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BRS 8: Gastroenterology > 8.1: Upper gastrointestinal tract > Flashcards

8.1: Upper gastrointestinal tract Flashcards

1
Q

Digestion is

A

The process of breaking down macromolecules to allow absorption

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2
Q

Absorption is

A

The process of moving nutrients and water across a membrane

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3
Q

4 basic layers of gut wall

A

Mucosa: epithelium
Submucosa : connective tissue
Muscularis : smooth muscle
Serosa/Adventitia : connective tissue with or without epithelium

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4
Q

How many teeth are in the oral cavity

A

32

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5
Q

Composition of oral cavity

A

8 incisors
4 canines
8 premolars
12 molars

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6
Q

What muscle is present in the oral cavity

A

Massater muscle - largest jaw muscle
-responsible for biting

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7
Q

Function of salivary glands

A

First step of digestion
Food mixed with saliva
Lingual lipase - fat digestion
Salivary amylase - carb digestion

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8
Q

What 2 muscle types are present in the tongue

A

Intrinsic and extrinsic muscles

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9
Q

What are intrinsic muscles in the tongue responsible for

A

Fine motor control and moving food

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10
Q

What are extrinsic muscles of the tongue responsible for

A

Gross movement of tongue (in, out, up, down)
Assist mechanical digestion

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11
Q

Function of the oesophagus

A

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

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12
Q

3 characteristics of oesophageal epithelium

A

Non-keritanising
Wear and tear lining - extremes of temp and texture
Lubrication - mucus secreting glands and saliva

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13
Q

2 characteristic of oesophageal muscle

A

Tonically active
Swallowing centre

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14
Q

2 functions of oesophageal muscle

A

Peristalsis
Circular muscle

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15
Q

4 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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16
Q

What occurs In stage 0 of swallowing

A

Chewing and saliva prepare bolts
Both oesophageal sphincters constricted

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17
Q

What occurs in stage 1 of swallowing

A

Pharyngeal musculature guides food bonus towards oesophagus
Both oesophageal sphincters open

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18
Q

What occurs in stage 2 of swallowing

A

Upper sphincter closes
Superior circular muscle rings contract and inferior rings dilate

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19
Q

What occurs in stage 3 of swallowing

A

Lower sphincter closes as food passes through

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20
Q

3 functions of gastro-oesophageal junction

A

Reflux - prevented by diaphragm
Epithelial transition
Gastric folds - rugae

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21
Q

Why are gastric folds present?

A

To increase surface area of epithelium of the gastrointestinal tract so more digestion and more absorption can occur

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22
Q

3 functions of the stomach

A

Breaks food into smaller particles (acid and pepsin)
Holds food, releasing it in controlled steady rate into duodenum
Kills parasites and certain bacteria

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23
Q

What do the cardia and pyloric region of the stomach secrete

A

Mucus only

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24
Q

What do the body and fundus of the stomach secrete

A

Mucus, HCL, Pepsinogen

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25
Q

What does the antrum of the stomach secrete

A

Gastrin

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26
Q

How much of acid does the stomach produce per day

A

2L/day

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27
Q

What are mucins

A

Gel coating
HCO3- trapped in mucus gel

28
Q

pH at epithelial surface

A

6-7

29
Q

pH at lumen of stomach

A

1-2

30
Q

Two types of movement in stomach

A

Peristalsis
Segmentation

31
Q

Process of Peristalsis

A

Propels chyme towards colon
More powerful as moved from LOS to pyloric sphincter
ANS essential

32
Q

Comparison of segmentation to peristalsis

A

Weaker
Fluid chyme towards pyloric sphincter
Solid chyme pushed back to body
Stretching activates enteric NS

33
Q

Two types of stomach cells

A

Chief cell
Parietal cell

34
Q

Characteristics of chief cell

A

Protein-secreting epithelial cell
Abundant RER
Golgi packing and modification for export
Masses of apical secretion granules
Secretes pepsinogen

35
Q

Characteristics of parietal cell at rest

A

Many mitochondria - lots of protein pumps
Internal canaliculi (secretory surface)
Cytoplasmic tubulovesicles (cont. H+/K+ ATPase)

