Breathing & Gas Exchange Notes PDF

## Breathing & Exchange's Gores ### Average Ventilation Rate: 12-16 Breaths / Min ### Pulmonary volume measurement device: Spirometer ### Types of Pulmonary Volume: 1. **TV (Tidal Volume) ~ 500 ml** * Volume of air inhaled or exhaled during normal breathing. * Total volume of air inh...

## Breathing & Exchange's Gores ### Average Ventilation Rate: 12-16 Breaths / Min ### Pulmonary volume measurement device: Spirometer ### Types of Pulmonary Volume: 1. **TV (Tidal Volume) ~ 500 ml** * Volume of air inhaled or exhaled during normal breathing. * Total volume of air inhaled or exhaled in one minute: 12-16 X 500 = 6000-8000 ml. 2. **IRV (Inspiratory Reserve Volume) ~ 2500-3000 ml** * Additional volume of air that can be inhaled by forceful breathing. 3. **ERV (Expiratory Reserve Volume) ~ 1000-1100 ml** * Additional volume of air that can be exhaled by forceful breathing. 4. **RV (Residual Volume) ~** * Volume of air remaining in the lungs after forceful exhalation. * This volume cannot be exhaled, even with a spirometer. 5. **IC (Inspiratory Capacity) ~ 3000-3500 ml** * Total volume of air that can be inhaled, starting from normal expiration. * IC = TV + IRV 6. **EC (Expiratory Capacity) ~ 1500-1600 ml** * Total volume of air that can be exhaled, starting from normal inspiration. * EC = TV + ERV 7. **VC (Vital Capacity) ~** * Maximum volume of air that can be inhaled after forceful exhalation following forceful inhalation. * VC = TV + IRV + ERV. 8. **TLC (Total Lung Capacity) ~** * Total volume of air in the lungs after a forceful inhalation. * TLC = TV + IRV + ERV + RV, or TLC = VC + RV. 9. **FRC (Functional Residual Capacity) ~** * Volume of air remaining in the lungs after a normal exhalation. * FRC = RV + ERV 10. **Diagram of Gas Exchange** * pO2 Max: O2 Air * pCO2 Min: CO2 Air * Breathing * Gas Exchange * Gas Transport * Cellular Respiration. * pO2 min: O2 Tissue * pCO2 max: CO2 Tissue ### Atmospheric Pressure: 760 mmHg * % of O₂: 21% * % of CO₂: 0.08-0.04% * pO₂: 159 mmHg * pCO₂: 0.3 mmHg ### Table 1: Partial Pressures of Gases in Different Regions | mmhg | Air in Alveoli | Pure Blood | Artery | Tissue | |---|---|---|---|---| | pO₂ | 159 | 104 | 95 | 40 | 40 | | pCO₂ | 0.3 | 40 | 40 | 45 | 45 | ### Steps of Respiration 1. **Ventilation (Breathing / Pulmonary Ventilation)** * Physico-chemical process involving exchange of O₂ and CO₂ between the alveoli and the atmosphere. * The muscles involved are The diaphragm, intercostal muscles: * Diaphragm: 75% effort. * Intercostal muscles: 25% effort. * The diaphragm and external intercostal muscles are involved during normal ventilation. 2. **Inspiration** * An active process where the intrapulmonary pressure decreases by expansion of the lungs. * Diaphragm flattens from its dome shape, and the external intercostal muscles (EICM) contract causing an increase in the anterior-posterior diameter of the chest. * This results in a decrease in the intrapulmonic pressure, which is less than the atmospheric pressure, causing air to rush into the lungs. 3. **Expiration** * A passive process where the intrapulmonary pressure increases, forcing air out. ### Notes * During forceful expiration, internal intercostal muscles (IICM) and abdominal muscles are also used. ### Exchange of Gases * The exchange of gases takes place between alveoli and blood capillaries. * The site of the most efficient exchange of gases is alveoli. ### Factors Involved In Gas Exchange: * **Partial Pressure:** The movement of gases is from higher partial pressure to lower partial pressure. * **Diffusion membrane:** The diffusion membrane is the thin barrier between alveoli and blood capillaries. * **Solubility:** The solubility of a gas in the fluid affects its diffusion rate. * Diagram of the structure of alveoli with labelled parts: simple squamous epithelium, endothelium, basal membrane, blood capillary, alveoli & the directional flow of O₂ and CO₂ between alveoli and blood. ### Transport of Gases 1. **Oxygen Transport** * Oxygen is transported in the blood by **Hemoglobin** (97-98%). * **Hemoglobin** is a conjugated protein. * Protein part: 2 alpha & 2 beta globin chains. * Non-protein part: Heme prosthetic group (Fe²⁺ + porphyrin ring). * **Hemoglobin** is an amphoteric protein. * **Hemoglobin** also acts as an allosteric protein. * Oxygen is also transported in the blood plasma (2-3%) by dissolving in it. 2. **Carbon Dioxide Transport** * Carbon dioxide is transported in the blood in three major ways: * **Bicarbonate ions (HCO₃-) :** (60- 70%). * **Carbaminohemoglobin ( H HbCO₂):** * **Dissolved in Plasma:** (5- 7%). * **Diagram showing formation of bicarbonate ions in RBC, their transport across the membrane and then reverse reaction in the lungs.