What is Respiration?

It is a process by which living organisms produce energy by the oxidation of complex organic substances, typically with the intake of oxygen and the release of carbon dioxide.

What is the Respiratory System?

The parts or organs of an organism's body involved in breathing or gas exchange together make the respiratory system. These respiratory organs generally exchange oxygen and carbon dioxide with the atmosphere.

The Function of the Respiratory System

  • It helps to breathe in or inhale and breathe out or exhale.
  • It facilitates voice production with the help of the vocal cords.
  • It helps in smelling.
  • It moisturizes the inhaled air and sets the temperature according to the body's needs.
  • It delivers oxygen to each cell of the body.
  • It removes waste gases, including carbon dioxide or oxygen-poor air, from the body.
  • It protects the airways from harmful particles and irritants.

Parts or Organs of the Respiratory System

It has many different parts, and each part has different components.

  • Mouth and nose: These are the openings that draw air into the respiratory system.
  • Sinuses: These are the hollow areas between the bones of the head. They control the temperature and humidity of the inhaled air.
  • Pharynx (throat): A passageway starts from the oral or nasal cavity to the esophagus or larynx. It provides air to the esophagus.
  • Larynx (voice box): It allows air to travel from the pharynx to the trachea and create sounds for speech. It consists of nine cartilages. Three single cartilages are thyroid, cricoid, epiglottis, and three paired cartilages: arytenoid, corniculate, and cuneiform.
  • Epiglottis: It is leaf-shaped cartilage situated in the lower pharynx or opening of the larynx. It opens and closes to prevent the entry of food into the windpipe.
  • Trachea (windpipe): It starts from the larynx to the primary bronchi. It provides passage to the air.
  • Bronchial tubes: These are also called bronchi (singular: bronchus). These tubes pass the air from the windpipe to the lungs. No gas is exchanged across the bronchi. The primary bronchi are divided into two branches, the right main bronchus and the left main bronchus. The left main bronchus further divides into two lobes, the left upper lobe and the left lower lobe. The right bronchus divides into three lobes, the right upper, right middle, and right lower lobe.

The trachea and bronchus together called bronchial tree or bronchoconstriction.

  • Lungs: These are the two spongy organs situated on both sides of the chest cavity or thorax. Each lung removes carbon dioxide from the blood and adds oxygen to it. The two lungs are divided into five lobes. The right and left lungs have three and two lobes, respectively.
  • Bronchioles: Each bronchiole leads to alveoli. The bronchioles are the smallest airways.
  • Alveoli: They are referred to as the workhorses of the respiratory system. These microscopic air sacs are the site of gas exchange.
  • Capillaries: These are the minute blood vessels that form a network in the walls of alveoli.

Some of the other components of the respiratory tract are:

  • Pleura: It is the serous membrane of the respiratory tract. It folds itself to form a two-layered membrane structure. The outer part of the pleura is connected to the chest wall.

The bloodstream delivers oxygen to all the organs with the help of red blood cells.

  • Diaphragm: This muscle helps the lungs to pull in and push out the air.
  • Ribs: It consists of bones that surround and protect the lungs and heart by forming rib cages.
  • Cilia: These are small hair-like structures present in certain parts of the respiratory tract, such as the trachea. The cilia produce a wave-like motion that filters the airways.
  • Glottis: It the opening of the vocal folds. It helps to pass the air into the trachea.
  • Hyoid bone: It is situated between the chin and the thyroid cartilage. It helps to hold up the tongue and the larynx.

The Process of Breathing

The inhaled oxygen reaches the blood from the airways through the nose or mouth, trachea, bronchi, lungs, bronchioles, alveoli, and capillaries. The oxygen-rich blood goes to the heart and spreads throughout the body. The cells and tissues of the body get the oxygen and release carbon dioxide into the blood. The blood takes the carbon dioxide to heart and then to the lungs. Ultimately, the carbon dioxide is pushed out from the lungs into the atmosphere through exhalation.

Inhalation and Exhalation 

Inhalation is the process by which oxygen gets into the body. The diaphragm, a large dome-shaped muscle, is the most important organ for this process. When the air is inhaled air, a vacuum is created as the diaphragm is pulled downwards. As a result, the air gets into the lungs.

