The Respiratory System
The respiratory system is a group of organs and
tissues that help you breathe. The main parts of this system are the
airways, the lungs and linked blood vessels, and the muscles that enable
breathing.
The Respiratory System
Figure A shows the location of the
respiratory structures in the body. Figure B is an enlarged image of airways,
alveoli, and the capillaries. Figure C shows the location of gas exchange
between the capillaries and alveoli.
Airways
The airways are pipes that carry oxygen-rich air to
your lungs and carbon dioxide, a waste gas, out of your lungs. The airways
include your:
- Nose and linked air passages called nasal
cavities
- Mouth
- Larynx (LAR-ingks), or voice box
- Trachea (TRA-ke-ah), or windpipe
- Tubes called bronchial tubes or bronchi, and
their branches
Air first enters your body through your nose or
mouth, which wets and warms the air. (Cold, dry air can irritate your lungs.)
The air then travels through your voice box and down your windpipe. The
windpipe splits into two bronchi that enter your lungs.
A thin flap of tissue called the epiglottis
(ep-i-GLOT-is) covers your windpipe when you swallow. This prevents food or
drink from entering the air passages that lead to your lungs.
Except for the mouth and some parts of the nose, all
of the airways have special hairs called cilia (SIL-e-ah) that are coated with
sticky mucus. The cilia trap germs and other foreign particles that enter your
airways when you breathe in air.
These fine hairs then sweep the particles up to the
nose or mouth. There, they're swallowed, coughed, or sneezed out of the body.
Nose hairs and mouth saliva also trap particles and germs.
Lungs and Blood Vessels
Your lungs and linked blood vessels deliver oxygen
to your body and remove carbon dioxide. Your lungs lie on either side of your
breastbone and fill the inside of your chest cavity. Your left lung is slightly
smaller than your right lung to allow room for your heart.
Within the lungs, your bronchi branch into thousands
of smaller, thinner tubes called bronchioles. These tubes end in bunches of
tiny round air sacs called alveoli (al-VEE-uhl-eye).
Each of these air sacs is covered in a mesh of tiny
blood vessels called capillaries. The capillaries connect to a network of
arteries and veins that move blood through your body.
The pulmonary (PULL-mun-ary) artery and its branches
deliver blood rich in carbon dioxide (and lacking in oxygen) to the capillaries
that surround the air sacs. Inside the air sacs, carbon dioxide moves from the
blood into the air. Oxygen moves from the air into the blood in the lungs.
The oxygen-rich blood then travels to the heart
through the pulmonary vein and its branches. The heart pumps the oxygen-rich
blood out to the body. (For more information on blood flow, see the Diseases
and Conditions Index
"How
the Heart Works" article.)
The lungs are divided into five main sections called
lobes. Some people need to have a diseased lung lobe removed. However, they can
still breathe well using the rest of their lung lobes.
Muscles Used for Breathing
Muscles near the lungs help expand and contract
(tighten) the lungs to allow breathing. These muscles include the:
- Diaphragm (DI-a-fram)
- Intercostal muscles
- Abdominal muscles
- Muscles in the neck and collarbone area
The diaphragm is a dome-shaped muscle located below
your lungs. It separates the chest cavity from the abdominal cavity. The
diaphragm is the main muscle used for breathing.
The intercostal muscles are located between your
ribs. They also play a major role in helping you breathe.
Beneath your diaphragm are abdominal muscles. These
help you breathe out when you're breathing fast (for example, during physical
activity).
Muscles in your neck and collarbone area help you
breathe in when other muscles involved in breathing don't work properly, or
when lung disease impairs your breathing. |