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ILA formatives > ILA5 - GORD > Flashcards

ILA5 - GORD Flashcards

1
Q

What is the order of the GI tract?

A

Oral cavity, pharynx, passes epiglottis into oesophagus. Then into stomach, duodenum, jejunum, ileum, through the iliocaecal valve into the caecum. Then up the ascending colon, round the hepatic flexure along the transverse colon, roung the splenic flexure then down the descending colon into the sigmoid colon then rectum and anus, poopy

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2
Q

What epithelium lines the mouth?

A

Stratified squamous.

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3
Q

What happens in stage 1 of swallowing?

A

(voluntary) Food is compressed against roof of mouth and pushed into oropharynx by tongue.

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4
Q

What happens in stage 2 of swallowing?

A

Involuntary. Nasopharynx closes off due to soft palate elevation. Trachea closed off by epiglottis. Elevation of hyoid bone shortens and widens the pharynx.

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5
Q

What happens in stage 3 of swallowing?

A

Involuntary.Pharyngeal muscles sequentually contract producing peristaltic waves. Propels bolus down oesophagus. Depression of hyoid bone.

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6
Q

Where does oesophagus pass through diaphragm?

A

T10 (oesophagus has 10 letters)

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7
Q

What is the epithelium of the pharynx?

A

Naso is pseudostratified columnar

Oro and laryngeo are non keratinizing stratified squamous

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8
Q

What muscle type is in the oesophagus?

A

Upper 1/3 is skeletal

Lower 2/3 is smooth

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9
Q

Epithelium of stomach?

A

Columnar

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10
Q

Parts of stomach?

A

Fundus, body, antrum and pylorous

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11
Q

What secretory cells are found in the fundus and body of the stomach? And what do they secrete?

A

Mucous neck (mucous), parietal (gastric acid and intrinsic factor), chief (pepsinogen) and G-cells (gastrin)

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12
Q

What cells are found in antrum and pylorous?

A

Mucous neck

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13
Q

What cells secrete somatostatin?

A

D-cells

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14
Q

What cells secrete histamine?

A

Enterchromaffin like cells

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15
Q

How long (rough) is the doudenum?

A

25cm

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16
Q

How many parts of the duodenum are there?

A

4

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17
Q

What secretes secretin, and what is its role?

A

S cells in the duodenum. Inhibits gastric acid production, stimulate production of bicarb from ductal cells of pancreas, stimulates bile production

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18
Q

What are the markers of the hind, mid and foregut?

A

Foregut: oesophagus-2nd part of duodenum
Midgut: 3rd part of duodenum - second third of transverse colon
Hindgut: final 1/3 transverse colon to anus

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19
Q

What is the Ampulla of Vatar?

A

Dilation in hepatopancreatic duct when common bile duct joins pancreatic duct.

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20
Q

Where do the pancreatic secretions and bile pass into the digestive system?

A

2nd part of duodenum, through the Sphincter of Oddi

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21
Q

What are the muscular layers of the stomach?

A

Circular, longitudinal and oblique

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22
Q

What are the muscular layers of digestive tract (except stomach)?

A

Circular and longitudinal

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23
Q

What is the transpyloric plane and what structures lie on it?

A

Plane 1/2 way between jugular notch and pubic symphysis. Pylorus of the stomach, D1 part of the duodenum, duodeno-jejunal flexure, root of the transverse mesocolon, hepatic flexure of the colon,
splenic flexure of the colon, fundus of the gallbladder,
neck of the pancreas, hila of the kidneys, hilum of the spleen, ninth costal cartilage, termination of spinal cord and superior portion of conus medullaris

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24
Q

What is the epithelium of the oesophagus?

A

Stratified squamous

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25
Q

What is the function of the pharynx (GI)?

A

Convey food from oral cavity to oesophagus. Prevent the bolus entering nasopharynx or trachea.

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26
Q

What is the function of oesophagus?

A

Lubrication, move food to stomach

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27
Q

What are the functions of the stomach?

A

Mixing, enzymes, lubricate, anti-microbial, release intrisic factor (vit B12 absorption)

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28
Q

What is the function of the duodenum?

A

Absorption of nutrients and water, neutralisation of chyme

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29
Q

Where does peristaltic wave begin?

A

Skeletal muscle just below upper oesophageal sphincter

30
Q

What is the order of peristaltic contraction?

