Oral and Esophageal Physiology Flashcards
What is the function of mastication?
Forms round bolus for deglutition
What nerve controls the muscles of mastication?
V3 (Mandibular branch of the Trigeminal nerve)
Achalasia
Increased esophageal tone at lower esophageal sphincter
GERD
Decreased esophageal tone at upper esophageal sphincter
What are the main muscles of the lips?
Orbicularis Ori
What are the main muscles of the cheek?
Buccinator
What are the main muscles of mastication?
Masseter, Temporalis
What are the main muscles of opening jaw/grinding?
Lateral Pterygoid Muscles (lowering jaw and moving sideways)
What are the functions of Saliva?
- Digestive
- Additional
- Protective
- Other examples
What are the protective functions of saliva?
- Dilution
- Buffering
- Lubrication
- Remineralization
- Antimicrobial actions
- Healing
- Cleansing
What are other examples of functions of saliva?
- Grooming
- Thermoregulation
- Olfactory signals
What are Additional examples of functions of saliva?
- Speech
- Excretion
- Trophic
- Social interaction
What are Digestive examples of functions of saliva?
- Chewing
- Bolus formation
- Swallowing
- Amylase, Lipase
- Taste
What are two main functions of Saliva?
- Has amylase which initiates digestion of carbohydrates
2. Creates lubrication/gel surrounding bolus
What secretes saliva?
Lobulated Exocrine Gland
What is the function of duct cells?
Acinus and ionic content of saliva is modified by duct cells.
What are seven components in salivary secretions?
- Water
- Digestive enzymes: salivary alpha-amylase (ptyalin), lingual lipase, RNAse, DNAse
- Mucins
- Defense molecules: Lysozyme, secretory immunoglobulin (IgA), lactoferrin, peroxidase, defensins
- Epidermal and nerve growth factors
- Bicarbonate
- Sex hormones
What suggests an endocrine role of saliva as well?
Some salivary substances are secreted into the blood, suggesting endocrine role.
What are the two types of salivary glands?
- Serous (watery, amylase)
2. Mucous (mucin) cells contain serous demilunes
What controls saliva flow rate?
Myoepithelial cells
How much saliva is produced/day?
1.5 L/day
What is the percentage of saliva produced by the parotid glands?
25% volume
What is the percentage of saliva produced by the submandibular glands?
70% volume
What is the percentage of saliva produced by the sublingual glands?
5% volume
What is the Parotid saliva made up of?
Entirely serous, watery
What is the submandibular saliva made up of?
Mixed serous and mucous
What is the sublingual saliva made up of?
Mainly mucous saliva
Why is saliva an alkaline solution?
Salivary duct cells secrete K+, HCO3-, Ca++, Mg++, phosphate to prevent demineralization of the tooth enamel and are impermeable to water
What is the pH of the oral cavity?
6.3
What is the oral cavity pH associated with?
When food is consumed, carbohydrates –> are fermented by bacteria producing lactic acid.
What nerves control the parasympathetic autonomic nervous system that controls saliva secretion?
Glossopharyngeal and facial
What nerves control the sympathetic autonomic nervous system that controls saliva secretion?
Cervical sympathetic chain
How does the parasympathetic ANS control saliva secretion?
Acts through VIP and ACh on muscarinic receptors to increase secretion of watery saliva.
How does the sympathetic ANS control saliva secretion?
Acts through NE on beta1-and alpha1 adrenergic receptors to secretion of viscous saliva.
What things stimulate the salivary nucleus of the medulla?
Higher centers Esophagitis Vomiting Water Brash Pressure in mouth
What things neg. stimulate the salivary nucleus of the medulla?
Sleep
Fatigue
Fear
What things stimulate the higher centers of the salivary pathway?
- Smell
- Taste
- Sound
- Sight
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
When are salivary enzymes increased?
During pancreatic insufficiency and in neonates
What functions is the tongue critical for?
Clearing obstructions, initiating swallowing, speech and taste
What innervates the tongue muscle?
Hypoglossal (XII)
What nerves terminate in the nucleus of the tractus solitariuss?
Glossopharyngeal (IX) and Facial (VII) sensory fibers
What must be dissolved in saliva and stimulate further saliva production?
Tastants
What primary elementary qualities are detectable?
