2.2 mechanics of breathing

ventilation

• process of breathing in (inspiration) and breathing out (expiration)

• replaces carbon dioxide rich air in the sacs (alveoli) with oxygen rich fresh air outside the body

• relies on the connection between the volume and pressure

mechanics

• if you increase the sze (volume) of the container you will have the same number of particles with more space to fill. this leads to low pressure

• increase in volume causes a decrease in pressure

• if you decrease the volume of the container, you have the same number of partciles in less space, so you increase pressure

• decrease in volume causes an increase in pressure

Inspiration

• external intercostal muscles contract - ribs move up and out

• the diaphragm contracts - chest cavity gets bigger

• the volume of chest cavity increases

• as volume increases, air pressure in the lungs decreases

• air rushes into the body through the nose and mouth from an area of high pressure outside the body to low pressure inside the lungs

Expiration

• external intercostal muscles relax- ribs rebound back into position

• diaphragm relaxes - returns to its domed shape

• the volume of the chst decreases, which increases the air pressure inside the lungs

• air is forced out of the lungs from an area of high pressure inside the lungs to lower pressure outside the body

• when breathing heavily, the internal intercostal muscles and abdominal muscles contract to reduce the volume of the chest cavity quicker