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brs - gi > Upper GI Tract > Flashcards

Upper GI Tract Flashcards

1
Q

What is digestion?

A

process of breaking down macromolecules to allow absorption

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2
Q

What is absorption?

A

process of moving nutrients & water across a membrane

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3
Q

What is the route of food through the GI system?

A

mouth ➜ oesophagus ➜ stomach ➜ duodenum ➜ jejunum ➜ illeum ➜ caecum ➜ ascending colon ➜ transverse colon ➜ descending colon ➜ sigmoid colon ➜ rectum ➜ anus

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4
Q

What are the glands in the mouth?

A
  • parotid
  • sublingual
  • submandibular
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5
Q

What is the basic structure of the gut wall?

A
  • mucosa
  • submucosa
  • muscularis
  • serosa/adventitia
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6
Q

What is the mucosa of the gut wall made up of?

A
  • epithelium
  • lamina propria (loose connective tissue)
  • muscularis mucosae
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7
Q

What is the submucosa of the gut wall made of?

A

connective tissue containing nerve plexus

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8
Q

What is the muscularis of the gut wall made of?

A

smooth muscle containing nerve plexus

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9
Q

What is the serosa / adventitia of the gut wall made of?

A

connective tissue +/- epithelium

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10
Q

How many teeth in the oral cavity altogether?

A

32

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11
Q

How many incisors in the oral cavity altogether?

A

8

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12
Q

How many canines in the oral cavity altogether?

A

4

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13
Q

How many premolars in the oral cavity altogether?

A

8

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14
Q

How many molars in the oral cavity altogether?

A

12

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15
Q

What is the masseter muscle?

A
  • largest jaw muscle

* responsible for biting

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16
Q

How many muscles control the position of the mandible?

A

several

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17
Q

What is the function of the salivary glands?

A

start digestion of food

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18
Q

How do the salivary glands digest food?

A

release of:
• saliva (aq secretion + digestive enzymes)
• lingual lipase (fat digestion)
• salivary amylase (carb digestion)

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19
Q

What is the function of the intrinsic muscles of the tongue?

A
  • fine motor control

* moving food

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20
Q

What is the function of the extrinsic muscles of the tongue?

A
  • gross movement of tongue (in out up down)

* assist mechanical digestion

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21
Q

What is the function of the oesophagus?

A

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

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22
Q

What vertebrae does the oesophagus span across?

A

C5 to T10

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23
Q

What are the features of the epithelium of the oesophagus?

A
  • Non-keratinising
  • ‘Wear & Tear’ lining (extremes of temp & texture)
  • Lubrication – Mucus secreting glands (& saliva)
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24
Q

What are the features of the muscle of the oesophagus?

A
  • Tonically active
  • Swallowing centre
  • Peristalsis (circular muscle pushes, longitudinal muscle propagates)
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25
Q

What are the sphincters of the oesophagus?

A
  • upper oesophageal

* lower oesophageal

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26
Q

What is Barret’s oesophagus?

A

pre-cancerous condition of the oesophagus, starts at the Z line of oesophagus

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27
Q

What is the Z line of the oesophagus?

A

the squamocolumnar junction (SCJ), the transition from the squamous oesophageal mucosa to the columnar mucosa lining the stomach

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28
Q

What can cause Barret’s oesophagus?

A

acid reflux

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29
Q

What is the gastro-oesophageal junction?

A

epithelial transition between oesophagus and stomach

30
Q

What is the function of the gastro-oesophageal junction?

A
  • prevents acid reflux by diaphragm + angle of stomach to oesophagus
  • protects against stomach acids
31
Q

What is the function of the gastric folds in the lining of the stomach?

A

gastric folds called rugae increase surface area

32
Q

What are the 4 stages of swallowing?

A
  • stage 0 : oral phase
  • stage 1 : pharyngeal phase
  • stage 2 : upper oesophageal phase
  • stage 3 : lower oesophageal phase
33
Q

What happens in Stage 0 of swallowing?

A
  • chewing & saliva prepare bolus

* both oesophageal sphincters constricted

34
Q

What happens in Stage 1 of swallowing?

A
  • Pharyngeal musculature guides food bolus towards oesophagus
  • Both oesophageal sphincters open
35
Q

What happens in Stage 2 of swallowing?

A

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

36
Q

What happens in Stage 3 of swallowing?

A

• Lower sphincter closes as food passes through

37
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
• Invaginates into mucosa – Tubular glands

38
Q

What are the major anatomic parts of the stomach?

