?

A 
Ingestion
Secretion
Motility
Digestion
Absorption
Defecation
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3
Q

What are the types of foods that the GIT digests best to worst?

A

Carbs (99%)
Fat (95%)
Protein (92%)

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4
Q

Which mechanisms control Propulsive, Secretory and Absorptive activities?

A

Neural and Hormonal

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5
Q

Why is the GIT longer in cadavers?

A

GIT is always under tone

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6
Q

List the layers of the GI wall

A 
From exterior to lumen:
Serosa
Muscularis externa
- longitudinal fibers
- circular fibers
Submucosa
Mucosa
- muscularis mucosae
- lamina propria
- Epithelial layer
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7
Q

What parts of the GIT are striated muscle? What tissue makes up the rest?

A

Upper third of esophagus and anus

Smooth muscle

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8
Q

True/False? The serosa is continuous with the mesentery

A

True

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9
Q

What is the role of the submucosa?

A

Loose connective tissue containing lymphatics and blood vessels

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10
Q

Where is the Enteric Nervous System located?

A

In the wall of the GIT

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11
Q

What are the three types of neurons found in the plexuses of the GIT?

A

Sensory neurons
Motor/effector neurons
Interneurons

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12
Q

True/False? The myenteric and submucosal plexuses behave independently because they are anatomically distinct

A

False

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13
Q

What are the effects of Acetylcholine on smooth muscle?

A

Excitatory

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14
Q

What are the effects of Non-Adrenergic/Non-Cholinergic NTs on smooth muscle cells?

A

Inhibitory

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15
Q

List the entities involved in short intramural reflexes

A

Stimulus -> sensory neurons -> nerve plexus -> smooth muscle/gland cell -> response

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16
Q

Parasympathetic Nerves are _____ whereas sympathetic nerves are ______
(in relation to ganglia)

A

Preganglionic

Postganglionic

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17
Q

True/False? Parasympathetic nerves act directly on smooth muscle since they don’t have a ganglion

A

False, modulate ENS

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18
Q

True/False? The PNS can act only on excitatory enteric neurons and vice versa for the SNS

A

False, PNS can inhibit inhibitory Nerves (& vice versa)

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19
Q

Sensory neurons allow for _____

A

Long Reflexes

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20
Q

Ghrelin is released by what, when? What does it do?

A

Stomach during fasting, stimulates hunger in the hypothalamic feeding centre

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21
Q

Leptin is released by what, when? What does it do?

A

Fat cells when overeating, stimulates satiety in the hypothalamic feeding centre

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22
Q

What is the Diffuse Endocrine System?

A

Largest, most diversified endocrine system in the body

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23
Q

What are the 5 most important GI hormones in the DES?

A 
Gastrin
CCK
Secretin
GIP
VIP
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24
Q

GIT regulatory hormones are released from ___

A

mucosa

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25
Q

True/False? There is usually little/no resistance in GIT

A

True

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26
Q

What are the three phases of deglutition?

A

Oral (“voluntary”)
Pharyngeal
Esophageal

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27
Q

What is the difference between the cortical and medullary deglutition centres?

A

Cortical is voluntary

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28
Q

What is more important in the pharyngeal phase, contraction of the glottis, or movement of the epiglottis?

A

Glottis

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29
Q

What happens in the pharyngeal phase?

A

Reflexes move bolus downwards, which presses on the epiglottis and in turn covers the glottis

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30
Q

What are the 4 key points of the pharyngeal phase?

A
  1. Passages to nose, mouth, trachea are blocked
  2. Apnea
  3. UES relaxes
  4. Pharynx muscles contract
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31
Q

True/False? The UES is closed in the absence of food

A

True

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32
Q

Closure of UES originates from the ____ division of the Vagus nerve

A

Somatic

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33
Q

During deglutition there is a _____ of impulses from the Somatic Vagus nerve resulting in muscle contraction

A

Cessation

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34
Q

Where does the body of the esophagus lie? What is the consequence of this?

A 
Thoracic cavity
Negative pressure (-5--10mmHg)
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35
Q

True/False? Gravity plays a major role in esophageal forces

A

False

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36
Q

When is a primary peristaltic wave generated?

