Gastro - Upper GI Flashcards

1
Q

Give a brief definition of digestion

A

Process of breaking down macromolecules to allow absorption

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2
Q

Give a brief definition of absorption

A

Process of moving nutrients and water across a membrane

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3
Q

Label the diagram of the components of the GI system

A
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4
Q

Label the diagram showing the layers of the gut wall

A

g - Epithelium

f - Lamina propria

e - Muscularis mucosae

d - Submucosa (connective tissue)

c - Longitudinal muscularis

b - Circular muscularis

a- Serosa/Adventia (connective tissue +/- epithelium)

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5
Q

Describe the distribution in the number of teeth in the oral cavity

A

32 teeth

8 incisors
4 canines
8 premolars
12 molars

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6
Q

What is the largest jaw muscle and the muscle in charge for biting?

A

Masseter

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7
Q

What are the 2 enzymes released by the salivary glands?

A

Lingual lipase (fat digestion)

Salivary amylase (carbohydrate digestion)

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8
Q

What are the intrinsic muscles of the tongue responsible for?

A

Fine motor control and moving food

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9
Q

What are the extrinsic muscles of the tongue responsible for?

A

Gross movement of tongue

Assists mechanical digestion

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10
Q

Which vertebrae is the oesophagus between?

A

C5 and T10

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11
Q

What are the 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

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12
Q

What is the function of the oesophagus?

A

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

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13
Q

How does the structure of the oesophageal epithelium relate to its function?

A

Non-keratinising squamous epithelium

Wear & Tear lining - to withstand extreme temperatures and aid texture

Lubrication - mucus secreting glands

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14
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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15
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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16
Q

Is the upper or lower oesophageal sphincter a true sphincter?

A

Upper

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17
Q

Is skeletal muscle found in the upper or lower oesophagus?

A

Both

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18
Q

Is smooth muscle found in the upper or lower oesophagus?

A

Lower

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19
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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20
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 prolongs exposure to the lower oesophagus, associating with acid reflux

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21
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

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22
Q

Why are the gastric folds present?

A

To increase the surface area of the epithelium of the gastro intestinal tract so that more amount of digestion and more absorption can occur

23
Q

Describe the 4 stages of swallowing?

A

Oral Phase

  • Chewing and saliva prepare bolus
  • Both oesophageal sphincters constricted

Pharyngeal Phase

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

Upper Oesophageal Phase

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

Lower Oesophageal Phase
-Lower sphincter closes as food passes through

24
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 parasite and certain bacteria

25
Q

Label the diagram below showing the anatomy of the stomach

A
26
Q

What do the cardia and pyloric regions of the stomach secrete?

A

Mucus only

27
Q

What do the body and fundus of the stomach secrete?

A

Mucus, HCl, Pepsinogen

28
Q

What does the antrum of the stomach secrete?

A

Gastrin

29
Q

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

A

2L

150mM H+

30
Q

What allows the pH of the epithelial 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

31
Q

Which layer of muscle carries out segmentational contraction?

A

Circular

32
Q

Which layer of muscle carries out peristalsis contraction?

A

Longitudinal

33
Q

Is segmentation or peristalsis the stronger contraction?

A

Peristalsis

34
Q

Which method of contraction occurs most often?

A

Segmentation - 80% of contractions

35
Q

Where does peristalsis propel chyme to?

A

Towards the colon

36
Q

Where does segmentation move chyme to?

A

Fluid chyme towards pyloric sphincter

Solid chyme pushed back to the body

37
Q

Describe the nervous stimulation of peristalsis?

A

Activated by the ANS

38
Q

Describe the nervous stimulation of segmentation?

A

Stretching activated enteric nervous system

39
Q

What do the chief cells of the stomach secrete?

A

Pepsinogen

40
Q

How are these chief cells adapted to secretion?

A

Abundant RER

Golgi packaging and modifying for export

Masses of apical secretion granules

41
Q

What do the paritetal cells of the stomach secrete?

A

Hydrochloric acid (HCl)

42
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

43
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 carbonic 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

44
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

45
Q

What is the function of Gastrin?

A

Stimulates release of histamine from chromaffin cells (lamina propria)

46
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

47
Q

Describe the gastric phase of gastric secretion

A

Food in stomach activates the stretch- and chemo-receptors

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

48
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

49
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

50
Q

What is the mechanism of action of Omeprazole?

A

Blocks the protein pumps (H+/K+ ATPase)

51
Q

What can Omeprazole be used as a treatment for?

A

Indigestion, heartburn and acid reflux

52
Q

What is the mechanism of action of Ranitidine?

A

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

53
Q

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

A

Decrease