lecture 2.1 - anatomy of salivation & swallowing Flashcards
what is saliva rich in? pH?
potassium and bicarbonate (pH slightly acidic, ~ 8)
how is saliva like pre-modification?
acidic, modified through ducts of salivary glands
what helps with lubrication?
mucins (glycoprotein component of mucous)
what is an important component secreted by salivary glands?
amylase
what is secreted by lingual glands (tongue)?
ligual lipase - start digestion of fat in mouth
what does saliva contain aside from enzymes and amylase)?
a diversity of immune proteins (e.g. IgA, lysozyme, lactoferrin)
mouth = first point of entry to GI tract, so need protection
what is the function of lactoferrin?
bactericidal and iron-binding properties
bacteria require iron to reproduce, lactoferrin holds onto the iron, preventing bacteria from obtaining it
what are the functions of saliva?
- lubricate oral structures
- lubricate & moistening food (hydrate making it pliable)
- kills things swallowed form nasal cavity (bactericidal)
- oral hygiene (teeth prone to attack from bacteria & acids in food)
- antibacterial effect - prevent bacteria enter stomach (also stomach acid)
- initiates digestive process - salivary amylase
- a solvent to help us taste food
what is xerostomia?
dry mouth condition
how does xerostomia present?
- sore inflamed tongue,
- looks dry (not shiny & reflective),
- sore lips (as we use tongue to moisten lips), difficulty eating,
- detrimented dental care (no actibacterial effects of saliva or ionic composition (Ca2+ etc.),
- can’t taste (saliva = solvent for taste) - although can taste slightly as they can still breathe
- if have false teeth, will fall out as saliva helps form seal
what are causes of xerostomia?
- cold - nose bung up, so breathe through mouth when sleeping
- dry mouth medications e.g. antidepressants
what are the salivary glands in our mouths?
3 pairs:
- parotid
- sublingual
- submandibular
what are the regulations of the salivary glands?
- neural (nerves) ANS, doesn’t really have hormones
- parasympathetic is main driver (increase saliva production) - rest & digest
- sympathetic also stimulates secretion of small amounts of saliva, but causes vasoconstriction
which nerve supplies the parotid glands?
9th cranial nerve (glossopharyngeal nerve)
which nerve supplies the sublingual and submandibular glands?
7th facial nerve - chorda tympani
where does the chorda tympani run?
runs through the middle ear
what is a clinical significance of chorda tympani running through middle ear?
if there is ear infection in the middle ear causing damage to chorda tympani, can loose parasympathetic to submandibular and sublingual glands, leading to dry mouth
where does the duct of the parotid gland penetrate?
penetrates buccinator, opposite crown of 2nd upper molar tooth
how is the sublingual gland like? where is it?
above floor of mouth, with lots of little ducts coming out directly under tongue
where is the submandibular gland and how does it secrete?
sits below floor of mouth
1 single big duct comes out over the tongue - 1 superficial to the floor of the mouth and 1 deep to it
if a child has been infected with mumps, which facial structure will be affected?
inflammation of the parotid gland (parotiditis) causing swelling on lateral face
what happens in parotiditis?
facial sheathe of parotid gland is not very distensible (don’t want baggy capsule as you want any saliva produced to be pushed out of the duct system)
so very painful as there is nowhere for the parotid gland to swell (tight capsule)
what is sialography?
radiographic examination of the salivary glands. It usually involves the injection of a small amount of contrast medium into the salivary duct of a single gland, followed by routine X-ray projections
how is parotid sialography carried out?
catheter inserted into parotid duct via flap in cheek, insert contrast medium (reverse direction of salivary release), which fills up parotid gland to show up any e.g. narrowing (where medium can’t go past) or tumour present
what happens in the oral preparatory phase (0-7.4 seconds) like?
voluntary
pushes bolus towards pharynx
once bolus touches pharyngeal wall, pharygeal phase begins
what happens in the pharyngeal phase (7.4-7.6 seconds)?
involuntary
soft palate seals off nasopharynx
pharyngeal constrictors push bolus downwards
larynx elevates, (to meet epiglottis) closing epiglottis (shuts off glottis)
vocal cords adduct (protecting airway) & breathing temporarily ceases
opening of upper oesophageal sphincter - enter oesophagus
what is the nasopharynx?
