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Gastrointestinal > Lecture 1: Functional Anatomy and General Principles of GI Regulation > Flashcards

Lecture 1: Functional Anatomy and General Principles of GI Regulation Flashcards

1
Q

4 Major physiological processes of GI tract

A

1) Motility
2) Secretion
3) Digestion
3) Absorption

also excretion and immune function

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2
Q

What is the name for the vasculature of the gut?

A

Splanchnic

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3
Q

What are the 6 sphincters of the GI tract?

A

1) UES (between pharynx and esophagus)
2) LES (esophagus and stomach)
3) Pyloric
4) Sphincter of Oddi (pancreatic and bile duct)
5) Ileocecal
6) Internal and external anal

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4
Q

What important nutrient travels in the lymph?

A

lipids and lipid-soluble molecules

they are too large to pass into capillaries

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5
Q

What does the celiac artery supply?

A

liver, spleen, stomach

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6
Q

What does the superior mesenteric artery supply?

A

pancreas, small intestine, proximal colon

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7
Q

What does the inferior mesenteric artery supply?

A

distal colon

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8
Q

What are the 4 layers of the gut?

A

1) Mucosa (innermost)
2) Submucosa
3) Muscularis externa
4) Serosa

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9
Q

What 3 things is mucosa made of?

A

1) epithelium
2) lamina propria
3) muscularis mucosae

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10
Q

What are the most abundant cells of the mucosal epithelium?

A

absorptive enterocytes (play vital role in digestion and absorption)

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11
Q

What cells of the mucosal epithelium regulate GI function by releasing regulatory peptides?

A

Enteroendocrine cells

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12
Q

What type of epithelial cells are found in the esophagus?

A

SQUAMOUS (no absorption, just food transport)

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13
Q

What type of epithelial cells are found in the intestinal epithelium?

A

COLUMNAR (lots of absorption)

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14
Q

What is the functional unit of absorption?

A

villus (increases surface area 600x)

Celiac disease has flattened villi leading to malabsorption

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15
Q

What do parietal cells produce?

A

HCl

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16
Q

What do chief cells produce?

A

pepsinogen

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17
Q

What molecules are found in abundance in the lamina propria?

A

collagen and elastin fibrils

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18
Q

Where are the lymph vessels, nodes, capillaries, and nerves found?

A

lamina propria

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19
Q

What is the muscularis mucosae?

A

smooth muscle cells in folded shape due to contractions

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20
Q

What follows the mucosal layer and what are some hallmarks of that next layer?

A

SUBMUCOSA - made of connective tissue (collagen and elastin) similar to lamina propria in that it has lymph nodes and nerves

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21
Q

What is Meissner’s plexus and where is it located?

A

submucosal plexus of the enteric nervous system (nerve bundle in gut) found in the SUBMUCOSA

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22
Q

What layer follows the submucosa and what role does it play?

A

Muscularis externa/propria - involved in CONTRACTIONS

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23
Q

Where is the myenteric plexus?

A

in the muscularis externa layer

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24
Q

What is the layer beneath the muscularis externa and makes up the outermost layer?

A

Serosa (made up of squamous mesothelial cells)

25
Q

What is the function of the serosa layer?

A

to secrete a viscous substance that reduces friction between abdominal organs during contractions. Also connected to mesentery to help suspend organs

26
Q

What is the name of the sensor cells of the GI system?

A

Enteroendocrine cells (EECs)

respond to stimulus by secreting a hormone

27
Q

Are most EECs “open” (meaning in contact with GI lumen and near capillaries) or “closed” (no contact with GI lumen)

A

OPEN

ECL cells of gastric epithelium are closed

28
Q

What is the main function of gastrin?

A

to stimulate acid secretion by the ECL and parietal cells

29
Q

What is the main difference between endocrine and paracrine signaling?

A

Endocrine: goes INTO THE BLOODSTREAM
Paracrine: diffuses thru interstitial space (not transported in circulation)

30
Q

What cells produce histamine?

