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Physiology > GI > Flashcards

GI Flashcards

1
Q

What % of Gi system receives CO?

A

33

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2
Q

Splanchnic circulation is organized into what?

A

Series & parallel components

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3
Q

Series components

A

Venous drainage empties into portal v. & perfuses liver

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4
Q

What 3 aa make up parallel circulation?

A
  • Celiac a.
  • SMA
  • IMA
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5
Q

Secretions stimulated by cephalic phase

A
  • Saliva (large volume)
  • Gastric acid (small)
  • Pepsin (small)
  • Pancreatic enzymes (small)
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6
Q

What reinforces the cephalic phase?

A

Chewing!

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7
Q

Cephalic phase characteristics

A
  • Activates enteric neurons via PNS traveling in vagus n.
  • Releases Ach
  • Stimulates secretions in salivary glands, parietal cells, & enzyme secreting cells.
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8
Q

Where is initial fluid (saliva) formation?

A

In acinar cells

  • via Cl- pump
  • isotonic solution
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9
Q

Where is NaCl reabsorbed during salivary secretion?

A

In ductal cells

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10
Q

Composition of salivary secretion

A
  • Low Na+, Cl-
  • High K+, HCO3-
  • Amylase, lipase (digestion)
  • Lysozyme, lactoferrin (antimicrobial)
  • Mucus (lubrication)
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11
Q

Factors that influence salivary flow

A
  • Hydration status (most important!)
  • Circadian rhythm (peaks at end of afternoon, 0 during sleep)
  • Medications
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12
Q

Which gland contributes the most during “stimulated” salivary flow?

A

Parotid

- Aqueous saliva

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13
Q

Which gland contributes the most during “unstimulated” salivary flow?

A

Submandibular

- Viscous, mucin glycoproteins

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14
Q

What is a good indicator of properly functioning salivary glands?

A

alpha-amylase

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15
Q

Muscular composition in upper vs lower esophagus

A
  • Upper 1/3 = skeletal
  • Middle 1/3 = skeletal & smooth
  • Lower 1/3 = smooth
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16
Q

Deglutition

A

Swallowing reflex

  1. Oral
  2. Pharyngeal
  3. Esophageal
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17
Q

Deglutition events

A
  1. Nasopharynx closes –> breathing inhibited
  2. Laryngeal mm contract to close glottis & elevate larynx
  3. Peristalsis begins in pharynx –> propels food toward esophagus
  4. Esophageal sphincter relaxes –> food enters
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18
Q

Oral phase

A
  1. Tongue pushes bolus toward pharynx
  2. Somatosensory receptors activated
  3. Signal travels to afferents
  4. Involuntary swallowing reflex initiated (info sent via glossopharyngeal, vagus, & hypoglossal)
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19
Q

Pharyngeal phase

A
  • Begins when receptors are stimulated
  • Block nasopharynx & trachea
  • UES opens
  • Respiration inhibited
  • CN IX & X
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20
Q

Esophageal phase

A
  • Begins when food enters esophagus
  • UES closes
  • Primary peristaltic wave
  • Secondary peristalsis (enteric NS): initiated by esophageal distention
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21
Q

Gastric phase

A
  1. Food stretches wall of stomach, neural reflex stimulates acid secretion
  2. Peptides & aa stimulate G cells to release gastrin
  3. Food acts as buffer –> ph increases –> removal of stimulus for somatostatin secretion from D cells
  4. When acid secretion sufficient to lower ph, somatostatin can inhibit gastrin release & digestion completed
22
Q

What forms H2CO3?

A

Aerobic metabolism combines w/ H2O

- catalyzed by carbonic anhydrase

23
Q

HCl secretion

A
  1. H2CO3 –> H+ & HCO3
  2. H+ secreted via H+-K+ATPase
  3. Cl- follows via Cl- channels
  4. HCO3 absorbed into blood via Cl-HCO3 exchanger = “alkaline tide”
24
Q

When do S cells release secretin?

A

When pH is 4.5 or less –> HCO3- secretion

25
Q

3 layers of smooth muscle in GI

A
  1. outer longitude
  2. inner circular
  3. muscular mucosa
26
Q

Smooth muscle cells are connected by what?

A

Gap jxns that form electrical syncytium

27
Q

In smooth muscle, interaction of actin & myosin is controlled by what?

A

Binding of Ca2+ to calmodulin

28
Q

Migrating motility complex: Type I

A

No contractions

29
Q

MMC: Type II

A
  • Intermittent peristaltic contractions

- Variable amplitude

30
Q

MMC: Type III

A

Strong peristaltic contractions

31
Q

MMC characteristics

A
  • Initiated during fasting
  • Begins in stomach
  • Moves undigested material to colon
  • Repeats every 90-120 mins
32
Q

Myogenic contractility

A

Gut has some contractility w/out any nervous input

33
Q

Importance of tonic inhibitory tone

A

Constant inhibitory tone of VIP & NO –> prevents, slows down contractility

34
Q

Major carbs

A
  • Complex starches
    (amylopectin, amylose) *Digestion begins at mouth
  • Disaccharides (sucrose, maltose, lactose, trehalose) *Digestion begins at intestine
35
Q

Digestion, absorption of carbs

A
  1. Enzyme active in mouth until stomach inactivates it
  2. Salivary & pancreatic amylase produce products
  3. Enzymes hydrolyze starch to glucose
36
Q

Alpha-amylase breaks down starch into what?

A
  • Alpha-dextrins
  • Maltose
  • Maltotriose
37
Q

What breaks maltose into glucose?

A

Maltase

38
Q

What breaks down alpha dextrins into glucose?

A

Alpha-dextrinase

39
Q

What breaks down maltotriose into glucose?

A

Sucrase

40
Q

Carb absorption: apical

A
  • Na+-glucose cotransporter
  • Na+-galactose cotransporter
  • Fructose facilitated diffusion
41
Q

Carb absorption: basolateral

A

Facilitated diffusion w/ GLUT 2 transporter

42
Q

Fxn of incretins

A

Hormones that help insulin

43
Q

Incretin hormones

A
  • GLP1

- GIP

44
Q

What produces GLP 1?

A

Intestinal cells

45
Q

GLP1 fxn

A
  • Stimulates insulin biosynthesis & secretion
  • Inhibits glucagon secretion
  • Protective effects in heart/brain
  • Improves insulin signaling –> insulin sensitivity increased, gluconeogenesis reduced
46
Q

Protein absorption: apical

A
  • Na+-aa cotransport

- H+-di/tripeptide cotransport

47
Q

Protein absorption: basolateral

A
  • Further breakdown to aa

- Facilitated diffusion

48
Q

What are the final digestive products of lipids?

A
  • Monoglycerides
  • Cholesterol
  • Lysolecithin
  • Free fatty acids
49
Q

What are the final digestive products of proteins?

A
  • AA
  • Dipeptides
  • Tripeptides
50
Q

How does absorption of lipids occur?

A

Via micelles & chylomicrons

51
Q

Cl- secretion from crypts

A

Requires activation by Ca2+ or cAMP

Physiology (7 decks)

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