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Human Respiratory System

Last Updated : 12 Jan, 2024
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The respiratory system is a biological system found in both animals and plants that consists of distinct organs and structures that allow for gas exchange. The respiratory system is an interconnected network of organs and tissues that help with breathing and respiration. Respiration is the process by which organisms exchange gases between their body cells and their surroundings. Breathing is the procedure of consuming oxygen and exhaling carbon dioxide. It is made up of your airways, lungs, and blood vessels.

Parts of the Respiratory System

  • Nose: Humans have exterior nostrils that are separated by a cartilaginous framework known as the septum. The body’s first line of defence against foreign pathogens is provided by tiny hair follicles that cover the interior lining of the nostrils. They also add humidity to the air we breathe.
  • Larynx: The larynx is supported by two cartilaginous chords. It is located in front of the neck and is in charge of vocals as well as respiration. As a result, it is also known colloquially as the voice box. When you swallow, an epiglottis flap folds over the top of your windpipe, preventing food from entering your larynx.
  • Pharynx: The nasal chambers open into a large hollow space known as the pharynx. It serves as a common route for both air and food. It works by preventing food particles from entering the windpipe. The epiglottis is elastic cartilage that acts as a switch between the larynx and the oesophagus, allowing air into the lungs and food into the gastrointestinal tract to pass through.
  • Trachea: The trachea, or windpipe, ascends from the larynx to the neck. The trachea’s walls are made up of C-shaped cartilaginous rings that give the trachea hardness and keep it from expanding completely. The trachea continues into the breastbone and divides into two bronchi, one for each lung.
  • Bronchi: The trachea divides into two tubes called bronchi, which enter each lung separately. The bronchi are divided into secondary and tertiary bronchioles, which branch out into small air sacs known as alveoli. Alveoli are single-celled air sacs with thin walls. It allows oxygen and carbon dioxide molecules to move into and out of the bloodstream.
  • Lungs: In humans and other vertebrates, the primary organs of respiration are the lungs. They are found on either side of the heart in the thoracic cavity of the chest. The lungs are spongy organs with a surface area of 50 to 75 square metres. The lung’s primary function is to facilitate gas exchange between the blood and the air. Surprisingly, the right lung is significantly larger and heavier than the left lung.
Human Respiratory System


Anatomy of the Human Respiratory System

The respiratory system is divided into two sections: the upper respiratory tract and the lower respiratory tract. The upper respiratory tract, as the names suggest, includes everything above the vocal folds, while the lower respiratory tract includes everything below the vocal folds.

  • These two tracts collaborate to perform respiration, or the exchange of carbon dioxide and oxygen between your body and the environment. From the nose to the lungs, the various elements of the respiratory tract play distinct but critical roles in the respiration process. Air can enter the body through the mouth in addition to the nasal cavity. When air enters the body, it flows into the upper respiratory system’s lower portion via the pharynx and larynx.
  • The pharynx, also known as the throat, allows air to pass from the nasal cavity or mouth to the larynx and trachea.
  • The larynx, or voice box, houses the vocal folds, which allow us to speak and make sounds.
  • After passing through the larynx, air enters the lower respiratory tract, which begins with the trachea.

Upper Respiratory System

The sinuses and nasal cavities, both located behind the nose, are the first stop on the upper respiratory tract.

  • Nasal cavity: It is the area directly behind the nose where outside air enters the body. As air enters the nose, it comes into contact with the cilia that line the nasal cavity. These cilia aid in the trapping and disposal of foreign particles.
  • Sinuses: are air spaces located behind the front of your skull on either side of your nose and along your forehead. As you breathe, your sinuses help to regulate the temperature of the air.

Lower Respiratory System

  • The trachea, also known as the windpipe, is the passage that allows air to enter the lungs directly. This tube is made up of multiple tracheal rings and is very rigid. Anything that narrows the trachea, such as inflammation or obstruction, reduces oxygen flow to the lungs.
  • The lung’s primary function is to exchange oxygen for carbon dioxide. The lungs inhale oxygen and exhale carbon dioxide when we breathe.
  • The trachea in the lungs divides into two bronchi, or tubes, one for each lung. These bronchi divide into smaller bronchioles. Finally, these bronchioles terminate in alveoli or air sacs that exchange oxygen and carbon dioxide.

