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oesophagus and stomach Flashcards

(52 cards)

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1
Q

anatomy of oesophagus

A

oesophageal sphincter and epiglottis direct food and air to the right place
epiglottis covers the opening of the trachea during swallowing
upper oesophageal sphincter relaxes - allowing it to fit in the oesophagus
oesophagus is a conduit tube
close proximity with the lungs and major bv

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2
Q

oesophageal sphincter

A

constrictor pharyngeal medius - commonality with circular muscle layer of GI tract
constrictir pharynges inferior - commonality with longitudinal muscle layer

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3
Q

physiology of the oesophagus

A

25cm long
wall made of skeletal and sm
upper oesophagus = skeletal muscle only
lower = sm
middle third = mixture of 2 as the proportion of skeletal muscle tapers along its length
under -ve pressure, stomach under +ve pressure
lining - non-keratinised straitifed sqaumous cells - all the way to the lower oesophageal sphincter where cells are arranged as simple columnar epithelium to9 resist strong stomach acid
the epithelial change occurs within the spincter along a jagged line called Z line

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4
Q

lower oesophageal sphincter

A

split into:
internal component - built into circular smooth muscle of oesophageal wall
external component - formed by right crus of diaphragm

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5
Q

swallowing

A

stage 0 - oral phase - chewing and saliva help prepare bolus for swallowing - both sphincters are constricted
stage 1 - pharyngeal phase [- bolus moves to back of pharynx, the pharengeal musculature helps to guide it towards the oesophagus. Both oesophageal sphincters open.
stage 2 - upper oesophageal phase - upper sphincter closes, superior rings of circular muscle contract as inferior rings dilate, Sequential contractions of longitudinal muscle help guide the food down the gullet.
stage 3 - lower oesophageal phase - food passes through the lower sphincter that too closes, the peristaltic wave continues to push food into the stomach

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6
Q

anatomical levels of the oesophagus

A

start from C5
close to trachea, aorta, recurrent laryngeal nerves
travel through diaphragm, only short region in abdo before reacing stomach

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7
Q

function

A

conduit for food

secretions from pharynx to stomach

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8
Q

epithelia organisation

A

non-keratinising
wear and tear lining
stratified squamous
lubrication - mucous secreting glands

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9
Q

muscle organisation - skeletal/smooth

A

sphincters - upper and lower oesophageal
tonically active - closed at rest
swallowing centre - recognise swallowing - more powerful effect on upper, cause to open
upper - skeletal muscle
lower - smooth/skeletal

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10
Q

layers of muscle

A

longitudinal near bottom of slide

circular near top

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11
Q

peristalsis in oesophagus

A

local effect
nerve stimulate contraction above bolus, relaxation below
if food not moved - 2nd peristaltic signal from brain

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12
Q

function of the gastrooesophageal sphincter

A

allow movement of food and fluids into the stomach, but ensure acidic contents of the stomach are separate from the vulnerable oesophageal tissue

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13
Q

z line - gastrooesophageal sphincter

A

visible threshold between epithelia and the oesophagus - stratified squamous and stomach - simple columnar

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14
Q

stomach and oesophageal lining

A

oesophageal epithelium - light pink - wear and tear lining
stomach epi - bright red - more resistant to low pH
mucosal gel lining of the stomach provides protection against corrosive acid

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15
Q

function of gastro-oesophageal sphincter

A

acid reflux stopped by the diaphragm

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16
Q

failure of the gastro-oesophageal sphincter

A 
in pregnancy 
stomach pushed up 
= oesophagus pushed up 
pressure difference inn thorax and abdomen 
acid reflux
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17
Q

structure of the gastro-oesophageal sphincter

A

epithelia change from stratified squamous to simple columnar because need to absorb
gastric folds/rugae - allow expansion
lower sphincter is less well defined than upper sphincter - it is made of diaphragm and fold in stomach - when stomach is empty, opening is narrow

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18
Q

functions of the stomach

A

digestion of macronutrients - chemical and mechanical
storage reservoir - until down stream organs are ready to receive stomach contents
immunological protection - strong acid helps to destroy ingested pathogens

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19
Q

structure of stomach

A

lined with columnar epithelia and it invaginates into gastric pits - contain exocrine and endocrine celks

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20
Q

anatomical regions

A 
pyloric canal
pyloric antrum
body 
fundus
cardia
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21
Q

where is gastric acid secreted from

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A

fundus and body in high volume

22
Q

stomach wall

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A

extra oblique layer of smooth muscle inside circular layer - aids in performance of complex grinding motions
in empty state - stomache contracted - mucosa and submucosa are in folds called rugae
when full - rugae are stretched -flat
rugae allow it to undertake resevoir function