A
  • fundus
  • body
  • cardia
  • pylorus: pyloric antrum, canal + sphincter
39
Q

What is the epithelial lining of the stomach made up of?

A

simple columnar

40
Q

What parts of the stomach only produce mucus?

A

pylorus + cardia

41
Q

What parts of the stomach produce mucus, HCL + pepsinogen?

A

body + fundus

42
Q

What parts of the stomach produce gastrin?

A

pyloric antrum

43
Q

How much acid does the stomach produce?

A
  • 2L/day

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

44
Q

What are mucins in the stomach?

A

• HCO3- trapped in mucus gel Pepsinogen HCl

45
Q

What is the pH of the stomach’s epithelial surface vs. the lumen?

A
  • Epithelial surface = 6-7

* Lumen = 1-2

46
Q

What is peristalsis?

A
  • Series of wave-like muscle contractions that move food
  • Propels chyme towards colon
  • Pylorus must relax for peristaltic wave - otherwise spasm occurs + food can’t stay down
47
Q

What percent of stomach contractions are peristalsis?

A

20%

48
Q

What is segmentation?

A
  • Weaker stomach muscle contractions
  • Fluid chyme towards pyloric sphincter
  • Solid chyme pushed back to body
  • Stretching activates enteric nervous system
49
Q

What percent of stomach contractions are segmentation?

A

80%

50
Q

What is the importance of the mucus layer in the stomach?

A

protects epithelium from being damaged by acid

51
Q

What muscles are responsible for segmentation?

A

circular muscles

52
Q

What muscles are responsible for peristalsis?

A

longitudinal muscles

53
Q

What is a gastric chief cell?

A

protein-secreting epithelial cell

54
Q

What is the importance of acid in the stomach?

A

converts pepsinogen to active form pepsin

55
Q

What are some features of gastric chief cells?

A
  • abundant RER
  • golgi packaging + modifying for export
  • masses of apical secretion granules
56
Q

What is the function of gastric chief cells?

A

secretes pepsinogen

57
Q

What are parietal cells?

A

acid-secreting epithelial cells in the stomach

58
Q

What are the two types?

A
  • resting

* secreting

59
Q

What are the features of a resting parietal cell?

A
  • Many mitochondria (requires lots of ATP)
  • Cytoplasmic tubulovesicles (contain H+/K+ ATPase)
  • Internal canaliculi (extend to apical surface)
60
Q

What are the features of a secreting parietal cell?

A
  • Tubulovesicles fuse with membrane

* Microvilli project into canaliculi

61
Q

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

A

decrease acid secretion

62
Q

What is Step 1 of HCL acid secretion in the parietal cells?

A

• CO2 + H2O –> H2CO3
enzyme : CARBONIC ANHYDRASE
• H2CO3 –> H+ + HCO3
== formation of H+ ions !!!

63
Q

Why is carbonic acid used to form H+ ions instead of water?

A

carbonic acid is a better source of H+ than water

64
Q

What is Step 2 of HCL acid secretion in the parietal cells?

A
  • cell exchanges HCO3- for Cl- ion on basal side
  • HCO3- diffuses into venous blood
  • causes alkaline tide phenomenon
65
Q

What is Step 3 of HCL acid secretion in the parietal cells?

A

• K+ and CL- ions diffuse into canaliculi

66
Q

What is Step 4 of HCL acid secretion in the parietal cells?

A

• H+ ions pumped out of cell into canaliculi + exchanged for K+ ions via H+ / K+ ATPase

67
Q

What is Step 5 of HCL acid secretion in the parietal cells?

A
  • no. of receptors increase on the lumenal side by fusion of tubulovesicles during activation of parietal cells + removed during deactivation
  • receptor maintains a million-fold difference in [H+]
68
Q

What provides the ATP for Step 4 of HCL acid secretion in parietal cells?

A

numerous mitochondria

69
Q

What is pepsinogen?

A

• powerful and abundant protein digestive enzyme
• secreted by the gastric chief cells as a proenzyme
• converted by gastric acid in the gastric lumen to
the active enzyme pepsin

70
Q

What is gastrin?

A
  • stimulates secretion of gastric acid by parietal cells
  • released by G cells in the pyloric antrum of the stomach, duodenum, and the pancreas
  • stimulates histamine release from chromaffin cells (lamina propia)
71
Q

What can an abnormal increase in gastrin cause?

A

ulcers

brs - gi (3 decks)

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