The Upper Respiratory Tract Flashcards
Why is the upper respiratory tract important
Often get infections here (rhinitis, laryngitis, bronchitis)
Generally less severe than lower resp tract where infections here can kill (pneumonia :( )
Describe the structure of the nasal cavities
What is the function of the nasal cavity and the structures inside
Ant nares => Vestibule with vibrisae => Nasal cavity => Post nares
Warms the air
Keeps it moist, both ensure that the moisture in the lungs is 100% saturated with O2
Vibrisae, filters inspired air
Describe the general structure of the whole pharynx
Muscular tube made up of nasal pharynx, oropharynx and hypopharynx
Where can the nasal pharynx be found
Extends from the base of the skull to the upper surface of the soft palate
Opening of auditory tube found here
Where can the oral pharynx be found
Between the soft a palate and superior border of the epiglottis
Where can the hypopharynx be found
Where the pharynx splits into the larynx and oesophagus
Describe the structure and function of the larynx
Made up of hyaline and elastic cartilage
Predominantly a sphincter for the airway, prevent food and fluids entering the lungs
Voice box also found here but not its main role
What is the function of the oesophagus
Food and fluids enter here => GBS
Describe the structure and function of the trachea
20C shaped cartilage rings, keeps airway open
Leads to carina (bifurcation of trachea => 2 bronchi at T4)
How does the bronchus divide and what changes as a result?
Pulmonary bronchus => Lobar bronchus => Segmentary bronchus => etc
23 divisions in total
As you divide, amount of hyaline cartilage decreases, amount of smooth muscle increases, amount of connective tissue increases
Epithelium transitions from ciliates pseudostratified columnar => simple squamous
Start to lose smooth muscle and connective tissue as you approach alveoli, site of gas exchange
Describe the pulmonary circulation (pulmonary arteries, veins, bronchial arteries and veins)
Pulmonary arteries branch along bronchiole very closely
Forms a plexus around alveoli with pulmonary vein capillaries
O2 in solution diffuses across 2nm
Pulmonary vein normally further away from bronchioles
Alveoli don’t need a blood supply, get their O2 from diffusion
Thoracic aorta => bronchial arteries => veins => pulmonary veins, azygos
What are the protective mechanisms of the upper respiratory tract
Mechanical (mucus and hairs) Goblet cells and serous glands Mucociliary escalator and cilia Macrophages WBCs Mast cells and histamine release
How does mechanical protection (mucus and hairs) protect the URT
Moistens air and traps pathogens
How do the goblet cells and serous glands protect the URT
Watery submucosal antibacteriocidal secretions
How does the mucociliary escalator and cilia protect the URT
On top of pseudocolumnar cells, wafts mucus up to oesophagus => stomach from bronchi
How do macrophages help protect the URT
How do WBCs help protect the URT
How do mast cells help protect the URT
Digests unwanted pathogens, travel up to pharynx to dispose of them
Aids in immune response
Mast cells release histamine, decreases lumen in airway, prevent pathogens from entering the lumen
Describe how airflow is directed from the nasal cavity to the nasopharynx
Upper, middle and lower conchae directs air flow to post nares
Warm because heat from blood vessels is close enough to the wall
Describe the 5 ways that ventilation is controlled
Peripheral and central chemoreceptors Proprioception Irritant/C receptors Stretch receptors Hypothalamus (pain, emotion)
How do peripheral and central chemoreceptors change ventilation
+ve
Conc of gases in blood (PO2, PCO2) altered by increased ventilation rate
How does proprioception change the rate of ventilation
+ve
When muscles move more, increased O2 needed
Ventilation rate increased
How do irritant/C receptors change the rate of ventilation
-ve
Causes a change in breathing pattern, reduces ventilation rate to remove source
How do stretch receptors change ventilation
-ve
Tells you when to stop inspiring and start expiring
How does the hypothalamus alter the rate of ventilation
+-ve
Pain and emotion affects the way we breathe
What controls our afferent responses to ventilation?