36
Q

Characteristics of parietal cell during secretion

A

Microvilli project into canaliculi
Tubulovesicles fuse with membrane

37
Q

What do cheif cells secrete

A

Pepsinogen
Needs HCL to change into pepsin

38
Q

Function of gastrin in the stomach

A

Stimulates release of histamine from chromaffin cells (lamina propria)

39
Q

3 Phases of gastric secretion

A

Cephalic phase
Gastric phase
Intestinal phase

40
Q

In the cephalic phase of gastric secretion

A

Though, sight, smell and taste of food stimulates pathways transmitted by vagus nerve
Vagus nerve activates parietal cells through ACH to trigger whole cascade

41
Q

In the gastric phase of gastric secretion

A

Food in stomach causes stretch and chemo-receptors involved
Vagus nerve sends signals to stomach to activate acid secretion

42
Q

In the excitatory 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

43
Q

How might you produce a useful drug to decrease acid secretion -

A

Omeprazole - stops K+/H+ pump
Ranitidine - stops histamine from binding to receptor

44
Q

Which vertebrae is the oesophagus between?.

A

C5 and T10

45
Q

Three subdivisions of the oesophagus

A

Cervical oesophagus- cricopharyngeal muscle to suprasternal notch
Thoracic oesophagus- suprasternal notch to diaphragm
Abdominal oesophagus - diaphragm to cardia of stomach

46
Q

What is the Z line of the oesophagus

A

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

47
Q

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

A

Here the epithelium of the lower oesophagus undergoes metaplasia
So gastric mucosa extends to oesophagus, meaning it would be important to determine the Z line in these cases

48
Q

Is the upper or lower oesophageal sphincter a true sphincter?

A

Upper

49
Q

Is skeletal muscle found in the upper or lower oesophagus?

A

Both

50
Q

Is smooth muscle found in the upper or lower oesophagus

A

Lower

51
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

52
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

53
Q

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

A

Stomach lies at an angle to the oesophagus

Other ligaments also suspend the gastro-oesophageal junction at an acute angle on the fringe oesophageal ligaments to prevent acid reflux

54
Q

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

A

Mucus coating with HCO3- trapped in mucus gel

55
Q

Which layer of muscle carries out segmentational contraction?

A

Circular

56
Q

Which layer of muscle carries out peristalsis contraction ?

A

Longitudinal

57
Q

Is segmentation or peristalsis the stronger contraction?

A

Peristalsis

58
Q

Which method of contraction occurs most often?

A

Segmentation - 80% contractions

59
Q

Describe the nervous stimulation of peristalsis?

A

Activated by ANS

60
Q

Describe the nervous stimulation of segmentation?

A

Stretching activated enteric nervous system

61
Q

Explain how the parietal cells secrete HCl?

A

Na+/K+ pump, transports Na+ into interstitial fluid from the parietal cell

K+ transported from interstitial fluid into the parietal cell and then into the canncaliculi that have fused with the tubulovesicles

CO2 taken up by parietal cells and reacts with H20 using carbonnic anhydrase, forming H+ and HCO3-

HCO3- transported out by AE1 antiporter and Cl transported into the parietal cell and then into cannaliculi

H+/K+ ATPase transports H+ into the canaliculi and moves K+ from the canaliculi back into the parietal cell

62
Q

How is this HCl secretion triggered?

A

H2 receptors which are found on the surface of the parietal cells

When histamine gets released from different triggers, this is detected by the H2 receptors which starts the process of HCl secretion

63
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

64
Q

What is the mechanism of action of Omeprazole ?

A

Blocks protein pumps (H+/K+ ATPase)

65
Q

What can Omeprazole be used as a treatment for?

A

Indigestion, heartburn and acid reflux

66
Q

What is the mechanism of action of Ranitidine?

A

Blocks the H2 receptors to prevent the triggering of the whole cascade by Histamine

67
Q

Would chyme fatty acid content and protein content increase or decrease acid secretion in the stomach?

A

Decrease

BRS 8: Gastroenterology (6 decks)

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