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BRS GASTROENTEROLOGY > Upper GI tract > Flashcards

Upper GI tract Flashcards

1
Q

What are the different system nomeclatures? (3)

A

Gastrointestinal system vs Alimentary system vs Digestive system

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2
Q

What is digestion?

A

Digestion is the process of breaking down macromolecules to allow absorption

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3
Q

What is absorption?

A

Absorption is the process of moving nutrients & water across a membrane

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4
Q

How is ingestion, digestion, absorption and excretion linked?

A

Ingestion-> digestion-> absorption

Ingestion-> digestion-> excretion

Ingestion-> absorption

Ingestion-> excretion

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5
Q

Label this diagram of the components of the GI system.

A
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6
Q

What is the basic plan of the gut wall? e.g., oesophagus

A

Mucosa
Submucosa
Muscularis
Serosa/ Adventitia

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7
Q

what are the layers of the mucosa?

A

Epithelium
Lamina propria (loose connective tissue)
Muscularis mucosae

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8
Q

What is the submucosa?

A

Connective tissue (containing nerve plexus)

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9
Q

What is the muscularis?

A

Smooth muscle (containing nerve plexus)

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10
Q

What is the serosa/ adventitia?

A

Connective tissue +/- epithelium

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11
Q

How many teeth and what are they?

A

TEETH - 32 in total
8 incisors
4 canines
8 premolars
12 molars

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12
Q

What is the masseter muscle?

A

Largest jaw muscle responsible for biting

Several muscles control position of mandible

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13
Q

What are the salivary glands?

A

Parotid
Sublingual
Submaxillary

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14
Q

What do salivary glands do?

A

Food mixed with saliva (aqueous secretion & digestive enzymes)
Lingual lipase (fat digestion)
Salivary amylase (carbohydrate digestion)

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15
Q

Describe the muscles of the tongue.

A

Intrinsic muscles
- fine motor control & moving food

Extrinsic muscles
- gross movement of tongue (in, out, up &
down)
- Assists mechanical digestion

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16
Q

Where does the oesophagus start and end?

A

Starts at C5
Ends at T10

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17
Q

What is the function of the oesophagus?

A

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

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18
Q

What is the epithelium of the oesophagus like (structure and function relationship)?

A

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

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19
Q

What is the muscle of the oesophagus like?

A

Tonically active
Swallowing centre

Skeletal and smooth muscle at lower oesophageal sphincter
Skeletal muscle at upper oesophageal sphincter

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20
Q

What is near the lower oesophageal sphincter?

A

Sub Hiatal fat ring

Zigzag (Z) line

Diaphragm

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21
Q

What muscle in the oesophagus is in charge of peristalsis?

A

Circular muscle

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22
Q

How does peristalsis work basic?

A

contract just before where the food is and relax just after where the food is?

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23
Q

What are the 2 muscle types in the oesophagus?

A

Circular and longitudinal

Skeletal/ smooth

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24
Q

How is the skeletal and smooth muscle split in the oesophagus (placement wise)?

A

Upper third is skeletal
middle third is skeletal and smooth
lower third is smooth

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25
Q

What are the stages of swallowing?

A

Stage 0: Oral phase
Stage 1: Pharyngeal phase
Stage 2: Upper oesophageal phase
Stage 3: Lower oesophageal phase

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26
Q

How would you describe swallowing?

A

a complicated and highly coordinated event

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27
Q

As the bolus travels down the oesophagus when do the superior and inferior muscles contract and dilate (close/ open)?

A

Superior muscles contract
Inferior muscles dilate

28
Q

What happens during stage 0 of swallowing?

A

Stage 0: Oral phase

  • Chewing & saliva prepare bolus
  • Both oesophageal sphincters constricted
29
Q

What happens during stage 1 of swallowing?

A

Stage 1: Pharyngeal phase

  • Pharyngeal musculature guides food bolus towards oesophagus
  • Both oesophageal sphincters open
30
Q

What happens during stage 2 of swallowing?

A

Stage 2: Upper oesophageal phase

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

The oesophageal phase is controlled centrally

31
Q

What happens during stage 3 of swallowing?

A

Stage 3: Lower oesophageal phase

  • Lower sphincter closes as food passes through
32
Q

What happens/ is at the gastro-oesophageal junction? (3)

A

Reflux – prevented by diaphragm

Epithelial transition

Gastric folds - rugae

33
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

34
Q

What are regions of the stomach? (5)

A

cardiac, pyloric, body, fundus, antrum

35
Q

What does each section of the stomach secrete?

