Secretions Flashcards
(47 cards)
What is the function of saliva?
Digest starches (amylase) and lipids (lingual lipase) and lubricate foods (mucus)
What are the 3 glands that secrete saliva?
Which gland accounts for the majority of saliva secretion?
Parotid gland (serous only)
Submandibular (serous and mucus)
Sublingual (serous and mucus)
Mixed glands secrete a majority of saliva
Explain the salivary gland structure with regards to: Acinus Myoepithelial cells Intercalated ducts Striated ducts
Acinus- secretes initial saliva
Myoepithelial cells- contract to eject saliva
Intercalated ducts- saliva at this point is isotonic
Striated ducts- lined with ductal cells and will secrete HCO3 and K into saliva and reabsorb NaCl
Why is saliva a hypotonic solution?
Ductal cells will reabsorb more NaCl than they secrete HCO3 and K
As well ductal cells are water impermeable
What are the main components of saliva? 6 components
Water Electrolytes A-amylase (starches) Lingual lipase (lipids) Kallikrien (increase blood flow during salivation) Mucus (lubrication)
With regards to innervation, what makes salivary glands special?
Exclusively under ANS control
Parasymp and symp BOTH stimulate saliva secretion (para>symp)
Explain the parasympathetic innervation of salivary glands with regards to pre and post ganglionic fibers and where they synapse
Presynaptic- facial and glossopharyngeal nerves
Postsynaptic- fibers from ANS ganglia will synapse on individual cells
Explain the sympathetic innervation of salivary glands including pre and post synaptic fibers
Presynaptic- arise from cervical ganglion
Postsynaptic- extend to glands via periarterial spaces between cells
Explain parasympathetic pathway and regulation of salivary glands
Excitatory stimulus- food, nausea, smell
Inhibitory stimulus- dehydration, fear, sleep
Pathway- stimulus triggers facial/glossopharyngeal nerve to travel to glands and release Ach triggering glandular cells to secrete saliva
Atropine inhibits AchR from triggering saliva release
What cells are responsible for secreting “gastric juice”?
Parietal cells, chief cells, and mucus cells
What are the 4 major components of gastric juice?
HCl- initiates protein digestion and activates pepsin
Pepsinogen- released by chief cells and activated by low pH
Mucus- protects stomach and along with HCO3 helps neutralize acid
Intrinsic Factor- required for vit B12 absorption
What are the 2 types of gastric mucosa glands? Where are they located and what do they secrete?
Oxyntic gland- proximal 80% of stomach, secrete acid
Pyloric gland- distal 20% of stomach, release gastrin
What do parietal cells secrete and with what purpose?
Parietal cells secrete HCl to lower stomach pH to begin protein digestion and activate pepsin
Explain the mechanism of parietal cell HCl secretion
Within cell CO2 and water create H2CO3 which splits into H and HCO3
H is secreted into lumen via K/H antiporter
HCO3 is reabsorbed into blood via HCO3/Cl antiporter
Cl exits into lumen passively and joins H to create HCl
Explain actions of the following with regards to parietal cells:
Omeprazole
Cimetidine
Atropine
Omeprazole- inhibits H/K ATPase and is used to treat uclers
Cimetidine- histamine H2 receptor antagonist prevents histamine from stimulating H secretion and is used to treat ulcers and GERD
Atropine- inhibits M3 AchR from binding Ach released due to vagus stimulation
Explain the role of vagus nerve in parietal cell stimulation (direct and indirect stimulation)
Direct- vagus stimulates release of Ach which binds M3 AchR on parietal cells which triggers release of HCl (atropine inhibits this pathway)
Indirect- vagus stimulates release of GRP which binds G cells which stimulates secretion of gastrin which binds CCKR receptor on parietal cells and triggers HCl secretion
Explain potentiation with regards to parietal cells, specifically the roles of histamine, Ach, and gastrin
Histamine, Ach, and gastrin stimulate HCl secretion
Histamine potentiates affects of Ach and gastrin
Ach potentiates affects of histamine and gastrin
What are the 3 phases of HCl secretion and how much HCl secretion occurs with each phase?
Cephalic phase- 30%
Gastric phase- 60%
Intestinal phase- 10%
What are the stimuli for the cephalic phase of HCl secretion?
Stimuli- smell, taste, chew, swallow
What is the mechanism of the cephalic phase of HCl secretion? Relate to vagotomy
Vagus n has the direct and indirect pathways of stimulating HCl secretion (direct-Ach binding M3 AchR on parietal) (indirect-GRP triggers gastrin release which stimulates parietal cells)
Vagotomy will abolish the cephalic phase of HCl secretion
What are the stimuli for the gastric phase of HCl secretion?
Stimuli- stomach distention, presence of food
What is the mechanism for the gastric phase of HCl secretion?
Distention- stimulates mechanoreceptors in mucosal glands which stimulate vagus nerve (direct and indirect pathways)
Antrum distention- activate pyloropyloric reflex which results in gastrin release which stimulates parietal cells to release HCL
Food- triggers gastrin secretion which stimulates parietal cells
What is the mechanism of the intestinal phase of HCl secretion
Distend SI- secrete acid
Digested proteins- stimulate acid secretion
What are the 2 “components” of gastric secretions?
Nonparietal and parietal
