Week 1 - the upper respiratory tract (URT) Flashcards
where is the URT?
the part of the respiratory tract which lies above the lower border of the cricoid cartilage (forms lower border of larynx)
what does the URT comprise of?
nose & paranasal sinuses
pharynx
larynx
what are the respiratory functions of the URT?
- conducting air from atmosphere to lower respiratory tract
- conditioning inspired air (warming, humidification and trapping of particles)
- protection of airway during swallowing (larynx)
what are other functions of the URT?
swallowing (oropharynx & larynopharynx)
smell (orfactory epithelium in nose)
speech (larynx)
what does the nose consist of?
external nose (bone & cartilage) nasal cavity (right & left)
what is the left & right nasal cavities divided by?
median nasal septum
where does each nasal cavity extend from?
nostril (anterior nares) to posterior nares
what is the function of the posterior nares?
nasal cavity communicates with nasopharynx (behind posterior nares)
what does the lateral wall of each nasal cavity contain?
3 bony projections (conchae / turbinates):
superior, middle, inferior
what is the space below each turbinate known as?
meatus:
superior, middle, inferior
what opens into the meatuses?
paranasal sinuses & naso lacrimal duct (drain tears from eyes)
what does the floor of the nasal cavity form?
roof of the mouth:
hard & soft palates
how many the paranasal sinuses are there and what are they?
4 paranasal sinuses:
frontal, ethmoidal, maxillary, spheroidal
(named from the skull bones within which they are situated)
what are paranasal sinuses?
they are air containing cavities in the skull which open into the nasal cavity
what are paranasal sinuses lined by?
respiratory epithelium (psuedostratified columnar)
what is the structure of the nose adapted to do?
filtering, warming & humidification of inspired air
how is filtering, warming & humidification of inspired air achieved by the nose>
the vascular mucosa (blood - warm air), and large surface area presented by conchae
what do the paranasal sinuses contribute to in terms of function of the nose?
the paranasal sinuses also contribute to warming and humidification of inhaled air
what is each nostril lined with?
coarse hairs trap large particles in inhaled air
what do the conchae do?
- they increase the SA for warming & humidification
2. cause turbulence (hence slow down airflow), increasing the time avaliable for warming & humidifying
what is air heated to in the nose?
approximately body temperature
how is the humidification achieved?
by transudation of fluid through the epithelium and to a lesser extent by mucus secretion
what is mucus secreted by? function?
mucus secreted by goblet cells - traps almost all particles >5 micrometers
what happens to the mucus containing trapped particles >5mm?
the cilia waft the mucus to oropharynx where it is swallowed
what happens when nose breathing becomes impossible?
the lower air passages will dry out & become more vulnerable to infection if nose breathing is impossible
what is the mechanism of bronchoconstriction which occurs when asthmatics exercise?
mouth breathing during exercise with consequent drying and cooling of the bronchial mucous membranes
where can infections of the URT involving the nasal cavity (e.g. common cold) spread to involve?
- paranasal sinuses (via openings of the sinuses)
- pharynx & larynx (continous)
- middle ear (eustachian tube)
- eye (naso lacrimal duct)
what does the pharynx consist of?
3 parts:
nasopharynx
oropharynx
laryngopharynx
where is the nasopharynx?
lies behind the nose
the part of the pharynx above the level of the soft palate
where is the oropharynx?
lies behind the mouth
the part of the pharynx between the soft palate & tip of epiglottis
where is the laryngopharynx?
lies behind the larynx
the part of the pharynx between the tip of the epiglottis and the lower border of the cricoid cartilage
what has common passage through parts of the pharynx? what does this mean?
air and food
therefore, mechanisms to prevent aspiration (inhalation) of food particles during swallowing are in place
what does failure of mechanisms preventing aspiration mean?
cause aspiration, leading to potentially life threatening airway obstruction and or infection (aspiration pneumonia)
what is the nasopharynx connected to the middle ear cavity via?
