Identify 5 components of saliva
- Mostly water
- Lingual lipase
- Immune proteins e.g. IgA, lysozyme, lactoferrin
In terms of osmolarity, what sort of fluid is saliva?
Which ions are found in high concentration in saliva?
- Potassium ions
- Bicarbonate ions
What is the role of mucins in saliva?
Mucins help with lubrication
Where are the following enzymes secreted from:
- Amylase – secreted by salivary glands
- Lipase – secreted by lingual glands
Identify 5 functions of saliva
- Lubricates mouth (maintains moisture)
- Begins chemical digestion
- Assists swallowing
- Allows tongue to taste food (solvent effect)
- Protects teeth
What is xerostomia?
- Xerostomia is the dryness of the mouth due to a change in the composition of saliva or reduced saliva in the mouth
- It is associated with dehydration
What are the 3 salivary glands in the body?
- Sublingual glands
- Submandibular glands
- Parotid glands
Describe the location and function of the parotid gland
- Location: each parotid is wrapped around the mandibular ramus
- Function: secretes serous saliva through the parotid duct into the mouth
Where are the sublingual glands located?
The sublingual glands lie directly under the mucous membrane covering the floor of the mouth beneath the tongue
Where are the submandibular glands located?
The submandibular glands lie near the inner side of the lower jawbone, in front of the sternocleidomastoid muscle
Describe the regulation of salivary secretion
- Driven by parasympathetic nervous system as it increases production of saliva
- Sympathetic nervous system also stimulates secretion of small amounts of saliva and causes vasoconstriction
Describe the neural control of the submandibular and sublingual glands
Submandibular and sublingual glands are supplied by the parasympathetic nervous system through the facial nerve
Describe the neural control of the parotid glands
Parotid glands are supplied by the parasympathetic nervous system through the glossopharyngeal nerve
Which drugs might have dry mouth as a side effect?
Drugs which target muscarinic ACh receptors
Identify and describe the 3 different stages in swallowing
- Oral preparatory phase (voluntary)
- Pharyngeal phase (involuntary)
- Oesophageal phase (involuntary)
What occurs in the oral preparatory phase of swallowing?
- Bolus is pushed towards pharynx
- Once bolus touches pharyngeal wall, the next phase begins
Describe the 5 events which occur in the pharyngeal phase of swallowing
⇒ Soft palate seals off nasopharynx
⇒ Pharyngeal constrictors push bolus down
⇒ Larynx elevates, closed by epiglottis
⇒ Vocal cords adduct
⇒ Upper oesophageal sphincter opens
Why do the vocal cords adduct during the pharyngeal phase?
- Protect airway
- Breathing temporarily ceases
What occurs in the oesophageal phase of swallowing?
- Closure of the upper oesophageal sphincter
- Peristaltic wave carries bolus downwards into oesophagus
If swallowing closes the airway and inhibits breathing, how are long periods of breast feeding possible?
Infants have a higher epiglottis which allows them to breath and swallow simultaneously
Decscribe the neural control of the gag reflex
Mechanoreceptors → Glossopharyngeal nerve → Medulla → Vagus nerve → Pharyngeal constrictors
How does the gag reflex vary with age?
Infants have a more anterior gag reflex
Why does dysphagia occur with a stroke?
Damage to the nerves and muscles which cause a stroke also involve damage to the nerves and muscles which control swallowing
Describe the muscular changes in the oesophagus
- First 1/3: skeletal muscle (voluntary control)
- Middle 1/3: skeletal + smooth muscle
- Last 1/3: smooth muscle (involuntary control)
Identify 4 anatomical mechanisms which prevent gastro-oesophageal reflux
- Lower oesophageal sphincter
- Mucosal ‘rosette’ at cardia
- Acute angle of entry of oesophagus