Salty, sour, sweet, bitter, umami
What is a myth about the tongue?
That certain regions of tongue detect certain elements
What are taste buds made up of?
Taste cells and support cells joined near the apical surface by tight junctions
What can dysguesia result from?
Infection, aging and nutritional deficiencies
What types of receptors does the tongue contain?
- Taste
- Pain
- Temperature
How are signals sent in the tongue to identify taste in sensory neurons?
- Taste ligands bind to receptors activating G proteins
2. Secondary messengers release NT onto primary sensory neurons
What leads to gastric acid secretion?
Taste signals to nucleus tractus solitarius
What type of absorption occurs in the oral cavity?
- Little nutrient absorption
- Buccal and sublingual absorption of drugs (glyceryl trinitrate), avoids hepatic first-pass metabolism
What is Sailometry?
- Used to measure saliva production
- Stimulate with citric acid
- Normal >1 mL/min
What is Xerostomia?
Subjective sensation of dryness of the oral mucosa.
What are causes of dry mouth/too little saliva?
- Sjogren syndrome
- Many medications: muscarinic antagonists (antidepressants and opiate analgesics)
- Secondary to hear and neck radiation
- Dehydrateion due to diarrhea, vomiting, fever, diuretics
- Sialolithiasis (submandibular)
- Nerve damage related to injury or diabetes
- Postmenopausal hyposalivation
What is Sjogren syndrome?
Autoimmune disorder that destroys exocrine glands
What are the consequences of dry mouth?
- Increased likelihood of opportunistic infections
- Halitosis 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 > Malnutrition
How do you treat and manage dry mouth?
- Gum, artificial saliva, switch medicines
- Parasympathetics (pilocarpine)
- Stimulate flow but also cause hypotension, respiratory distress and GI disorder
Most saliva is subsequently…
…swallowed
What happens when a bolus is small enough (2 cm)?
An involuntary reflex is initiated by mucosal mechanoreceptors
What can be voluntary overriden?
Swallowing reflex (swallow pill) – subsequent events are involuntary
What happens to the UES and LES between swallows?
Between swallows UES and LES are closed to prevent entry of air and gastric contents since the esophagus is presenting low pressure environment of the thorax.
When can you not swallow?
With mouth open
What is the mechanism behind swallowing?
- Mucosal mechanoreceptors transmit message through glossopharyngeal and vagus nerves to the medullary center in brain stem
- Somatic nerves cause contraction (ACh - nicotinic) of striated muscles in the UES and top third of the esophagus
- Autonomic nerves regulated smooth muscle in the bottom two thirds - ACh on nicotinic and muscarinic
What coordinates swallowing with respiration and speech?
Central input
What does obstruction of the esophagus cause?
Patient can’t swallow and drools continuously
What is the function of the Nasopharynx during swallowing?
Prevents bolus from entering the nasal cavity
What is the function of the Oropharynx in swallowing?
Contraction propels bolus into esophagus
What is the function of the Hypopharynx/Laryngopharynx in swallowing?
Relaxes, segregate food and air
How long do the oral and pharyngeal phases of swallowing take?
Less than 1 sec to complete
What is the most important action of the tongue? What nerve controls the tongue?
Plunging action. Hypoglossal (CN XII)
What is the first step in swallowing?
Tongue contacting the hard palate pushes bolus against soft palate triggering swallowing reflex.
- Soft palate elevates, closing off the nasopharynx
- Larynx moves up and forward
- Tonically contracted upper esophageal sphincter
What is the second step in swallowing?
Breathing is inhibited as the bolus passes the closed airway.
- Longitudinal muscles of posterior pharynx contract
- Epiglottis folds fown to prevent material from entering the trachea
- Relaxation of cricopharyngeal muscle (innervated by vagus CN X) leads to opening of distal pharynx and upper esophageal sphincter.
What is the third step in swallowing?
Food moves downward into the esophagus, propelled by peristaltic waves and aided by gravity.
What does Dysphagia/Odynophagia lead to? What can cause it?
Can lead to aspiration and malnutrition.
- Structural abnormalities (esophageal cancer or diverticula)
- Functional abnormalities (stroke leading to neural disorder)
What is the predominant diagnostic technique for Dysphagia/Odynophagia?