A

Cardia & Pyloric Region: Mucus only

Body & Fundus: Mucus, HCl, pepsinogen

Antrum: Gastrin

36
Q

Describe the structure of tubular glands?

A

Simple columnar- invaginates into mucosa

37
Q

What are the details of the layers of the gut wall? e.g., longitudinal muscle in muscularis (9)

A

Mucosa
Submucosa
Muscularis
Serosa

38
Q

How much acid does the stomach produce?

A

2L/ day

39
Q

What is the concentration of the acid in the stomach?

A

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

40
Q

What is the pH at the epithelial surface of the stomach and the lumen?

A

Epithelial surface = 6-7
Lumen = 1-2

41
Q

Describe the cells present in the different regions of the stomach.

A
42
Q

What cells secrete pepsinogen?

A

Chief cells

43
Q

What cells secrete HCl?

A

parietal cells (they can be resting or active)

44
Q

What cells secrete mucus?

A

mucous neck

45
Q

What secretes gastrin?

A

Enteroendocrine (they can be closed or open)

46
Q

What are the 2 methods of stomach contraction and how much of each is split as stomach contractions?

A

20% is peristalsis

80% is segmentation

47
Q

What is peristalsis?

A

20% stomach contractions
Propels chyme towards colon
More powerful as moves from LOS to pyloric sphincter
ANS essential

48
Q

What is segmentation?

A

80% stomach contractions
Weaker
Fluid chyme towards Pyloric sphincter
Solid chyme pushed back to body
Stretching activates enteric NS

49
Q

What are chief cells?

A

Gastric Chief Cell
- Protein-secreting epithelial cell
- Abundant RER
- Golgi packaging and modifying for export
- Masses of apical secretion granules
- Secretes pepsinogen

50
Q

What are resting parietal cells?

A

Parietal Cell: Resting
- Many mitochondria (requires lots of ATP)
- Internal canaliculi (secretory surface)
- Cytoplasmic tubulovesicles (contain H+/K+ ATPase)

51
Q

what are secreting parietal cells?

A

Microvilli project into canaliculi
Tubulovesicles fuse with membrane

52
Q

What is inside parietal cells?

A
53
Q

What is the role of pepsinogen?

A

Pepsinogen and HCl form pepsin
pepsin is used to break/ digest proteins

54
Q

What is gastrin?

A

Pyloric antrum

Reaches parietal cell via systemic circulation

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

Acts on receptors on parietal cell

Stimulate histamine release from chromaffin cells (lamina propia)

55
Q

What are the phases of gastric secretion?

A

Cephalic phase
Gastric phase
Intestinal phase

56
Q

Describe the first phase of gastric secretion?

A

Cephalic phase

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

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

57
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

58
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 Gastric inhibitory peptide, Cholecystokinin and Secretin

59
Q

Give a summary of gastric secretion.

A
60
Q

What drugs reduce acid secretion?

A

ranitidine and omeprazole

61
Q

How do omeprazole and ranitidine work?

A

Ranitidine is a competitive inhibitor of histamine H2-receptors. The reversible inhibition of H2-receptors in gastric parietal cells results in a reduction in both gastric acid volume and concentration. Leading to less H+ being formed inside the cell.

Omeprazole is a proton pump inhibitor that inhibits secretion of gastric acid by irreversibly blocking the enzyme system of hydrogen/potassium adenosine triphosphatase, the “proton pump” of the gastric parietal cell.

62
Q

Which vertabrae does the oesophagus lie between?

A

C5 to T10

63
Q

What are the controls of motility and acid secretion in the stomach?

A

Local control
Nervous control
Gut hormone control

64
Q

Describe the process of HCl secretion from parietal cell.

A
65
Q

What triggers production and secretion of HCl from parietal cells?

A

Histamine acting on H2 histamine receptors on parietal cells

  • ACh
  • gastrin

ECL (endocrine cells in stomach) cells secrete histamine in response to gastrin stimulation, and histamine acts on the H2 receptor of parietal cell, which provide a stronger stimulus for parietal cell acid secretion than direct gastrin action.

66
Q

What cells make gastrin?

A

pyloric antrum by G cells
- gastrin is a local peptide hormone
- stimulates histamine release from chromaffin cells (lamina propria) which triggers HCl secretion

67
Q

When is pepsinogen cleaved?

A

Pepsinogen is secreted via chief cells and is cleaved at low pH (HCl) into pepsin to digest proteins

BRS GASTROENTEROLOGY (25 decks)

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