Pons/respiratory centres of medulla oblongata
How does the cough reflex change as the irritation goes down the resp tract
If irritation in upper tract, violent reaction
If irritation in lower tract, less of a reaction
What receptors trigger the cough reflex
Rapidly adapting irritant receptors
Non myelinated C fibres
What afferent reflexes are triggered as a result of the afferent receptors being triggered
Bronchial submucosal glands produce more mucus to trap irritation
What nerve do the sensory afferents go up in the cough reflex
Ipsilateral vagus
Where is the cough center
Integration of afferent fibres in medulla, separate to breathing centres
What are the efferent nerves in the cough reflex and what do they trigger
Via phrenic and other somatic nerves, stimulates breath and sudden chest wall mv
Recurrent laryngeal vagal efferents to bronchial tree
What muscles are effected by the nervous efferents from the cough center
Expiration muscles
Larynx
Trachealis
Bronchial SM
What can stimulate the cough reflex
Sinusitis Asthma Laryngotracheatis Tuberculosis Emphysema Foreign body
Describe the structures in the larynx
Larynx, behind the tongue
Oesophagus, most posterior
Aryepiglottic fold surrounds epiglottis
False/vestibular fold => true vocal fold => glottis
Arytenoid cartilage found at the bottom of the aryepiglottic fold
What structures are found in the aryepiglottic folds and what is the function
Aryepiglottic muscles found in aryepiglottic folds, acts as sphincter of airway, prevents foods from going down lung
How can the glottis be altered
Glottis diameter can be altered by rotation of artenoid cartilage => abduction and addiction of the vocal folds
How do the different positions of the glottis affect the possible range of functions
When arytenoid cartilages adduct => vocal folds come together => glottis closed
For swallowing food, prevent food from falling into lung
Arytenoid cartilage rotated => vocal folds separate => glottis open
For breathing
Arytenoid cartilage rotated and abducted => vocal folds separate => glottis really open
For deep breathing
Arytenoid cartilage abducted only, no rotation => vocal folds closed => glottis open
For whispering
Describe the structure of the larynx
Hyoid bone
Thyrohyoid membrane between hyoid and thyroid cartilage. Membrane has opening for vagus to enter
Thyroid cartilage
Muscles between thyroid and cricoid cartilage
Cricothyroid membrane
Trachea
How is the cricoid cartilage different from the tracheal cartilage
Cricoid, complete cartilage ring, thicker at the back
Tracheal, C shaped cartilage rig
Where are the false folds, laryngeal ventricles and true folds in relation to the larynx in a coronal section
All at level of thyroid cartilage
False fold
Laryngeal ventricle
True fold
How to do an emergency laryngotomy and what to watch out for
Target cricothyroid membrane
However, some people have a pyramidal 3rd thyroid lobe covering this membrane, don’t puncture the artery here
If they do have a 3rd lobe, move it out of the way before puncturing membrane
When would you do a tracheotomy and why
Opening made in trachea in surgery
Keep the airways open
What nerves innervate the larynx
From inf vagal ganglion => sup laryngeal
Sup laryngeal branches into int and ext laryngeal
Inf vagal ganglion => L vagus => L recurrent laryngeal
Inf vagal ganglion => R vagus => R recurrent laryngeal
What is innervated by the int laryngeal
Thyrohyoid membrane => sensory above vocal folds
What is innervated by the ext laryngeal
Cricothyroid muscle
Describe the route of the L vagus
What does it innervate
L vagus => through superior thoracic aperture => chest => branch comes off the bottom and passes up groove between trachea and oesophagus (L recurrent laryngeal)
Sensory to lower half of larynx, below vocal folds and supply muscles
Describe the route of the R vagus
Describe the innervations of the R vagus
From inf vagal ganglion => passes in front of and behind R subclavian artery => larynx
Supplies trachea and oesophagus on route
Sensory to lower half of larynx, below vocal folds to supply muscles
Describe the relative structures of the R and L bronchi and the importance of this
R bronchi = straighter and wider than L
Foreign objects more likely to fall down into R
What is the level of the cricoid cartilage and the carina
Cricoid C6
Carina T4-5
Describe the structure of a cross section of the trachea
Function of each section
C shaped cartilage
Submucus glands
Trachealis muscle between cartilage and oesophagus
Trachealis muscle innervated by PNS vagus
Submucus gland release mucus for protection
