Physiology 1 Flashcards
What is meant by “internal respiration?”
The intracellular mechanisms, which consume oxygen and produce carbon dioxide.
What is meant by “external respiration?”
The sequence of events that lead to exchange of oxygen and carbon dioxide between the external atmosphere and the body cells.
What are the four steps of external respiration?
- Ventilation
- Exchange of O2 and CO2 between air in the alveoli and blood
- Transport
- Exchange of O2 and CO2 between blood and tissues
What is meant by ventilation?
The process of moving gas in and out of the lungs
Which three body systems are involved with external respiration?
- Respiratory
- Cardiovascular
- Haematological
What does Boyle’s law state?
At any constant temperature the pressure exerted by a gas varies inversely with the volume of a gas
i.e. as volume increases pressure decreases
Which two forces hold the thoracic wall and the lungs together?
- Intrapleural fluid cohesiveness
- Negative intrapleural pressure
What is “intrapleural fluid cohesiveness?”
Water molecules in the intrapleural fluid are attracted to each other and resist being pulled apart, hence the pleural membranes tend to stick together.
What is meant by “negative intrapleural pressure?”
The sub-atmospheric intrapleural pressure creates transmural pressure gradient across lung wall and chest wall. The lungs are forced to expand and the chest is forced inwards.
Which three pressures are important in ventilation?
- Atmospheric pressure
- Intra-alveolar pressure
- Intrapleural pressure
Is inspiration and active or passive process?
Why?
Active- It depends on muscle contraction
Which muscle causes the thorax volume to increase vertically?
Diaphragm
Which direction does the diaphragm move during contraction?
Inferiorly
Which nerves supply the diaphragm?
C3, C4 and C5 phrenic nerves
Where do the nerves which supply the diaphragm originate?
C3, C4 and C5 vertebrae
What is the “bucket handle mechanism?”
Contraction of the external intercostal muscles lifting the ribs and moving the sternum outwards
Is expiration an active or passive process?
Passive
What causes air to move into the alveoli?
The increase in size of the lungs–> decreased pressure, Air moves in down pressure gradient. (Boyle’s law)
What causes air to move out of the alveoli?
Decrease in size of lungs due to their elastic properties–> Pressure increase–> Air moves out down pressure gradient
(Boyle’s law)
What is a pneumothorax?
Air in the pleural space
What causes the lungs to recoil during expiration?
- Elastic connective tissue in the lungs
- Alveolar surface tension
What is alveolar surface tension?
The attraction between water molecules at the liquid air interface.
What is surfactant?
A complex mixture of water and lipid molecules that line alveoli
What is the function of surfactant?
It prevents the collapse of alveoli.
What type of cells secrete surfactant?
Type 2 alveolar cells
Type 2 pneumocytes
What is LaPlace’s Law?
Smaller alveoli (with smaller radius-r) have a higher tendency to collapse
Does surfactant reduce the surface more greatly in smaller or larger alveoli?
Smaller alveoli
Why does respiratory distress syndrome occur in new born?
They are unable to produce surfactant until late pregnancy, hence may have not produced enough by birth
What is alveolar interdependence?
If an alveolus starts to collapse, the surrounding alveoli are stretched and recoil causing expanding forces to be placed upon the collapsing alveolus, hence opening it.
Which three forces keep the alveoli open?
- Alveolar interdependence
- Pulmonary surfactant
- Transmural pressure gradient
