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GASTROENTEROLOGY > Upper GI Tract > Flashcards

Upper GI Tract Flashcards

1
Q

What is digestion?

A

The process of breaking down macromolecules to allow absorption

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2
Q

What is absorption?

A

The process of moving nutrients and water across a membrane

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3
Q

What are the 4 main layers of the gut wall?

A

Mucosa
Submucosa
Muscularis
Serosa/ Adventitia

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4
Q

What are the three layers of the mucosa?

A
  • epithelium
  • lamina propria (loose connective tissue)
  • muscularis mucosae
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5
Q

Which layers of the gut wall contain nerve plexuses?

A

Submucosa and muscularis

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6
Q

What are the two types of muscles found in the muscularis?

A

Circular and longitudinal

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7
Q

What is found in the submucosa?

A

Nerve plexuses and submucosal glands

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8
Q

What is found in the muscularis layer?

A

Longitudinal muscle
Circular muscle
Nerve plexuses

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9
Q

How many teeth are present in adults in total?

A

32

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10
Q

How many of each type of teeth are present in the oral cavity?

A

8 incisors
4 canines
8 premolars
12 molars

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11
Q

Which muscle is the largest jaw muscle and responsible for biting?

A

Masseter

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12
Q

What does saliva contain?

A

Aqueous secretion and digestive enzymes

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13
Q

Which digestive enzymes does saliva contain?

A

Lingual lipase - fit digestion and salivary amylase - carbohydrate digestion

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14
Q

What are the main salivary glands?

A

Parotid gland
Sublingual gland
Submaxillary gland

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15
Q

What are the intrinsic muscles of the tongue responsible for?

A

fine motor control & moving food

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16
Q

What are the extrinsic muscles of the tongue responsible for?

A

gross movement of tongue (in, out, up & down)

Assists mechanical digestion

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17
Q

What are the subdivisions of the oesophagus?

A

Cervical
Thoracic
Abdominal

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18
Q

Which vertabrae does the oesophagus lie between?

A

C5 to T10

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19
Q

What is the function of the oesophagus?

A

Conduit for food, drink & swallowed secretions from pharynx to stomach

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20
Q

Describe the epithelium of the oesophagus?

A
  • Non-keratinising
    ‘- Wear & Tear’ lining (extremes of temp. & texture)
  • Contains mucus secreting glands
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21
Q

What are the muscles found at the top and bottom of the oesophagus?

A

Upper oesophageal sphincter and lower oesophageal sphincter

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22
Q

what is the role of mucus in the oesophagus?

A

Aids the pasage of food and drink

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23
Q

What is the Z line in the oesophagus?

A

Line where the pink mucosa of the oesophageal sqaumous epithelium meets the red mucosa of the gastric columnar epithelium

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24
Q

What is the significance of this Z line in Barrett’s oesophagus?

A

Here, the epithelium of the lower oesophagus undergoes metaplasia

So the gastric mucosa extends into the oesophagus, meaning it would be important to determine the Z line in these cases

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25
Q

Why does this epithelial transition at the gastro-oesophageal junction occur and how does this develop to cancers?

A

Acid reflux means that the upper oesophagus is more acidic than normal

To cope with this, the squamous cells above the gastro-oesophageal junction become columnar epithelium

This change to columnar epithelium makes the cells unstable, leading to dysplasia and then becomes cancers

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26
Q

Is skeletal muscle found in the upper or lower oesophagus?

A

Both

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27
Q

Is smooth muscle found in the upper or lower oesophagus?

A

Lower

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28
Q

How does the anatomical orientation of the stomach to the oesophagus reduce the risk of acid reflux?

A

reflux is prevented by the diaphragm and the angle of the stomach to the oesophagus

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29
Q

What are gastric folds called and what is their purpose?

A

Rugae - they increase surface area so more digestion and absorption can occur

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30
Q

What is the role of circular and longitudinal muscle in peristalsis?