The following steps are used to exchange carbon dioxide and oxygen in the alveoli:

  • Deoxygenated blood is pumped to the lungs by the heart. Carbon dioxide, a byproduct of our normal cellular metabolism, is present in this deoxygenated blood.
  • When deoxygenated blood reaches the alveoli, it exchanges carbon dioxide for oxygen. The blood has now been oxygenated.
  • The oxygenated blood is then returned from the lungs to the heart and released back into the circulatory system.
  • This exchange of carbon dioxide in the lungs, along with the exchange of minerals in the kidneys, is responsible for helping to maintain the pH balance of the blood.

Conditions that Affect the Respiratory System

  • Asthma: In asthma, airways are congested, and produce an abnormally large amount of mucus.
  • Bronchiectasis: is a condition in which the bronchial walls thicken as a result of inflammation and infection.
  • COPD (chronic obstructive pulmonary disease): is a lung disease that affects millions of people worldwide (COPD). This long-term ailment worsens over time. Bronchitis and emphysema are among the most common causes.
  • Pneumonia: Infection causes alveolar inflammation, which leads to pneumonia. There’s a chance they’ll become clogged with pus or fluid.


  • Tuberculosis: A bacterium causes this lethal infection. It usually affects the lungs, but it can also affect the kidneys, spine, or brain.
  • Lung Cancer is a medical condition that affects the lungs. Cancer develops when cells in the lungs change and expand. This is often caused by smoking or inhaling other substances.
  • Cystic Fibrosis is a disease that is distinguished by the presence of cysts in the lungs. This condition develops gradually and is caused by a genetic problem. It causes recurring lung infections.
  • Pleural Effusion is a condition that causes fluid to build up in the lungs. Too much fluid accumulates between the tissues that line the lungs and chest.
  • Idiopathic Pulmonary Fibrosis is a condition in which the tissue of the lungs becomes damaged and unable to function properly.
  • Sarcoidosis: Granulomas are small clusters of inflamed cells that grow in the lungs and lymph nodes.

Functions of the Human Respiratory System

Function Description
Inhaling and exhaling The respiratory system facilitates breathing (also known as pulmonary ventilation.) The air we breathe in through the nose travels through the pharynx, larynx, trachea, and lungs. The same pathway is used to expel the air. Changes in lung volume and pressure aid in pulmonary ventilation.
The exchange of gases between the lungs and the bloodstream Inside the lungs, oxygen and carbon dioxide enter and exit via millions of microscopic sacs known as alveoli. The oxygen that is inhaled diffuses into the pulmonary capillaries, binds to haemoglobin, and is pumped through the bloodstream. Carbon dioxide diffuses from the blood into the alveoli and is expelled through exhalation.
The exchange of gases between the bloodstream and body tissues The blood transports oxygen from the lungs throughout the body and releases it when it reaches the capillaries. The oxygen is diffused into the body tissues via the capillary walls. Carbon dioxide diffuses into the bloodstream and is carried back to the lungs for expulsion.
The Vocal Cords Vibration The arytenoid cartilage is moved by the muscles of the larynx while speaking. The vocal cords are pushed together by these cartilages. When air passes through the vocal cords during exhalation, it causes them to vibrate and create sound.
Smell or Olfaction When air enters the nasal cavities during inhalation, certain chemicals in the air bind to it and activate nervous system receptors on the cilia. The brain sends the signals to the olfactory bulbs.

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FAQs on Human Respiratory System

Question 1: What are the phases of aerobic respiration?


The process of breaking down glucose to produce energy is known as aerobic respiration. It occurs in several stages, including glycolysis, pyruvate oxidation, the citric acid cycle or Krebs cycle, and the electron transport system.

Question 2: Why do cells require oxygen?


To produce energy, our body cells require oxygen. The oxygen inhaled during respiration is used to break down food into energy.

Question 3: What is the primary distinction between human breathing and respiration?


The physical process of inhaling oxygen and exhaling carbon dioxide in and out of our lungs is known as breathing. On the other hand, respiration is the chemical process by which oxygen is used to break down glucose in order to generate energy for various cellular processes.

Question 4: What are the essential components of the human respiratory system?


The nose, larynx, pharynx, trachea, bronchi, and lungs are all important parts of the human respiratory system.

Question 5: How does the respiratory system work in detail?


Air enters your lungs and transports oxygen to your blood when you inhale (breath in). Simultaneously, waste gas carbon dioxide travels from your blood to your lungs and is exhaled (breathed out). This process, known as gas exchange, is critical to life.

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