the mechanism of breathing

Breathing/ventilation definition

movement of air into and out of lungs

respiration

chemical reaction to release energy in form of ATP

gaseous exchange definition

diffusion of oxygen from air in the alveoli to blood and carbon dioxide from blood into air in the alveoli

inspiration

when air pressure of atmosphere is greater than the air pressure in lungs air is forced into lungs

expiration

when the air pressure in lungs is greater than air pressure in atmosphere air is forced out of lungs

what is the diaphragm

Sheet of muscles that separate the thorax from the abdomen

where do the intercostal muscles lie

between ribs

what are the internal intercostal muscles

contraction leads to expiration

what are external intercostal muscles

contraction leads to inspiration

arrangement of lungs diagram

describe the process of inspiration (active process)

• external intercostal muscles contract, and internal intercostal muscles relax

• ribs pulled up and outwards, increasing volume of thorax

• the diaphragm muscles contract and flatten, increasing volume of thorax

• pressure reduces in lungs

• atmospheric pressure is greater than pulmonary pressure so air is forced into lungs

describe process of expiration (passive)

• Internal intercostal muscles contract, external intercostal muscles relax

• the ribs move downwards and inwards, decreasing volume of thorax

• the diaphragm muscles relax and pushed up again by abdomen. The volume of thorax is reduced.

• increase pressure in lungs

• the pulmonary pressure is greater than atmosphere so air is forced out of lungs

what is pulmonary ventilation rate

total volume of air that is moved into lungs during one minute

formula for pulmonary ventilation rate

tidal volume * breathing rate

what is tidal volume (dm3)

Volume of air taken in at each breath when body is at rest (0.5cm3)

breathing rate (min-1)

number of breaths taken in one minute (12-20)