A

Circular muscle pushes, longitudinal muscle propagates

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31
Q

Which type of epithelium can tolerate acidic conditions?

A

Simple columnar epithelium

32
Q

What happens to the level of the Z line in Barrets oesophagus?

A

Z line is raised due to acid reflux from the stomach

33
Q

Describe the swallowing process.

A

Stage 0: Oral phase

  • Chewing & saliva prepare bolus
  • Both oesophageal sphincters constricted

Stage 1: Pharyngeal phase

  • Pharyngeal musculature guides food bolus towards oesophagus
  • Both oesophageal sphincters open

Stage 2: Upper oesophageal phase

  • Upper sphincter closes
  • Superior circular muscle rings contract & inferior rings dilate
  • Sequential contractions of longitudinal muscle

Stage 3: Lower oesophageal phase
- Lower sphincter closes as food passes through

34
Q

Describe what happens to the upper oesophageal sphincter during each stage of swallowing?

A

1: Oral = Closed
2: Pharyngeal = open
3: Upper oesophageal = closed
4: Lower oesophageal = Closed

35
Q

Describe what happens to the lower oesophageal sphincter during the swallowing process

A

1: Oral = Closed
2: Pharyngeal = open
3: Upper oesophageal = open
4: Lower oesophageal = Closed

36
Q

What are the functions of the stomach?

A
  • Breaks food into smaller particles (acid & pepsin)
  • Holds food, releasing it in controlled steady rate into duodenum
  • Kills parasites & certain bacteria
37
Q

What are the secretions of the cardia and pyloric regions of the stomach?

A

Mucus only

38
Q

What are the secretions of the body and fundus regions of the stomach?

A

Mucus, HCl, and pepsinogen

39
Q

What does the antrum of the stomach secrete?

A

Gastrin

40
Q

Why is a hiatus hernia a risk factor for developing cancer of the oesophagus?

A

Because the opening of the diaphragm causes it to be larger and so there is a portion of the stomach that slips into the chest which prolongues exposure to the lower oesophagus, associating with acid reflux

41
Q

How much acid is produced per day by the stomach and what is the H+ concn. of this acid?

A

2L/day

150mM H+ (3 mill x that in blood)

42
Q

What allows the pH of the epitheliual surface to be between 6 and 7 when the lumen is between 1 and 2?

A

Mucus coating with HCO3- trapped in the mucus gel

43
Q

Which layer of muscle carries out segmentational contraction?

A

circular

44
Q
  • Which layer of muscle carries out peristalsis contraction?
A

longitudinal

45
Q

What are the proportions of stomach contractions which are peristatic and segmental?

A

Peristaltic - 20%

Segmental - 80%

46
Q

Which type of stomach contraction is stronger?

A

Peristaltic - Propels chyme towards colon

47
Q

Which stomach contraction is dependant on the autonomic nervous system?

A

Peristalsis

48
Q

What does segmentation do?

A
  • Pushes fluid chyme towards Pyloric sphincter

- Solid chyme pushed back to body

49
Q

What does the stretching due to segmentation activate?

A

Enteric nervous system

50
Q

What does the gastric chief cell secrete?

A

Pepsinogen

51
Q

Which cellular component is abundant in chief cells?

A

Rough endoplasmic reticulum and Golgi - due to protein secretion = needed for packaging, modifying and exportation

52
Q

What are the parietal cells responsible for producing and secreting?

A

HCl

53
Q

What are three structures found in parietal cells in the resting state?

A

Mitochondria
Internal Canaliculi
Cytoplasmic tubulovesicles

54
Q

What do cytoplasmic tubulovesicles contain?

A

contain H+/K+ ATPase

55
Q

How does the appearance of the parietal cell change in the secreting stage?

A

Microvilli project into canaliculi

Tubulovesicles fuse with membrane

56
Q

How would the inhibition of H+ carbonic anhydrase influence stomach acid secretion?

