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Gastrointestinal System > Session 2 - Physiology Of The Gastrointestinal System > Flashcards

Session 2 - Physiology Of The Gastrointestinal System Flashcards

1
Q

What systems have control over the gut?

A

Autonomic nervous system
Enteric nervous system
Hormones and paracrine substances

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2
Q

GI function is regulated by what three divisions of the autonomic nervous system?

A

Parasympathetic nervous system
Sympathetic nervous system
Enteric nervous system

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3
Q

What neurotransmitter is released by preganglionic fibres?

A

Acetylcholine

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4
Q

What effect does sympathetic input have on the gut?

A

Negative effect. Reduces blood flow to the gut.

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5
Q

Do sympathetic nerves supplying the gut synapse in the sympathetic trunk?

A

No, they pass through and synapse outside the sympathetic trunk.

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6
Q

Name the presynaptic sympathetic nerves supplying the gut and their roots.

A 
Greater splanchnic (T5-9) 
Lesser splanchnic (T10-11)
Least splanchnic (T12)
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7
Q

Give examples of ganglia with which these splanchnic nerves synapse.

A

Coeliac (greater splanchnic nerve)
Superior mesenteric (lesser splanchnic)
Inferior mesenteric
Aorticorenal (least splanchnic)

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8
Q

What parasympathetic nerves supply the gut?

A 
Vagus nerve (CN X)
Pelvic splanchnic nerves (S2-4)
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9
Q

Where do the presynaptic fibres of parasympathetic nerves supplying the gut synapse?

A

Preganglionic fibres synapse in the walls of the viscera. Innervates smooth muscle and endocrine/secretory tissues.

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10
Q

What do postganglionic fibres of parasympathetic nerves supplying the gut release?

A

Acetylcholine

Peptides (e.g. gastrin releasing peptide, vaso-inhibitory peptide)

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11
Q

Which parts of the GI tract does the vagus nerve innervate?

A

Oesophagus to transverse colon

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12
Q

Which parts of the GI tract does the pelvic splanchnic nerve innervate?

A

Transverse colon to anal canal

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13
Q

What are the two main plexuses of the enteric nervous system and where are they found?

A

Submucosal (Meissner’s) - submucosa

Myenteric (Auerbach’s) - between circular and longitudinal muscle

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14
Q

What are the layers of the GI tract wall?

A

Mucosa (epithelium, lamina propria, muscularis mucosa)
Submucosa (Meissner’s plexus)
Muscularis propria (circular muscle, Auerbach’s plexus, longitudinal muscle)
Serosa/adventitia

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15
Q

What do the submucosal and myenteric plexuses control?

A

Submucosal

  • secretions
  • blood flow

Myenteric
- motility

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16
Q

What type of cells in the mucosa of the GI tract secrete hormones?

A

Enetroendocrine cells - generally identified by letters, e.g. G,S,D.

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17
Q

What cells in the GI tract secrete histamine?

A

Enterochromafin like cells (ECL cells)

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18
Q

What cells in the GI tract secrete somatostatin?

A

D cells in the antrum of the stomach and the pancreas.

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19
Q

What is the effect of somatostatin in the GI tract?

A

Inhibits G cells - less gastrin released

Inhibits histamine release

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20
Q

What stimulates somatostatin secretion?

A

H+ in the stomach lumen

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21
Q

What are the two broad categories of gastrointestinal hormones?

A

Gastrin family

Secretin family

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22
Q

What hormones are in the gastrin family?

A

Gastrin

Cholecystokinin (CCK)

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23
Q

Name the two hormones of the secretin family which are significant to the GI tract.

A

Secretin

Gastric inhibitory polypeptide (GIP)

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24
Q

Where is gastrin released from and what is its action?

A

G cells in the antrum of the stomach

Increases gastric acid secretion

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25
Q

Where is cholecystokinin (CCK) released from and what is its action?

A

I cells in the duodenum and jejunum

Increases pancreatic/gallbladder secretions

26
Q

Where is secretin released from and what are its actions?

A

S cells in the duodenum
Increases HCO3 from pancreas/gallbladder
Decreases gastric acid secretion

27
Q

What stimulates secretin release?

A

H+ and fatty acids

28
Q

Where is gastric inhibitory peptide (GIP) released from and what are its actions?

A

Cells in the duodenum and jejunum
Increases insulin secretion
Decreases gastric acid secretion

29
Q

What stimulates cholecystokinin release?

A

Fat and protein

30
Q

What is appendicitis?

A

Appendicitis is a painful swelling of the appendix. Usually caused by swelling of lymph tissue following a viral infection which blocks the lumen of the appendix and it therefore becomes inflamed.

