The Respiratory System (2024)

The airways are pipes that carry oxygen-rich air to the alveoli in your lungs. They also carry the waste gas carbon dioxide out of your lungs. The airways include these body parts:

• Mouth
• Nose and linked air passages called the nasal cavity and sinuses
• Larynx (voice box)
• Trachea (windpipe)
• Tubes called bronchial tubes, or bronchi, and theirbranches
• Smaller tubes called bronchioles that branchoff ofthe bronchialtubes

Air comes into yourbody

Air first enters your body through your nose or mouth, which moistens and warms the air since cold, dry air can irritate your lungs. The air then travels past your voice box and down your windpipe. Rings of tough tissue, called cartilage, acts as a support to keep the bronchial tubes open.

Inside your lungs, the bronchial tubes branch into thousands of thinner tubes called bronchioles. The bronchioles end in clusters of tiny air sacs called alveoli.

Air fills your lung’s airsacs

Your lungs have about 150 million alveoli. Normally, your alveoli are elastic, meaning that their size and shape can change easily. Alveoliare able toeasily expand andcontract becausetheir insides are coated with a substance called surfactant. Surfactant reduces the work it takes to breathe by helping the lungs inflate more easily when you breathe in. It also prevents the lungs from collapsing when you breathe out.

Each of these alveoli is made up of a mesh of tiny blood vessels called capillaries. The capillaries connect to a network of arteries and veins that move blood through your body.

Blood low in oxygen flows through the lungs

The pulmonary artery and its branches deliver blood to the capillaries that surround the alveoli. This blood is rich in carbon dioxide and low in oxygen.

Oxygen flows into your blood

Carbon dioxide moves from the blood into the air inside the alveoli. At the same time, oxygen moves from the air into the blood in the capillaries.