A

Every time we swallow

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37
Q

What is the difference between Somatic contraction vs autonomic contraction of deglutition?

A

Somatic: sequential activation, from proximal to distal

Autonomic: Synchronous activation, but latency becomes present distally

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38
Q

True/False? A transthoracic cut will cease propagation of the peristaltic wave

A

False

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39
Q

What happens if the bolus gets stuck in the esophagus?

A

Secondary peristalsis
(initiated by local distension)
(mediated by enteric and long reflexes)

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40
Q

Does the LES have a significant size increase?

A

No

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41
Q

True/False? The LES is contracted at rest

A

True

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42
Q

What is the pressure of the LES at rest?

A

20 mm Hg

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43
Q

Increases in the intraabdominal pressure ____ pressure on the stomach and intra abdominal LES

A

Increase

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44
Q

What happens during hiatus hernia?

A

The LES is displaced into the thorax - Intra abdominal pressure increases do not increase LES pressure

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45
Q

True/False? GIT Hormones modulate the LES

A

False (not at physiological doses)

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46
Q

What lowers resistance in LES?

A

Progesterone

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47
Q

What are the three components of the stomach?

A

Fundus
Body
Antrum

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48
Q

Which section of the stomach is thickest?

A

Distal

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49
Q

How is the stomach wall different from the rest of the GIT?

A

Gastric mucosa
- Consists of folds (“rugae”)
Contains many different cells arranged in pits and glands
Muscularis externa (contains extra layer of smooth muscle)

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50
Q

What is the volume of an empty stomach?

A

50 mL

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51
Q

How does the stomach accomodate a meal?

A

Receptive relaxation (in proximal stomach ONLY)

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52
Q

True/False? Receptive Relaxation is one of the deglutition reflexes

A

True

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53
Q

Which section of the stomach performs peristalsis?

A

Antrum

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54
Q

What is the purpose of the antrum?

A

Physical disruption and regulated propulsion

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55
Q

What determines the amplitude of peristaltic waves?

A

Magnitude of stimulus

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56
Q

What determines the frequency/Direction/Velocity of Peristalsis?

A

Electric characteristics of smooth muscle

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57
Q

True/False? The upper stomach has a steady resting potential

A

True

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58
Q

What would you observe if you measure the electrophysiology of the distal stomach?

A

You would see rhythmic waves of partial depolarization

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59
Q

How often does the distal stomach undergo partial depolarization? What are these waves called?

A

Every 20 seconds, Basic Electrical Rhythm

or Electrical Control Activity

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60
Q

True/False? BER/ECA occur with delay more distally in the stomach

A

True

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61
Q

What is Electrical Response Activity?

A

The Spikes along the peak of BER Depolarization, associated with contraction

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62
Q

Where does the BER originate from?

A

The interstitial Cells of Cajal (maybe)

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63
Q

ERA spikes are dependent on what ion?

A

Ca

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64
Q

How to spikes propagate?

A

Gap junctions

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65
Q

Strength of ERA becomes ____ and ___ as it approaches the Pyloric sphincter

A

Stronger

Wider

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66
Q

What happens when the BER reaches the pyloric sphincter?

A

Antral systole: The sphincter closes

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67
Q

True/False? The pyloric sphincter is closed at rest

A

False

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68
Q

What is the main mechanism for gastric emptying of liquids?

A

Emptying due to dP between proximal stomach and duodenum
Normally dP is smol due to Receptive relaxation
- Vagotomy to proximal stomach - dP is large
- Vagotomy to distal stomach: not much change

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69
Q

How does gastric emptying of solids work

A

Stored in fundic resevoir

Distal stomach acts as antral pump

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70
Q

True/False? Factors in the duodenum also control the rate of gastric emptying/antral peristalsis

A

True

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71
Q

What are the factors in the duodenum that also control the rate of gastric emptying/andtral peristalsis?

A 
Distension
pH < 3
Osmolarity
Chemical composition
Fat >> Protein >> Carbohydrates
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72
Q

What factors increase stomach motility?

A

Gastric factors

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73
Q

What factors will decrease stomach motility?

