Respiratory System – Gas Exchange and Lung Structure

What's the Point?

By the end of this lesson, you will be able to describe the structure and function of the respiratory system, explain how gas exchange occurs in the lungs, and identify how this system works with others to deliver oxygen and remove carbon dioxide.

Every cell in your body needs oxygen to survive. The respiratory system provides that oxygen and removes carbon dioxide, a waste product created when your cells use energy. Breathing is more than inhaling and exhaling—it’s a precise system that keeps your blood chemistry balanced.

Jordan’s Story

As Jordan rebuilds his stamina, his breathing exercises help strengthen his lungs and improve oxygen flow. His doctors monitor how quickly his respiratory rate returns to normal after activity to measure his progress.

Maya’s Story

During her marathon training, Maya’s breathing rhythm becomes more efficient. Her lungs and diaphragm work together to pull in oxygen while her heart and muscles use it to produce energy. The stronger her respiratory system, the longer she can sustain her performance.

Structure of the Respiratory System

The respiratory system includes several structures that work together to move air and exchange gases.

Respiratory System Structure
Structure	Function
Nose and Nasal Cavity	Filter, warm, and moisten incoming air.
Pharynx (Throat)	Connects the mouth and nasal passages to the trachea.
Larynx (Voice Box)	Contains the vocal cords; allows sound production.
Trachea (Windpipe)	Tube that carries air to the lungs; lined with cilia to trap particles.
Bronchi and Bronchioles	Branching airways that direct air into each lung.
Lungs	Main organs of respiration; contain alveoli for gas exchange.
Alveoli	Tiny air sacs surrounded by capillaries where oxygen and carbon dioxide exchange occurs.
Diaphragm	Dome-shaped muscle that controls breathing by contracting and relaxing.

Diagram labeling nasal cavity, trachea, bronchi, lungs, alveoli, and diaphragm.

Gas Exchange: How Oxygen and Carbon Dioxide Trade Places

Gas exchange happens in the alveoli, the microscopic air sacs at the end of the bronchioles. Here’s what happens every time you take a breath:

You inhale, bringing oxygen into the lungs.
Oxygen moves across the thin walls of the alveoli into the capillaries.
Red blood cells carry oxygen through the bloodstream to every cell.
Carbon dioxide (CO₂), a waste gas, moves from the blood into the alveoli.
You exhale, releasing the carbon dioxide out of the body.

This exchange keeps oxygen levels stable and prevents waste gases from building up.

Diagram showing alveoli surrounded by capillaries where oxygen enters the blood and carbon dioxide leaves.

My Body Tracker – Respiratory System Entry

You will add information about the respiratory system to your ongoing tracker. This entry should include:

- - The main structures of the respiratory system in order of airflow
  - A diagram or description of how gas exchange works in the alveoli
  - A short paragraph explaining how the respiratory system connects with at least two other systems

Connections to Other Systems

Cardiovascular System: Transports oxygen and carbon dioxide between lungs and tissues.
Muscular System: Uses oxygen to power movement; the diaphragm is a major breathing muscle.
Nervous System: Controls breathing rate automatically and during exercise.
Endocrine System: Adjusts breathing and heart rate during stress or activity.

When Jordan practices controlled breathing or Maya sprints toward the finish line, their respiratory and cardiovascular systems must synchronize perfectly to keep oxygen flowing.

Test Yourself

Review what you have learned by completing the activities below.

Breathing happens every second, often without thought, but it powers everything your body does. From Jordan’s recovery to Maya’s training, oxygen is the invisible fuel that keeps cells alive and active. The respiratory system connects every heartbeat and movement, maintaining the delicate balance between oxygen and carbon dioxide.

Consider the following...

Think about how your breathing changes when you are resting versus exercising. What causes this difference, and how do your respiratory and cardiovascular systems work together to adjust?

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