Human Respiratory System


The human respiratory system is a system of organs, tissues, and cells that transport oxygen from the atmosphere to our blood and release carbon dioxide from our blood to the atmosphere. It's made up of several organs that work together to get oxygen into your lungs and then into your red blood cells.

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The respiratory system is composed of two main parts− the conducting zone and the gas-exchange zone. The conducting zone is made up of the nose, nasal cavity, pharynx, larynx (voice box), trachea (windpipe), bronchial tree, and lungs. The conducting zone helps air move through the body. As air moves through this part of the respiratory system, it's warmed or cooled before it reaches out gas-exchange zones.

The gas-exchange zone (also known as the pulmonary region) is made up of alveoli and pulmonary capillaries. It's where gas exchange takes place between your red blood cells and the environment.

The major functions of this system are exchanging gases (oxygen in and carbon dioxide out) and removing water vapor from the body.

Major organs

  • Nose

    The nose is an organ that detects odors and warms and moistens incoming air before it reaches other parts of the respiratory tract. The nasal cavity has three parts− a nasal vestibule where the nostrils are located; a middle meatus that contains two small openings known as choanae (singular choanal); and a posterior nasal cavity.

  • Larynx

    The larynx houses the vocal cords or folds that vibrate during a speech. It also contains structures such as the epiglottis (the flap of cartilage that prevents food from entering your windpipe). The epiglottis closes off the glottis when you swallow to prevent food from entering your lungs instead of going down your esophagus to your stomach.

  • Pharynx

    The pharynx is the part of the respiratory system that connects the nose and mouth to the esophagus. It is made up of two tubes, called the nasopharynx and oropharynx. The nasopharynx runs from the nasal cavity to just under your jawbone. The oropharynx runs from your lips to the back of your mouth.

  • Trachea

    The trachea (also called the windpipe) is a tube that carries air from your throat to your lungs. Your vocal cords are located in this tube, so when you speak or sing, you can control how much air goes through them and change the sound of your voice by regulating this flow of air.

    The trachea splits into two branches called bronchi (singular− bronchus). Alveoli, clusters of air sacs, end each bronchus. Each bronchus is divided into smaller portions called bronchioles.

  • Bronchi

    Bronchi are two thin tubes that carry air from your throat to your lungs. The main bronchi split into smaller branches called bronchioles. These divide again into even smaller tubes called alveoli, which have tiny blood vessels surrounded by a thin layer of tissue called an alveolar sac. The alveoli are where oxygen enters your bloodstream and carbon dioxide leaves it for exhalation through your nose or mouth (or both).

  • Lungs

    Cone-shaped organs in the thoracic cavity, shielded by the rib cage, make up the lungs. Air is exchanged between the alveoli and respiratory bronchial tubes in the lungs, which are made up of millions of tiny cells. The livers' main function is to promote gas exchange between the blood and the air breathed in by humans. This allows for a continuous flow of oxygen throughout our bodies and prevents our cells from dying because they are deprived of oxygen.

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Respiratory Tract

The respiratory tract is where air travels while you breathe. Your nose, mouth, and throat are the visible parts of your respiratory system.. (called the upper respiratory tract). The trachea, bronchi, and bronchioles make up the section of your respiratory system you can't clearly see (called the lower respiratory tract).

If you breathe in, air first goes into your nose or mouth. If the air goes into your nose, it travels down the back of your throat to your larynx (voice box) and then into the trachea, which leads to each of your lungs. If the air goes into your mouth, it travels down the back of your throat to the same places.

The air then enters one or both of your lungs through tiny tubes called bronchi. The bronchi branch out like a tree and connect with smaller tubes called bronchioles.

The alveoli are the small sacs into which oxygen is transported from the outside world. In the lungs, blood arteries round the lungs' air sacs. These blood veins carry oxygen from the alveoli to the rest of the body, where it nourishes cells. When you breathe out, carbon dioxide passes from these blood vessels back into the alveoli. Carbon dioxide is then exhaled through your nose or mouth.

Respiratory System Functions

Inhalation and Exhalation

Inhalation is the process of drawing air into the lungs.

Exhalation is the process of breathing out or exhaling carbon dioxide and other gases from the lungs.

The Respiratory System also has two main functions−

  • Gas Exchange – oxygen enters the bloodstream and carbon dioxide leaves it.

  • Air Circulation – air moves in and out of the lungs and other air passages (such as the nose, mouth, pharynx, larynx, trachea, and bronchi) to keep them moist and clean.

Exchange of Gases between Lungs and Bloodstream

The respiratory system exchanges gases between the lungs and blood to keep your blood at a constant volume and composition. The lungs take in oxygen from inhaled air and remove carbon dioxide from your bloodstream. They also release carbon dioxide into the exhaled air

Exchange of Gases between Bloodstream and Body Tissues

The respiratory tract also helps transport oxygen from your lungs to all the cells in your body. From there, it picks up carbon dioxide produced by those cells and transports it to the lungs for exhalation.

The Vibration of the Vocal Cords

The vocal cords are made up of two bands of muscle tissue called the anterior and posterior cricoarytenoid muscles. These muscles connect to the thyroid cartilage in the larynx and pull back, causing the vocal cords to vibrate.

It is the lungs' job to exchange oxygen and carbon dioxide with the outside world. Alveoli, the little air sacs at the termini of each bronchus, are the entry points for oxygen into your lungs. Surfactant protects the alveoli from collapsing as you exhale by covering them in a thin coating of tissue.

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To get air into your lungs, it must first travel down your windpipe (trachea) from the nose or mouth into your pharynx. The diaphragm contracts and moves downward, expanding the chest cavity and allowing more room for air to enter the lungs. This downward movement also creates negative pressure within the pleural cavities (pockets) surrounding each lung, which helps draw air into them through their bronchial tubes located within the lungs themselves.

Olfaction or Smelling

Olfaction is the sense of smell. The majority of what we know about olfaction comes from studies in which researchers measure electrical signals generated by the olfactory receptor neurons in anesthetized animals. These studies have revealed that olfactory receptor neurons express receptors for many thousands of different odorants, and they are remarkably diverse in their response profiles.

The sense of smell is used to detect chemicals in the environment. As odors enter the nose and reach the nostrils, small hair-like structures called cilia move back and forth along their surface to activate nerve cells (receptor neurons) inside the nose.


In conclusion, the human respiratory system is an amazing and complex system that is responsible for bringing oxygen into our bodies and removing carbon dioxide. This system is made up of many different parts, all of which work together to ensure that we can breathe properly.


1. What are the parts of the human respiratory system?

As you breathe, oxygen enters your body through the nose or mouth and travels through your lungs to every cell in your body. These organs include your nose and mouth, lungs, diaphragm (a muscle under your lungs), bronchi (airways that carry air into your lungs), windpipe, esophagus, and rib cage all make up the human respiratory system.

2. What is respiration?

Respiration refers to the act or process of inhaling and exhaling air by breathing; especially− inhalation followed by an exhalation as in living organisms.

3. What does the respiratory system do?

The respiratory system plays an important role in breathing. Breathing allows us to take in oxygen from the air we breathe in and get rid of carbon dioxide (CO 2 ). CO 2 is a waste product produced when cells use oxygen for energy. The lungs also keep our blood at a normal pH level by absorbing carbon dioxide from our blood and releasing oxygen into it.

4. How do the respiratory organs work?

Oxygen is given to the body by the respiratory system, which also gets rid of waste.


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