Oral & Esophageal Physiology - A.Prunuske

Question 1

What is the function of saliva production?

Answer 1

• Digestive:
  
  • -Contains amylase => initiates digestion of Carbs
  • -Lipase
  • -Swallowing
  • -Bolus formation
• Protective:
  
  • -contains IgA => antimicrobial actions
  • -Lubrication
  • -Cleansing
  • -Dilution
• Other:
  
  • -Speech
  • -Excretion
  • -Grooming
  • -Thermoregulation

Question 2

What glands contribute to saliva production?

Answer 2

• Salivary glands:
  
  • Serous (watery, amylase)
  • Mucous (mucin) cells contain serous demilunes
  • Secreted by lobulated exocrine gland
  • Acinus and ionic content modified by duct cells.
  • Parotid – entirely serous, watery (25% volume)
  • Submandibular- mixed (70% volume)
  • Sublingual – mainly mucous (5% volume)

Question 3

What are the causes of too little saliva production?

Answer 3

• -Sjrogren’s syndrome => autoimmune disorder that destroys exocrine glands
• -Many medications: muscarinic antagonists (antidepressants and opiate analgesics)
• -Secondary to head and neck radiation
• -Dehydration due to diarrhea, vomiting, fever, diuretics
• -Sialolithiasis (blocked submandibular gland)
• -Nerve damage related to injury or diabetes
• • Postmenopausal hyposalivation
• -Cystic fibrosis
• -Methamphetamines

Question 4

What are the consequences of too little saliva production?

Answer 4

• -Dry mouth
• -Difficulty swallowing
• -Increased likelihood of opportunistic infections
• -Halitosis (bad breath) => due to production of hydrogen sulfide by bacteria and accumulation of dead cells
• -Decrease in oral pH leads to tooth decay
• -Decrease in taste
• -Problems with speech
• -Dysphagia (swallowing issues) => Malnutrition

Question 5

What processes of digestion occur in the oral cavity?

Answer 5

• -Mastication- mechanical digestion by teeth and tongue
• -Salivary amylase: activated by Cl- in saliva and hydrolyzes alpha-1,4 glycosidic linkages in starch. Active until acid penetrates the bolus.
• -Lingual lipase: breaks down triglycerides
• -Salivary enzymes increased during pancreatic insufficiency and in neonates

Question 6

What are the main muscles of the Lips?

Answer 6

Obiularis ori

Question 7

What are the main muscles of the Cheek?

Answer 7

Buccinator - positioning of the food in the mouth

Question 8

What are the main muscles of Mastication?

Answer 8

Masseter and Temporalis (raise mandible)

Question 9

What are the main muscles of Opening the jaw and grinding?

Answer 9

Pterygoid Muscles

Question 10

What is the main nerve that innervates the muscles of chewing?

Answer 10

Trigeminal Nerve (CN V)

Question 11

What are the 7 secretions contained in Saliva?

Answer 11

1. Water
2. Digestive Enzymes: salivary α-amylase (ptyalin), lingual lipase, RNAase, DNAase
3. Mucins
4. Defense molecules: Lysozyme, secretory immunoglobulin (IgA), lactoferrin, peroxidase, defensins
5. Epidermal and nerve growth factors.
6. Bicarbonate
7. Sex hormones

Question 12

How much saliva does a typical human produce per day?

Answer 12

Total 1.5 L/ day and myoepithelial cells control flow rate

Question 13

Why is saliva an alkaline solution?

Answer 13

• -If you vomit or reflux acid from the stomach, it will neutralize it.
• -Neutralize acid produced by bacteria.
• -Salivary duct cells secrete K+, HCO3-, Ca++, Mg++, phosphate to prevent demineralization of the tooth enamel and are impermeable to water
• -When food is consumed, carbohydrates are fermented by bacteria producing lactic acid (pH of oral cavity 6.3).

Question 14

What regulates saliva production?

Answer 14

• Salivatory nucleus of medulla interprets external stimuli.
• Parasympathetic (glossopharyngeal and facial): acts through VIP (vasoactive inhibitory protein) and acetylcholine on muscarinic receptors to increase secretion of watery saliva.
• Sympathetic (cervical sympathetic chain): acts through norepinephrine on β1- and α1 adrenergic receptors to secretion of viscous saliva

Question 15

What external stimuli stop saliva production?

Answer 15

• -Fear
• -Fatigue
• -Sleep

Question 16

What are the primary (5) elementary qualities are detectable by taste buds?

Answer 16

• Salty, sour, sweet, bitter, umami.
• Myth that certain regions of tongue detect certain elements.
• Taste buds are made up of taste cells and support cells joined near the apical surface by tight junctions.

Question 17

What kind of sensory receptors are located on the tongue?

Answer 17

• Taste, Pain, and Temperature receptors
• Taste ligands bind to receptors activating G-proteins and secondary messengers release neurotransmitters onto primary sensory neurons.
• Taste signals to nucleus tractus solitarius leading to gastric acid secretion.

Question 18

What processes of absorption occur in the oral cavity?

Answer 18

• -Little nutrient absorption
• -Buccal and sublingual absorption of drugs (glyceryl trinitrate), avoids hepatic first-pass metabolism

Question 19

What is Xerostomia?

