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Principles of Gastrointestinal Regulation Flashcards

1
Q

What are the main functions of the gastrointestinal tract?

A
  • To absorb nutrients and water into circulation

- To participate in the excretion of waste substances.

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2
Q

What are the 5 main physiological processes that the GI tract participates in?

A
  • Motility
  • Secretion
  • Digestion
  • Absorption
  • Excretion
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3
Q

How does the duodenum deal with the high acidity of the substances coming in from the stomach?

A

It has a high amount of bicarbonate in order to neutralize the acid

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4
Q

What causes motility in the digestive system?

A

It is a consequence of contractions of layers of smooth muscle cells in the GI tract.

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5
Q

What is the function of secretion in the GI tract?

A

It is the release of enzymes, biological detergents, mucus, ions and water in the GI lumen

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6
Q

What is the function of digestion?

A

It breaks down food so that it can be absorbed for nutrients by the body

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7
Q

What are the 3 saccharides that the body can absorb?

A

Glucose
Fructose
Galactose

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8
Q

What is the function of absorption in the GI tract?

A

Process by which nutrients, electrolytes and water are absorbed from the GI lumen into the bloodstream

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9
Q

What is the function of excretion in the GI tract?

A

Stores and excretes waste substances from the body ranging from cholesterol to drug metabolites

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10
Q

What is the relation of the GI tract to the immune system?

A

The GI tract is open to the external environment and as a result it is exposed to many organisms so it must have immune cells to protect the body non specifically

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11
Q

What is the flow of the GI tract?

A 
Mouth
Pharynx
Esophagus
Stomach
Small Intestine
Large Intestine
Rectum
Anus
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12
Q

What is the function of the upper esophageal sphincter?

A

It is between the pharynx and the esophagus and it keeps food out of the trachea

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13
Q

What is the function of the lower esophageal sphincter?

A

It is between the esophagus and the stomach and it keeps acid out of the esophagus

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14
Q

What is the function of the pyloric sphincter?

A

It is between the stomach and the duodenum and it keeps acid out of the duodenum

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15
Q

What is the function of the sphincter of Oddi?

A

Controls the flow of bile and pancreatic fluid

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16
Q

What is the function of the ileocecal sphincter?

A

Prevents back flow into the small intestine

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17
Q

What are the major arteries of the splanchnic region?

A

Celiac
Superior Mesenteric
Inferior Mesenteric

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18
Q

What does the celiac artery supply?

A

Liver
Spleen
Stomach

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19
Q

What does the superior mesenteric artery supply?

A

Pancreas
Small Intestine
Proximal Colon

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20
Q

What does the inferior mesenteric artery supply?

A

Distal Colon

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21
Q

What is unique about the venous drainage of the GI tract?

A

It does not drain into the systemic circulation and instead goes into the portal system

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22
Q

What is the advantage of the portal venous system?

A

It allows blood to go through the liver for detoxification as an additional defense mechanism

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23
Q

What is the importance of the lymphatic drainage in the GI tract?

A

Lipids and lipid soluble molecules cannot cross the capillaries so they are drained via the thoracic duct

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24
Q

What are the layers of the GI tract from innermost to outermost?

A

Mucosa
Submucosa
Muscularis Externa
Serosa

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25
Q

What is the role of absorptive enterocytes in the mucosal epithelium?

A

Important in digestion and absorption

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26
Q

What is the role of enteroendocrine cells in the mucosal epithelium?

A

Release regulatory peptides

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27
Q

What is the role of gastric mucosal cells in the mucosal epithelium?

A

Produce H+

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28
Q

What is the role of mucin-producing cells in the mucosal epithelium?

A

Produce mucin

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29
Q

What cell type is found in esophageal epithelium?

A

Squamous

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30
Q

What cell type is found in intestinal epithelium?

A

Columnar

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31
Q

What are found on the surface of the small intestine lining?

A

Villi and crypts

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32
Q

What is the importance of the crypts?

A

Crypts house the intestinal stem cells

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33
Q

What is the importance of the villi?

A

They are the unit of absorption and increase the surface area available and also have microvilli along their own surface to increase this further

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34
Q

What layers make up the mucosa?

A

Epithelium
Lamina Propria
Muscularis Mucosa

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35
Q

What is in the mucosal lamina propria?

A

Connective tissue, glands and vascularization

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36
Q

What is in the muscularis mucosa?

A

Thin smooth muscle layer

37
Q

What is found in the submucosa of the GI tract?

A

Connective tissue, glands and nerves.

The brain in the gut is found here

38
Q

What makes up the little brain in the gut?

A

Meissner’s/Submucosal Plexus

Auerbach’s/Myenteric Plexus

39
Q

What is found in the muscularis externa of the GI tract?

A

Inner circular muscular layer

Outer longitudinal muscular layer

40
Q

What is the function of the outer longitudinal muscular layer?

A

Shortens/lengthens the gut

41
Q

What is the function of the inner circular layer?

A

Opens/closes the tract and moves food through it

42
Q

What is the serosa of the GI tract?

A

It is the outermost layer and it is part of the mesentery that lines the surface of the abdominal wall and keep the organs suspended in the cavity.

Its secretion is viscous, lubricates the abdominal organs to reduce friction between the abdominal organs during contraction/relaxation of GI tract.

43
Q

What are the sensor cells of the GI tract?

A

Enteroendocrine cells (EECs)

44
Q

How do EECs work?

A

They respond to a stimulus by secreting a regulatory peptide or hormone, which travels via circulation to a target cell at distant location.

The target cells express specific receptors for the GI hormone.

45
Q

How does paracrine regulation differ from hormonal regulation?

