Breathing and Exchange of Gases Notes

 The "Breathing and Exchange of Gases" chapter, often found in biology textbooks, explains the process of how organisms, including humans, obtain oxygen and expel carbon dioxide, crucial for cellular respiration and energy production. 

Breathing (Pulmonary Ventilation):

The mechanical process of moving air in and out of the lungs, involving inspiration (inhaling) and expiration (exhaling). 

Respiration:

The overall process of gas exchange, including breathing, diffusion of gases across membranes, transport of gases by blood, and cellular respiration where oxygen is used and carbon dioxide is produced. 

• Respiratory Organs:

  Specialized organs like lungs (in humans and other vertebrates) or gills (in aquatic animals) facilitate gas exchange. 

• Mechanism of Breathing:

  Breathing involves creating pressure gradients between the lungs and the atmosphere, facilitated by muscles like the diaphragm and intercostal muscles. 

• Cellular Respiration:

  The process where cells use oxygen to break down glucose and other nutrients to produce energy, releasing carbon dioxide as a waste product. 

• Gas Exchange:

  Oxygen from the inhaled air diffuses into the blood, while carbon dioxide from the blood diffuses into the lungs to be exhaled. 

Alveoli and alveolar ducts together take part in the exchange of gases. Bronchi, bronchioles and alveoli together constitute a lung. Each lung is covered by the pleural membrane. It is a double-layered membrane, pleural fluid is present between the two layers, which reduces friction.

RESPIRATORY ORGANS  

Mechanisms of breathing vary among different groups of animals depending mainly on their habitats and levels of organisation. Lower invertebrates like sponges, coelenterates, flatworms, etc., exchange O2 with CO2 by simple diffusion over their entire body surface. Earthworms use their moist cuticle and insects have a network of tubes (tracheal tubes) to transport atmospheric air within the body. Special vascularised structures called gills (branchial respiration) are used by most of the aquatic arthropods and molluscs whereas vascularised bags called lungs (pulmonary respiration) are used by the terrestrial forms for the exchange of gases. Among vertebrates, fishes use gills whereas amphibians, reptiles, birds and mammals respire through lungs. Amphibians like frogs can respire through their moist skin (cutaneous respiration) also.