A

Decrease acid secretion

57
Q

What three drugs could be used to decrease stomach acid secretion?

A
  1. Carbonic anhydrase inhibitor
  2. Histamine receptor antagonist
  3. K+/H+ ATPase inhibitor
58
Q

What is the name of the histamine receptor antagonist used to decrease stomach acid?

A

Ranitidine

59
Q

What is the name of the H+/K+ ATPase inhibitor antagonist used to decrease stomach acid, heart burn and indigestion?

A

Omeprazole

60
Q

What stimuli is most likely to

decrease acid secretion in the stomach?

A

Chyme fatty acid content - due to the enterogastric fatty acid content

61
Q

What triggers the process of HCl secretion?

A

The binding of histamine to histamine receptors on the parietal cells

62
Q

Describe the process of HCl secretion

A
  1. Carbonic anhydrase catalyses the conversion of Water and Carbon Dioxide into H+ and HCO3-
  2. The Bicarbonate ion is exchanged for a Cl- ion which enters into the parietal cell, and bicarbonate into the blood
  3. Na+/K+ ATPase pumps sodium out the parietal cell and K+ into the cell and therefore canaliculi
  4. Then, the H+ ions are pumped out the Parietal cell into the canaliculi through the H+/K+ ATPase pump, as K+ ions are pumped from the canaliculi into the parietal cell
  5. The Cl- ions then enter the canaliculi as well through Cl- ion channels
  6. Combine to make HCl
63
Q

What is pepsinogen?

A

A powerful and abundant protein digestive enzyme which is secreted by the chief cells as a proenzyme

64
Q

What effect does HCl have on pepsinogen?

A

Converts pepsinogen into pepsin

65
Q

What can an abnormal increase in gastrin cause?

A

Stomach ulcers

66
Q

what does pepsin do?

A

Breaks down dietary proteins into partially digested proteins

67
Q

Which part of the stomach secretes gastrin?

A

Pyloric antrum

68
Q

What is gastrin secretion stimulated by?

A

Stimulated by distention, small peptides & amino acids, stimulation of vagus nerves

69
Q

What does gastrin stimulate the release of?

A 
Stimulate histamine release from
      chromaffin cells (lamina propia)
70
Q

What is the pH of gastric venous blood?

A

Alkaline

71
Q

What are the three phases of gastric secretion?

A

Cephalic
Gastric
Intestinal

72
Q

How is the parietal cell adapted for this function?

A

It has many mitochondria

It has H+/K+ ATPase which is largely responsible for the secretion of HCl into the lumen of the stomach

HCl secreted into tubulovesicles which then fuse with the membrane of the cell and secrete HCl into lumen of stomach

73
Q

Describe the cephalic phase of gastric secretion

A

Thought, sight, smell and taste of food stimulates gstric secretion

Vagus nerve activates parietal cells through ACh to trigger the whole cascade

74
Q
  • Describe the gastric phase of gastric secretion
A

Food in stomach activates the stretch- (distension) and chemo-receptors (pH of food chemicals) - G cells secrete gastrin which stimulates HCl secretion

Signals sent to and from the brain via vagus nerve to activate the secretion of acid

75
Q

Describe the intestinal phase of gastric secretion

A

Once the chyme with pH less than 2 reaches the duodenum

Signal is transmitted by the vagus nerve and this causes secretion of hormones that inhibit the secretion of gastric HCl and pepsin too

These hormones are Gatric inhibtory peptide, Cholecystokinin and Secretin

76
Q

What are the three enterogastrones?

A

GIP = Gastric inhibitory Peptide
Cholecystokinin
Secretin

77
Q

What is the enterogastric reflex?

A

Nervous reflex where stretching of the wall of the duodenum results in inhibition of gastric motility and reduced rate of emptying of the stomach

It is a feedback mechanism used to regulate the rate at which partially digested food leaves the stomach and enters the small intestine

GASTROENTEROLOGY (25 decks)

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