Respiratory Organs
* The process of breathing accompanied by the breakdown of foods to produce energy is called respiration.
* Among all animals, mammals have a well-developed respiratory system.
* In humans beings, and generally in all mammals, the organs of respiration include the nose, pharynx, larynx, trachea, bronchi, lungs and diaphragm.
* Based on function, the respiratory system is divided into two parts- the conducting part and the respiratory part.
* The conducting part spreads from the external nostrils to the terminal bronchioles.
* The respiratory part contains the alveoli and alveolar ducts.
Mechanism of Breathing
* Respiration involves: breathing, external respiration, internal transport, internal respiration and cellular respiration.
* As carbon dioxide is twenty to twenty five times more soluble than oxygen, the amount of carbon dioxide that can diffuse through the diffusion membrane is much higher compared to that of oxygen.
* The volume of air inspired and expired by the lungs can be estimated by using a procedure called spirometry.
Exchange of Gases
* Oxygen and carbon dioxide are exchanged by simple diffusion based on the pressure and concentration gradients of these respective gases.
* Oxygen and carbon dioxide are transported to various organs of the body by blood.
* Haemoglobin is a red-coloured, iron- containing protein. Each haemoglobin molecule can carry four molecules of oxygen.
* About ninety-seven percent of oxygen is transported by red blood cells, whereas the remaining three percent is carried in a dissolved state through plasma.
* For every hundred millilitres of deoxygenated blood, haemoglobin releases approximately four millilitres of carbon dioxide to the alveoli.
* The whole respiratory system, including the exchange and transport of gases, works to a rhythm controlled by the human brain.