Human Body: Respiratory System

C-shaped rings of cartilage

Step 1: The trachea is a tube that carries air from the larynx to the bronchi. Step 2: It needs to stay open all the time so that air can flow freely. Step 3: The wall of the trachea is strengthened by C-shaped rings of cartilage, which are firm but flexible. Step 4: These rings prevent the trachea from collapsing or being squeezed shut. Step 5: Muscles, mucus, and pleural fluid are not the structures that provide this structural support to the trachea.

Alveoli

Step 1: Air travels from the nose through the trachea and bronchi into millions of tiny air sacs in the lungs. Step 2: These tiny air sacs are called alveoli (singular: alveolus). Step 3: The walls of the alveoli are very thin and surrounded by blood capillaries. Step 4: Oxygen from the air in the alveoli diffuses into the blood, and carbon dioxide from the blood diffuses into the alveoli to be breathed out. Step 5: The trachea, bronchi, and larynx are all passageways for air — they do not perform gas exchange.

The process of releasing energy by breaking down food (glucose)

Step 1: Many students confuse breathing with respiration, but they are different. Step 2: Breathing is just a physical process of inhaling and exhaling air. Step 3: Respiration is a biochemical process that happens inside every cell of the body. Step 4: In respiration, glucose (food) is broken down using oxygen to release energy that the body can use. Step 5: Transporting oxygen is called gaseous transport, and filtering dust is done by the nose — neither of these is the definition of respiration.

It pushes downward and flattens

Step 1: The diaphragm is a muscular sheet below the lungs that separates the chest cavity from the abdominal cavity. Step 2: During inhalation (breathing in), the diaphragm contracts and pushes downward, becoming flat. Step 3: At the same time, the ribs move upward and outward. Step 4: Together, these movements increase the volume of the chest cavity, causing air pressure inside to drop. Step 5: Lower pressure inside the lungs causes outside air (at higher pressure) to rush in. Moving upward and becoming dome-shaped is what happens during exhalation.