Anatomy of salivation and swallowing Flashcards
Describe the compostion of saliva
- Mainly water
- Generally hypotonic
- Rich in K+ and Bicarbonate
- pH slightly alkaline
Why does saliva need to be slightly alkaline?
Teeth are made from calcium salts → would dissolve if it were acidic
What is the function of mucins in saliva?
Helps with lubrication
What are the 7 main functions of saliva?
- Speech
- Hydrate food → form food bolus
- Maintain teeth health
- Defence against pathogenic food
- Solvent → releases flavour from food
- Begins Digestion
- Infection transmission
What is Xerostomia?
Dry Mouth
Caused by not enough saliva
What things may cause xerostomia?
- Side effect of drugs → mainly SSRI’s
- Mouth breathing
- Salivary gland surgery
- Radiotherapy
What are some of the consequences of xerostomia?
- Bacterial overgrowth
- Bad Breath
What are the 3 main pairs of salivary glands and where are they located?
- Parotid
- Submandibular
- Sublingual
Which nerves innervate the salivary glands?
- Parotid → Glossopharangeal (CNIX)
- Submandibular → Facial Nerve (CNVII)
- Sublingual → Facial Nerve (CNVII)
How is salivary gland secretion regulated?
- Autonomic NS not hormonal
- Parasympathetic increased saliva production
- Sympathetic stimulates small amounts of saliva but also causes vasoconstriction → dry mouth
What is the underlying pathology of mumps?
Viral infection causing swelling of the parotid gland
Parotid gland surrounded by capsule → no room for swelling makes it very painful
What is parotid sialography?
CT scan of parotid gland using contrast
Identifies areas of blockage
What are the 3 steps involved in swallowing?
- Oral Preparatory Phase
- Pharyngeal Phase
- Oesophageal Phase
Describe the Oral Preparatory Phase of Swallowing
- Oral Preparatory Phase
- voluntary
- pushes bolus of food back towards pharynx
- Bolus touching pharyngeal wall triggers pharyngeal phase
Describe the Pharyngeal Phase of Swallowing
- Pharyngeal Phase v.short
- Involuntary
- Soft palate moves up and seals nasopharynx
- Pharyngeal contrictors push bolus downwards sequentially
- Larynx elevates to close epiglottis
- Vocal cords adduct → breathing temporarily stops
- Upper Oesophageal Sphincter Opens
Describe the Oesophageal phase of Swallowing
- Oesophageal Phase
- Involuntary
- Upper Oesophageal Sphincter closes
- Peristaltic wave pushes bolus down
Why can babies swallow and breathe at the same time?
- short neck means epiglottis sits higher
- epiglottis overlaps the soft palate protecting the airway
- drinking milk goes around the epiglottis
Explain the neural control of the gag reflex
- Mechanoreceptors in pharyngeal wall detect presence of bolus
- Glossopharyngeal nerve sensory to pharynx sends signal to medulla
- Motor nerve to pharynx = Vagus nerve
- Causes pharyngeal constrictions
How does stroke cause dysphagia?
Stroke affects muscles of facial expression and pharyngeal nerves
Uncoordinated response when swallowing
Why would an oesophageal tumour cause dysphagia?
Physical blockage down oesophagus
Eating solid food is diffucult to go around the tumour
Liquids will be ok
There are 4 narrowings of the oesphagus, where are they?
- Narrowing at junction between pharynx and oesophagus
- Where oesophagus crosses arch of aorta
- Where oesophagus compressed by left main bronchus (at a more acute angle than right)
- Oesophageal hiatus (entering diaphragm)
How does the muscular compostion of the oesphagus change along its legnth?
Skeletal muscle at top → transitions to smooth muscle towards bottom
How is Gastro-Oesophageal reflux prevented?
- The diaphragm forms a functional sphincter where the oesophagus enters the stomach
- Acute angle of entry means an ingrease in intra-andominal pressue closes flap valve
