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ESA3 GI > Stomach > Flashcards

Stomach Flashcards

1
Q

What are the main function of the stomach ?

A
  • Receive food
  • Disrupt food
  • Continue digestion
  • Disinfect
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2
Q

Describe the basic structure of the stomach

A

LOS, Cardia , Fundus , Body , Antrum , Pylorus

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3
Q

What are the different type of cells in the stomach ?

A 
Parietal 
Enteroendocrine cells (G, D)
Chief cells 
Enterochromaffin like cell 
Mucous cells
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4
Q

How is the stomach different in terms of wall composition ?

A

Extra Oblique layer of muscle

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5
Q

Where is the main site of strong peristalsis and why ?

A

Lower stomach : contractions every 20 seconds ,proximal to distal

Can’t be upper stomach because needs to be able to relax when receiving food to prevent increase of pressure , and reflux

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6
Q

What mechanism allow the stomach to receive food and how is it mediated ?

A

Receptive relaxation : allows food to enter stomach without raising pressure > prevents reflux of stomach content during swallowing

Possible thanks to Rugae and mediated by Vagus nerve

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7
Q

How does acidic conditions aid digestion ?

A
  • unravel proteins
  • activates protease (pepsinogen > pepsin )
  • disinfect stomach
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8
Q

What does the stomach secrete in the lumen ?

A

HCL
IF
Mucus / HCO3
Pepsinogen

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9
Q

Which cells are predominant in the cardia ?

A

Mucous cells

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10
Q

What type of cells are found in the fundus and body ?

A

Mucous cells
Parietal cells
Chief cells

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11
Q

What cells are found in the Pylorus ?

A

Enteroendocrine cells : D cells and G cells

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12
Q

Which cells secrete Gastrin and when(stimuli )?

A

G cells (Antrum)

Stimulated by :

  • Peptides/amino acids (made by pepsinogen from proteins )
  • Vagal stimulation : Gastrin releasing peptide GRP and Ach
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13
Q

How is Gastrin production inhibited ?

A

Food leaves : pH drops
Stimulates D cells
Secrete Somatostatin which inhibits G cells

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14
Q

Which cells produce HCL and when (stimuli )?

A

Parietal cells

Stimulated by Gastrin ,Histamine , Ach from vagus nerve

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15
Q

How is HCL production inhibited ?

A
  • Drop of pH when food leaves > D cells secrete Somatostatin > inhibition of G cells > no Gastrin
  • Somatostatin also inhibits Enterochromaffin like cells > no histamine
  • Stomach distension reduced when food leaves > reduced Vagal activity
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16
Q

Explain the “alkaline tide “phenomenon

A

HCL production needs H+ to be excreted in lumen by HKATPase
H+ produced in cell from H2O
By product is HO- which react with CO2 to form HCO3 which is released at basolateral membrane in blood

> > blood leaving stomach slightly alkaline

17
Q

What are the phases of digestion ? (In relation to secretion )

A

Cephalic
Gastric
Intestinal

18
Q

Briefly describe the cephalic phase of digestion

A

Smelling,tasting,chewing,swallowing induce parasympathetic stimulus by vagus nerve of Parietal cells and G cells (Ach + GRP)

Anticipating food also increases gastric motility

19
Q

Briefly describe the gastric phase of digestion

A
  • distension of stomach: vagus stimulation>parietal cells and g cells stimulation
  • Presence of aa and small peptides >stimulation of G cells
  • Food act as buffer to remove Gastrin inhibition (from D cells)
  • Enteric NS and Gastrin cause SM contraction
20
Q

What are the two phases of Intestinal digestion ?

A
  • Chyme initially stimulate Gastrin secretion( protein detected )
  • But presence of lipids activates enterogastric reflex (reduced vagal stimulation ,secretion of CCK and Secretin > inhibition of G cells)
21
Q

What are the 3 defence mechanisms of the stomach to acid damage ?

A
  • Mucus/HCO3 : released by surface mucous cells , for alkaline protection
  • High turnover of epithelial cells
  • Prostaglandins : maintain mucosal blood flow for nutrients
22
Q

Why do NSAIDs cause gastric side effects ?

A

NSAIDs inhibit prostaglandins release > less vasodilation >less blood flow to epithelium > damage

23
Q

Which substances can breach stomach defences ?

A

Alcohol : dissolve mucus
Helicobacter pylori : chronic gastritis
NSAIDS: prostaglandin inhibition

24
Q

Give some eg of common gastric disorders

A
  • GORD
  • Gastritis
  • Peptic ulcer disease
  • Zollinger-Ellison disease
  • Cancer
  • Stress ulcers
25
Q

What is GORD , symptoms ?

A

Reflux of stomach contents in oesophagus

Heartburn
Cough
Sore throat
Dysphagia

26
Q

What can be the cause of GORD ?

A
  • LOS pbm
  • Delayed gastric emptying causing raised intra gastric pressure
  • Hiatus hernia (cardia and fundus herniated through oesophagus hiatus of diaphragm )
  • -Obesity
27
Q

What complications can derive from GORD ?

A
  • Oesophagitis
  • Strictures (narrowing : dysphagia)
  • Barrett’s oesophagus : metaplasia from stratified squamous to columnar epithelium : increased risk of adenocarcinoma
28
Q

Give some eg of possible treatment for GORD

A
  • Life style changes : eat early ,loose weight , sleep up
  • Antacids
  • proton pump inhibitor
  • H2 antagonist
  • Surgery
29
Q

How do H2 antagonist help with GORD ?

A

Block H2 receptor on parietal cells
>no histamine stimulation of parietal cells from Enterochromaffin like cells
»reduced HCL production

30
Q

What is acute gastritis and what can cause it ?

A

Acute mucosal inflammatory process

Heavy use of NSAIDs
Lots of alcohol
Chemotherapy
Bile reflux

31
Q

What are the symptoms of acute gastritis ?

A

pain, nausea, vomiting

Occasionally bleeding (heavily )

32
Q

What can cause chronic gastritis ?

A
  • H pylori infection
  • Autoimmune : AB against parietal cells
  • Chemical reaction : chronic alcohol abuse, NSAIDs
33
Q

Why is pernicious anaemia often seen in chronic gastritis ?

A

Auto antibodies against parietal cells cause chronic gastritis
>also cause deficiency in Intrinsic Factor which is usually produced by parietal cells
»IF necessary for Vit B12 absorption

34
Q

Which symptoms are often seen in autoimmune induced chronic gastritis ?

A
  • anaemia
  • Glossitis (big red tongue)
  • anorexia
  • neurological symptoms
35
Q

What is a peptic ulcer ? Where do they often occur ?

A

Defect (hole) in mucosa . Often in first part of duodenum or lesser curve of stomach

36
Q

What can be the cause of a peptic ulcer ? What are the symptoms associated ?

A

Cause: stomach acid , H pylori, NSAIDs

Symptoms : Epigastric pain (burning,after meals , at night ) , Back pain if duodenal , Bleeding/anaemia, weight loss

37
Q

How doEs H pylori survive in the stomach and what does it cause ?

A
  • Produce urease : converts urea to ammonium = increase pH around so protects from acid
  • Flagellum allow motility
  • Adheres to epithelia
  • Release cytotoxins: direct injury
  • Ammonia toxic to epithelium
  • Promotes inflammatory response
38
Q

In which condition does stress ulceration occur ?

A

Severe burns
Sepsis
Severe trauma
Raised intracranial pressure

ESA3 GI (9 decks)

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