S5) Function and Pathology of the Stomach Flashcards Preview

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Flashcards in S5) Function and Pathology of the Stomach Deck (65)
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What do epithelial cells do in the stomach?

Epithelial cells cover the surface and extend into pits/glands


Identify 4 epithelial cells in the stomach

- Mucous cells

- Parietal cells

- Chief cells

- G cells 


Identify the muscle layers in the stomach

- Circular

- Longitudinal

- Oblique


What is the effect of stomach muscle contractions?

- Mix/grind contents

- Move contents along 


What is the function of the upper stomach?

The upper stomach has sustained contractions (tonic) to create basal tone 


The lower stomach is more muscular.

Describe its function

The lower stomach has strong peristalsis which mixes stomach contents


Describe how contractions occur in the stomach

- Contractions are coordinated

- Contractions occur every 20 seconds

- Contraction are proximal to distal 


What is receptive relaxation?

Receptive relaxation is the vagally mediated relaxation of orad stomach 


What is the purpose of receptive relaxation?

- Allows food to enter stomach without raising intra-gastric pressure too much

- Prevents reflux of stomach contents when swallowing

- Gastric mucosal folds (rugae) allow distension 


Identify 3 functions of the acidic conditions of the stomach

- Helps unravel proteins

- Activates proteases: pepsinogen → pepsin

- Disinfects stomach contents 


Identify 4 substances which are secreted by the stomach

- HCl

- Intrinsic factor

- Mucus/HCO3-

- Pepsinogen (pepsin) 


Identify the substances secreted from the following cells:

- Parietal cell

- G cell

- Enterochromaffin like cell

- Parietal cell: HCl & intrinsic factor

- G cell: gastrin

- Enterochromaffin like cell (ECL): histamine


Identify the substances secreted from the following cells:

- Chief cell

- D cells

- Mucous cells

- Chief cell: pepsinogen

- D cells: somatostatin

- Mucous cells: mucus


Identify the substances secreted from the following regions in the stomach:

- Cardia

- Fundus/body

- Pylorus

Cardia: predominantly mucus secretion

- Fundus/body: mucus, HCL, pepsinogen

- Pylorus: gastrin, somatostatin


Identify the 3 substances which stimulate HCl production and state their origins

- Gastrin from G cell

- Histamine from ECL cells

- Acetylcholine from vagus nerve


Where are G cells located?

G cells located in antrum 


Identify the 2 factors which stimulate Gastrin secretion

- Peptides/AA in stomach lumen

- Vagal stimulation:

I. Acetylcholine

II. Gastrin-releasing peptide (GRP) 


When food leaves the stomach, the pH drops. 

How can HCl production be inhibted?

- Low pH stimulates D cells which release somatostatin

- Somatostatin inhibits G cells and ECL cells

- Stomach distension reduces due to reduced vagal activity 


Identify the 3 phases of digestion

- Cephalic

- Gastric

- Intestinal 


How much HCl is produced in the cephalic phase?

30% of total HCl


Outline the parasympathetic stimuli in the cephalic phase of digestion

- Smelling, tasting, chewing, swallowing

- Direct stimulation of parietal cells by vagus nerve

- Vagus nerve releases GRP which stimulates of G cells


How much HCl is produced in the gastric phase of digestion?

60% of total HCl


State 4 events which occur in the gastric phase of digestion

- Stomach distension stimulates vagus nerve

- Vagus nerve stimulates parietal cells and G cells

- Amino acids and small peptides stimulates G cells

- Presence of food acts removes inhibition on Gastrin production (buffer)


What is the role of the enteric nervous system in the gastric phase of digestion?

ENS and gastrin causes strong smooth muscle contractions 


How much HCl is produced in the intestinal phase of digestion?

10% of total HCl production


State the 4 events occurring in the intestinal phase of digestion

- Chyme stimulates gastrin secretion due to the detection of partially digested proteins by duodenum

- G cells are then inhibited

- Enterogastric reflex is activated by lipids which reduces vagal stimulation

- Chyme then stimulates CCK and secretin


Which substances are released to protect the stomach lining?

- Mucus

- HCO3


Where are mucus and hydrogen carbonate secreted from in the stomach?

- Surface mucus cells

- Neck cells in gastric glands 


What are the effects of mucus and hydrogen carbonate secretion in the stomach?

- Thick alkaline viscous layer is formed which adheres to epithelium

- Epithelial surface kept at higher pH 


Apart from mucus/HCO3-, identify and describe 2 other stomach defences

High turnover of epithelial cells to keep epithelia intact

- Prostaglandins to maintain mucosal blood flow and supply epithelium with nutrients