Mouth, pharynx and oesophagus Flashcards
What are the functions of saliva?
Lubricates food for swallowing
Aids taste
Begins digestion
Protects oral environment
What enzymes are in saliva that aid digestion?
Alpha amylase (digestion of starch) Linguinal lipase (digestion of lipids)
What is the composition of saliva?
Hypotonic
Lower osmolarity than plasma
Contains water, mucus, digestive enzymes, antibacterial agents, high concentrations of potassium, bicarbonate and calcium, low concentrations of sodium and chloride
What is the pH of saliva?
6.2-8.0 (dependent on whether it is stimulated or not)
How much saliva is produced per day?
800-1500ml
What are the salivary glands?
- Parotid (serous saliva)
- Sublingual (mucus saliva)
- Submandibular (mixed saliva)
[Nb. Also buccal glands and Von Ebner’s glands on tongue]
What do Von Ebner’s glands produce?
Lingual Lipase
What is the structure of salivary glands?
Appearance like bunch of grapes
Acini (lined by acinar cells) produce initial secretion
Duct cells modify secretions
Myoepithelial cells contract to eject saliva
What happens during saliva production?
Isotonic ultrafiltrate from blood plasma is diffused through acinar cells where it is mixed with enzymes - saliva then drains into ducts
What happens during ductal modification?
Overall net absorption of solute but not water (ductal cells impermeable to water) leaving a hypotonic solution
Why does the composition of saliva differ when stimulated compared to resting?
At rest, saliva flow rate is lower allowing more time for ductal modification
What is Xerostomia?
Dry mouth
What are the key signs and symptoms of Xerostomia?
Burning sensation in mouth Dry throat/ tongue/ lips Difficulty swallowing and speaking Altered taste Halitosis
What are potential causes of Xerostomia?
Medication side effects Dehydration Anxiety Sjogren's Syndrome Radiation therapy
What are the 5 taste classifications?
Sweet Sour Bitter Salty Umami
Where are taste buds found?
Tongue (papillae)
Palate
Larynx
Pharynx
What cells do taste buds contain?
Taste receptor cells
Supporting cells
Basal cells (replace cells sloughed off the tongue)
What type of receptors are taste receptor cells?
Chemoreceptors
What is mastication?
Chewing - breaking up food to increase surface area for enzyme action - creates bolus for swallowing
What muscles are involved in mastication?
Masseter muscles
Temporalis muscles
Medial and lateral pterygoid muscles
Suprahyoid muscles
What are the 4 points of oesophageal narrowing?
- Junction between pharynx and oesophagus
- Crossing with aortic arch
- Where oesophagus is posterior to the left main bronchus
- Oesophageal hiatus in the diaphragm
What kind of sphincter is the LOS?
Physiological
What is the function of the LOS?
Prevents reflux of gastric contents into the oesophagus
What are the components of the LOS that allow it to function normally?
- Right crus of diaphragm
- Acute angle at which oesophagus enters stomach
- Mucosal folds at gastro-oesophageal junction
- Positive intra-abdominal pressure
What are the features of GORD?
Reflux of acidic contents through LOS Heartburn Acid brash Regurgitation Water brash
What is Barrett’s Oesophagus?
Metaplasia of squamous epithelium of oesophagus to columnar mucosa
What does Barrett’s Oesophagus increase likelihood of?
Oesophageal Adenocarcinoma
What are the 3 phases of swallowing?
- Oral phase
- Pharyngeal phase
- Oesophageal phase
What happens during the oral phase of swallowing?
Tongue moves bolus towards oropharynx
Cranial nerves relay information to swallowing centre in medulla
Swallowing reflex initiated
Which phase of swallowing is voluntary?
Oral phase
What happens during the pharyngeal phase of swallowing?
Soft palate elevates and blocks nasopharynx
Upper oesophageal sphincter opens
Food propelled through sphincter into oesophagus
What happens during the oesophageal phase of swallowing?
Upper oesophageal sphincter closes to prevent reflux
Primary peristaltic wave coordinated by swallowing reflex propels food down oesophagus
Lower oesophageal sphincter relaxes
What is achalasia?
Loss of coordination of peristalsis of lower oesophagus and spasm of LOS
What is Achalasia characterised by?
Intermittent dysphagia
Regurgitation
Retrosternal chest pain
What is the sympathetic innervation to the salivary glands?
Superior Cervical Ganglion (part of paravertebral chain)
Nb. Sympathetic stimulation INHIBITS saliva secretion
What is the parasympathetic innervation to the parotid gland?
- Begins with glossopharyngeal (CN IX)
- Glossopharyngeal synapses with Otic Ganglion
- Auriculotemporal nerve carries parasympathetic fibres from Ganglion to parotid gland
Nb. Parasympathetic stimulation INCREASES saliva secretion
What is the parasympathetic innervation to the submandibular gland?
- Originates from superior salivatory nucleus (through pre-synaptic fibres which travel through chorda tympani branch of CN VII)
- Chorda Tympani unifies with Lingual branch of CN Vc
- Synapses at submandibular Ganglion
- Post Ganglionic innervation from secretomotor fibres
What is the parasympathetic innervation to the sublingual gland?
- Originates from superior salivatory nucleus (through pre-synaptic fibres which travel through chorda tympani branch of CN VII)
- Chorda Tympani unifies with Lingual branch of CN Vc
- Synapses at submandibular Ganglion
- Post Ganglionic innervation from secretomotor fibres
What is the clinical term for painful swallowing?
Odynophagia
What problems in the mouth can make swallowing difficult?
Problems with chewing and pushing food back including muscles of mastication, tongue, dental problems or lack of saliva
What problems with the pharynx can make swallowing difficult?
Obstructions (e.g. tonsillitis or malignancy)
What problems with the oesophagus can make swallowing difficult?
External obstruction (e.g. from trachea, thyroid goitre, left atrium) Internal obstruction (e.g. malignancy, foreign body) Oesophagitis (infection or ulcers) Abnormal motility (e.g. achalasia or scleroderma)
What is scleroderma?
Smooth muscle is replaced by fibrous tissue leading to strictures
What problems with the stomach can make swallowing difficult?
Malignancy (esp. in cardia region)
What neuromuscular problems can make swallowing difficult?
Stroke
Neurodegenerative disorders (e.g. MND, MS)
Myasthenia Gravis
Syringobulbia (fluid filled cavities in spinal cord and brainstem)
What signs and symptoms indicate dysphagia?
Coughing/ choking
Gurgling
Shortness of breath/ signs of chest infection (e.g. due to aspiration)
Holding food in mouth/ not chewing
Food/ drink falling out of mouth
Weight loss (e.g. due to being scared to eat)
What is aspiration pneumonia?
LRTI due to inhalation of material from GI tract into respiratory tract
What is progressive dysphagia indicative of?
[Dysphagia initially for more solid foods and then for softer foods as well]
Indicates an obstructive lesion (e.g. benign or malignant strictures, foreign body, oesophageal webs) or an external obstruction (e.g. thoracic aortic aneurysm, retrosternal goitre)