upper part of the pharynx, connecting with the nasal cavity - seal off during swallowing to prevent aspiration
what happens in the oesophageal phase? (~7.6-9secs)
involuntary
closure of the upper oesophageal sphincter (so food doesn’t travel back up during peristaltic wave)
peristaltic wave carries bolus downwards into oesophagus
why does upper oesophageal sphincter open?
to allow food down the oesophagus to stomach
how does soft palate seal off nasopharynx?
soft palate flows up and back to seal off nasal cavity - forms flap
how is bolus pushed down oesophagus initially (prior to peristaltic wave)?
pharyngeal constrict to push bolus down towards oesophagus
how does bolus leave mouth to enter GI?
convulsion wave over the tongue pushes bolus over the throat (voluntary phase - decide when bolus pushed into pharynx)
once bolus is pushed into pharynx, it enters involuntary phase of swallowing reflux (afferent to brain stem) - receptors on oropharynx
how does epiglottis and larynx close off airways?
epiglottis closes off airways whilst larynx lifts up to close off airway
larynx also ADduct to close off airway (glottis opening)
what does opening of lower oesophageal sphincter in the final stage allow?
sphincter and bolus to enter the stomach
why do babies have wide noses?
to allow them to breathe sideways when sucking breast (face squished against breast nearly completely)
how can babies eat and breathe at the same time?
epiglottis extends up to nasopharynx in babies (no need to flap around - covers entirely), so when babies are drinking, they can breathe and drink at the same time - air goes in and out uninterrupted passageway
drink - via soft palette (no need to flow up and back to seal off nasal cavity)
what is the mechanism of the gag reflex?
mechanoreceptors –> glossopharyngeal nerve –> medulla –> vagus nerve –> pharyngeal constrictors
how does swallowing compare to gagging?
both reflexes are the same
BUT gag did not have voluntary movement of tongue to set it off
what do the mechanoreceptors detect?
presence of bolus
what is the function of the glossopharyngeal nerve in gag reflex?
carry sensory information form the pharyngeal wall to the medulla
which part of the medulla is the information from the glossopharyngeal nerve sent to?
lowermost part of the medulla
what is the function of the vagus nerve in gag reflex?
(motor nerve to pharynx), to move pharyngeal constrictors - to allow for swallowing reflex
what type of gag reflex do babies have?
hyperactive gag reflex
what does hyperactive gag reflex in babies mean anatomically?
their gag reflex sits more anteriorly - stimulate front of mouth as they don’t have a properly functioning swallow function yet, which is why they spit anything out apart from a nipple - baby not ready for solids yet
dysphagia following stroke
stroke might affect swallowing as part of the brain supplying face has been affected, so give patient IV fluids as he is not safe to drink (can aspirate fluids) causing pneumonia, thickened fluids during rehabilitation to help patient swallow better
dysphagia - tumour
tumour of oesophagus means difficulty swallowing solid bolus, but liquids are ok - held up by tumour
where is the oesophagus situated?
relatively midline behind trachea
what are the areas of narrowing within the oesophagus?
- junction with the pharynx - upper oesophageal sphincter
- where it crosses the aortic arch
- left main bronchus
- where it passes the diaphragm (around lower oesophageal sphincter)
what is the significance of the narrowing within the oesophagus?
foreign bodies are more likely to lodge at these levels
which type of muscle dominates each 1/3 of the oesophagus?
upper: skeletal straited - voluntary
middle - half skeletal straiter, half smooth
bottom: smooth (involuntary)
what features are there to prevent gastro-oesophageal reflux?
- functional sphincter formed from smooth muscle of distal oesophagus (lower oesophageal sphincter)
- diaphragm (narrowing - oesophageal hiatus)
- intra-abdo oesophagus (lumen) gets compressed when intra-abdo pressure rises
- mucosal ‘rosette’ at cardia
- acute angle of entry of oesophagus
how does the diaphragm prevent gastro-oesophageal reflux?
tone in diaphragm muscle squashes oesophagus - act as functional valve to prevent reflux
(when pressure in stomach increases, will push valve and close it to prevent content from pushing up into oesophagus)
what are mucosal ‘rosette’ at cardia of stomach?
folds of gastric mucosa present in the gastro-oesophageal junction
(longitudinal folds of cardia of stomach pocket together to act as anti reflux mechanism)
