What is the superior thoracic aperture?
The opening of the thoracic cage, at the neck containing blood vessels and nerves
What is contained in the superior compartment of the mediastinum?
The ascending aorta, the aortic arch, the thymus
What is contained in the posterior compartment of the mediastinum?
the oesophagus and descending aorta
what is the first branch of the aortic arch and what does this supply?
Brachiocephalic trunk - right common carotid and right subclavian artery
What vessels drain into and make up the superior vena cava?
Right and left brachiocephalic vein - which the right and left jugular and subclavian veins drain into
What nerve supplies the diaphragm?
Phrenic Nerve from C3-5
What structures pass through the diaphragm?
Oesophagus and IVC, aorta does not
What is the respiratory epithelium?
Pseudostratified ciliated columnar
What is the role of the conchae?
To humidify air, so it is not too cold and damages the trachea and bronchus
What is the role of the paranasal sinuses?
to lighten skull and voice resonance
Why is the structure of the paranasal sinus flawed?
these drain into the internal nose, however the drainage duct is at the top of the sinus. Therefore, the infection or tumour has to grow all the way to the top before it is drained and the symptoms are seen
What is the name given to the abnormal connection of the epithelium between the oral mucosa and the paranasal sinus?
what is the only cartilage at the larynx that is a complete ring?
what is the connection between cricoid cartilage and thyroid cartilage and how can this be useful clinically?
crico-thyroid ligament, if airway blocked (food, chocking at thyroid) membrane can be pierced and a tube inserted through here to provide an airway
Where does the trachea begin?
at c6, after the cricoid cartilage
what muscle is associated with the trachea and where is this situated?
trachealis, lies at the posterior trachea, no cartilage here
why is the right bronchus more susceptible to pneumonia?
it is more vertical from the bronchus, so anything swallowed, e.g. foreign objects, are more likely to end here
when is a tracheostomy used?
in terminally ill patients that require mechanical ventilation
What is the pressure of oxygen in the alveolar sacs?
What are the differences between quiet breathing and strenuous breathing?
Diaphragm is contracted more in strenuous - only 1cm in quiet, 10cm in strenuous
Accessory respiratory muscle required in strenuous inhalation - sternocleidomastoid e.g.
Exhalation is active during strenuous breathing, abdominal muscles and internal intercostal muscles required. In quiet breathing, it is passive - elastic recoil
What is the transpulmonary pressure in the lungs and what does this cause in breathing?
transpulmonary pressure is the difference between alveolar pressure and the pleural pressure. In inhalation, alveolar pressure is equal to the atmospheric pressure, but the pleural pressure decreases even further as the diaphragm contracts, increasing the transpulmonary pressure which causes the lungs to expand
What pulls air into the lungs?
The pressure difference, as the volume increases in the thorax with the diaphragm and external intercostal contracting, the pressure decreases, so air flows from a high pressure outside to a low pressure inside the lungs
What drives exhalation of air, in terms of pressure difference?
As the diaphragm stops contracting, air flows in to the lungs, the alveolar pressure is equal to the barometric pressure. The lungs then elastic recoil, and the pleural and transpulmonary pressure return to normal. The air is then compressed in the alveoli, the pressure here is larger than the pressure in the barometric pressure and air flows out of the lungs.
What is the functional residual volume?
The volume of air left in the lungs after exhalation
What forces are acting on the FRV?
elastic recoil of the lungs is forcing the air out of the lungs, the recoil of the chest wall is retaining air in the lungs - these are equal and cancel one another out so the air is kept in the lungs
What is the anatomical dead space in the lungs?
The conducting airways, bronchus containing cartilage and non-respiratory bronchioles, don’t participate in gas exchange, but 30% of the air in each breath stays here
How can the volume of air increase during exercise?
during exercise, more muscles contracting, increasing the pressure changes so recruits more capillaries and alveolar sacs, not normally used in quiet breathing
What is the pressure of gases in the pulmonary artery?
O2 - 40mmHg CO2 - 45mmHg
What is the pressure of gases in the alveolar sac?
O2 - 100mmHg CO2 - 40mmHg
What is the pressure of gases in the pulmonary vein?
