Physiology Flashcards
What are the four steps to external respiration?
Ventilation
Gas exchange between alveoli and blood
Gas transport in the blood
Gas exchange at the tissue level
What are the body systems involved in external respiration?
Respiratory system
CV system
Haemotology system
Nervous system
What is ventilation?
The mechanical process by which air is moved between the atmosphere and alveolar sacs
What is the gas exchange between alveoli and blood?
The exchange of oxygen and carbon dioxide between the air in the alveoli and the blood in the pulmonary capillaries
What is the gas transport in the blood?
The binding and transport of oxygen and carbon dioxide in the circulating blood
What is the gas exchange at the tissue level
The exchange of oxygen and carbon dioxide between the blood in the systemic capillaries and the body cells
What is boyles law?
At any constant temperrature, the pressure exerted by a gas varied inversely with the volume of the gas. As the volume of a gas increases, the pressure exerted by the gas decreases
How will air flow?
Air will flow down a pressure gradient from a region of high pressure to a region of lower pressure.
What must the intra-alevolar pressure become less than?
The atmospheric pressure to allow air to flow into the lungs during inspiration.
What is the intra-alveolar pressure before inspiration?
The intra-alveolar pressure is equivalent to atmospheric pressure but during inspiration the thorax and lungs expand as a result of contraction of inspiratory muscles
How are the lungs connected to the thorax?
Intrapleural fluid cohesivness
Negative intrapleural pressure
What is the intrapleural fluid cohesivness?
The water molecules in the intrapleural fluid are attracted to each other and resist being pulled apart and hence the pluerla membranes tend to stick together
What is the negative intrapleural pressure?
The sub-atmospheric intrapleural pressure creates a transmural pressure gradient across the lung wall and across the chest wall so the lungs are forced to expand outwards which forces the chest to squeeze inwards
What are the pressures associated with the alveoli?
760 mm Hg atmospheric pressure at sea level
760 mm Hg intra-alveolar pressure
756 mm Hg intrapleural pressure
What does inspiration depend on?
It is an active process and so depends on muscle contraction
What way is the volume of the thorax increased?
Vertically by contraction of the diaphragm flattening out its dome shape
What nerves supply the diaphragm?
The phrenic nerve from cervical regions 3, 4 and 5
What muscle contracts to lift the ribs and move out the sternum?
The external intercostal muscles
What is the name of the mechanism that the external intercostal muscles perform?
Bucket Handle mechanism
What happens to the intra-alveolar pressure when the size of the lungs increases?
It falls which is needed for boyle’s law as air can then enter the lungs down a pressure gradient until the intra-alveolar pressure becomes equal to the atmospheric pressure
What type of process is expiration?
A passive process by which the inspiration muscles are relaxed
How do the chest wall and stretched lungs recoil to their preinspiraotry size?
They have elastic properties
What does the recoil of the lungs make happen to the intra-alveolar pressure?
It rises
Why does the intra-alveolar pressure rise when the lungs recoil?
The air molecules become contained within a smaller volume and therefore the air will leave the lungs don its pressure gradient until the intra-alvoelar pressure becomes equal to the atmospheric pressure