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GI Unit > 1.1 Intro to the gut and control > Flashcards

1.1 Intro to the gut and control Flashcards

1
Q

What are the main functions of the mouth?

A

Physical breakdown of food
Initial digestive enzymes released
Infection Control

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2
Q

What is the main function of the oesophagus?

A

Rapid transport of the bolts to stomach through thorax via peristalsis

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3
Q

What is the function of the upper oesophageal sphincter?

A

To prevent air from entering the GI tract

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4
Q

What is the function of the lower oesophageal sphincter?

A

To prevent reflux from the stomach into the oesophagus

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5
Q

What are the four major functions of the stomach?

A
  1. Storage facility
  2. To produce chyme ( physical and chemical breakdown of food)
  3. Infection control
  4. Secrete Intrinsic Factor for absorption of vitamin B12
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6
Q

What are the 2 main function of the duodenum?

A

Neutralisation/osmotic stabilisation of chyme

Continuation of digestion ( pancreatic secretions and bile )

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7
Q

What is the main site of nutrient absorption?

A

Jejunum

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8
Q

Where is the main site of water and electrolyte absorption?

A

Mainly Ileum

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9
Q

Where is bile reabsorbed?

A

Ileum

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10
Q

Where is vitamin B12 absorbed?

A

Terminal ileum

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11
Q

What are the 5 main functions of the large bowel?

A 
Temporary storage of faeces 
Final water absorption
Final electrolyte absorption
Some bile salt reabsorption
Production of some SCFAs
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12
Q

What are the main function of saliva?

A

Chemical digestion via amylase enzymes
Lubrication of food bolus
Infection control via lysozymes

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13
Q

What is the function of the pyloric sphincter?

A

To release chyme into the duodenum

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14
Q

What are the 2 main functions of the acidic environment of the stomach?

A
  1. Denatures and unravels proteins to assist in their digestion by proteases.
  2. Forms an innate barrier towards live toxins therefore protecting against infection through the gut.
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15
Q

How long is the duodenum?

A

25cm

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16
Q

What is the main function of bile?

A

To help emulsify fats.

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17
Q

Describe the structure of the jejunum

A

Longest part of the gut.

Contains plicae circulares to increase SA

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18
Q

What is chyme?

A

A fluid that passes out of the stomach consisting of gastric secretions and partially digested food.

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19
Q

From proximal in the gut to distal, what are the different sections of the large gut?

A 
caecum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
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20
Q

Why is it important that the large intestine produces SCFA?

A

To support the bacteria in the micro biome of the large intestine.

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21
Q

What occurs in the rectum to stimulate the urge to deficate?

A

The rectum is usually empty. When it begins to fill and stretch is detected we get the urge to deficate.

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22
Q

What is Cullens sign?

A

Superficial oedema and bruising around the belly button/umbilicus.

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23
Q

What causes cullens sign?

A

Acute pancreatitis
Bleeding from blunt abdominal trauma
Bleeding from aortic rupture
Bleeding from ruptured ectopic pregnancy

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24
Q

What is grey Turners sign?

A

Bruising of the flanks, usually with a blue discolouration.

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25
Q

When does grey Turners sign develop?

A

During a retroperitoneal hemorrhage.

Acute pancreatitis, pancreatic haemorrhage, blunt abdominal trauma, ruptured ectopic pregnancy

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26
Q

Where do cell bodies of neurons of the autonomic nervous system reside?

A

Reside within the CNS (brain or spinal cord)

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27
Q

What chemical do preganglionic fibres of the autonomic nervous system secrete?

A

Acetyl choline

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28
Q

What chemical(s) do postganglionic fibres of the autonomic nervous system secret?

A

ACh
neuropeptides
Norepinephrine

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29
Q

From what area of the spinal cord does the parasympathetic nervous system come from?

A

Craniosacral (CN3,CN7,CN9,CN10,S2-S4)

30
Q

What action does the parasympathetic nervous system have on the gut?

A

Stimulates gut activity.

31
Q

What parasympathetic nerves act upon the gut?

A

Vagus nerve CN10

Pelvic Splanchnic nerves (S2 - 4)

32
Q

What affect does the sympathetic nervous system have on the gut?

A

Constricts blood vessels supplying the gut, redirecting blood to muscles. This dampens the action of the gut.

33
Q

Why is sympathetic outflow to the gut different from sympathetic outflow to the rest of the body?

A

preganglionic sympathetic fibres usually synapse within the sympathetic chain.
Preganglionic sympathetic fibres supplying the gut do NOT synapse in the sympathetic chain and instead pass through the sympathetic chain to from the 3 splanchnic nerves. These synapse at prevertebral ganglia

34
Q

What are the 3 presynaptic splanchnic nerves?