Video fluoroscopic swallowing study (VFSS) is predominant diagnostic technique. Barium (radioopaque) swallowed with food observed by x-ray
What happens during the Esophageal phase/primary peristalsis of swallowing?
- Sphincter pressures are higher than atmospheric and fall during a swallow
- Esophageal pressure increases as the peristaltic wave sweeps down the esophagus
How long might the esophageal phase last?
10 seconds or more and is aided by gravity.
What do mechanoreceptors in the esophagus sense? What do they cause?
They sense distention or changes in pH.
This leads to contraction (ACh) above and relaxation (NO/VIP) below.
What boluses are propelled with greater force but more slowly?
Larger and colder boluses
What is primary peristalsis controlled through?
Neural control - long and short reflexes
What nerves are involved in primary peristalsis?
Parasympathetic nerves and enteric neurons
How does esophageal contraction work?
Circular muscles contract upstream of the bolus and relax downstream while longitudinal muscles relax upstream and contract downstream
What controls Secondary Peristalsis?
Restricted to smooth muscles, elicited by distention of GI tract or acid in the esophagus
What do enteric neurons produce in Secondary Peristalsis?
A very strong peristaltic wave starting just above the obstruction.
What are Retrograde Movements?
Include eructation, vomiting and regurgitation require relaxation of the upper and lower sphincters, but do not require additional esophageal movements.
What are Diffuse esophageal spasms?
Uncoordinated contractions can cause the regurgitation of food or liquids
What is Nutcracker Esophagus?
Painful contractions
What risk is associated with sword swallowing?
Perforating esophagus
Who was the first endoscopy done on?
Sword swallower
What is needed in order to effectively ‘swallow’ a sword?
- Need to hyperextend neck
- Inhibit pharyngeal reflex
- Flip epiglottis
- Relax upper and lower esophageal sphincters
What does control of the Lower Esophageal Sphincter (LES) depend on?
Enteric plexus neurons
What causes the Lower Esophageal Sphincter (LES) to be open or closed?
- Closed between swallows due to cholinergic neurotransmission
- Relaxed during swallows due to NO and VIP neurotransmission
What is the tone of the LES due to?
A combination of stimulatory and inhibitory neural and hormonal inputs
What things Reduce LES tone?
- Chocolate
- Peppermint
- Caffeine
- Alcohol
- Fatty meals
- Progesterone
- Isoproterenol
- Secretin
- Vasoactive Intestinal Peptide
- Nitric oxide
- Neurotensin
- Prostaglandin E1
- Cholecystokinin
What things Increase LES tone?
- Protein meal
- Acetylcholine
- Phenylephrine
- Serotonin
- Gastrin
- Pancreatic Polypeptide
- Substance P
- Motilin
- Neuropeptide Y
What is GERD?
Gastro-Esophageal Refluz Disease - reflux of acidic gastric contents into the esophagus due to relaxation of lower esophageal sphincter.
What is reflux?
Normal physiologic process cleared by peristalsis
What is mid reflux?
Heartburn
What is severe reflux?
Epithelial erosion, Barrett’s esophagus
What are the causes of GERD?
Obesity, Pregnancy (increased progesterone), Eructation, and Hiatal Hernia (diaphragmatic hiatus widens with age)
What are treatments for GERD?
Elevation of bed, diet?, Proton pump inhibitors and antacids
When are you more likely to have GERD/heartburn?
After a meal (rather than before)
What is Achalasia?
Failure of lower esophageal sphincter to relax and in some cases lack of proximal peristalsis, regurgitation, dysphagia of solids. Dilation of esophagus and “bird beak”. Loss of myenteric ganglion cells.
How might treating with botulinum toxin be an effective strategy?
Inhibits ACh stimulation of the esophageal sphincter
What happens during portal hypertension?
Blood diverts to form varices
What is the pathway of venous drainage from the esophagus?
- Venous drainage of esophagus forms a submucosal venous plexus that drains directly into systemic circulation
- Plexus anastomoses with veins in the stomach that drain into the hepatic portal system
What are the main functions of Saliva?
Provides lubrication to generate bolus formation, initiates digestion, dissolves taste molecules, helps neutralize gastric acid, and has antimicrobial properties.
What is critical for transfer of contents between the oral cavity and stomach?
Relaxation of tonic contractions at the sphincters is critical for transfer of contents between the oral cavity and stomach.
