Session 3: The Anatomy of Salivation and Swallowing Flashcards
Give the different salivary glands.
Parotid gland
Submandibular gland
Sublingual gland
Buccal glands
Composition of saliva.
Mostly water
It is hypotonic and rich in potassium and bicarbonate.
Mucins (mucous)
Amylase (serous from parotid gland mainly, ptyalin)
Lingual lipase
Immune proteins like IgA, lysozymes and lactoferrin
What causes the degree of tonicity to vary in saliva?
The flow rate of the saliva through the ductal cells. If the flow rate is high the saliva won’t have enough time to transport correct ions in and out.
Functions of saliva.
Speech Hydrate food to form food bolus to alleviate swallowing. Oral hygiene Transmission of disease First line of defence to pathogenic food Solvent to dissolve flavour molecules Begins the digestion of food
Explain how saliva helps in oral hygiene.
Since saliva contains immune proteins it will help against bacteria in the mouth from feeding off the teeth.
During nights we salivate less which means deterioration can occur.
What is xerostomia?
Deficiency of saliva i.e. dry mouth.
What can xerostomia be caused by?
A blocked nose Drug side-effects like from SSRIs Radiotherapy to the head Removal of salivary glands Neural damage
Neural control of the salivary glands.
Autonomic where the parasympathetic nervous system is the main driver to increase production (rest and digest).
Sympathetic can also stimulate secretion of small amounts of saliva but can also be a hindrance.
Why might increased sympathetic response lead to a dry mouth instead of helping in secretion?
Because it can cause vasoconstriction of blood vessels to the salivary glands leading to less secretion of saliva.
Innervation of the parotid gland.
Cranial nerve IX (glossopharyngeal nerve)
Innervation of the submandibular gland.
Submandibular ganglion.
Innervation of the sublingual gland.
Submandibular ganglion.
Why is mumps painful?
Because it causes swelling of the parotid gland. This swelling is contained by the fibrous capsule of the parotid gland and cannot expand. The fibrous capsule is innervated by the trigeminal nerve and the trigeminal nerves sensory branches will pick up on the swelling and pain will be produced.
What else might cause pain of the parotid gland?
Salivary stones leading to obstruction and swelling of the parotid gland.
How can you detect stones of the parotid gland?
Via parotid sialography
What are the phases of swallowing?
1: Oral preparatory phase
2: Pharyngeal phase
3: Oesophageal phase
Explain the oral preparatory phase.
It is a voluntary mechanism where the food bolus is pushed towards the pharynx and once the bolus touches the pharyngeal, the pharyngeal phase will begin.
This phase takes anything from 0-7.4 seconds.
Explain the pharyngeal phase.
It only takes about 0.2 seconds.
It is an involuntary mechanism where the soft palate seals off the nasopharynx to prevent food to go up into the nasal cavity.
The pharyngeal constrictors push the bolus downwards.
The larynx will elevate due to the suprahyoid muscles and this elevation causes the epiglottis to close. The epiglottis does not close on its own.
The vocal cords adduct to protect the airways from getting food into it. This also temporarily cease breathing.
Lastly the upper oesophageal sphincter relaxes and causes it to open. The food bolus can now go into the oesophagus.
Explain the oesophageal phase.
It is involuntary and the food bolus is pushed down by peristalsis.
The upper oesophageal sphincter closes to prevent retrograde flow.
How is it possible for a baby to eat and breathe at the same time if swallowing closes the airways?
Because in babies the epiglottis is much higher up and overlaps the soft palate and some of it goes into nasopharynx.
This means that air can still move and babies can still breathe.
Briefly explain the neural control of swallowing.
Mechanoreceptors causes the glossopharyngeal nerve (sensory part of the pharynx) to send information to the medulla. The medulla forwards the signal to the vagus nerve which is the motor nerve of the pharynx to cause the pharyngeal constrictors to contract.
Give examples of dysphagia.
Stroke causing the pharyngeal muscles to not contract.
Oesophageal carcinoma where drinking is possible but eating becomes difficult as there is a sense of something sticking in the oesophagus.
Where in the oesophagus might food get stuck?
In the narrowings. There are 4 narrowings in total.
State the narrowings of the oesophagus and explain them.
Junction of the oesophagus with pharynx
Where the oesophagus is crossed by the arch of the aorta
When there oesophagus is compressed by the left main bronchus
At the oesophageal hiatus where it passes through the diaphragm.
How is gastro-oesophageal reflux prevented?
By the lower oesophageal sphincter and the diaphragm.
By intraabdominal oesophagus which gets compressed when intra-abdominal pressure increases.
By mucosal ‘rosette’ at cardia
By the acute angle of entry of oesophagus.