A

Duodenal factors

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74
Q

Which parts of the GIT are involved with vomiting?

A

None
Vomiting results from the action of the diaphragm and abdominal muscles to increase intraabdominal pressure (GIT is passive)

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75
Q

What causes the unpleasant symptoms often associated with vomiting?

A

Imbalance between parasympathetic and sympathetic activities (i.e. sweating, vasoconstriction, salivation, alternating bradycardia/tachycardia)

All precede/accompany vomiting

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76
Q

What causes vomiting?

A

Afferent impulses to Vomiting Center (can arise from many places)
Agents in blood act on Chemoreceptor Trigger Zone in medulla (distinct from vomiting center, outside BBB)

CTZ sends signals to vomiting center
Vomitinc center is Necessary for vomiting

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77
Q

What are the three stages of vomiting?

A

Nausea (psychic experience)
Retching (abrupt, uncoordinated respiratory movements with glottis closed)
Emesis (actual expulsion of upper GIT contents)

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78
Q

What are the processes of emesis?

A

Individual takes deep breath, glottis closes, abdominal muscles contract, exerting pressure on gastric contents

Emesis is completed with the reversal of thoracic pressures (negative to positive) as the diaphragm is displaced upwards, forcing esophageal contents to be expelled through mouth

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79
Q

Where does most digestion/absorption of nutrients take place?

A

Small intestine

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80
Q

What are the three regions of the small intestine?

A

Duodenum
Jejunum
Ileum

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81
Q

What are the 4 functions of the USI (upper small intestine)

A

Neutralization (chyme entering from the stomach is neutralized, not protected like stomach)
Osmotic Equilibration (chyme will be isotonic by the time it leaves duodenum)
Digestion
Absorption

82
Q

What consitutes the intestinal juice secreted by the small intestine?

A

Water, mucus and Ions

83
Q

Which juices are secreted into the small intestine?

A 
Intestinal juice
Pancreatic Juice (enzymes)
84
Q

Where are brush border enzymes located?

A

Attached to the villi of small intestine cells

85
Q

Define mechanical and chemical digestion

A

Mechanical: involves segmentation
Chemical: Occurs as chyme mixes with pancreatic juice, intestinal juice, and bile

86
Q

How are intestinal contractions governed?

A

By electerical characteristics of smooth muscle
(BER/ECA)
ERA - number determines amplitude of contraction

87
Q

The intrinsic frequency of BER ______ systematically from proximal to distal intestine

A

Decreases

88
Q

Compare the proximal vs distal small intestine in terms of 1. Frequency of BER, 2. Excitability of smooth muscle, 3. Thickness of smooth muscle, 4. Frequency and amplitude of contractions

A
  1. Greater in small
  2. Greater in small
  3. Greater in small
    4 Greater in small
89
Q

What is the most common type of contractile activity after a meal? What is its function?

A

Standing rings of contraction - Segmentation

Myogenic response to distension
ENS organizes contraction over a length of SI
ANS and hormones modulate

Functions to mix contents and slowly propulse towards distal intestine

90
Q

Why are contents of the small intestine propulsed aborally?

A

Because the contractions are more vicorous and frequent proximally

91
Q

What method of prepulsion is predominant in the small intestine, Peristalsis or Segmentation?

A

Segmentation

In the Intestine, peristalsis is Infrequent, irregular, weak, shallow, and only travels for short distances

92
Q

How is intestinal peristalsis mediated?

A

A series of local reflexes
Involves interaction of longitudinal/circular muscle
Modulated by ANS and HORMONSE

93
Q

Can the frequency of intestinal peristalsis exceed the frequency of BER?

A

NO

94
Q

Can intestinal peristalsis continue without an autonomic nervous system?

A

NO

95
Q

Describe the law of the intestine

A

Radial stretch activates receptors
Neural mediation causes
1. Contraction of longitudinal muscle and relaxation of circular muscle AHEAD of bolus

  1. Relaxation of longitudinal muscle and contraction of circular muscle BEHIND bolus
96
Q

Is the ileocecal sphincter typically open or closed?

A

Closed

97
Q

Is the Colon Contractile Activity similar to SI?

