3.2 Saliva And Swallowing Flashcards
Describe the content of saliva
- Mostly water
- Hypotonic (depending on flow rate)
- Rich in potassium and bicarbonate (pH slightly acidic to ~8)
- Mucins help with lubrication
- Amylase
- Lingual lipase
- Contains a diversity of immune proteins (e.g. IgA, lysozyme, lactoferrin)
How is amylase secreted into saliva?
Via salivary glands
How are lipases secreted into the saliva?
Lingual glands
How is salivary secretion primarily regulated?
Autonomic nervous system
• Parasympathetic is main driver (increases production)
• Sympathetic also stimulates secretion of small amounts of less watery saliva, but also causes vasoconstriction of blood vessels supplying salivary glands
How is saliva modified after secretion by the acinus?
Initial saliva is secreted by acinus
Moved out of acinus into ducts by myoepithelial cells
Ductal cells are relatively impermeable to water
However removes Na+ and Cl-
Secrete K+ and HCO3- ion
More Na+ and Cl- removed than K+ and HCO3- ions secreted
Saliva ends up hypotonic
How does the rate of flow of saliva affect its composition?
At low flow rates, most significant modification takes place, becomes more hypotonic
At higher flow rates less modification takes place
Except for HCO3- ions which are selectively secreted at higher flow rates
What are the 3 stages of swallowing?
Oral phase
Pharyngeal phase
Oesophageal phase
What occurs in the oral phase of swallowing?
- preparing bolus
- Tongue pushes bolus towards oropharynx
Bolus touches pharyngeal wall and pharyngeal phase begins
What occurs in the pharyngeal phase?
- Soft palate elevates to seal off nasopharynx
- Pharyngeal constrictors push bolus downwards
- Larynx elevates, closing epiglottis
- Vocal cords adduct (protecting airway) and breathing temporarily ceases
- Opening of the upper oesophageal sphincter
Describes what happens in the oesophageal phase
- Closure of the upper oesophageal sphincter
* Peristaltic wave carries bolus downwards into oesophagus
What is dysphagia?
Problems swallowing
How do neurological problems cause problems swallowing?
• Usually harder to swallow fluids (than solids) as these are more difficult to coordinate and
move as a unit into the GI tract
• Can more easily get into respiratory tract than solids
How does physical obstruction to lumen cause problems swallowing?
Makes solids harder to swallow than fluids
What may cause physical obstruction to the lumen?
- Fibrous rings
- Tumours
- Achalasia-failure of LOS to relax
What may progressive dysphagia indicate?
Malignant changes - As tumour size increases it will become harder to swallow as lumen gets more obstructed
What are the 3 main functions of saliva?
Lubrication
Protection
Digestion
Why does saliva provide lubrication?
To assist in swallowing and speech
How does the saliva confer protection?
Cooling effect on hot food/drinks
Buffers acid (saliva enters mouth before vomit)
Washes away debris stuck in teeth
Antibacterial
How does saliva act as an antibacterial?
Lysozymes : attacks bacteria cell wall
Lactoferrin : collates iron, reducing iron availability for bacteria, stopping them from multiplying
What type of glands are salivary glands?
Exocrine glands
What are exocrine glands?
Glands that have ducts that open into an epithelial lined structure
What are the 3 paired salivary glands?
Parotid
Sublingual
submandibular
How much saliva is produced a day?
1500ml
Which salivary gland produces the most saliva?
Submandibular
Describe the secretions of the parotid gland?
25% of saliva
Serous (watery)
Lots of enzymes
Describe the secretions of the submandibular gland
70% of saliva Mixed secretions (mucous and serous)
Describe the secretions from sublingual glands
5% of saliva
Mucous
Little enzymes
When is secretion of HCO3- into the ductal system of the salivary glands increased?
During high flow rate (active saliva secretion)
When is saliva most hypotonic?
At rest, when there is low flow rate. There is increased contact time with ductal cells and therefore more removal of sodium and chloride
What innervated the parotid gland?
Glossopharyngeal nerve
What innervated the submandibular and sublingual nerve?
Facial nerve
What is xerostomia?
Xerostomia is defined as dry mouth resulting from reduced or absent saliva flow.
What causes xerostomia?
Medications Autoimmune conditions Dementia Radiotherapy Dehydration
What can xerostomia result in?
Infections (bacteria multiply easier
Tooth decay
Halitosis
What is halitosis?
Bad breath
Name a viral infection of the salivary glands
Mumps (swollen parotid gland)
How do we protect against mumps?
MMR vaccine
What is Sjogerns syndrome?
Autoimmune condition. Causes dry mouth, dry eyes and painful/swollen salivary glands
What are sialoliths?
Calcified salivary gland stones.
Where is the most common place for sialoliths?
Wharton’s duct - where the submandibular gland drains into the mouth
What are symptoms of a sialolith?
Pain in region of stone. Worsens before/during eating as producing more saliva.
What are examples of neurological causes of dysphagia?
Cerebrovascular accident
Stroke
Parkinson’s disease
Multiple sclerosis
What are symptoms of neurological dysphagia?
Ineffective swallow causing dribbling
Material entering respiratory tract causing coughing, choking and infections (pneumonia) if persistent.
Difficulty swallowing fluids
What are signs of an oesophageal cancer?
Progressive dysphagia (solids harder to swallow) Weight loss
What is achalasia?
Failure of the LOS to relax
