The respiratory system works with the circulatory system to supply oxygen to the cells and expel carbon dioxide in a two-stage process. External respiration brings air into the
through the mouth
and nose. The air is warmed, moistened, and filtered by
membranes and cilia. The pharynx,
commonly known as the
is divided into three sections. The
is only intended to
carry air, while the oropharynx is a passageway for both food and air. The
keeps food and
liquids out of the larynx and trachea. The
creates sound as air passes through the vocal
cords. It sits behind the large thyroid cartilage, which moves when you swallow. Cartilage rings keep
the
open during breathing. The air travels down the left and right bronchi, leading to the
lungs. The
are smaller airways within the lungs, which end in tiny
wrapped in
capillaries to allow the exchange of oxygen and carbon dioxide. Each pressurized lung is surrounded by an
airtight
within the chest cavity. Pressure changes caused by contraction of the
intercostals, and abdominal muscles pull air into the lungs. When the muscles relax, the air is forced out.
The lungs are divided into three
on the right, but only
on the left to allow room
for the heart