A

Yes, but Slower, Sluggish, Irregular

98
Q

What are the functions of the colon?

A

Mixing (promotes absorption of water/ions)
Propulsion (slow - ~60h for conversion of chyme to feces)
Storage

99
Q

How is motor activity governed in the colon?

A

Segmentation and peristalsis (governed by IRREGULAR BER)

100
Q

What happens to the activity in the colon/SI after intake of a new meal?

A

activity is increased

101
Q

What are the long reflexes of the GIT that are stimulated by a new meal? What do they do?

A

Gastroileal Reflex
Gastrocolic Relex
Ileocolic Reflex
Empty stomach contents into intestine to make room

102
Q

What happens to GI motility during the interdigestive period?

A

Organized into intense pattern of cyclic myoelectric activity

  • Recurring at regular (~90 min) intervals
  • Moving sequentially over DISTAL STOMACH AND SMALL INTESTINE

“Migrating myoelectric complex” or MMC

103
Q

Describe the three phases of the MMC

A 
Phase I (60 min) - no spike potentials/contractions
Phase II (20 min) - Irregular Spike potentials and contractions
Phase III (10 min) - regular spike potentials and contractions
104
Q

True/False? The MMC is in phase throughout the GIT

A

False

It is offset to maintain a constant propagation rate

105
Q

What is the function of the MMC?

A

“Housekeeping” to sweep out all the trash in your system (because the pyloric sphincter is open at rest, large undigestibles can leave)

106
Q

What are the three types of enzymes involved with digestion?

A

Amylases
Proteases
Lipases

107
Q

Regulation of digestion is predominantly _____ in the upper GIT and becomes preogressively _____ near the large intestine/colon, with the midpoint being ______

A

Nervous (ANS)
Hormonal (Gut Peptides)
Small intestine

108
Q

What are the three mouth glands that produce saliva?

A

Parotid
Submandibular
Sublingual

109
Q

What do amylases do?

A

Breakdown of polysaccharides to disaccharides

110
Q

What enzyme does the tongue produce?

A

Lingual lipase

111
Q

Saliva is unique in that it is the only ________ solution in the body

A

Hypotonic

112
Q

What ions are present in saliva?

A

Na K Cl and HCO3

113
Q

What is the pH of saliva?

A

6.5-7

114
Q

What are the important proteins in saliva?

A

Ptyalin and mucin

115
Q

How is salivary gland secretion unique in terms of regulation

A

It is the only case where PNS and SNS do the same thing

Parasympathetic releases more though (ACh)

116
Q

What triggers salivation?

A

perception through “higher Centers” in cortex feeding into “salivary centers” in medulla

or

Sensory receptors in mouth acting on salivary centers

Salivary centers parasympathetically affect salivary glands

117
Q

What are the 3 phases of secretion ?

A

Psychic (conditioned reflex)
Gustatory (taste)
These two make up the cephalic phase

(Gastric/Intestinal)

118
Q

What is the most important ion in gastric juice?

A

H+

119
Q

What is the pH of gastric juice?

A

1-2

120
Q

What are the proteins in gastric juice?

A

Pepsinogen (zymogen, becomes pepsin)
Intrinsic Factor (for vitamin B absorption)
Mucin

121
Q

Where are acid, enzymes and IF released in the stomach?

A

In the fundus and body (not antrum)

122
Q

Describe the various gastric glands of the fundus and corpus, and the enzymes they secrete

A

Parietal cell - HCl
Chief cell - Pepsinogen
Mucus neck cell - Mucin

123
Q

What is the purpose of canaliculi?

A

To increase surface area

124
Q

Describe the pathway for HCl secretion in parietal cells

A
  1. Cl- entering the cell is actively transported across the canalicular membrane
  2. H+ (available from the dissociation of intracellular water) is actively pumped into the canaliculi in exchange for K+
  3. The secretion of H+ leaves an escess of OH- in the cell, resulting in an increase in intracellular pH
  4. The change in pH causes CO2 to diffuse into the cell from plasma, which combines with water to form H2CO3 (Using carbonic anhydrase)
  5. H2CO3 reacts with the excess OH- to yield H2O and HCO3-
  6. HCO3- diffuses into the circulation, restoring intracellular status quo and giving rise to increased alkalinity in VENOUS blood
  7. Water moves into canaliculi passively
125
Q

What are the functions of HCl?

