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Y1 Alimentary > Stomach > Flashcards

Stomach Flashcards

1
Q

What are the key functions of the stomach?

A

Digestion of macronutrients: this can be chemical (acid and enzymes) and mechanical (mixing and churning)
Storage reservoir for food: until downstream organs are ready to receive the stomach contents
Immunological protection: Strong acid helps to destroy ingested pathogens

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2
Q

What kind of epithelia is the stomach mucosa lined with

A

Columnar that invaginates into gastric pits that contain specialist exocrine and endocrine cells

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3
Q

What are the 5 anatomical regions of the stomach

A 
Cardia
Fundus
Body
Pyloric antrum
Pyloric canal
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4
Q

What is structurally different in the stomach wall compared to the rest of the digestives tract? What does this do?

A

has an extra oblique layer of smooth muscle inside the circular layer, which aids in performance of complex grinding motions (mechanical digestion)

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5
Q

What does the stomach look like in it’s empty state

A

stomach is contracted and its mucosa and submucosa are thrown up into folds called rugae

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6
Q

What happens to the stomach structure after consumption of food and fluids

A

as the volume of the stomach increases, the rugae are stretched and become flat

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7
Q

What do the rugae allow the stomach to do?

A

Undertake its reservoir function

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8
Q

Where do fluids and foods move into the stomach

A

From the lower oesophageal sphincter

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9
Q

What is the z line?

A

visible threshold between epithelia of the oesophagus (stratified squamous cells) and the stomach (simple columnar cells)

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10
Q

What does the mucous gel lining of the stomach do

A

Provide considerable protection against corrosive acid

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11
Q

What do mucous cells do?

A

secrete a bicarbonate-rich mucous which helps to protect the stomach lining by keeping the pH next to the lining much closer to 7. Also helps to protect the stomach lining from active lipase and proteases, which may interfere with the lipid bilayer and its membranous transporter

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12
Q

Where are the secretory cells of the stomach found

A

gastric pits, which are deep pores within the stomach mucosa, which lead to multiple gastric glands

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13
Q

What are parietal cells?

A

acid-secreting cells of the stomach and secrete intrinsic factor

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14
Q

What is the acid in the stomach for?

A

1) to kill ingested pathogens; 2) activate protease zymogens; 3) alter protein structure to help digestion

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15
Q

What is intrinsic factor

A

glycoprotein essential for the absorption of vitamin B12.

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16
Q

What happens to parietal cells when activated

A

Tubovesicles in the cytoplasm fuse with the small invaginations on the apical surface to make complicated canalicular surface with large SA for acid secretion

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17
Q

What will a deficiency in intrinsic factor lead to?

A

Deficiency in this substance will lead to pernicious anaemia.

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18
Q

What do chief cells do

A

protease zymogen (pepsinogen) and a lipase (gastric lipase)

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19
Q

How is pepsinogen activated?

A

Pepsinogen is activated to pepsin in the presence of HCl in the gastric lumen store them in granules until they are stimulated to exocytose them into the stomach lumen

20
Q

Why is pepsinogen secreted as a precursor?

A

Prevent it autodigesting the chief cells

21
Q

What does pepsin do?

A

breaks dietary proteins into smaller peptide chains

22
Q

What does gastric lipase do?

A

enzyme that digests fats by removing a fatty acid from a triglyceride molecule

23
Q

What are G cells?

A

enteroendocrine cells found at the bottom of the gastric pits and release GASTRIN

24
Q

What stimulates gastrin release

A

Vagus nerves stimulation in presence of peptides in stomach and stomac distension

25
Q

What does gastrin do in stomach?

A

stimulates gastric secretion and motility and leads to stronger contractions of the stomach and the opening of the pyloric sphincter to move food into the duodenum

26
Q

What does gastrin do in pancreas and gallbladder

A

Increases the secretion of pancreatic juice and bile

27
Q

What do Enterochromaffin like cells do?

A

ecrete histamine which stimulates the secretion of acid from the parietal cells

28
Q

What are enterochromaffin like cells? Where are they found?

A

type of neuroendocrine cell found deep in the gastric glands, usually in the vicinity of parietal cells

29
Q

What do D cells do?

A

Enteroendocrine cells that secrete somatostatin, GI function inhibitory effect. Within the gastric gland somatostatin inhibits ECL production of histamine and parietal cell activity, both of which inhibit the secretion of hydrochloric acid

30
Q

What do gastric stem cells do?

A

differentiating into all of the different cells of the stomach, under the influence of different factors. The development pathway varies for different parts of the stomach

31
Q

What happens to carbon dioxide when it diffues into the parietal cell?

A

in the presence of carbonic anhydrase, is combined with water to form carbonic acid, which dissociates into bicarbonate and a proton

32
Q

What happens to bicarbonate in the parietal cell?

A

bicarbonate is exchanged with a chloride ion in the interstitial space. This causes chloride ions to move down their concentration gradient into the stomach lumen via chloride channels

33
Q

How are protons pumped into the lumen

A

Cell move K+ from interstitial cell to lumen via Na+/K+ enchanger in basolateral membrane and chloride channels in apical membrane so K+ pumped into cell in exchange for protons

34
Q

How do protons re-enter lumen from parietal cell? What happens to it there?

A

through the potassium channels and the secreted proton combines with chloride to form hydrochloric acid

35
Q

What does lipase do?

A

break triglycerides into FA and a diglyceride

36
Q

What are the three phases of stomach activity?

A

Cephalic phase
Gastric phase
Intestinal phase

37
Q

What are afferents for the cephalic phase?

A

Sight, smell, taste and thought of food.

38
Q

What are efferents of the cephalic phase

A

Vagus nerve (neurons secreting ACh) stimulate secretion from mucous cells, chief cells, parietal cells and G-cells via the submucosal plexus. Gatsrin (from G-cells) and histamine (from ECL cells) also stimulate parietal cell secretion

39
Q

What are effects of the cephalic phase?

A

Small secretion for a few minutes

40
Q

What are the effects of the gastric phase

A

3-4 hours of gastric activity (secretion of acid, enzymes and hormones) and mechanical digestion

41
Q

What are the afferents of the gastric phase

A

Distension of stomach and chemoreception of nutrients and a reduced pH.

42
Q

What are the efferents of the gastric phase

A

Vagus nerve (neurons secreting ACh) stimulate secretion from mucous cells, chief cells, parietal cells and G-cells via the submucosal plexus and increase motility (mixing waves) via the myenteric plexus. Gatsrin (from G-cells) and histamine (from ECL cells) also stimulate parietal cell secretion.

43
Q

What are the effects of the intestinal phase

A

Gastric emptying slows down to allow downstream organs to deal with current contents.

44
Q

What are the afferents of the intestinal phase

A

Duodenal stretch and chemodetection of reduced pH and duodenal distension

45
Q

What are the efferents of the intestinal phase

A

I-cells secrete cholecystokinin (CCK) and S-cells secrete secretin into the blood. This decreases parietal cell secretion and inhibits gastric motility and emptying. Stretch receptors input into the enteric nervous system, which reduces activation of the stomach.

Y1 Alimentary (21 decks)

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