Answer 19

subjective sensation of dryness of the oral mucosa

Question 20

How do you measure saliva production?

Answer 20

• Sialometry:
  
  • Collect baseline saliva, then => Stimulate with citric acid
  • (Normal >1 mL/min)
  • Sialochemistry

Question 21

How do you treat/manage inadequate saliva production?

Answer 21

• -Gum, artificial saliva, switch medicines
• -Parasympathomimetics (pilocarpine) => stimulate flow
  
  • but also cause hypotension, respiratory distress, and gastrointestinal disorder

Question 22

When does Swalloing or Deglutition occur?

Answer 22

• -When bolus is small enough (2 cm) an involuntary reflex is initiated by mucosal mechanoreceptors
• -Can be voluntarily overridden voluntarily (swallow pill) subsequent events are involuntary.

Question 23

How is swallowing coordinated with respiration & speech?

Answer 23

• Central Input:
  
  • -Mucosal mechanoreceptors transmit message through glossopharyngeal and vagus nerves to the medullary swallowing center in the brain stem
  • -Somatic nerves cause contraction (Ach- nicotinic) of striated muscles in the UES and top third of the esophagus
  • -Autonomic nerves regulate smooth muscle in the bottom two thirds => Ach on nicotinic and muscarinic

Question 24

What happens when swallowing is unsuccessful?

Answer 24

• -Choking: aspirate into trachea, bolus gets stuck
• -Reflux out nose

Question 25

How does the pharynx assist in Deglutition?

Answer 25

* Nasopharynx- prevent bolus from entering the nasal cavity * Oropharynx- contraction propels bolus into esophagus * Hypopharynx/Laryngopharynx- relax, segregate food and air

Question 26

Plunging action of the tongue is most important. Damage to which nerve would interfere with this tongue function?

Answer 26

Hypoglossal (CN XII)

Question 27

What is the role of the lower esophageal sphincter in swallowing?

Answer 27

* Control of the Lower Esophageal Sphincter: * -depends on enteric plexus neurons * -closed between swallows due to cholinergic neurotransmission * -relaxed during swallows due to NO and VIP neurotransmission

Question 28

What is the neural control of primary peristalsis?

Answer 28

* long and short reflexes- involving parasympathetic nerves and enteric neurons * Circular muscles contract upstream of the bolus and relax downstream * while longitudinal muscles relax upstream and contract downstream

Question 29

What happens if bolus becomes stuck during primary peristalsis?

Answer 29

* Secondary Peristalsis * -restricted to smooth muscle, elicited by distension of GI tract or acid in the esophagus * -enteric neurons produce a very strong peristaltic wave starting just above the obstruction

Question 30

What happens with retrograde movements in the esophagus?

Answer 30

* eructation, vomiting, and regurgitation * -require relaxation of the upper and lower sphincters, but do not require additional esophageal movements

Question 31

What are the three steps in swallowing?

Answer 31

1. Tongue contacting the hard palate pushes bolus against soft palate triggering swallowing reflex. Soft palate elevates, closingoff the nasopharynx. Larynx moves up and forward. Tonically contracted upperesophageal sphincter 2. Breathing is inhibited as the bolus passesthe closed airway. Longitudinal muscles of posterior pharynx contract. Epiglottis folds down to prevent material fromentering the trachea. Relaxation of cricopharyngeal muscle (innervated by vagus CN. X) leads to opening of distal pharynx and upper esophageal sphincter. 3. Food moves downward into the esophagus, propelled by peristaltic waves and aided by gravity.

Question 32

How does sword swallowing work?

Answer 32

* -Need to hyperextend neck * -Inhibit pharyngeal reflex * -Flip epiglottis * -Relax upper and lower esophageal sphincters

Question 33

What condition results when you get significantly increased Lower Esophageal Sphincter?

Answer 33

Achalasia (impaired relaxation)

Question 34

What condition results when you get significantly decreased Lower Esophageal Sphincter?

Answer 34

GERD

Question 35

What is GERD?

Answer 35

* Gastro-Esophageal Reflux Disease (GERD) - reflux of acidic gastric contents into the esophagus due to relaxation of lower esophageal sphincter. * Reflux- normal physiologic process cleared by peristalsis * Mild reflux - heartburn * Severe reflux - epithelial erosion, Barrett’s esophagus

Question 36

What are some of the potential causes of GERD?

Answer 36

* Obesity * Pregnancy (increased progesterone) * Eructation * Hiatal Hernia (diaphragmatic hiatus widens with age)

Question 37

How do you treat GERD?

Answer 37

* -Elevation of bed * -Diet changes * -Proton pump inhibitors * -Antacids

Question 38

What is Achalasia?

Answer 38

* -Failure of lower esophageal sphincter to relax and in some cases lack of proximal peristalsisregurgitation, dysphagia of solids * -Dilation of esophagus and “bird beak” on swallow study * -Loss of myenteric ganglion cells

Question 39

How might treating Achalasia with botulinum toxin be an effective strategy?

Answer 39

Inhibits ACh stimulation (allows relaxation of LES)