Breathing

• Respiration is the oxidation of nutrients in the living cells to release energy for biological work.
• Breathing is the exchange of O2 from the atmosphere with CO2 produced by the cells.
• The conducting part of the respiratory system transports atmospheric air into the alveoli.
• The conducting part of the respiratory system clears air from foreign particles.
• The conducting part of the respiratory system humidifies and brings the air to body temperature.
• Cigarette smoking is the major cause of alveolar damage.
• Alveolar walls are damaged due to which the respiratory surface is decreased.
• The role of oxygen in the regulation of respiratory rhythm is insignificant.
• Wheezing is caused by the difficulty in breathing, which is often due to inflammation of bronchi and bronchioles.
• Silicosis is a lung disease caused by breathing in silica.
• Asbestosis is a lung disease caused by breathing in asbestos particles.
• Exposure to fumes or dust can also lead to alveolar damage.
• The external nostrils lead to the nasal passage, nasal chamber, nasopharynx, glottis, larynx, trachea, primary bronchi, secondary bronchi, tertiary bronchi, bronchioles, terminal bronchioles, respiratory bronchiole, and alveolar duct.
• The larynx, also known as the sound box or voice box, is a cartilaginous box which helps in sound production.
• During swallowing, the glottis is closed by the epiglottis, a thin elastic cartilaginous flap, to prevent the entry of food into the larynx.
• The trachea, primary, secondary, and tertiary bronchi, and initial bronchioles are supported by incomplete cartilaginous half rings.
• The lungs are a branching network of bronchi, bronchioles, and alveoli.
• Alveoli and their ducts form the respiratory or exchange part of the respiratory system.
• Alveoli are the structural and functional units of lungs.
• Thoracic pressure is reduced during normal respiration.
• Lungs expand and pulmonary volume increases during normal respiration.
• Intra-pulmonary pressure decreases during normal respiration.
• Air moves from outside into the lungs during normal respiration.
• External inter-costal muscles contract during normal respiration, causing ribs and sternum to lift up, increasing volume in the dorso-ventral axis.
• The diaphragm contracts during normal respiration, increasing vertical volume (anterior-posterior axis).
• Inter-costal muscles and diaphragm relax during normal respiration, causing the thorax to regain its original position, reducing thoracic volume and pulmonary volume.
• Normal respiratory rate: 12-16 times/min.
• Functional residual capacity (FRC) is the volume of air that will remain in the lungs after a normal expiration, which is calculated as ERV + RV.
• Respiratory cycle= an inspiration + an expiration
• Total lung capacity (TLC) is the total volume of air in the lungs after a maximum inspiration, which is calculated as RV + ERV + TV + IRV or VC + RV.
• Residual volume (RV) is the volume of air remaining in the lungs after a forcible expiration.
• Inspiratory reserve volume (IRV) or complemental air is an additional volume of air that can inspire by forceful inspiration.
• Inspiratory capacity (IC) is the volume of air that can inspire after a normal expiration, which is calculated as TV + IRV.
• Dead air volume is about 150 ml.
• Vital capacity (VC) is the maximum volume of air that can breathe in after a forced expiration or the maximum volume of air that can breathe out after a forced inspiration, which is calculated as ERV + TV + IRV.
• Gas exchange occurs between alveoli and blood.
• Tidal volume (TV) is the volume of air inspired or expired during a normal respiration, which is the volume of air renewed in the respiratory system during each breathing.
• Expiratory capacity (EC) is the volume of air that can expire after a normal inspiration, which is calculated as TV + ERV.
• Expiratory reserve volume (ERV) or supplemental air is an additional volume of air that can expire by a forceful expiration.
• Oxygen and carbon dioxide are exchanged by simple diffusion.