Anatomy of Salivation and Swallowing Flashcards
Describe the functions of saliva
- Lubricate food
- Lubricate mouth - speak (tongue, cheeks)
- Oral hygiene
- Lysozyme - enzyme that destroys microorganisms
- Amylase
- Transmitting diseases - eg. Rabies virus
- Solvent that carries taste molecules to taste buds
List the components of saliva
- Mostly water
- Hypotonic
- Rich in potassium and bicarbonate
- Mucus
- Enzymes including amylase and lingual lipase
- Immune proteins - IgA, lysozyme, lactoferrin
State the 3 salivary glands
Parotid, submandibular, sublingual
State where the parotid gland is located and its duct
- Largest of salivary glands
- Sits lateral to mouth
- Parotid duct passes over masseter and penetrates through buccinator into oral cavity
State where the submandibular gland is and its duct
- Has a deep and superficial segment
- Gland is a pacman shape around mylohyoid (muscle that forms floor of mouth)
- Can be felt from below chin
- Submandibular duct opens on floor of mouth medially
State where the sublingual gland is and its ducts
- Located above mylohyoid
- Sublingual gland has many ducts that open more laterally into the oral cavity
Describe the control of salivary secretion
- Control autonomic
- Parasympathetic is main driver (increases saliva production)
- Sympathetic also stimulates secretion of small amounts of saliva, but also causes vasoconstriction of arterioles
- Sublingual and submandibular glands are supplied by parasympathetic from facial nerve
- Parotid gland innervated by glossopharyngeal nerve (IX)
- Any drug that inhibits mACh receptors inhibit salivary glands - inhibits parasympathetic system
Explain how an isotonic solution is secreted from salivary glands
- Isotonic solution excreted from the acinus of the salivary glands
- Myoepithelial cells move the salivary solution down the ducts
- Ductal cells extract NaCl from the solution, creating an hypotonic solution
- If the flow rate through the ducts is greater, then the solution becomes less hypotonic
Describe the structure of the oesophagus
- Oesophagus posterior to larynx and trachea
- Lies right of aorta and pierces diaphragm at T10
- Oesophagus has many narrowing points
- Junction of oesophagus with pharynx
- Where oesophagus is crossed by arch of aorta
- Where oesophagus is compressed by left main bronchus
- At the oesophageal hiatus (at diaphragm)
State the distribution of muscle types along the oesophagus
Skeletal muscle at cranial end and smooth muscle at caudal end
State the 3 phases of swallowing
- Oral prepatory phase
- Pharyngeal phase
- Oesophageal phase
Describe the oral prepatory phase
- Voluntary
- Tongue pushes bolus towards pharynx
- Once bolus touches pharyngeal wall, pharyngeal phase begins
Describe the pharyngeal phase
- Involuntary
- Soft palate seals off nasopharynx
- Pharyngeal constrictors push bolus downwards
- Larynx elevates, closing epiglottis
- Vocal cords adduct and breathing temporarily ceases
- Opening of the upper oesophageal sphincter
- Airway at risk of aspiration in pharyngeal phase
Describe the oesophageal phase
- Involuntary
- Closure of the upper oesophageal sphincter
- Peristaltic wave carries bolus downwards into oesophagus
Describe how swallowing in a baby differs from adults
- Epiglottis in baby projects upwards into nasopharynx
- Able to breathe and feed at same time
- Can’t speak
- As baby grows, neck elongates to pull epiglottis down
- Milk diverted laterally around epiglottis to oesophagus
- Piriform fossa guides bolus down to oesophagus
