Mechanics of breathing Flashcards
Pulmonary ventilation
> The process by which we move air into and out of the lungs
Inspiration: (rest)
1) External intercostal muscles and diaphragm contract
2) Ribs and sternum move upwards and outwards
3) Diaphragm flattens
4) Thoracic cavity increases in volume and lung volume increases
5) Pulmonary air pressure falls below atmospheric air pressure
6) Causing atmospheric air to be forced into the lungs
7) Until lung pressure equals atmospheric pressure pressure again
Inspiration: (during exercise)
> Additional muscles in the chest also contract. The chest cavity volume further increases and more air is forced into the lungs.
Expiration: (at rest)
1) External intercostal muscles and diaphragm relax
2) Ribs and sternum move inwards and downwards
3) Diaphragm moves upwards and into a dome shape
4) Thoracic cavity decreases in volume and lung volume decreases
5) Pulmonary air pressure is higher than atmospheric air pressure
6) Causing more atmospheric air to be forced out of the lungs via respiratory passages
7) Until lung pressure equals atmospheric pressure again
Expiration: (during exercise)
> Internal intercostal muscles and abdominal muscles contract powerfully, acting on the ribs
Chest cavity volume is further reduced and more air is forced out of the lungs
Diffusion:
> The exchange of gases from an area of higher concentration to an area of lower concentration
Diffusion gradient:
> The concentration of molecules is greater on one side of a space than the other side of the same space
Partial pressure:
> The pressure a gas exerts within a mixture of gases
(pO2, pCO2)
Pressure gradient:
> The force that results when there is a difference in pressure across two areas - which direction a molecule will move in
Ventilation:
> Movement of air from the environment to inside of the lungs
Pressure gradients during ventilation:
> Air moves from areas of high pressure to lower pressure
Pressure gradients allow air from outside of the body, into the respiratory tract
The diaphragm contracts, reducing lung and thoracic pressure
Reduced pressure. creates a gradient, allowing air to enter the lungs
The diaphragm relaxes, increasing pressure inside the lungs
Increased pressure forces air out
Gaseous exchange:
> The process whereby oxygen diffuses from the alveoli to the blood, and carbon dioxide diffuses from the blood to the alveoli
Gaseous exchange: in tissues
> Oxygen diffuses from blood to the tissues, and carbon dioxide moves from the tissues into the blood
Gaseous exchange: in alveoli
> Oxygen moves from alveoli into blood
Partial pressure of oxygen un alveoli is higher than in capillaries (as it is transferred to working muscles)
Oxygen moves down pressure gradient
Factors affecting gaseous exchange:
> pO2, pCO2
gas solubility, temperature, ventilation
surface area and diffusion distance of alveoli
RBC, myoglobin, haemoglobin concentration
moist alveolar lining