23
Q

cardiac and pyloric region

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A

when immediately enter and leave respectively

mucus secretion

24
Q

body and fundus

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A

mucus
HCl
pepsinogen

25
Antrum
gastrin -endocrine hormone
26
purpose of HCO3- in mucus gel
neutralise acid that comes into contact with the cell wall pH at epithelial surface 6-7 pH at lumen 1-2
27
stomach secretions
2L /day | 150 mM H+
28
peristalsis in stomach
propel chime to colon more peowerful proximally ANS essential 'move food from 1 end of tube to other'
29
segmentation in stomach - movement
weaker than peristalsis move fluid chime to pyloric sphincter - it is digested so can move onto the next bit solid chime pushed back up stretching activates enteric nervous system - local
30
what are gastric pits
deep pores within stomach mucosa lead to multiple gastric glands - house functional secretory cells of stomach contain cells for secreting gastric juice - cocktail of hydrochloric acid, enzymes and enzyme zymogens cells also secrete mucous, paracrine siugnals and hormones
31
mucous cells
abundant secrete a bicarbonate-rich mucous which helps to protect the stomach lining keeps pH next to lining near 7 rather than 2-3 protects lining form active lipase and proteases which may interfere with lipid bilayer and membrane transporters
32
parietal cells
acid secreting cells quiescent until activated then tubovesicles in the cytoplasm fuse with the small invaginations on the apical surface to make canalicular surface with large SA for acid secretion rich in mt secrete intrinsic factor - a glycoprotein essential for absorption of vitamin B12
33
HCL function
kill ingested pathogens activate protease zymogens alter protein structure to help digestion
34
chief cells
produce protease zymogen - pepsinogen and a lipase - gastric lipase pepsinogen is activated to pepsin in the presence of HCl in gastric lumen precurser stops it autodigesting the chief cells pepsin breaks dietry proteins into smaller peptide chains gastric lipase is an enzyme that digests fats by removing a fatty acid from triacylglyceride molecule
35
G cells
enteroendocrine cells at bottom of gastric pit release hormone gastrin into blood stream in response to the presence of peptides in the stomach, and stomach distension.
36
gastrin
travels through blood to receptor cells in stomach stimulates gastric secretion and motility stimulation of smooth muscles by gastrin leads to stronger contraction and the opening of the pyloric sphincter to move food into the duodenum also binds to receptors on pancreas and gall bladder - increases secretion of pancreatic juice and bile
37
Enterochromaffin-like cells
ECL neuroendocrine cell in gastric glands in vicinity of parietal cells secrete histamine - stimulates the secretion of acid from the parietal cells
38
D cells
enteroendocrine cells secrete somatostatin - inhib affect of GI func somatostatin inhibits ECL production of histamine and parietal cell activity - both inhibit the secretion of HCl
39
gastric stem cells
`pluripotent stem cells are capable of differentiating into all the stomach cells
40
structure of chief cell
abundant RER Golgi apical secretion granules
41
features of parietal cells
tubovesicles contain H+/K+ ATPase | internal canaliculi - internal reservoir near lumen
42
parietal cell secreting
tubovesicles fuse with membrane and microvilli | canaliculi combine and project into the lumen of the stomach
43
action of parietal cell
CO2 enter - carbonic anhydrase: CO2 + H2O -> HCO3- + H+ bicarbonate is exchanged for chloride chloride diffuse into canaliculi k enters cell in exchange for na canaliculi absorb K for exchange K+/H+ ATPase take H+ into canaliculi and K+ out - active transport H+ secreted
44
gastrin and histamine
gastrin stimulates histamine release from chromaffin cells
45
3 phases of the activities of the stomach
cephalic phase gastric phase intestinal phase
46
cephalic phase
Afferents: Sight, smell, taste and thought of food efferents: vagus nerve stimulate secretion from mucous cells, chief cells, parietal cells and G-cells via the submucosal plexus, gastrin and histamine also stimulate parietal cell secretion effects: small secretion for new minutes
47
gastric phase
afferents: distention of stomach and chemoreception of nutrients and a reduced pH. efferents: 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, gastrin and histamine also stimulate parietal cell secretion effect: 3-4 hours of gastric activity and mechajnical digestion
48
intestinal phase
Afferents: Duodenal stretch and chemodetection of reduced pH and duodenal distension efferents: I-cells secrete cholecystokinin (CCK) and S-cells secrete secretin into the blood. decrease parietal secretion and inhibit gastric motility and emptying, stretch receptors input into enteric nervosu system which reduces activation of the stomach effect: Gastric emptying slows down to allow downstream organs to deal with current contents.
49
cephalic phase processes
vagus nerve release ACh stimulate histamine causes cAMP to enter cell
50
gastric phase processes
stretch and chemo receptors - activate tissue activate muscle and gland to release mucin and acid stomach distension - switch on vagus
51
intestinal phase
mainly inhibitory chime in intestine - intestine respond to pH and consistency - inhibit stomach if lipid conc is high enterogastric reflex: inhibited by gastric inhibitory peptide, cholecytokinin, secretin, enterogastric reflex. inhib from vagus nerve - centrally inhibited if protein conc high - stim gastrin secretion
52
pharmacology
ranitidine - histamine receptor antagonist | omeprazole - protein pump inhibitor

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