Flashcards in Salivary and Gastric Secretions Deck (30):
How are proteins (enzymes) secreted?
Exocytosis in response to neuroendocrines
How are fluids (electrolytes and water) secreted?
Osmotic pressure in the lumen
Function of salivary secretions?
1. lubrication (help swallowing and speech)
What does lysozyme do?
Effective against gram positive bacteria
What does lactoferrin do?
Effective against gram negative bacteria
Where is lingual lipase activated?
In the stomach by acid
Why are digestive enzymes in saliva necessary?
(1) if a baby does not have mother who can provide breast milk, someone can chew food and feed it to baby which now has secretory IgA
(2) if an adult has pancreatic insufficiency (salivary enzymes can compensate)
Characteristics of saliva
(1) concentrations of electrolytes vary with rate of secretion
(2) always hypotonic
(3) always lower in sodium and chloride than plasma
(4) always higher in potassium than plasma
(5) rich in bicabonate
What are the two cells in a salivary duct?
(1) acinar cells
(2) ductal cells
Fluid and Ions secreted by acinar ells
H2O, HCO3-, Na+, K+, Cl-
Ions secreted by ductal cells? Ions absorbed by ductal cells?
absorbed: Cl-, Na+
secreted: HCO3-, K+, H2O
stimulation of salivary nucleus of the medulla?
Conditioned reflex, smell, taste, pressure, nausea
inhibtion of salivary nucleus of the medulla?
fatigue, lack of sleep, fear, dehydration
What myoepithelial cells?
Epithelial cells that acquired muscle cell characteristics
What nerves do salivary nucleusof the medulla stimulate?
(1) Sympathetics T1-T3 -> Superior Cervical Ganglion -> NE
(2) Parasympathetics CN IX, X and FN VII -> Ach, VIP (more stimulated than sympathetic)
Two components of gastric secretion?
(1) oxyntic component
(2) non-oxyntic component
What is the oxyntic component of gastric secretion?
H+, Cl-, K+, IF (parietal cells)
- highly stimulated by feeding
What is the non-oxyntic component of gastric secretion?
mucus, Na+, HCO3- (mucous cells), pepsinogen (chief cells), diffused interstitial fluids (Cl-, H2O)
- rate remains relatively constant (major component at resting, but is highly diluted by the oxyntic component upon feeding)
A. Severe vomiting result in loss in what?
B. Extensive loss of saliva result in what?
A. loss of gastric acid, H+ and Cl-
B. loss of plasma K+
Functions of gastric secretions?
(2) aiding absorption
How does gastric secretion aid digestion?
- acidic pH activated pepsinogen and lipases (lingual)
- HCL denatures proteins for optimal digestion by pepsin
How does gastric secretion aid absorption?
- HCL solubilizes minerals
- Intrinsic factor is required for the absorption of Vit. B12
How does gastric secretion protect lumen?
- HCl inactivates microbes
- Mucus, HCO3-, and Cl- provide containment for H+
How does stimulation of parietal cell change its morphology?
In response to stimulation, tubulovesicle rich in H+ pumps in resting parietal cell fuse with intracellular canaliculi open to the lumen of the gastric pit to secrete H+
What is an alkaline tide?
pH increase in the gastric or portal vein because HCO3- absorption in portal vein is coupled to H+ secretion in lumen
When does the alkaline tide occur?
(1) after a major meal: postprandial alkaline tide (physiological)
(2) severe vomiting: sustained alkaline tide (metabolic alkalosis)
What stimulates acid secretion?
PS, gastrin, histamine
How is HCl contained?
(1) Cl- current
(2) muscosal barrier (mucus gel and HCO3-)
(3) cytoprotection by prostagladins
What do prostagladins do?
(1) inhibition of HCL secretion
(2) stimulation of mucus gel and HCO3- production