A

Enterochromaffin-like cells (ECL) in the stomach

31
Q

What does histamine do and where does it act?

A

histamine diffuses thru the interstitial space and binds to nearby parietal cells to secrete HCl

32
Q

What important neurotransmitter is released from enteric neurons, mucosal mast cells, and ECLs that is responsible for regulating contractile activity of smooth muscle cells in GI tract?

A

Seratonin

33
Q

Where is cholecystokinin produced?

A

I cells of the duodenum

34
Q

What hormones signal both endocrine and paracrine?

A

1) CCK
2) Secretin
3) Peptide YY
4) Proglucagon

35
Q

What two nervous systems feed the gut?

A

1) Extrinsic (cell bodies located outside gut wall - ANS)

2) Intrinsic (cell bodies located inside gut wall)

36
Q

What are the 2 intrinsic or enteric nervous system cell bodies?

A

1) submucosal plexus

2) myenteric plexus

37
Q

Which part of the autonomic nervous system is responsible for activating GI function?

A

PARASYMPATHETIC (via vagus)

38
Q

Postganglionic neurons of the parasympathetic innervation are either _________ or _________

A

cholinergic (Ach) or peptidergic (VIP vasoactive intestinal peptide)

39
Q

Vagus nerve is a mixture of afferents and efferents with the majority being _______

A

afferents (75%)

40
Q

What effect does sympathetic stimulation have on GI function?

A

INHIBITS (but activates sphincter contraction)

41
Q

True or false: enteric nervous system can act autonomously from extrinsic system?

A

true “little brain of the gut”

42
Q

Where is striated muscle located in the GI tract?

A

1) pharynx
2) upper 1/3rd of esophagus
3) external anal sphincter

43
Q

What type of muscle is contractile in the gut?

A

smooth

44
Q

What allows for rapid communication between smooth muscle cells?

A

gap junctions with interstitial cells of Cajal (ICCs) –> allows rapid transduction of action potentials

45
Q

Where are phasic contractions found and what are they employed to do?

A

esophagus, gastric antrum, small intestine

mix and propel

46
Q

Where are tonic contractions?

A

orad (upper) region of stomach and lower esophageal, ileocecal, and internal anal sphincters

47
Q

What does the vagus nerve innervate?

A

esophaguse, stomach, gallbladder, pancreas, 1st part of intestine, cecum, proximal part of colon

DOES NOT INNERVATE SALIVARY GLANDS

48
Q

What doe the pelvic nerves innervate?

A

the distal part of the colon and anorectal region

49
Q

What are Slow Waves?

A

unique feature of GI smooth muscle electrical activity (not large enough to elicit action potential) oscillations of depolarization and repolarization of membrane potential

50
Q

Where do slow waves originate?

A

Interstitial cells of Cajal (ICCs) between longitudinal and circulaf layers of muscularis externa (PACEMAKER CELLS)

51
Q

What are tonic contractions with respect to slow waves?

A

sub-threshold slow waves producing weak contractions without action potentials

52
Q

What are phasic contractions with respect to slow waves?

A

when action potentials occur on top of slow waves generating stronger, powerful contractions

53
Q

In GI smooth muscle, how do individual action potentials add?

A

summate into one long contraction

54
Q

What are segmentation contractions?

A

happen in intestines - split chyme and send it both directions, exposing more of it to enzymes. Then the chyme merges again and mixes

55
Q

What are peristaltic contractions?

A

propel chyme along GI tract, contraction occurs orad to bolus and caudad portion relaxes, sending bolus forward

56
Q

Where do peristaltic contractions occur?

A

pharynx, esophagus, gastric antrum, small and large intestines

57
Q

Which neurotransmitters stimulate orad contraction in peristalsis?

A

Ach and substance P

58
Q

Which neurotransmitters stimulate caudad relaxation in peristalsis?

A

VIP and NO

Gastrointestinal (8 decks)

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