A
  • Primary peristaltic wave. Coordinated by the swallowing centre of neurons in the
    medulla and pons via the vagus
  • Circular layer of muscle contracts and raises pressure on oral side of bolus pushing it into
    the area of low pressure
  • Longitudinal muscles contract and pull Oesophagus up over the bolus
  • Occurs in distal direction
  • Lower oesophageal sphincter relaxes due to vagal innervation
  • If any food is left then second peristaltic wave is initiated
31
Q

What is the lower oesophageal sphincter located?

A

Last 1-2cm of the smooth muscle in the distal oesophagus, it prevents reflux (most of the time).

32
Q

In a healthy individual, how is reflux prevented?

A
  • Reflux prevented by the valve produced by the Angle of His
  • This angle creates a valve which prevents duodenal bile, enzymes and stomach acid from
    travelling back into the Oesophagus
  • Lower oesophageal sphincter
33
Q

What is GORD/GERD?

A

Chronic symptom of mucosal damage caused by
stomach acid coming up from stomach into Oesophagus. Usually caused by abnormal changes in barrier, the backflow is driven by the motility of the stomach. Can progress into Barrett’s oesophagus.

34
Q

What is Barrett’s oesophagus?

A

Change of epithelium from stratified squamous to simple columnar (like stomach), this is considered a pre-malignant condition.

35
Q

How much HCl is secreted per day?

A

2L

36
Q

What is the rough pH of gastric acid?

A

2

37
Q

Concentration of H+ in gastric acid

A

> 150mM

38
Q

Which cells produce HCl?

A

Parietal

39
Q

Is gastric acid production energy dependant?

A

yes

40
Q

In gastric acid production what ions are secreted into the stomach lumen?

A

H+ (to form HCl), Cl- (to form HCl) and K+ (to maintain electrical balance of the parietal cell)

41
Q

In gastric acid production, which ions are absorbed from the stomach lumen?

A

K+ (antiporter channel, H+ out for K+ in)

42
Q

In gastric acid production, which ion is excreted into the blood?

A

HCO3-

43
Q

In gastric acid production, which ion is absorbed from the blood?

A

Cl-

44
Q

What is the mechanism for gastric acid production?

A

a) Hydrogen ions are generated within the parietal cell from dissociation of water. The hydroxyl ions formed in this process rapidly combine with carbon dioxide to form bicarbonate ion, a reaction cataylzed by carbonic anhydrase.
b) Bicarbonate is transported out of the basolateral membrane in exchange for chloride. The outflow of bicarbonate into blood results in a slight elevation of blood pH known as the “alkaline tide”. This process serves to maintain intracellular pH in the parietal cell.
c) Chloride and potassium ions are transported into the lumen of the cannaliculus by conductance channels, and such is necessary for secretion of acid (passive).
d) Hydrogen ion is pumped out of the cell, into the lumen, in exchange for potassium through the action of the proton pump; potassium is thus effectively recycled.
e) Accumulation of osmotically-active hydrogen ion in the cannaliculus generates an osmotic gradient across the membrane that results in outward diffusion of water - the resulting gastric juice is 155 mM HCl and 15 mM KCl with a small amount of NaCl.

45
Q

What are the phases in regulation of gastric acid secretion?

A

Cephalic, gastric on, gastric off, intestinal

46
Q

Give some examples of stimuli in the cephalic phase of gastric acid secretion regulation.

A

Sight, smell, taste of food, and chewing stimulate the PNS

47
Q

What happens in the cephalic phase of gastric acid secretion?

A

a) Parasympathetic stimulation by cephalic stimuli
b) Acetylcholine release in stomach mucosa by nerve ends (via vagus nerve and enteric system)
c) ACh acts directly on parietal cells stimulating M3 receptors: results in activation of proteins involved in K+/H+ ATPase (by phosphorylation)
d) ACh triggers release of gastrin (G-cells) and histamine (enterochromaffin-like cells)
- Gastrin stimulates Histamine synthesis from ECL cells (neuroendocrine)-and directly affects as stated below
- Histamine stimulates secretion of gastric acid
e) Net effect = increased acid production

48
Q

What happens in the gastric ON phase of gastric acid secretion regulation?

A

a) Gastric distension (stretch), presence of peptides and amino acids
- Stimulates Gastrin release from neuroendocrine cells
- Gastrin acts directly on parietal cells to induce the insertion of K+/H+ ATPase pumps into the apical membrane of parietal cells (which in turn increases H+ release into the stomach cavity)
- Gastrin triggers release of histamine
- Histamine acts directly on parietal cells
- Also mediates effects of gastrin and histamine
- Net effect = increased acid production
b) Protein in the stomach
- Direct stimulus for gastrin release
- Proteins in the lumen act as a buffer, mopping up H+ ions, causing pH to rise:
- +ve feedback loop
- decreased secretion of somatostatin→ more parietal cell activity (lack of inhibition)

49
Q

What happens in the gastric OFF phase of regulation of gastric acid secretion?