A
  • Precipitates soluble proteins (allowing them to stay longer in stomach)
  • Denatures proteins (to be digested better)
  • Activates Pepsin (provides optimal pH for pepsin activity)
126
Q

How is pepsinogen activated into pepsin?

A

Low pH from HCl
AND
Through autocatalysis

127
Q

What is the only secretion in the stomach essential to life?

A

Intrinsic Factor

128
Q

What is intrinsic Factor?

A

A glycoprotein secreted by parietal cells that is required for the absorption of Vitamin B12 in the ileum

129
Q

What happens if you don’t have Intrinsic Factor?

A

Pernicious anemia

130
Q

Where is Mucin secreted in the stomach?

A

All surface epithelial cells
Cardiac/pyloric tubular glands
Mucous neck cells (in fundus and corpus)

131
Q

What is the Mucibicarb layer?

A

A layer of mucous gel and CO2 that protects surface epithelial cells from the harsh pH of stomach acid

132
Q

What is the layer Between the Mucous Gel and Surface Epithelial cells?

A

The Gastric Mucosal Barrier (apical surfaces and tight junctions)

133
Q

What are the stomach’s 3 methods of protection from the gastric mucosa?

A

Muci-bicarb layer
GMB
Rapid Cell turnover or “re-epithelialazation”

134
Q

What are the two factors contributing to ulcers?

A

Weak barrier (Aspirin and NSAIDs) or Excessive HCl output (Gastrin-producing tumors)

135
Q

What are the two types of enteric neuron that regulate secretion?

A

Cholinergic (+) and NANC (-)

136
Q

What is a result of sympathetic tone on the stomach that is not a release of enzyme?

A

Vasodilation

137
Q

What are secretagogues?

A

Amino acids/partially digested proteins which act on gastrin-releasing cells (G-cells)

138
Q

Which cell is affected by gastrin release? How is it affected?

A 
Parietal cells (HCl released)
Gastrin work on heart which then acts on parietal cells (somehow)
139
Q

Gastrin is released by endocrine cells in the antrum in response to which cells?

A

Secretagogues (products of protein digestion)
Local enteric reflexes (distention in antrum)
Vagally-mediated reflexes (eg vago-vagal reflexes)

140
Q

True/False? Gastrin release is self-regulating

A

True

141
Q

What are the physiological roles of gastrin?

A 
Stimulates HCl Secretion
Trophic effect (stimulates production of more parietal cells)
142
Q

What role does Histamine play in digestion?

A

Lots of histamine in gastric mucosa, Histamine administration elicits large volumes of gastric juice with lots of HCl

143
Q

What is the Common mediator hypothesis? Is it correct?

A

Gastrin and ACh cause Histamine release which represents the FINAL local COMMON CHEMOSTIMULATOR

NO

144
Q

What is the Separate receptor Receptor Interaction hypothesis?

A

There is an interaction among 3 separate receptors (Histamine, ACh, Gastrin)
Blockade/Stimulation of one receptor, changes the properties of one/both of the other 2 receptors

145
Q

What is the Permissive Hypothesis?

A

Histamine is constantly released and presented to the parietal cells as a tonic background, sensitizing them to other stimuli

Blocking this tonic/background release of Histamin (or using H2-receptor antagonists) inhibits acid secretion (in response to ACh and Gastrin

146
Q

How does the heart act on the Parietal cell to release HCl

A

We don’t know (Gastrin? Entero-Oxyntin?)

147
Q

True/False? Both Motor and Secretory activities of the stomach (at any given moment in time) reflect a balance between Excitatory and Inhibitory influences on the Muscular and Glandular cells in the gastric wall

A

True

148
Q

What are the 3 pre intestinal changes?

A
  • Meal is reduced to semi-liquid consistency
  • Acidified, osmotic pressure
  • Limited Digestion

Some polysaccharides -> Disaccharides
Some proteins -> polypeptides
Lipids -> Di/monoglycerides, fatty acids

149
Q

What happens in the upper intestine?

