Lungs Design And Purpose
Medically Reviewed by: Melissa Conrad Stöppler, MD
What are the lungs?
The lungs are a pair of organs in the chest, which are
primarily responsible for the exchange of oxygen and carbon
dioxide between the air we breathe and the
blood.
What does breathing accomplish?
The cells in the body constantly need a new supply of
oxygen to produce energy. With lack of oxygen, cellular
function is impaired and damage or
cell death may occur. As
energy is utilized, waste products are created, one of
which is the gas
carbon dioxide. Eliminating carbon
dioxide from the body is just as important as breathing in
oxygen from the air. If carbon dioxide builds up in the
blood it will lead to headaches, drowsiness,
coma, and
eventually even death.
What is the structure of the respiratory system?
Air enters the body via the nose (preferably) or the
mouth. The air enters the main windpipe, called the
trachea, and continues en route to each lung via either the
right or left bronchi. The lungs are separated into
sections called lobes, two on the left and three on the
right. The air passages continue to divide into ever
smaller tubes, which finally connect with tiny air sacs
called alveoli. This gradually branching array of tubes is
referred to as the tracheobronchial "tree" because of the
remarkable similarity to the branching pattern of a tree.
The other half of the respiratory system involves blood
circulation. Venous blood from the body is returned to the
right side of the heart and then pumped out via the pulmonary
artery. This artery splits in two for the left and right
lungs and then continues to branch much like the
tracheobronchial tree. These vessels branch into a fine
network of very tiny tubes called capillaries. The
capillaries are situated adjacent to the alveoli and are so
small that only one red blood cell at a time can pass
through their openings. It is during this passage that
gases are exchanged between the blood and the air in the
nearby alveoli. After passing the alveoli, capillaries
then join together to begin forming the pulmonary veins,
which carry the blood back to the left side of the heart.
Next: How is air moved into and out of the lungs during respiration? »
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