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What is the Respiratory System: Diagram and Function

Updated on December 28, 2017
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Edmund has spent the last ten years working in clinical research. He has written many articles on human anatomy and physiology.

We take on average 20 000 breaths each day. When we breathe in, oxygen is delivered into our body and when we breath out carbon dioxide is expelled from our body.

What is the respiratory system? The human respiratory system is a biological system that pushes air into the lungs where gaseous exchange occurs between the exterior and the blood stream. The respiratory system consists of the airways, the lungs and muscles.

Diagram of the Respiratory System

Respiratory System Diagram
Respiratory System Diagram

Respiratory System Functions

During inspiration, the rib cage moves outwards and upwards and the diaphragm lowers increasing the volume of the thoracic cavity. This causes the internal pressure in the lungs to be lower than the atmospheric pressure. The difference in pressure forces air (introducing oxygen to the alveoli) in to the lungs.

During expiration, the opposite of inspiration occurs. The rib cage relaxes to its normal position and the diaphragm moves upwards reducing the volume of the thoracic cavity. This causes the internal pressure in the lungs to be greater than the atmospheric pressure. The difference in pressure forces air out of the lungs expelling carbon dioxide.

Anatomical features of the respiratory system

Mouth and Nasal Cavity: Incoming air is filtered, warmed and moistened in this part of the respiratory system.

Pharynx: The pharynx is located posterior to the larynx. It opens into the esophagus for food passage. It also opens into the trachea for air passage.

Larynx: it connects the lower section of the pharynx with the trachea. The larynx also helps to warm and moisten incoming air.

Trachea: The trachea is vertical tube of 2.5 cm in diameter and ten centimeters in length and it made of the hyaline cartilage. It conducts air from the larynx to the bronchi.

Bronchi: The trachea divides into the right and left bronchi. The bronchi further divides to give rise to bronchioles.

Illustration of gaseous exchange in the alveoli
Illustration of gaseous exchange in the alveoli | Source

Bronchioles: The bronchi further divides into finer branches and give rise to the bronchioles. The bronchioles terminate in circular sacs called alveoli.

Alveoli: Gaseous exchange occurs in the alveoli of the lungs through diffusion. The alveoli are surrounded by blood vessels. This is where oxygen diffuses from air in to the blood.


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      Abhishek Pandya 

      20 months ago

      Thanks for the information.

    • profile image

      rietch cashmie 

      23 months ago

      Very educatif helping me to recover from old school teachings

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      5 years ago

      Very usefull


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