CPL » Human Factors » Circulation and Respiratory Systems
34.8 Circulation and Respiratory Systems
34.8.2 Describe the basic anatomy (structure) of the respiratory system.
The respiratory system consists of the airways, lungs and associated structures that allow air to enter and leave the body and enable the exchange of oxygen and carbon dioxide.
Air enters through the nose or mouth and passes through the pharynx (throat) and larynx (voice box) into the trachea (windpipe).
The trachea divides into two main bronchi, with one bronchus entering each lung.
Within the lungs, the bronchi divide repeatedly into progressively smaller airways called bronchioles.
At the ends of the bronchioles are millions of tiny air sacs called alveoli.
The alveoli are surrounded by very small blood vessels called capillaries. This is where the exchange of gases between the lungs and the blood takes place:
oxygen passes from the alveoli into the blood; and
carbon dioxide passes from the blood into the alveoli to be exhaled.
The diaphragm, a large muscle beneath the lungs, is the principal muscle involved in breathing. Its movement changes the volume of the chest cavity, causing air to move into and out of the lungs.