A

Paracrine regulation is local and does not enter the circulation whereas hormonal regulation enters the circulation.

46
Q

What are some chemicals that are important in paracrine signaling?

A

Histamine
Serotonin
Cholecystokinin

47
Q

What is the function of histamine in paracrine signaling?

A

It is released by enterochromaffin-like cells (ECL) in the stomach diffuses through the interstitial space and binds to neighboring parietal cells that then secrete HCl.

48
Q

What is the function of serotonin in paracrine signaling?

A

It is released from enteric neurons, mucosal mast cells and specialized EECs called enterochromaffin cells regulate the contractile activity of smooth muscle cells in the GI system.

49
Q

What is the function of cholecystokinin in paracrine signaling?

A

It can be both paracrine and endocrine regulator- it is released from the duodenum in response to dietary protein, lipid- acts locally on nerve terminals (paracrine effect) and on pancreas (endocrine effect).

50
Q

What is the effect of celiac disease?

A

It is an allergic response to gluten that causes inflammation in the small intestine that reduces the absorption of nutrients

51
Q

What is the signaling mechanism of gastrin?

52
Q

What is the signaling mechanism of cholecystokinin (CCK)?

A

Endocrine

Paracrine

53
Q

What is the signaling mechanism of secretin?

A

Endocrine

Paracrine

54
Q

What is the signaling mechanism of glucoinsulinotropic peptide?

55
Q

What is the origin an effect of gastrin?

A

G cells.

Increases H+ secretion in parietal cells
Increased histamine secretion of ECL cells
Increased growth of gastric mucosa

56
Q

What is the origin an effect of CCK?

A

I cells of duodenum.

Decreased gastric emptying, food intake and H+ secretion

Increase pancreatic secretion and contraction of gallbladder

57
Q

What is the origin an effect of secretin?

A

S cells of duodenum.

Increased pancreatic secretion

58
Q

What is the origin an effect of glucoinsulinotropic peptide?

A

K cells of duodenum and jejunum

Increased insulin secretion from pancreas

59
Q

What is the signaling mechanism of peptide YY?

A

Endocrine

Paracrine

60
Q

What is the signaling mechanism of proglucagon derived peptides?

A

Endocrine

Paracrine

61
Q

What is the origin and effect of peptide YY?

A

L cells of intestine

Decreased gastric emptying, acid secretion, pancreatic secretion, intestinal motility and food intake

62
Q

What is the origin and effect of proglucagon derived peptides?

A

L cells of intestine

Increased epithelial cell proliferation

63
Q

What are the 2 sets of nerves that innervate the GI tract?

A

Extrinsic

Intrinsic

64
Q

What is the extrinsic nervous system?

A

Nerves that innervate the gut, with cell bodies located outside the gut wall.

These extrinsic nerves are part of autonomic nervous system (ANS).

65
Q

What is the intrinsic nervous system?

A

Have cell bodies that are contained within the wall of the gut

  • submucosal plexus
  • myenteric plexus
66
Q

What are the divisions of the extrinsic innervation?

A

Parasympathetic

Sympathetic

67
Q

What nerves comprise the parasympathetic innervation?

A

Vagal Nerve - esophagus to the proximal colon

Pelvic Nerves - distal colon to anorectal area

68
Q

What is the general function of the parasympathetic innervation?

A

Activates GI function

69
Q

What is the general function of the sympathetic innervation?

A

Inhibits GI function

70
Q

What is the exception of the sympathetic innervation of the GI tract?

A

Activates the sphincter muscles

71
Q

What are the 2 divisions of the intrinsic nervous system?

A

Myenteric Plexus

Submucosal Plexus

72
Q

Where is the myenteric plexus located?

A

Between the longitudinal and circular muscle layers

73
Q

Where is the submucosal plexus located?

A

In the submucosa

74
Q

In the intrinsic system, what are the roles of the neurons and the interneurons?

A

Neurons are afferent, interneurons are efferent

75
Q

What is the function of acetylcholine?

A

Increased salivary, gastric and pancreatic secretions

76
Q

What is the function of norepinephrine?

A

Increased salivary secretion

77
Q

What is the function of vasoactive intestinal peptide?

A

Increased intestinal and pancreatic secretion

78
Q

What is the function of gastrin releasing peptide?

A

Increased gastric secretion

79
Q

What is the function of enkephalin?

A

Decreased intestinal secretion

80
Q

What is the function of neuropeptide Y?

A

Decreased intestinal secretion

81
Q

What is the function of substance P?

A

Increase salivary secretion

82
Q

What are phasic contractions and where are they found?

A

They are periodic contractions followed by relaxation – found in esophagus, gastric antrum, small intestine – involved in mixing and propulsion.

83
Q

What are tonic contractions and where are they found?

A

They are a constant level of contraction or tone without regular periods of relaxation – found in orad (upper) region of stomach and lower esophagheal, ileocecal and internal anal sphincters.

84
Q

What do slow waves of the GI tract show?

A

Weak tonic contractions of the GI tract

85
Q

Where do the slow waves originate from?

A

Interstitial cells of Cajal (pacemaker cells of GI)

86
Q

What are segmentation contractions?

A

A small section contracts, splitting the chyme, sending it in both orad and caudad directions. This section then relaxes allowing chyme to merge – this serves to mix chyme but produces no forward movement.

87
Q

What are peristaltic contractions?

A

These contractions help to propel the chyme along the GI tract.

88
Q

What chemicals are involved in orad contraction?

A

ACh and Substance P

Orad = towards mouth

89
Q

What chemicals are involved in caudad relaxation?

A

VIP and NO

Physiology (81 decks)

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