A

Greater splanchnic nerve (T5 - T9)
Lesser splanchnic nerve (T10 - T11)
Lesser splanchnic nerve (T12)

35
Q

What structures do the postganglionic fibres of the sympathetic nervous system to the gut usually supply?

A

Blood vessels.

36
Q

What structures of the gut does the vagus nerve supply?

A

Oesophagus to the Transverse colon

37
Q

What structures of the gut does the pelvic nerve supply?

A

Transverse colon to the anal canal

38
Q

Describe the location of postganglionic fibres of the parasympathetic chain supplying the gut?

A

Short postganglionic fibres essentially lie in the visceral wall. Supplies enteric nervous system .

39
Q

What are the 3 post ganglionic nerves of the sympathetic nervous system of the gut?

A

Coeliac nerve
Superior mesenteric nerve
Inferior mesenteric nerve

40
Q

What are the 2 main plexuses of the Enteric nervous system?

A

Submoucosal (meissner’s) plexus

Myenteric (Auerbach’s)plexus

41
Q

Where is Meisser’s plexus located?

A

In the enteric nervous system, between the mucosa and submucosa

42
Q

What is Meisser’s plexus involved with innervating?

A

Secretions and blood flow

43
Q

Where is the myenteric nervous system located?

A

Between the circular and longitudinal muscle of the muscularis propria.

44
Q

What does the myenteric plexus innervate?

A

Muscles of the GI tract, involved in motility.

45
Q

What divisions of the nervous system communicates with the enteric nervous system?

A

Parasympathetic

Sympathetic

46
Q

What is a ganglion?

A

A collection of cell bodies existing outside of the CNS

47
Q

What is the general name for cells in the GI tract that secrete hormones?

A

Enteroendocrine cells

48
Q

What cells in the GI tract secrete histamines?

A

Enterochromafin like cells ( ECL cells)

49
Q

Describe the path of endocrine hormones released from the stomach

A

Release from enteroendocrine cells into portal system.
Pass through liver
Enter systemic circulation
Transported back to GI tract in blood

50
Q

What is a paracrine hormone?

A

A hormone which has its affect only within the vicinity of the gland secreting it.

51
Q

What are neurocrine hormones?

A

Hormones released from neurones in the GI tract. Released after action potential

52
Q

What are the 2 broad categories of GI hormones?

A

Gastric family

Secretin family

53
Q

What 2 hormones of the GI tract are in the gastric family?

A

CCK cholecystokinin

Gastrin

54
Q

Where is gastrin secreted?

A

Secreted in the antrum of the stomach by G cells.

55
Q

What is the function of gastrin?

A

Increases gastric acid secretions.

56
Q

Where is CCK secreted?

A

In the Ileum and Jejunum by I cells.

57
Q

What is the function of CCK?

A

Increases pancreatic / gallbladder secretions.
Causes contraction of the gallbladder.
Stimulates pancreas to secrete digestive enzymes
Relaxes sphincter of Oddi.

58
Q

Where is the sphincter of Oddi located?

A

At the entrance of the pancreatic duct into the duodenum

59
Q

What stimulates CCK secretion form I cells?

A

Fat and protein breakdown products.

60
Q

What 2 hormones are part of the secretin family?

A

Secretin

Gastric Inhibitory peptide.

61
Q

Where is secretin produced?

A

Produced by S cells in the duodenum

62
Q

What stimulates secretin production?

A

H+ and fatty acids in the duodenum

63
Q

What is the function of secretin?

A

To increase the pH of the chyme

  • increases HCO3- secretion from pancreas/gallbladder
  • decreases gastric acid secretion
64
Q

Where is gastric inhibitory peptide released?

A

In the duodenum and jejunum by the vagus nerve

65
Q

What stimulates the release of gastric inhibitory peptide?

A

Sugars/amino acids/ fatty acids. Breakdown products of all main food groups.

66
Q

What is the action of Gastric inhibitory peptide?

A

Inhibits the release of gastric acid.

Increases the secretion of insulin.

67
Q

Give an example of a paracrine hormone of the GI tract?

A

Somatostatin.

68
Q

What stimulates gastrin to be released?

A

Breakdown products of proteins (amino acids)
Vagus nerve
Stretch cells in the stomach

69
Q

What is the function of somatostatin?

A

Switches off G cells that produce gastrin.

70
Q

Where is somatostatin produced?

A

Produced by D cells in the duodenum.

71
Q

What stimulates D cells to release somatostatin?

A

A low pH in the duodenum

GI Unit (14 decks)

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