The lungs are the site for [[Gas Exchange - Anatomy & Physiology|gaseous exchange]], and are situated within the thoracic cavity. They occupy approximatley 5% of the body volume in mammals when relaxed, but generally have no fixed size or shape since their volume is constantly changing with the processes of [[Ventilation - Anatomy & Physiology#Inspiration|inspiration]] and [[Ventilation - Anatomy & Physiology#Expiration|expiration]]. | The lungs are the site for [[Gas Exchange - Anatomy & Physiology|gaseous exchange]], and are situated within the thoracic cavity. They occupy approximatley 5% of the body volume in mammals when relaxed, but generally have no fixed size or shape since their volume is constantly changing with the processes of [[Ventilation - Anatomy & Physiology#Inspiration|inspiration]] and [[Ventilation - Anatomy & Physiology#Expiration|expiration]]. |