Overview of the respiratory system Flashcards
What is meant by internal respiration?
The mechanisms of O2 consumption and CO2 production by cells
What is meant by external respiration?
The sequence of events that leads to the exchange of O2 and CO2 between cells and the outside environment
What are the 4 steps of external respiration?
Ventilation
Exchange of O2 and CO2 in alveoli
Transport of O2 and CO2 in blood
Exchange of O2 and CO2 between blood and tissue
What is meant by ventilation?
The mechanical process of moving air between the atmosphere and the alveolar sacs
What forces keep the alveoli open?
Transmural pressure gradient
Pulmonary surfactant (Reduced surface tension)
Alveolar interdependance
What forces promote alveolar collapse?
Elastic recoil of lungs and chest wall
Alveolar surface tension
How do the lungs adhere to the chest wall?
Transmural pressure gradient, as the sub-atmospheric, inter-pleural pressure creates a pressure gradient across the lung wall and chest wall
Interpleural fluid molecules adhere to each other, meaning the pleural membranes stick together
What is meant by intrapleural or intrathoracic pressure?
Pressure in the pleural cavity
What is meant by intrapulmonary pressure?
Pressure in the lungs
How do you convert from mmHg to kPa?
mmHg ÷ 7.5 = kPa
What is pneumothorax?
Air in the pleural space
How does pneumothorax cause problems?
It can abolish the transmural pressure gradient, meaning that the pressure in the pleural cavity is no longer lower than that of the lungs, so the lungs can collapse
What are some symptoms of pneumothorax?
Shortness of breath
Chest pain
What are some of the physical signs of pneumothorax?
Hyper-resonant percussion note
Decreased breath sounds
What are the main causes pneumothorax?
Spontaneous
Iatrogenic
Traumatic
What is Boyle’s law?
At any constant temperature, the pressure exerted by a gas varies inversely with the volume of the gas
What occurs during inspiration?
the thorax and lungs expand due to contraction of inspiratory muscles (Diaphragm and external intercostal muscles)
This increases intra-thoracic and intra-alveolar pressure as volume increases
This creates a pressure gradient into the lungs
What occurs during expiration?
The wall and stretched lungs recoil to return to original size
This causes idntraalveolar pressure to rise as volume decreases
The air then moves out of the lungs, down a pressure gradient
What is surfactant and what is its purpose?
It is a phospholipid and protein rich substance with a much lower surface tension than water, decreasing adhesion and so allowing alveoli to open
Which law determines that the smaller the alveoli, the higher its tendency to collapse?
LaPlace’s law
What occurs in respiratory distress syndrome of the newborn?
Developing foetal lungs are unable to synthesise surfactant until later on in pregnancy, so premature babies may not have enough
This means the baby must make strenuous effort to overcome the high surface tension in the lungs
What is meant by alveolar interdependence?
If an alveolus starts to collapse, it stretches the surrounding alveoli, which recoil and open the collapsing alveolus