eustachian tube (auditory tube)
what does the eustachian tube connecting the nasopharynx to middle ear allow?
allows the air pressure in the middle ear cavity to be equalised to atmospheric pressure
clinical: middle ear infection (acute otitis media) - how does it occur? what age group?
upper respiratory tract infections can spread into middle ear cavity via auditory tube - results in middle ear infection
more likely in children than adults
what does the larynx link?
the pharynx to the trachea
what makes up the larynx?
a cartilaginous skeleton made up by 3 unpaired cartilage (epiglottis, thyroid cartilage & cricoid cartilage)
what are the 5 cartilages of the larynx linked by?
ligaments and muscles
what does the larynx contain?
vocal cords which guard the entrance to the trachea
what are the vocal cords also known as?
vocal folds or vocal ligaments
what is glottis?
the vocal cords + the aperture (opening) between the cords
what is the rima glottides?
the aperture between the 2 vocal cords
what is adduction of the vocal cords? what does it result in? when? what is it referred to as?
movement of the vocal cords towards the midline resulting in closing of the aperture e.g. during swallowing
closure of the glottis
what is abduction of the vocal cords? results in?
movement of the vocal cords away from the midline, resulting in opening of the aperture (opening of the glottis)
when are vocal cords abducted?
during respiration, allowing free movement of air through the open aperture
when are vocal cords partially abducted? what is produced?
during speech (phonation) sound is produced by the vibration of the vocal cords due to passage of air through the narrowed aperture
when are vocal cords adducted? why?
during swallowing, preventing inhalation of food
happens involuntarily and is coordinated by the brain
when are vocal cords adducted voluntarily?
during straining
what are the vocal cords movement due to?
the action of the intrinsic laryngeal muscles (NOT extrinsic laryngeal muscles)
what do extrinsic laryngeal muscles move?
entire larynx but NOT vocal cords
which nerve supplies all intrinsic muscles? except?
recurrent laryngeal nerve supplies all intrinsic muscle (except the cricothryroid muscle)
which recurrent laryngeal nerve has a long course?
the left side, part of which is inside the thoracic cavity
what can result in a horse voice? why?
intra thoracic disease compressing / infiltrating the nerve can result in a horse voice - from paralysis of the left vocal cord
what do the vocal cords act as?
sphincter protecting the entrance to the trachea
aside from the vocal cords adducting during swallowing, what else is in place to prevent aspiration of food /liquid during swallowing into the respiratory tract?
- narrowing of the laryngeal inlet
2. epiglottis folds downwards (like a lid) over the laryngeal inlet, preventing food from entering the laryngeal inlet
what happens in cough reflex?
the ability to close vocal cords is necessary to build up intra thoracic pressure during the early part of the cough reflex
the sudden opening of the vocal cords (cough) causes air to be expelled at high velocity
what is the cough reflex useful for?
protective mechanism to expel inhaled particles and also as a clearance mechanism for disposing of excessive secretions from the airways
how can laryngeal disease be presented?
as airway obstruction & difficulty in breathing
what can voice change be the first sign of?
serious intra-thoracic disease, due to involvement of left recurrent laryngeal nerve in the thorax
what are causes of upper airway obstruction?
narrowing of the larynx (glottis) due to:
- laryngeal tumours / vocal cord tumours
- laryngeal oedema (swelling of the mucosal lining of the larynx) due to allergic reactions (e.g. anaphylaxis) or severe infections e.g. croup or acute epiglottis
- bilateral vocal cord paralysis
obstruction of pharynx - airway of an unconscious person - how does it occur?
an unconscious person lying on his back may be obstructed by the tongue falling backwards to obstruct the oropharynx - put in recovery position
also allows secretions in mouth to drain out of mouth (rather than aspire into lungs)
what is sleep apnoea syndrome?
loss of tone in the pharyngeal muscles during sleep causes them to become floppy an obstruct the airways during sleep