A

Chyme Neutralization
Osmotic equilibration
Digestion continues
ABsorption begins

150
Q

What is the exocrine portion of the pancreas made up of?

A

Acini, made of Duct cells and acinar cells

Acinar cells secrete enzymes, Duct cells secrete bicarbonate-rich fluid

151
Q

Where is pancreatic juice released? How does it travel?

A

Duodenum

Pancreatic duct

152
Q

What enzymes are found in pancreatic juice?

A 
Pancreatic amylase
Trypsin
Chymotrypsin
Elastase
Pancreatic Lipase
Ribonuclease
Deoxyribonuclease
153
Q

Describe the duct between the liver, pancreas and duodenum and their relation to each other

A

Bile flows from liver in common hepatic duct
Bile flows from Gallbladder in Cystic duct
Common hepatic duct meets up with Cystic duct to form common bile duct

Pancreatic fluid flows down pancreatic duct
Meets up in Ampulla of Vater and is released into duodenum (under control of sphincter of Oddi)

154
Q

What is the key electrolyte in pancreatic juice?

A

HCO3- (juice is more basic)

155
Q

How is trypsin formed and what does it do?

A

IN SMALL INTESTINE
Trypsinogen becomes Trypsin using enterokinase

Activates all proenzymes (trypsin inhibitor inactivates trypsin)

156
Q

How are fats broken down in the small intestine?

A

Pro-colipase is activated by trypsin
Triglycerides are broken down by lipase (and colipase) into FA, di-mono glycerides
Bile salts

157
Q

What does the liver secrete?

A

Bile

158
Q

How does the liver aid in carbohydrate metabolism?

A

After a meal when blood glucose is high, the liver converts glucose to glycogen/triglycerides (storage)

159
Q

How does th eliver aid in lipid metabolism?

A 
Stores some triglycerides
Breaks down fatty acids to generate ATP
Synthesizes lipoproteins
Synthesizes cholesterol
Uses cholesterol to make bile salts
160
Q

How does the liver aid in protein metabolism?

A

Deaminates amino acids so that the amino acids can be used for ATP production

161
Q

What are the main non-digestion functions of the liver?

A 
Processing of drugs and hormones
Excretion of bilirubin
Synthesis of Bile Salts
Storage (glycogen, Vitamins, Minerals)
Phagocytosis (kupffer cells)
Activation of Vitamin D
162
Q

What do bile salts do?

A

Emulsify fats to make them more easily digested

163
Q

True/False? Bile is secreted from the liver only after meals, with more bile being secreted after a fat-rich meal

A

False, bile is secreted continuously

164
Q

What are the 3 functions of the gallbladder?

A

Concentrates solids
Reduces pH
Increases viscocity

165
Q

True/False? The gallbladder does not synthesize its own bile salts

A

True

166
Q

When is a cholecystectomy a problem?

A

If you eat a lot of fat (Otherwise fine)

167
Q

How are most bile salts reabsorbed into portal blood?

A

Enterohepatic Circulation

168
Q

What is the difference between the hepatic vein and the hepatic portal vein?

A

Hepatic: Liver-heart

Hepatic portal: SI-Liver

169
Q

What happens if more Bile Salt is returned via portal blood?

A

Larger VOLUME of bile secreted (+ve feedback)

170
Q

What happens to bile volume if we remove the ileum?

A

Decreases (less +ve feedback)

171
Q

The more bile salt returned in portal blood, the ___ the amount of NEW bile salts being synthesized

A

Smaller (negative feedback)

172
Q

What will happen to bile salt synthesis if we remove the ileum?

A

Increase (less -ve feedback)

173
Q

What happens without bile salts?

A

Cholesterol precipitates and gives rise to gallstones

174
Q

Absorbtion of what two species are inhibited by Bile Salts?

A

Na+ and H2O

175
Q

What happens if there is excess bile salt in colon?

A

Diarrhea

176
Q

What do choleretics do?

A

Cause the LIVER to secrete a larger volume of bile

177
Q

What do Cholagogues do?

