salivary, gastric + pancreatic secretion Flashcards
what do the salivary glands secrete ?
- electrolytes
- proteins
what are the names of the salivary glands ?
sublingual gland
submandibular gland
parotid gland
buccal glands
what is the maximum rate of saliva flow ?
1ml/min.g
describe the acinar cells
arranged as end pieces
surround small central lumen
describe the organisation of the salivary glandular epithelium :
acinar cells - intercalated duct- large ducts- excretory ducts - mouth
how is parasympathetic stimulation of the salivary gland mediated ?
chorda lingual nerve
what does parasympathetic stimulation cause ?
- evoke fluid secretion
- increase blood flow
- increase 02 consumption
how does sympathetic secretion effect the salivary gland ?
causes vasoconstriction
scanty viscous secretion in rich proteins
what stimulates the salivary reflex ?
- taste
- touch
- smell
how is salvia formed ?
2 stage process
isotonic primary fluid formed by acinar cells
fluid is modified in the striated duct by reabsorption of Na + Cl
and secretion of K + HCO3
what is the effect of neurotransmitters + hormones on the basolateral membrane of the acinar cells ?
increase intracellular Ca = activation of K channels in basolateral membrane
possible increase of Cl channels in luminal membrane
what are the 3 operating basolateral transport proteins in a steady state ?
K+ channel
Na/K pump
N/K/2Cl co transporter
how does Na cross the apical membrane ?
follows through paracellular space drawing water through + between cells
what happens to the Cl + K conductance ?
increases when stimulation stops
Na/K pump + co transporter restore intracellular KCL concentrations
how is the voluntary phase of swallowing initiated ?
separation of bolus of food in mouth
bolus is moved upwards + backwards by tongue
this forces bolus into esophagus + activates tactile receptors that initiate swallowing
what does the pharyngeal phase of swallowing involve ?
pulling of soft palate upwards
inward movement of palatopharyngeal fold towards one another
prevents reflux into the nasopharynx
how is the entry of food into the trachea prevented ?
vocal cords are pulled together
epiglottis covers the opening to larynx
how is food forced through ?
upper esophageal sphincter relaxes
pharynx contracts forces bolus into pharynx
persistatic waves force food bolus through relaxed esophageal sphincter
how is the gastirc surface protected and what by ?
thin film of mucous
produced by epitheilal cells
what are the 3 glands in the gastric mucosa ?
- cardiac glands
- pyloric glands
- oxyntic glands
where is the cardiac glands found ?
what is there role ?
found in the esophageal end is highly branched
is coiled with few/no peptic or oxyntic cells
secretes mucous + some electrolytes
where are the pyloric glands found ?
what is there role ?
found in deep gastric pits , duodenum of stomach, pyloric sphincter and antrum of stomach
secrete alkaline mucous juice + some electrolytes
where are the oxyntic glands found?
what is there role ?
occupy fundus + body of stomach
key site of gastric HCl secretion
what are surface mucus cells made up of ?
what do they secrete ?
columnar epithelium
neutral carbohydrates
what are mucous neck cells ?
what do they secrete ?
they are stem cells for epithelial replacement
acidic glycoproteins
describe the cell structure of parietal/ oxyntic cells :
lots of mitochondria
specialised intracellular canaliculi
microvilli on lumen
what is a benefit of canaliculi ?
increase SA
where does HCL secretion occur ?
how does HCL secretion occur ?
on parietal cells
basolateral receptors become activated by Ach, histamine and gastrin
what are chief cells ?
cells that secrete pepsinogen
where is gastrin released from ?
G cells of antral mucosa
where does gastrin bind to ?
bind to CCK-2 receptor on enterochromaffin like cells
how does gastrin release cause HCL production ?
binds to enterochromaffin like cells which causes the release of histamine
histamine binds to H2 receptors on parietal cells
what is released to inhibit further gastrin release ?
where is it released from ?
somatostatin
D-cells
what is gastric juice made from ?
HCl from parietal cells
alkaline component containing peptic cells + electrolytes
what are the 5 phases of gastric acid secretion ?
- basal (fasting)
- post-prandial (stimulated)
- cephalic
- gastric
- intestinal
what activated the cephalic phase ?
what is it mediated by ?
activated by sight , smell, taste + chewing of food
mediated by efferent impulses through vagus fibres to stomach
what activates gastric secretion ?
distension + chemical composition of food factors
what activates intestinal secretion ?
when does it occur ?
stimulated by liver extract, peptone, amino acid mixtures
occurs after all extrinsic nerves between intestines + stomach are severed
what is zollinger- ellison syndrome ?
condition where one or more tumours form in your pancreas or the duodenum
what causes zollinger-ellison syndrome ?
large amounts of gastrin is secreted which stimulate ECL , which release histamine which binds to parietal cells = more HCL produced
excess HCL leads to peptic ulcers + diarrhea
how is the head, body + tail of the pancreas drained ?
drained by main pancreatic duct
enters the duodenum through ampulla of Vater
describe the bloody supply + lymphatics of the pancreas :
accompany duct system to finest termini in pancreatic acini
what nerves innervate the pancreas ?
vagus + sympathetic
where is secretin released from ?
how does this act on the small intestine ?
small intestine
enters pancreas via circulation + causes the release of bicarbonate
where is cholecystokinin released from ?
what effect does it have on the pancreas ?
released from small intestine
acts on acinal cell receptors + release proenzyme secretion
