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
