Salivary Secretion, Swallowing, and the Esophagus Flashcards
What are the functions of salivary secretions?
Digestion
Lubrication
Protection
Taste depends on adequate salivation
What is the acinus?
Blind end of each salivary duct, lined with acinar cells that secrete initial saliva
What is the intercalated duct?
Connects the acinus with the striated duct
What is the striated duct?
Modifies inorganic composition of saliva
How is the control of the saliva glands regulated?
Under total ANS control
Unique in that both parasympathetic and sympathetic nerves increase secretion
PNS provides much stronger input than SNS
What is the result of PNS stimulation on salivary glands?
Increases transport processes of acinar and ductal cells
Stimulates vasodilation of blood vessels
What is the result of sympathetic stimulation on salivary glands?
Transiently increases production of saliva and growth of salivary glands
Causes contraction of myoepithelial cells
Causes constriction of blood vessels
What proteins are present in saliva and what are their functions?
a-amylase - digests starches
lingual lipase - digests fats
Mucin - lubricates food and protexts oral mucosa
Epidermal and nerve growth factors
What is the ionic composition of saliva?
Hypotonic to plasma
Higher K and HCO3 due to secretion in the striated duct
Lower Na and Cl due to reabsorption in the striated duct
What are the mechanisms of ion exchange in the striated duct?
Cl exchanged for HCO3
Na exchanged for H
H exchanged for K
How does flow rate affect concentrations of ions in saliva?
Higher rates means there is less time for reabsorption to occur, so saliva is more isotonic (more Na and Cl)
HCO3 increases with increasing flow rate because its secretion is stimulated when salivation is stimulated
What is xerostomia?
Lack of salivary secretion
Associated with denal caries, chronic infections of the buccal mucosa, and speech, taste and swallowing dysfunction
Treated with water, flavored lozenges, artificial saliva, pilocarpine mouthwashes and tablets
What are the two phases of swallowing?
Oral (voluntary) - forces bolus into oropharynx
Pharyngeal (involuntary) - breathing inhibited, laryngeal muscles contract, Peristalsis begins
How is swallowing controlled?
Reflex response coordinated in swallowing center in the medulla
Can be initiated voluntarily, but requires something to trigger swallowing
Dysphagia - difficulty swallowing
What is the structure of muscle in the esophagus?
Upper 1/3 all striated muscle, lower 1/2 all smooth muscle, gradient in between
What is the primary peristaltic contraction?
Initiated by swallowing
Creates zone of increased pressure behind food bolus
What is the secondary peristaltic contraction?
Initiated by presence of food in esophagus
Stretches mechanical receptors, causing another peristaltic wave
What is GERD?
Caused by decreased tone of Lower esophageal sphincter, which leads to reflux of stomach acid
Causes heartburn and esophagitis
What is a hiatal hernia?
Esophagus passes through opening in diaphragm
LES and part of stomach moved up, acid reflux barrier weakened
What is Barrett’s esophagus?
Constant injury to the esophagus causes continuous cell growth
Can lead to esophageal cancer
What is achalasia?
Neuromuscular disorder of lower 2/3 of esophagus, leading to absence of peristalsis and failure of LES to relax
Food accumulates in esophagus, taking hours to enter stomach
Patients experience dysphagia, regurgitation, and weight loss