31
Q

What are the symptoms of appendicitis?

A 
Initially central abdominal pain
Nausea 
Loss of appetite 
Diarrhoea 
Raised temperature 
Pain will later move to the right iliac fossa, becomes more severe
32
Q

Is visceral pain well localised or vague?

A

Vague

33
Q

Is parietal pain well localised or vague?

A

Localised

34
Q

In what abdominal region would visceral pain of foregut structures present?

A

Epigastric

35
Q

In what abdominal region would visceral pain of midgut structures present?

A

Periumbilical

36
Q

In what abdominal region would visceral pain of hindgut structures present?

A

Suprapubic/hypogastric

37
Q

Where would pain due to gallstones present?

A

Right upper quadrant, radiating to right shoulder tip

38
Q

What is the purpose of motility in the GI tract?

A

Moving things along
Mixing contents
Grinding contents

39
Q

All muscle in the GI tract is smooth except for where?

A

Pharynx
Upper 1/3 of the oesophagus
External anal sphincter

40
Q

Describe peristalsis.

A

Contraction of smooth muscle proximal to lumen contents. Relaxation distal to contents. Propels content in one direction.

41
Q

Describe segmentation.

A

Food is moved forward and backwards, mixing contents. Contraction splits contents, then relaxes. Primarily mixes food and breaks it down mechanically, some propulsion may occur.

42
Q

Describe mass movement.

A

Occurs in the distal colon. Rapid movement of contents into rectum.

43
Q

What is the effect of sympathetic and parasympathetic stimulation on gut motility?

A 
Sympathetic stimulation (noradrenaline) - reduces motility 
Parasympathetic stimulation (acetylcholine) - increases motility
44
Q

What is paralytic ileus?

A

Obstruction of the intestines due paralysis of intestinal muscles. Can occur following GI surgery.

45
Q

What is achalasia?

A

Rare condition where there is failure of the lower oesophageal sphincter to relax. Causes dysphagia.

46
Q

What is Hirschsprung’s disease?

A

Failure in the development of the myenteric and submucosal plexuses causes functional obstruction due to lack of contraction.

47
Q

What are the main gastrointestinal secretions?

A 
Stomach acid
HCO3
Waste products
Emulsifiers
Mucus
Enzymes
48
Q

What is the function of stomach acid?

A

Innate barrier to infection
Prepares proteins for digestion
Activates enzymes

49
Q

What is the function of HCO3 in the digestive tract?

A

Neutralises acid (food acidity and stomach acid) in the:

  • saliva
  • stomach
  • duodenum
  • pancreas
  • liver (in bile)
50
Q

Where do the majority of waste products secreted into the intestines come from?

A

Mainly from the liver
This is done through bile
- cholesterol
- bilirubin

51
Q

What is the function of emulsifiers (bile salts)?

A

Increase the surface area of lipids. This aids digestion by lipase and allows lipid breakdown products to be transported in the gut (micelles).

52
Q

What is the function of mucus?

A

Protects against acidic environment in the stomach
Protects against bacteria in the small intestine (contains antibacterial compounds)
Harbours bacteria in the large intestine
Lubricates

53
Q

What enzymes are secreted into the GI tract?

A

Proteases
Lipases
Amylases

54
Q

Where are the digestive enzymes found?

A

Saliva
Stomach
Pancreas
Lining of the intestine

55
Q

Where do GI secretions come from?

A 
Acini of salivary glands
Gastric glands (stomach)
Brunner’s glands (duodenum)
Intestinal glands (crypts of Lieberkuhn)
Acini of exocrine pancreas
Hepatocytes (storage by gallbladder)
Goblet cells (increasing numbers from duodenum to colon)
56
Q

Across which cells does absorption occur?

A

Enterocytes

57
Q

How is a large surface area created in the intestines?

A

Permanent folds (plicae circulares)
Villi
Microvilli (brush border)

58
Q

Disruption to absorption in the GI tract can lead to what conditions?

A

Diarrhoea
Malnutrition
Anaemia

59
Q

What molecules are absorbed in the intestines?

A 
Nutrients:
 - carbohydrates, proteins, lipids
 - fat soluble vitamins
 - water soluble vitamins
 - vitamin B12
 - bile salts
 - Ca2+
 - Fe2+
Electrolytes
Water
60
Q

Which parts of the gastrointestinal tract are supplied by the greater splanchnic nerve?

A

Oesophagus to proximal duodenum

61
Q

Which parts of the gastrointestinal tract are supplied by the lesser splanchnic nerve?

A

Proximal duodenum to proximal transverse colon

Gastrointestinal System (13 decks)

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