Exhalation is the process by which carbon dioxide is released from the body. In this process, the diaphragm and intercostal muscles relax and move upwards, pushing the air towards the nose and eventually out of the body.

Gas Exchanges

Air is a mixture of gases, and each gas has a partial pressure. The pressure of each gas is called partial pressure, and the sum of all partial pressure is called atmospheric pressure. The inhaled air becomes humified when it reaches the bronchioles. The amount of gas exchange in the system can be determined by the partial pressure. The high and low air pressure gradients control the oxygen and carbon dioxide flow across the alveoli.

How does the Respiratory System Inhale Clean Air?

  • The respiratory system has its in-built mechanism to restrict the entry of harmful air particles.
  • The hair present in the nostrils filter the air, especially the large particles.
  • The small hair (cilia) found in the air passageways have a sweeping motion thus, clean the airway.
  • The mucus creates moisture in the air passageways and traps the microorganisms entering the respiratory tract.


  • Asthma: In asthma, the airways become inflamed, swollen, narrow, and produce extra mucus. The symptoms are breathlessness, coughing, wheezing, and chest pain.
  • Chronic obstructive pulmonary disease(COPD): When a bunch of lung diseases block the airflow and cause difficulty in breathing, it leads to COPD.
  • Chronic bronchitis: It is the irritation and swelling in the bronchial tube.
  • Emphysema: The inner wall of the alveolus ruptures, which generates a large air space instead of many small spaces. The emphysema causes damage to air sacs.
  • Acute bronchitis: It is short-term bronchitis. Generally, acute bronchitis is a viral infection that causes swelling in the bronchi.
  • Cystic fibrosis: It is a serious genetic disorder that causes severe damage to the lungs and the digestive system.
  • Pneumonia: A bacterial or viral infection characterizes it in the alveoli. The COVID-19 (coronavirus disease 2019) infection is also responsible for pneumonia.
  • Tuberculosis: It is pneumonia caused by the bacterium Mycobacterium tuberculosis.
  • Pulmonary edema: It is caused by excess fluid accumulated in the lungs.
  • Lung cancer: Generally, lung cancer occurs due to smoking. This cancer damages the lungs and affects their functionality.
  • Acute respiratory distress syndrome (ARDS): Severe and sudden injury in the lungs that generates a need for ventilation for the patient is referred to as ARDS. For example, COVID-19.
  • Pneumoconiosis: It is caused due to the inhalation of toxic substances like coal dust. Pneumoconiosis damages the lungs and affects their function.
  • Interstitial lung disease (ILD): It is caused by the long-time inhalation of hazardous materials like coal and asbestos. It is an irreversible disease and can result in secondary lung disorders.
  • Pulmonary embolism(PE): PE is characterized by a blood clot that affects the arteries, decreasing the level of oxygen in the body. Consequently, the person is forced to take air through the mouth.
  • Pulmonary hypertension: It is caused by high blood pressure in the pulmonary arteries. It can cause chest pain and shortness of breathing.
  • Pleural effusion: It is caused due to the deposition of fluid in the space between the lungs and chest cavity or between the pleura. It destroys the respiratory process and the heart.
  • Pneumothorax: It is the medical term for "lung collapse." This condition develops due to a leakage in between the lungs and chest wall.
  • Obesity hypoventilation syndrome: It appears in over-weighted individuals, causing difficulty in breathing.

How to Maintain a Healthy Respiratory System?

The following points should be kept in mind for keeping the respiratory system healthy:

  • Avoid pollutants, including counter smoke, chemicals, and radon (a radioactive gas that can cause cancer). 
  • Wear a face mask around fumes, dust, or any other types of pollutants.
  • Avoid smoking.
  • Take healthy foods, including fruits and green vegetables.
  • Keep the body hydrated.
  • Try to keep fresh air surroundings.
  • Yoga can help keep the respiratory system healthy.
  • Keep the hands clean.
  • Get a vaccine for flu. 

Context & Application

This topic is significant in professional exams like 

  • Bachelor of Science in Physiology
  • Master of Science in Physiology
  • Bachelor of Science in Respiratory Therapy
  • Master of Science in Respiratory Therapy
  • Bachelor of Science in Anatomy
  • Master of Science in Anatomy

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