Salivary Secretion, Swallowing, and the Esophagus

Question 1

What are the functions of salivary secretions?

Answer 1

Digestion

Lubrication

Protection

Taste depends on adequate salivation

Question 2

What is the acinus?

Answer 2

Blind end of each salivary duct, lined with acinar cells that secrete initial saliva

Question 3

What is the intercalated duct?

Answer 3

Connects the acinus with the striated duct

Question 4

What is the striated duct?

Answer 4

Modifies inorganic composition of saliva

Question 5

How is the control of the saliva glands regulated?

Answer 5

Under total ANS control

Unique in that both parasympathetic and sympathetic nerves increase secretion

PNS provides much stronger input than SNS

Question 6

What is the result of PNS stimulation on salivary glands?

Answer 6

Increases transport processes of acinar and ductal cells

Stimulates vasodilation of blood vessels

Question 7

What is the result of sympathetic stimulation on salivary glands?

Answer 7

Transiently increases production of saliva and growth of salivary glands

Causes contraction of myoepithelial cells

Causes constriction of blood vessels

Question 8

What proteins are present in saliva and what are their functions?

Answer 8

a-amylase - digests starches

lingual lipase - digests fats

Mucin - lubricates food and protexts oral mucosa

Epidermal and nerve growth factors

Question 9

What is the ionic composition of saliva?

Answer 9

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

Question 10

What are the mechanisms of ion exchange in the striated duct?

Answer 10

Cl exchanged for HCO3

Na exchanged for H

H exchanged for K

Question 11

How does flow rate affect concentrations of ions in saliva?

Answer 11

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

Question 12

What is xerostomia?

Answer 12

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

Question 13

What are the two phases of swallowing?

Answer 13

Oral (voluntary) - forces bolus into oropharynx

Pharyngeal (involuntary) - breathing inhibited, laryngeal muscles contract, Peristalsis begins

Question 14

How is swallowing controlled?

Answer 14

Reflex response coordinated in swallowing center in the medulla

Can be initiated voluntarily, but requires something to trigger swallowing

Dysphagia - difficulty swallowing

Question 15

What is the structure of muscle in the esophagus?

Answer 15

Upper 1/3 all striated muscle, lower 1/2 all smooth muscle, gradient in between

Question 16

What is the primary peristaltic contraction?

Answer 16

Initiated by swallowing

Creates zone of increased pressure behind food bolus

Question 17

What is the secondary peristaltic contraction?

Answer 17

Initiated by presence of food in esophagus

Stretches mechanical receptors, causing another peristaltic wave

Question 18

What is GERD?

Answer 18

Caused by decreased tone of Lower esophageal sphincter, which leads to reflux of stomach acid

Causes heartburn and esophagitis

Question 19

What is a hiatal hernia?

Answer 19

Esophagus passes through opening in diaphragm

LES and part of stomach moved up, acid reflux barrier weakened

Question 20

What is Barrett’s esophagus?

Answer 20

Constant injury to the esophagus causes continuous cell growth

Can lead to esophageal cancer

Question 21

What is achalasia?

Answer 21

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