Respiratory System Organs Study Guide


There are eleven organ systems found in the human body that work 24/7 to keep us alive and healthy. These systems function so subconsciously that you probably don’t even notice them working. Every time you speak, sing, sneeze, or smell, you’re using one organ system in particular—so get ready and take a deep breath, because today we’re talking about the respiratory system 🫁 👃 🌬.

Lesson Objectives

  • Understand the respiratory system and its function.
  • Understand the organs of the respiratory system.

What is the Respiratory System?

This study guide covers the Respiratory System, a collection of organs and tissues whose primary function is to take in oxygen and release carbon dioxide through a process called Physiological Respiration, or breathing. During physiological respiration, oxygen and carbon dioxide are exchanged during the inhalation and exhalation of air from the atmosphere.

Three processes work in conjunction with one another to make physiological respiration possible. They’re called ventilation, gas exchange, and cellular respiration. Here’s an overview of how they work together to allow us to breathe.

  • Physiological respiration begins with Ventilation —the physical action of breathing (also called external respiration). When you inhale, oxygen from the atmosphere travels through your airway from your nasal cavity to tiny air-filled sacs called alveoli in your lungs.

  • Once the oxygen reaches the alveoli, the process of Gas Exchange begins. During gas exchange, oxygen and carbon dioxide are transferred between the lungs and the bloodstream via passive diffusion between the alveoli and millions of capillaries embedded within the lung tissue.

  • Once the oxygen has diffused into the bloodstream, it is used by cells to convert sugars into energy in a crucial process called Cellular Respiration. Without the energy produced by cellular respiration, our bodies would not be able to sustain life.

  • Cellular respiration produces carbon dioxide as a waste product. Once the cells release the carbon dioxide into the bloodstream, it travels back to the capillaries and diffuses into the , at which point it can be exhaled, and the entire process repeats.

The Respiratory Organs

The process of physiological respiration occurs across the six major organs of the respiratory system: the nasal cavity, the pharynx, the larynx, the trachea, the bronchi, and the lungs.

These organs form a continuous passage system known as the Respiratory Tract —basically one giant tube that runs all the way from your mouth to your lungs. The respiratory tract is divided into two parts: the upper and lower respiratory tracts. Let’s talk about the upper tract first.

  • Pro Tip: If you’re having trouble remembering the names and order of the organs, use the mnemonic device “No Person Lives To Be Liked” (or feel free to come up with your own, less weirdly philosophical version if you want. It won’t hurt our feelings or anything) (😔)

The Upper Respiratory Tract

Three organs comprise the Upper Respiratory Tract: the nasal cavity, the pharynx, and the larynx. These organs make up the first half of the passage for us to breathe air in and out of the body during ventilation. They’re also responsible for heating, humidifying, and filtering the air that you inhale. Let’s get a basic idea of their functions below.

  • Nasal Cavity -The nasal cavity is a large air-filled space in the skull just behind and above the nose. It’s filled with mucus to moisten the air you breathe, little hairs to trap foreign particles like pollen or other allergens, and chemoreceptors that give you the ability to smell. See the model below to visualize the location of the nasal cavity.

  • Pharynx -The pharynx, also known as the throat, is a tube-like structure through which air passes from the nasal cavity to the larynx. Both food and liquids are also all able to pass through the pharynx.

  • Larynx -The larynx is a passage that connects the pharynx to the trachea, marking the transition from the upper respiratory tract to the lower. Unlike the pharynx, food and fluids cannot pass through the larynx. A flap-like structure called the *epi

  • sits at the top of the larynx and only remains open while breathing, diverting food into the esophagus and ensuring the only substance able to travel through to the lower respiratory tract is air.

The Lower Respiratory Tract

The Lower Respiratory Tract consists of three major organs–the trachea, the bronchi, and the lungs. The passage itself looks like an upside-down tree, where the trachea is the trunk, the bronchi are the branches, and the lungs are the leaves surrounding them (flip screen for reference 🌳). It’s the part of the respiratory system in which gas exchange occurs. Let’s learn a little bit more about its organs below. See the model below to visualize the structure of the lower respiratory tract.

  • Trachea -The trachea, or windpipe, is the widest passage in the respiratory tract. It is formed by rings of cartilage, making it both resilient and strong.

  • Bronchi –The bronchi, located inside the lungs, branch from the base of the trachea into two tubes that we refer to as the right and left bronchi, each of which goes into its respective lung. As the bronchi progress deeper into the lungs, they branch off into tinier and tinier passages, the smallest of which are called Bronchioles.

  • Lungs -The lungs are the respiratory tract’s largest organ. They’re suspended in the pleural cavity located in the thorax. Each lung is divided into sections called lobes that are separated by connective tissues. Tiny air-filled sacs of lung tissue called Alveoli are found at the end of the bronchioles. Gas exchange occurs through the blood vessels found in the alveolar walls, facilitating cellular respiration.

💡 Summary

  • The respiratory system is a collection of organs and tissues whose primary function is to take in oxygen and release carbon dioxide, a process done through physiological respiration.

  • Ventilation is the physical action of inhaling and exhaling air.

  • Gas exchange, the primary purpose of the lungs, is a process in which oxygen and carbon dioxide are exchanged between the lungs and the bloodstream.

  • The oxygen transferred from the lungs to the bloodstream is used in cellular respiration, a process during which cells use oxygen to convert sugars into energy.

  • Ventilation, gas exchange, and cellular respiration all work together to facilitate physiological respiration.

  • Six major organs form the respiratory tract, which is divided into the upper respiratory tract and the lower respiratory tract.

  • The upper respiratory tract is comprised of the nasal cavity, pharynx, and larynx.

  • The lower respiratory tract is comprised of the trachea, bronchi, and lungs.

  • The bronchi splits into two bronchial tubes that branch out into smaller and smaller tubes, the smallest of which are called bronchioles.

  • Gas exchange occurs at the alveoli —tiny sacs of air found at the tips of the bronchioles in the lungs.

✅ Conclusion

Whew! Okay, we made it—hope you’re not too out of breath. Usually when you think about breathing, lungs are the first thing that come to mind. Now that we’ve gone through this lesson, it’s cool to see how many other organs and processes are involved with respiration!

Now that you know all about the respiratory system (🫁👃🌬🆒😌👩‍🎓🥳), check your understanding by answering some practice FAQs below.


We hope you enjoyed studying this lesson and learned something cool about the Respiratory System Organs! Join our Discord community to get any questions you may have answered and to engage with other students just like you! Don’t forget to download our App to experience our fun, VR classrooms – we promise, it makes studying much more fun!😎


  1. Lungs and Respiratory System. Accessed on 25 Nov, 2021.
  2. Structure and Function of the Respiratory System. Accessed on 25 Nov, 2021.
  3. Libretexts. (2020, August 14). 21.9b: Internal Respiration. Medicine LibreTexts. Retrieved December 22, 2021, from
  4. Body, V. (2021). Lower respiratory system: Respiratory anatomy. Visible Body Learn Anatomy. Retrieved December 22, 2021, from
  5. Respiratory system: Functions, facts, Organs & Anatomy. Cleveland Clinic. (2020, January 24). Retrieved December 23, 2021, from
  6. OpenStax, L. L. &. (n.d.). Anatomy and physiology II. Gas Exchange | Anatomy and Physiology II. Retrieved December 23, 2021, from

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