A

Increase the emptying of the GALL BLADDER

178
Q

What happens to bile/pancreatic juice regulation under vagal tone?

A

Liver: +
GB Contraction/sphincter relax: +++
Pancrease (low vol/high enzyme/low pH): +++
Pancreas (High vol/low enzyme/high pH): –

Cephalic phase, prepares rest of GIT for meal

179
Q

What does gastrin do to bile/pancreatic juice regulation?

A

Liver: +
GB Contraction/sphincter relax: +
Pancrease (low vol/high enzyme/low pH): +
Pancreas (High vol/low enzyme/high pH): +

Gastric phase, not much effect

180
Q

What does CCK do to bile/pancreatic juice regulation?

A

Liver: –
GB Contraction/sphincter relax: +++
Pancrease (low vol/high enzyme/low pH): +++
Pancreas (High vol/low enzyme/high pH): –
Released during high fat/protein meal

181
Q

What does Secretin do to bile/pancreatic juice regulation?

A

Liver: + (vol/HCO3)
GB Contraction/sphincter relax: –
Pancrease (low vol/high enzyme/low pH): –
Pancreas (High vol/low enzyme/high pH): +++

Released during low pH in duodenum

182
Q

What do bile salts do to bile/pancreatic juice regulation?

A

Liver: +++
GB Contraction/sphincter relax: –
Pancrease (low vol/high enzyme/low pH): –
Pancreas (High vol/low enzyme/high pH): –

Feedback looping

183
Q

Where are crypt cells found?

A

In the crypt region of small intestine villi

184
Q

Do crypt cells secrete any enzyme?

A

No, but they secrete a large amound of alkaline fluid called “Succus Entericus”
(Villi don’t secrete anything)

185
Q

How do Villi complete digestion?

A

Enterocytes in Villi synthesize digestive enzymes which remain in brush border, and absorb nutrients/fluids

186
Q

True/False? Crypt cells mature as they migrate up out of the crypt region into the villus region, whereas the cells at the tip build into dense peaks

A

False, but cells at tip apoptose and slough off into lumen

187
Q

Name the 6 reactions that take place in the microvillus of the brush border (substrate, product, and enzyme)

A

Trypsinogen (enterokinase) trypsin
alpha dextrin (alpha destrinase) n x glucose
Sucrose (sucrase) glucose, fructose
Lactose (lactase) glucose, galactose
Maltose (maltase) 2 x glucose
peptide (aminopeptidase) Amino acid
Nucleotide (nucleosidase) base, pentose, phosphate

188
Q

How are monosaccharides absorbed?

A

Through facilitated diffusion into blood capillary of villus

189
Q

How are amino acids absorbed?

A

Through facilitated diffusion into blood capilary of villus

190
Q

How are short chain fatty acids absorbed?

A

Through simple diffusion into blood capilary of villus

191
Q

How are tryglycerides absorbed?

A

Through simple diffusion of a chylomicron into lacteal of villus, then into left sublavian vein (near heart)

192
Q

True/False? the large intestine takes up the last amount of nutrients left behind in SI

A

False

193
Q

What is secreted by the colon?

A

Alkaline, mucous, (no digestive enzymes/absorption)

BACTERIAL ACTIVITY

194
Q

How much digestive fluid is secreted in a day? How much is absorbed?

A

7L of secretions, ~9L absorbed

195
Q

True/False? Most of absorption is REabsorption

A

True

196
Q

What is the only GI organ essential to life?

A

SI

197
Q

What does the Duodenum absorb the most?

A

Iron, Calcium, CHO, Proteins, Lipids, Sodium, Water

198
Q

What does the Jejunum absorb most?

A

CHO Proteins, Lipids, Sodium Water

199
Q

What does the Ileum absorb most?

A

CHO, Proteins, Lipids, Sodium, Water, Vitamin B12, Bile Acids

200
Q

What are the requirements for absorption?

A

Adequate Digestion
Adequate sites of absorption
Adequate transit time for absorption
Adequate cofactors/transporters

201
Q

True/False? Oligopeptides may be absorbed faster than free amino acids

A

True

PHGY 210 (5 decks)

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