breathing

• For efficient gas exchange, air in lungs must be continually changed
• Ventilation is the process of inhalation and exhalation; breathing
• Air flows from high pressure to low pressure, air flows into and out of lungs due to pressure differences
• Increase volume of lungs decreases pressure in lungs, causing air to rush in during inspiration
• during inspiration the diaphragm contract by flattening and intercostal muscles contracts, lifting the rib cage up and out; increasing volume of chest cavity
• the pleura allows the lungs to expand with the chest cavity, increasing the volume of the lungs. Air flows through until pressure becomes equal
• during normal breathing, the diaphragm is mainly responsible for changing the volume of the chest cavity. Movement of rib cage becomes more important during heavier breathing
• during expiration the diaphragm and intercostal muscles relax. diaphragm bulges into the chest cavity and the rib cage moves in and downwards
• the volume in the lungs decrease causing the pressure to become greater in the lungs than outside, letting the air flow out
• expiration is a passive process when breathing at rest involving the relaxation of muscles that contracted during inspiration
• exhalation during heavier breathing and when forcefully exhaling involves more forceful expiration with the intercostal muscles contracting to actively lower the rib cage