Published On: Thu, Sep 13th, 2012

Human Respiratory System : Parts and Functions

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Posted under Category : Health Fundas

Human Respiratory System

Respiratory System is an anatomical system that helps in the exchange of the gases.

We need for doing the external activities and for carrying out the functions of the internal organs. Energy is released with the help of oxygen present in the air, oxygen reacts with the food and releases energy by a process known as “oxidation”. During the oxidation of the food carbondioxide is released which is a and it has to be sent out.

The above function is performed by the respiratory system. The taking in of oxygen and release of carbondioxide is known as “respiration”. The organs which carry out the respiration are called as respiratory organs and the system is called as respiratory system.

Parts of the Human Respiratory System:

Respiratory system consists of

  • Nose
  • Pharynx
  • Larynx
  • Trachea
  • Bronchi
  • Lungs


The nose is in the shape of a pyramid and consists of a cavity known as nasal cavity. The nasal septum divides the nasal cavity into two nasal passages which are lined internally by a moist mucous membrane. This mucous membrane makes the air moist and warm as the air passes through it and protects the lungs from the ill effects of the dry and cold air. Fine hairs are present in the nasal passages whose function is to filter the dust particles that enter along with the air and are trapped in the mucous membrane. The nose opens outside through a pair of external nostrils. Internally it opens at the upper end of pharynx through a pair of internal nostrils.


Pharynx is a junction for the food and air passages. Near the pharynx there are a pair of tonsils and adenoids that are used for filtration of microbes etc.


Larynx is called as the “voice box“. Larynx is found just below the pharynx. At the top of larynx, a flap like structure known as epiglottis is present and is made of cartilage. The function of the epiglottis is to prevent the food and fluid from entering into the larynx. Larynx consists of a pair of cords known as vocal cords that produces sounds when the air comes out of the lungs.
The larynx of man is larger than that of an woman, and consists of long vocal cards, so the voice of a man is deep-pitched. The larynx then opens into trachea.


Trachea is also known as “wind pipe” and it is a long tube like structure. It travels through the and enters the chest cavity or thorasic cavity. The wall of the trachea consists of “C” shaped cartilaginous rings. The C shaped rings may range from 16 to 20 rings, which are useful for regulating the air pressure. Trachea is also lined internally by the mucous membrane and it consists of millions of cilia, that sweep away the tiny dust particles that enter along with the air.

Bronchi and bronchioles:

Trachea in the chest cavity get divided into the right and left branches. These branches again divide into smaller branches called as bronchi. This bronchi in each lung divide into a number of very small tubes known as bronchioles. These bronchioles end in air sacs or alveoli.
Alveoli are the basic structural units of the lungs. They are very minute and consists of a very thin wall. They are also called as air sacs. In an adult human being there are about 600,000,000 alveoli. The walls of the alveoli consists of extensive network of very small blood vessels called as capillary network. During the entry of air into the lungs, the oxygen present in it diffuses into the blood of these minute blood vessels and carbondioxide goes out from these vessels.


There are a pair of lungs in the chest cavity, one on either side of the heart. The lungs are covered by the pleural membranes that protects the lungs.
The lungs are slate coloured and are elastic in nature. Lungs are made up of a mass of spongy tissue with minute passages for air. Lungs are protected from the external injury by sternum or breast bone in the front, vertebral column on the back and ribs on the sides which altogether form a bony box and protect the lungs.

Entry into and Exit of air from lungs:

Air –> External Nostrils –> Nasal Passages –> Internal Nostrils –> Pharynx –> Larynx –> Trachea –> Bronchi –> Bronchiloes –> Air Sacs (Alveoli) of Lungs.
The above sequence is the entry of air into the lungs. The exit is from the air sacs to external nostrils.

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