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Respiratory System 

Grade 8
Aug 19, 2022

Key Concepts

  1. What is respiratory system ?
  2. Parts of respiratory system
  3. Functions and various parts of respiratory system


Respiratory system is the network of organs and tissues that help us to breathe. This system helps our body to absorb oxygen from the air so that our organs can work. It also cleans waste gases, such as carbon dioxide, from our blood. 

Respiratory system

Respiratory System 

The respiratory system is the system which consists of organs, and other parts of our body involved in breathing, when we exchange oxygen and carbon dioxide.  

Respiration is made up of two phases called inspiration and expiration. We inhale (breathe in) oxygen during inspiration. We exhale (breathe out) carbon dioxide during expiration. 

Parts of the Respiratory System 

Respiratory system is divided into the upper respiratory tract and the lower respiratory tract. 

The Upper Respiratory Tract includes the: 

Mouth and nose: Air enters and leaves the lungs through the mouth and nostrils of the nose. 


Nasal cavity: Air passes from the nose into the nasal cavity, and then the lungs. 

Throat (pharynx): Air from the mouth is sent to the lungs via the throat. 

Voice box (larynx): This part of the throat helps air to pass into the lungs, and keeps out food and drink. 

The Respiratory System

Nose and nasal cavity: The main external opening of the respiratory system. Air is taken in through nostrils, and the air is filtered while passing through the nostrils by fine hairs and mucus that line the passage. 

Sinuses: Sinuses are hollow areas between the bones in our head that help to regulate the temperature and humidity of the air you inhale. 


Pharynx: The pharynx, or throat, is a versatile muscular tube, shaped like a funnel, that delivers air from the mouth and nose to the trachea, or windpipe. 

Larynx: The larynx has a double function in the respiratory system: as an air canal to the lungs (while stopping food and drink from blocking the airway) and as the ‘voice box’ (which contains vocal cords for speech). 

The Lower Respiratory Tract: 

The lower respiratory tract is made up of: 

  • Lungs 
  • Trachea (windpipe) 
  • Bronchi 
  • Bronchioles 
  • Alveoli

Trachea (windpipe): Passage connecting your throat and lungs. This is composed of rings of cartilage. 

Cartilaginous rings prevent the collapse of the trachea in the absence of air. It divides into two major bronchi; one bronchus enters to left lung and the other enters to right lung. 

Epiglottis: Tissue flap at the entrance to the trachea that closes when you swallow to keep food and liquids out of your airway. 

Bronchial tubes: Tubes at the bottom of your windpipe that connect into each lung. 

Lungs: The lungs are the primary organs of the respiratory system, as they perform a vital role in breathing: gas exchange. The spongy, pinkish organ looks like two upside-down cones in your chest. The right lung is made up of three lobes. The left lung has only two lobes to make room for your heart. 

The lungs are the center of the respiratory (breathing) system. 

Every cell of the body needs oxygen to stay alive and healthy. Our body also needs to get rid of carbon dioxide. This gas is a waste product that is made by the cells during their normal, everyday functions. Our lungs are specially designed to exchange these gases every time you breathe in and out. 

Diaphragm: Muscle that helps your lungs pull in air and push it out. 

Other components that work with the lungs and blood vessels include: 

Alveoli: Tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place. 

Bronchioles: Small branches of the bronchial tubes that lead to the alveoli. The bronchi branch off into smaller bronchi and even smaller tubes called bronchioles. Like the branches of a tree, these tiny tubes stretch out into every part of our lungs. Some of them are so tiny that they have the thickness of a hair. 

Each bronchiole tube ends with a cluster of small air sacs called alveoli (individually referred to as alveolus). They look like tiny grape bunches or very tiny balloons. There are about 600 million alveoli in your lungs. This means there’s plenty of room for vital oxygen to pass into your body. 

Capillaries: Blood vessels in the alveoli walls that move oxygen and carbon dioxide. 

Lung lobes: Sections of the lungs — three lobes in the right lung and two in the left lung. 

Pleura: Thin sacs that surround each lung lobe and separate your lungs from the chest wall. 

Working of respiratory system  

There are two phases of breathing: in and out. 

Working of respiratory system  
Working of respiratory system  

As a person inhales, the diaphragm contracts and moves downward. The space left in the chest allows the lungs to expand. Muscles in the ribs also help enlarge the chest cavity, pulling the rib cage upward and outward. 

Once the lungs expand, air moves in through the nose and mouth. The air travels down the trachea and into the lungs, allowing a person to breathe. 

The exchange of oxygen and carbon dioxide occurs before exhalation. When a person exhales, the diaphragm relaxes, the lungs recoil, and the air moves out of the lungs. 

The Pathway of a breath: 

When you breathe in, air enters through your mouth and nose and travels: 

  • down the throat into the trachea 
  • into the lungs through the right and left main bronchi 
  • into the smaller bronchi airways 
  • into the even smaller bronchiole tubes 
  • into the alveoli 

Each alveolus is covered by a net of tiny blood vessels called capillaries. Oxygen and carbon dioxide exchange happens here. Your heart sends deoxygenated blood to the lungs. This is blood that is carrying carbon dioxide rather than oxygen. 

As the blood passes through the tiny, thin-walled capillaries, they get oxygen from the alveoli. They return carbon dioxide through the thin walls to the alveoli. 

The oxygen-rich blood from your lungs is sent back to your heart, where it’s pumped to your entire body. The carbon dioxide is breathed out of the lungs and alveoli through your mouth and nose. 

Functions of the respiratory system: 

  • Allows us to talk and to smell. 
  • Warms air to match our body temperature, and moisturizes it to the humidity level our body needs. 
  • Delivers oxygen to the cells in our body. 
  • Removes waste gases, including carbon dioxide, from the body when we exhale. 
  • Protects our airways from harmful substances and irritants. 

Respiratory system diseases: Asthma, bronchitis, pneumonia, sinusitis and lung cancer.


  • The human respiratory system consists of a group of organs and tissues that help us to breathe. Aside from the lungs, there are also muscles and a vast network of blood vessels that facilitate the process of respiration.
  • The important human respiratory system parts include- Nose, larynx, pharynx, trachea, bronchi and lungs.
  • The respiratory tract is made up of nostrils, nasal chamber, larynx, pharynx, epiglottis, trachea, bronchioles, bronchi, alveoli, and lungs.
  • Our body cells require oxygen to release energy. The oxygen inhaled during respiration is used to break down the food to release energy.
  • Breathing is the physical process of inhaling oxygen and exhaling carbon dioxide in and out of our lungs. Respiration is the chemical process.


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