A

a) Low luminal pH (high [H+])
- Directly inhibits gastrin secretion
- Indirectly inhibits histamine release (via gastrin)
- Stimulates somatostatin release which inhibits parietal cell activity

50
Q

What happens in the intestinal (OFF) phase?

A

a) In the duodenum:
-Duodenal distension
-Low luminal pH
-Hypertonic luminal contents
-Presence of amino acids and fatty acids
-ALL stimulate release of enterogastrones
Secretin (inhibits gastrin release, promotes somatostatin release)
Cholecystokinin (CCK)
b) And short and long neural pathways, reducing ACh release

51
Q

what are the 5 defences of gastric and duodenal mucasa against acid damage?

A

a) Apical cell membrane has an inherent resistance to acid
b) Mucus
c) Mucus bicarb buffer
d) Increased blood flow to mucosa during increased acid secretion
e) High replacement of cells

52
Q

How does mucus defend the gastric and duodenal mucosa?

A
  • Secreted by exocytosis from intercellular vesicles by simple columnar epithelial cells on luminal surface
  • The mucus gel covers the inner surface of the stomach.
  • This viso-elastic mucus gel layer slows the diffusion of protons to the epithelial surface and sets up a pH neutral barrier (95% water)
  • Also acts as a holding space for bicarbonate secretions
  • Stimulated by prostaglandin E
53
Q

What does the mucus bicarb barrier do?

A
  • Mucus and bicarbonate, secreted by mucus cells (Foveolar cells), create a pH gradient by maintaining the epithelial cell surface at near neutral pH
  • Protects mucosa from auto digestion by pepsin and from erosion by acid
54
Q

Give two ways in which bicarb is produced in the gastric mucosa?

A

a) Directly in epithelial cells from carbon dioxide and water by carbonic anhydrase
b) Indirectly in Parietal cells:
- H2O +CO2 (Carbonic anhydrase) → H2CO3→ H+ (for HCl secretion) + HCO3-
- Therefore increased acid secretion results in increased bicarbonate secretion and so increased defence
- Bicarbonate secreted in to bloodstream in cotransport with Cl-
- Delivery of bicarbonate ions from the basal border of the parietal cell to the lamina propria by mucosal blood
- Secreted by surface epithelial cells

55
Q

How does the bicarb neutralise the gastric acid?

A

HCO3- + H+→ H2O +CO2

56
Q

Is secretion of bicarb active or passive?

A

Active

57
Q

Is secretion of bicarb higher in the stomach or the duodenum? And why?

A

Duodenum. To neutralise the chyme.

58
Q

How does increased blood supply to mucosa in times of increased acid production protect the mucosa?

A
  • Increased supply of nutrients needed for bicarbonate and mucus secretion
  • Increased movement of bicarbonate to surface for secretion
  • Increased delivery of stimulants for mucous and bicarbonate secretion e.g. Prostaglandins
59
Q

How long does it take for epithelial cells of the stomch take to be replaced?

A

30 mins

60
Q

How long does it take for superficial mucosa cells to be completely replenished?

A

1hr

61
Q

Where are the natural narrowing in the oesophagus?

A

At aorta and left main bronchus (L4/5)

62
Q

What run with oesophagus?

A
  • Oesophagus, vagus, azygous→ run alongside Oesophagus
  • Between Oesophagus and azygous is the thoracic duct
  • Vagus lies on Oesophagus
63
Q

What are the 4 parts of the duodenum?

A

Superior, descending, inferior and ascending (duojejunal flexure)

64
Q

What is the Papilla major?

A

Where common bile duct and pancreartic duct enters the duodenum.

65
Q

What is the upper GI tract?

A

Above the descending part of the duodenum

66
Q

What is the lower GI tract?

A

Below the desc part of the duodenum.

67
Q

How do nicotine and alcohol increase the risk of reflex?

A

They relax the lower oesophageal sphincter

68
Q

What are the symptoms of reflux?

A

Bloating, bloody or black stools, bloody vomiting, pain

69
Q

What is dysphagia?

A

Narrowing of the oesophagus. Patient gets the sensation of a lump of some food is stuck. Can also get nausea, hiccups, cough and hoarseness.

70
Q

What is dyspepsia?

A

Pain/ uncomfort in upper/middle part of stomach. Can cause bleeding, poor appetite, nausea, diarrhoea, constipation and pumps

ILA formatives (10 decks)

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