Respiratory System

What is respiratory system?

Respiration means intake of oxygen, it utilisation in and removal of carbon dioxide produced thereof. The respiratory system of human being goes on through the following processes:

the lungs expand and the air of the atmosphere which is rich in oxygen is drawn into the lungs. This is called inspiration. From the inspired air, oxygen selectively absorbed by the blood and carried to the tissues all over the body. For oxidation of food that tissues utilise the oxygen and produce carbon dioxide. The carbon dioxide is carried by blood from tissues or lungs. The lungs the deflate and discharge the impure deoxygenated and reach with carbon dioxide air to the atmosphere. This is called expiration.

The respiratory system of the human beings is a complex physicochemical process which is conventionally divided into three major phases. Those are:

i) Breathing: - it means inspiration that this, entry of oxygen rich atmosphere air into the lungs and followed by expiration or expulsion of deoxygenated and carbon dioxide rich impure air from the lungs to the atmosphere. This process is also called pulmonary ventilation, which is a physical process effected by change of pressure in the lungs.

ii) Transport of gasses: – the gases oxygen and carbon dioxide transportation between lungs and tissues is effected by the circulating blood carries oxygen from the lungs to tissues, and carbon dioxide from tissues to lungs. It involves the physical process of diffusion of gases across the capillaries in lungs and tissues, and formation of chemical compounds of oxygen and carbon dioxide in blood.

iii) Tissue respiration or cellular respiration: – it indicates the utilisation of oxygen in the tissues for oxidation of food to carbon dioxide and water, wheat release of energy, which means production of ATP. This involves a number of energy in catalysed biochemical pathways such as glycolysis, TCA cycle, electron transfer systems, etc.

Human Respiratory Tract: -

Human Respiratory Tract

Human Respiratory Tract

During respiration or breathing the air normally flows through the pathway is called the respiratory tract or respiratory system. This tract extends from nostrils to alveoli of lungs. It includes Nasal cavity, pharynx, larynx, trachea with its branches the bronchi, bronchioles and alveoli, and the lungs. The first part of the respiratory tract starts from nostrils to larynx is called upper respiratory tract. The portion below larynx is called lower respiratory tract. Organs concerned with breathing are called respiratory organs. They include different parts of the respiratory tract as well as the organs concerned with breathing movements.
For details of the human respiratory organs click here →

Functions of Respiration or Respiratory System: -

The fallowing functions of respiration are to be noted:
i) Exchange of gas and supply of energy: - respiratory system helps in exchange of oxygen and carbon dioxide between atmospheric air and blood to maintain oxygen supply to the tissue for release of energy from oxidation of food and removal of carbon dioxide produced in the tissues.



ii) Excretion: – not only carbon dioxide, certain other volatile materials like alcohol, acetone, ether, chloroform etc. may also be excreted from blood through the expired air.

iii) Acid base balance: – carbon dioxide forms carbonic acid (H2CO3) in blood by reacting with water. So, removal of carbon dioxide true expired air reduces acidity and raises the pH of blood. When blood pH falls and blood becomes acidic breathing is increased to remove from more carbon dioxide for maintaining the blood pH as well as acid base balance in the body.

iv) Thermoregulation: – expulsion of water vapour and heat through the expired air provides a channel for heat loss from the body. In case the body temperature rises breeding is stimulated for increasing heat loss from the body and thus helps to maintain the temperature of the body.

v) Production of voice: – Vocal cord vibration due to rushing out of expired air through the larynx which helps in production of voice.

vi) Sensation of smell: –
by inhalation of air containing odoriferous substances in gaseous state through the nasal cavity gives the sensation of smell.

vii) Protective functions: – mucus secretions and ciliary movements of the respiratory tract help to trap bacteria and dust particles from the inspired air before it can enter the alveoli. The temperature and humidity of the inspired air to prevent crusting and infection of lungs is adjusted by nasal cavity. To remove foreign matters present in the respiratory tract Cough reflex originating from the tracheo-bronchial tree and sneeze reflex originating from the nasal cavity is also a non respiratory function of the respiratory system.