Unit I B: Breathing and Respiration - Respiratory Organs in Animals; Respiratory System in Humans; Mechanism of Breathing and Its Regulation in Humans - Exchange of Gases, Transport of Gases and Regulation of Respiration; Respiratory Volumes; Respiratory Disorders: Asthma, Emphysema, Occupational Respiratory Disorders – Asbestosis, Silicosis, Siderosis, Black Lung Disease in Coal Miners