O2 - 100mmHg CO2 - 40mmHg
Describe how exercise can alter the oxyhaemoglobin saturation.
During exercise, pH decreases due to lactic acid formation. At low pH, for the same given PO2, haemoglobin saturation is reduced. Also, the core temperature increases during exercise. At higher temperatures, for a given PO2, the haemoglobin saturation is also reduced.
Below which partial pressure of O2 is a big reduction seen in haemoglobin saturation.
What is the main way in which CO2 is transported around the body?
In bicarbonate - CO2 + H2O gives carbonic acid, bicarbonate can be formed
Define the respiratory exchange ratio.
The number of molecules of CO2 expired to the number of molecules of O2 uptake, normally 0.8
What are chemoreceptors and where are they located?
Receptors that detect levels of PO2, PCO2 and pH in the blood. Peripheral receptors are located in the aortic arch and carotid sinus, these respond to decrease in PO2 - hypoxia. Central chemoreceptors are located at the brainstem and detect increase in PCO2 or decrease in pH
What is different in the functioning of the central and peripheral chemoreceptors?
Central are very sensitive, a small increase in PCO2 results in a change in ventilation. Whereas, peripheral receptors don’t alter ventilation until PO2 drops below 60mmHg
What do mechanoreceptors detect in the lungs?
A stretch in the lungs, the alveolar epithelium or respiratory epithelium
How do mechanoreceptors control breathing?
When stretch on epithelium detected, signal to NTS to stop inhalation and stop respiratory muscles contracting
When do mechanoreceptors and chemoreceptors send their signals to?
The nucleus tractus solitarius, in the dorsal respiratory group at the medulla in the brainstem
What controls normal, quiet breathing?
The central pattern generator, the ventral respiratory group in the brainstem. Produces a constant signal to the respiratory muscles via inhalation neurones or exhalation neurones, even if removed from body, signal is constant
How can the CPG be modified to alter ventilation?
The NTS (receiving signals from chemo and mechanoreceptors) can send signals to the NTS, to tell it to change the firing to respiratory muscles. Can also receive input from the pontine respiratory group for volitional control of breathing
Describe how ventilation is distributed throughout the lungs.
At the apex of lungs, due to gravity, pleural pressure is more negative resulting in a larger transpulmonary pressure. This causes the alveolar sacs to be more distended, therefore the change in volume of the sacs is much less, pressure difference is reduced so less air is drawn in here
How can compliance change the ventilation
If the alveoli are less compliant, cannot stretch as much so cannot take in a high volume of air. Less air - less gas exchange
How can resistance alter the ventiliation
A blockage or narrowing of airways results in a higher resistance, so it takes longer for air to flow in to alveoli. Although the same volume can be reached, there is not enough time in a breath to allow it, so less air taken in and less gas exchange
What is physiological dead space?
The alveolar capillaries that are ventilated but not perfused
Describe the distribution of blood flow through the lungs
The apex of the lungs have a much lower blood flow than the base of the lungs due to gravity and pressure difference
How does the V/Q relationship differ throughout the lungs?
At apex - lower perfusion to ventilation, so blood comes out saturated with oxygen, high VQ ratio
At base - perfusion much higher but ventilation not increased as much, blood is less saturated and VQ ratio lower - these balance out to give overall 0.8 ratio
Describe an antaomical shunt in regards to ventilation
When blood is being shunted from right to left to avoid it from being oxygenated. Results in deoxygenated blood mixing with oxygenated blood. Patent foramen ovale - mixing of blood from right atria to left atria
describe a disease that has a low VQ ratio
low VQ ratio occurs when ventilation is blocked but perfusion is maintained. Bronchitis is where mucous is produced in the airways, blocking the air coming in so ventilation is decrease
describe a disease that has a high VQ ratio
high VQ when ventilation is maintained but blood flow through alveoli is poor. Emphysema - the alveolar sacs are inflammed, damage the capillaries so flow is poor despite good ventilation. exhalation is difficult as lungs have lost elastic ability
where does the apex of the lung lie
1 inch above the medial 3rd of the clavicle
what forms the pulmonary ligament
a double folding of pleura