Exam #5: Mouth & Esophagus

Question 1

Where is the majority of saliva produced? What are the two types of secretions from the salivary glands?

Answer 1

90% of saliva is produced from the parotid, submandibular, and sublingual salivary glands. Two secretions are:

1) Serous
2) Mucous

Question 2

Describe the composition of the serous portion of saliva.

Answer 2

Serous or watery secretion contains:

• alpha-amylase
• water

Question 3

Describe the composition of the mucous portion of saliva.

Answer 3

Mucous secretion contains:

• Water
• Electrolytes
• Phospholipids
• Mucin

*****Mucin has a number of functions, but the primary one is protection of the GI tract by coating the mucosa

Question 4

Describe the mechanism by which water and salt are secreted into the lumen of the salivary gland. What happens in the duct of the salivary gland?

Answer 4

Water
- ACh stimulation of apical membrane chloride channel
causes secretion of Cl- into the lumen of the salivary duct
- Na+/ H20 follow
- ACh also stimulates the release of a-amylase

Duct

• Na+ & Cl- are reabsorbed as fluid moves through the duct
• Water does NOT follow b/c of tight junctions between ductal cells
• Bicarbonate & K+ are secreted

Final product= HYPOTONIC

Question 5

Identify the composition of saliva and the function of those components.

Answer 5

Saliva functions to:

1) Water–>prevent dehydration of oral mucosa
2) Water & mucin–>Lubrication for swallowing
3) IgA, lysozyme, & lactoferrin–>Oral hygeine
4) Alpha-amylase–>digestion
5) Smell/taste
6) HCO3—>neurralize gastric acid

Question 6

What would happen if the ability to secrete saliva was impaired?

Answer 6

1) Dehydration of oral mucosa
2) Impaired swallowing
3) Higher risk of infection
4) Impaired starch digestion
5) Impaired smell & taste
6) Inability to neutralize reflexed gastric acid

Question 7

What is the primary stimulus that increases salivary secretion? What are the secondary stimuli?

Answer 7

ACh–ACh is the KEY EZYME for both fluid and enzyme secretion into the salivary fluid, which is why anti-cholinergic drugs–>dry-mouth

Secondary=

1) Substance P
2) NE (paradoxical increases secretion but decreases blood flow)

Question 8

What are the three phases of swallowing? What happens in each phase?

Answer 8

1) Oral=
- tongue pushes against hard palate
- food bolus stimulates touch receptors
- swallowing reflex

2) Pharyngeal=
- food into pharynx
- soft palate pulled down to prevent nasal reflux
- epiglottis swings down to cover trachea
- UES relaxes
- Peristalsis is initiated

3) Esophageal
- UES contracts
- primary peristaltic wave moves food into stomach
- IF primary isn’t enough, a secondary peristaltic wave is initiated FROM THE SITE OF DISTENSION

Question 9

What is the role of skeletal muscle in swallowing?

Answer 9

Upper 1/3 of the esophagus is striated muscle that is under “voluntary” control

Question 10

What is the role of smooth muscle in swallowing

Answer 10

Lower 2/3 of the esophagus is smooth muscle that is under involuntary control of the enteric nervous system

Question 11

What is the difference between primary & secondary peristalsis in swallowing?

Answer 11

Primary= moves food into the stomach from mouth

Secondary= Occurs from the site of bolus distension
- protective & clears H+ into the stomach

Question 12

What neurotransmitters coordinate peristalsis?

Answer 12

Motor input is regulated by vagal input onto smooth & striated muscle

• Upstream of bolus= ACh leads to contraction
• Downstream of bolus= NO/VIP cause relaxation that allows clearance

Question 13

How is the physiology of the mouth & esophagus altered in GERD?

Answer 13

• GERD= reflux of the gastric contents into the esophagus caused by:
  1) Delayed gastric emptying
  2) Decreased LES tone
  3) Transient LES relaxtation
  4) Loss of secondary peristalsis following transient LES relaxation
  5) Increased acidity that damages the LES

**GERD leads to inflammation of mucosal surface & continued reflux–>ulcer, edema, precancerous lesion, bleeding

Question 14

How is the physiology of the mouth & esophagus altered in Barrett’s Esophagus?

Answer 14

• Barrett’s esophagus is characterized by replacement of the esophageal epithelium with gastric epithelium i.e. squamous with columnar due to damage of the squamous from GERD
• This is a cell type in the wrong anatomical location–>lack of proliferative control & neoplasia

Question 15

How is the physiology of the mouth & esophagus altered in dsyphagia?

Answer 15

Dsyphagia i.e. difficulty swallowing can be separated into two classes of impairment, mechanical or functional:

1) Mechanical= structural e.g. tumor, stricture, herniation caused by:
- GERD
- Alcohol/tobacco
- Viral infeciton

2) Functional= neuronal
- CVA
- PD
- Achalasia (denervation of esophageal smooth muscle)

Question 16

How is the physiology of the mouth & esophagus altered in hiatal hernia?

Answer 16

Normally, the stomach sits below the diaphragm; hiatal hernia occurs when weakness in the diaphragm leads to protrusion of the stomach into the thoracic cavity

• Sliding= goes back & forth
• Paraesophageal= stays

Symptoms= reflux esophagitis & vascular disruption

Question 17

How is the physiology of the mouth & esophagus altered in Sjogren Syndrome?

Answer 17

This is an autoimmune disorder characterized by auto-antibodies directed at the salivary glands; primary symptom is dry mouth

Question 18

How is the physiology of the mouth & esophagus altered in Cystic Fibrosis?

Answer 18

Mutations in the CFTR= inability to secrete Cl- into the salivary duct; water doesn’t follow & Bicarbonate secretion is impaired

• Ducts consequently clog & damaged tissue is replaced with fibrotic & fatty tissue
• Dry mouth occurs as well