Respiratory Physiology- Intro Flashcards
Steps of External Respiration
Ventilation
Gas exchange between alveoli and blood
Gas transport in blood
Gas exchange at tissue level
Systems involved in external respiration
Respiratory
Cardiovascular
Haematology
Nervous
Ventilation
Mechanical process of gas being moved in and out of lungs
Gas exchange between alveoli and blood
Exchange of O2 and CO2 between air in alveoli and blood in pulmonary capillaries
Gas transport
Binding and movement of O2 and CO2 in circulating blood
Gas exchange at tissue level
Exchange of O2 and CO2 between blood in systemic capillaries and body cells
Boyle’s Law
Pressure exerted by a gas is inversely proportional to the volume of gas at any constant temperature
Two forces which hold thoracic wall and lungs in close opposition
Intrapleural fluid cohesiveness
Negative Intrapleural pressure
Intrapleural fluid cohesiveness
Water molecules in intrapleural fluid resist pulling apart, causing pleural membranes to stick together
Negative intrapleural pressure
A transmural pressure gradient is created across the lung wall and chest wall by the sub atmospheric inreapleural pressure. therefore lungs are forced to expand and chest to squeeze in
Important pressures in ventilation
Atmospheric
Intra-alveolar/ intrapulmonary
Intrapleural/ intrathoracic
Atmospheric pressure
Pressure caused by weight of gas in the atmosphere on the Earth’s surface
Average: 760mmHg/ 101kPa
Intra-alveolar pressure
Pressure in the lung alveoli
760mmHg when equilibrated with atmospheric pressure
Intrapleural
Pressure exerted outside lungs within the pleural cavity
Usually less than atmospheric pressure
Inspiration
Active process caused by constriction of inspiratory muscles
Why does intralveolar pressure fall during inspiration?
Lungs inflate, causing size to increase and pressure to fall
*Boyle’s Law
Expiration
Passive process (in normal circumstances) caused by relaxation of inspiratory muscles
Types of pneumothorax
Spontaneous
Traumatic
Iatrogenic
Why does a pneumothorax cause lung to collapse?
The transmural pressure gradient is abolished as air from outside or from lungs enter the pleural space
Signs and symptoms of a pneumothorax
Signs:
hyperressonant percussion
decreased/ no breath sounds
Symptoms:
SOB
chest pain
What causes lungs to recoil during expiration?
Elastic connective tissue in lungs
Alveolar surface tension (more significant)
Alveolar surface tension
A foster is produced (due to attraction between water molecules at liquid-air interface) which resists lung stretching
If alveoli were only lined with water, the surface tension would be too high and they would collapse
LaPlace’s Law
P=2T/r P= inward directed collapsing pressure T= surface tension r= radius of alveoli/bubble smaller r=higher tendency to collapse
Pulmonary surfactant
Mix of lipids and proteins which type 2 alveoli produce
Lowers alveoli surface tension by dispersing themselves between water molecules
Why are premature babies prone to developing RDS?
developing foetal lungs do not make pulmonary surfactant until late pregnancy
Alveolar interdependance
Surrounding alveoli will start to stretch and recoil if an alveolus starts to collapse. Therefore expanding forces are exerted on collapsing alveolus
