GI 03 And 04: Saliva + Cephalic Flashcards
Cephalic phase
The GI is activated in readiness for meal (stimuli are cognitive; include idea of food, smelling food, seeing food, or hearing the sounds of food). These trigger responses in GI system even without ingestion of food
Oral phase
Food is actually in the mouth now -manny responses are same as in cephalic phase, however - you’re just getting additional activation of GI because of taste buds and mechanical receptors in mouth and upper pharynx
Area of brain associated with cephalic phase
Lower pons and upper medulla (brain stem)
General function of PSNS on GI function
Activation
General function of SNS action on GI
Inactivation
Percent of gastric secretion which occurs as a result of cephalic preparation
33%
Effect of SNS on saliva
Leads to increased mucosal secretion —> this increased mucus in saliva makes it more viscous, but SNS also makes there be less volume overall
Enzymes present in saliva that begin digestion
Salivary amylase; lingual lipase
What is absorbed by the mouth
Nothing except some drugs and alcohol
Extrinsic salivary glands means the glands are
Outside the mouth itself
Intrinsic salivary glands means the salivary glands are located -_____
Inside the mouth
3 extrinsic salivary glands
Parotid, submandibular, sublingual
Do extrinsic or intrinsic salivary glands account for the majority of saliva
Extrinsic
Parotid salivary glands
Generate a serous (watery) saliva that has a lot of electrolytes and enzymes
Sublingual salivary glands
Mucosal salivary glands that produce mucin glycoprotein that leads to high viscosity of saliva and helps with the lubrication of food
Submandibular salivary glands
Mixed salivary glands that produce saliva with both serous and mucosal properties
Composition and formation of saliva
Also include what is primary saliva and what is secondary saliva
Saliva begins in acinus where cells work to produce primary saliva that has similar tonicity to plasma. This saliva then passes through intercalated and striated ducts that have ductal cells, that eventually generate the final (secondary) saliva.
The primary saliva is squirted in after myoepithelial cells contract
Tonicity of primary vs secondary saliva
Isotonic; hypotonic
Inorganic components of saliva
Electrolytes (including fluoride) and water
Organic components of saliva
Salivary alpha amylase (starts starch digestion)
Lingual lipase (starts lipid digestion
Glycoproteins (mucin forms mucous when hydrated)
Lysozyme (antibacterial)
Opiates (so eating bread is not painful)
How does saliva become hypotonic
Ductal cells have many transporters that bring Na out, Cl out, bicarb in, and K out. H is exchanged across a few different of these electrolytes. N/H exchanger Cl/HCO3 exchanger K/H exchanger On basalateral side NKA keeps this going
More NaCl is absorbed than we secrete so there is net absorption (hypotonic product)
Are ductal cells permeable to water
No
Phases of swallowing
Oral phase (voluntary) Pharyngeal phase (involuntary) Esophageal phase (involuntary)
How does food move through the esophagus
It rides a peristaltic wave
Role of upper esophageal sphincter
Protect airway from swallowed material
Role of lower esophageal sphincter
Protect esophagus and airway from swallowed material and acidic contents of the stomach
Where would you see the diaphragm in a diagram of swallowing
A peak around 20mN/Sq inch
Epithelium present in esophagus
Should be simple squamous
If you see columnar this is a sign of GERD / back flow and called Barrett’s esophagus (puts patient at risk of cancer)
