L23 Respiration - Movement Of Air Flashcards
What is compliance?
Refers to the ability of a biological structure to change its volume in response to a change in pressure
Veins are more compliant than arteries, allowing them to store larger volumes of blood at lower pressures
How would you calculate compliance?
Change in volume / change in pressure
What does it mean to have low/high compliance?
Low compliance - more work required to inspire (less flexible) (Imagine a stiff balloon. It takes a lot of effort to inflate it even a little bit)
High compliance - can undergo a large change in volume with a small increase in pressure
(a thin rubber balloon. It inflates easily with minimal effort)
Will lung compliance decrease or increase for someone who has emphysema (damage to air sacs which loses elasticity of alveoli walls)?
- Lung compliance will increase
- Emphysema causes destruction of tiny of alveoli (tiny air sacs) in the lungs. This leads to a decrease in the elastic recoil of the lungs
- With less elastic recoil, lungs become easier to inflate therefore defined as increased lung compliance
What are the two major components contributing to the elastic recoil of the lungs?
- Anatomical component (elastic nature of cells)
- The surface tension generated on the inner surface of the alveoli
How does surface tension develop within the lungs?
Due to the difference in the forces on water molecules at the air/water interface a surface tension develops
What does Laplace equation describe?
The relationship between the pressure inside a sphere or cylinder and its surface tension and radius at the gas/water border
What is Laplace’s equation?
P=(2T/r)
T - surface tension of the fluid
What would the pressure be in a small alveoli compared to a larger alveoli ?
Small alveoli would have a larger pressure according to Laplace’s law
Air will flow from smaller alveoli to larger, leading to their collapse
What is the role of surfactant for alveoli cells ?
Surfactant disrupts the cohesive forces between water molecules at the air-liquid interface within the alveoli which reduces surface tension
- Ultimately preventing smaller alveoli from collapsing
How is surfactant in alveoli’s produced ?
They are produced by type II pneumocyte. Surfactant is composed of a number of lipids and proteins
How are all the lung volumes measured?
With the exception of residual lung volume, all the other lung volumes are measured by a spirometer
What is anatomical dead space?
It’s the volume of the conducting airways that does not participate in gas exchange (doesn’t come into contact with the alveoli)
Why does anatomical dead space exist ?
The conducting airways are necessary to transport air to the alveoli, but they don’t have the specialised structures for gas exchange
. It allows for rapid and efficient delivery of air to the alveoli
What is physiological dead space?
Physiological dead space is the volume of air that is inhaled but does not participate in gas exchange, like anatomical dead space. Physiological dead space includes both the anatomical dead space and the alveolar dead space