** * **The Bohr effect:** * In the blood plasma, bicarbonate ions combine with Na⁺ to form Sodium bicarbonate (NaHCO₃). * The Haldane effect: Removal of CO₂ from the blood, increases Hb's oxygen binding affinity. ### Regulation of Breathing * The process of breathing is regulated by the Respiratory Control Center in the brain. * Diagram of the respiratory control center: * **Respiratory Rhythm: Apneustic center** * **Respiratory Rhythm: Pneumotaxic center** * Chemosensitive Area * Respiratory control center interacts with the respiratory muscles to increase or decrease breathing rate. * The chemosensitive area of the brain senses changes in CO₂ & H⁺ in the blood. * O₂ concentration in the blood does not have much effect on the respiratory rate. * **The chemosensitive area sends signals to the respiratory center to adjust the breathing rate based on the concentration of CO₂ and H⁺ in the blood.** ### Anatomy of the Respiratory System * Diagram showing pathway of the respiratory system starting from the nasal cavity to the alveoli. * **External nostrils:** Inlets of the nasal passage. * **Nasal passage:** Covered with mucous membranes. * **Internal nostrils:** Openings from the nasal passage to the nasal pharynx. * **Nasopharynx:** The upper part of the pharynx. * **Pharynx:** Common passage for food and air. * **Larynx:** Between pharynx & trachea. * **Trachea:** Windpipe. * **Primary Bronchi:** Two branches into the lung. * **Secondary Bronchi:** Branches of the primary bronchi. * **Terminal Bronchioles:** Subdivision of secondary bronchi. * **Respiratory Bronchioles:** Subdivision of terminal bronchioles. * **Alveoli:** Tiny air sacs, air sacs, site of gas exchange. * **Conducting zone:** The path of air flow, without gas exchange. * **Exchange zone:** The area of gas exchange. ### Conducting Zone: * **Dead Space Volume (DSV) = 150 ml.** * This is the volume of air which remains in the conducting zone and does not reach the alveoli. * **Pharynx:** * **Nasopharynx:** Uppermost part of the pharynx, connected to nasal passage. * **Oropharynx:** Middle part of the pharynx, connects to the oral cavity. * **Laryngopharynx:** Lowermost part of the pharynx, connects to the larynx. * **Larynx:** The voice box. * Composed of cartilaginous rings. * **Laryngeal cavity:** Main part, has vocal cords. * **Thyroid cartilage:** Largest cartilage, forms Adam’s Apple. ### Respiratory zone: * **Trachea:** * It is a 10-12 cm long tube, lined by pseudostratified ciliated epithelium with hyaline cartilage rings. * The hyaline cartilage rings prevent trachea from collapsing. * **Lungs:** * The lungs are located in the thoracic cavity surrounded by pleural membranes which are lined by fluid. * **Pleural fluid:** Reduces friction during breathing. * **Alveoli:** * Tiny air sacs, site of the exchange of gases. * **Two types of pneumocytes:** * **Type 1:** Simple squamous epithelial cells, for gas exchange. * **Type 2:** Secrete surfactant which reduces surface tension and facilitates gas exchange. ### Respiratory Disorders 1. **COPD (Chronic Obstructive Pulmonary Disease)** * **Asthma:** A chronic inflammatory disease of the airways. * **Emphysema:** Condition characterized by the destruction of alveolar walls and loss of elasticity of the lungs, leading to difficulty in breathing. * **Bronchitis:** Inflammation of the bronchi, causing mucus buildup and coughing. 2. **Occupational Lung / Respiratory Diseases (OLD/ORD)** * **(Asbestosis):** Inflammation of the lungs caused by inhaling asbestos fibers. * **(Silicosis):** Inflammation of the lungs caused by inhaling silica dust. * **(Siderosis):** Inflammation of the lungs caused by inhaling iron dust. * **(Black lung disease (coal):** Inflammation of the lungs caused by inhaling coal dust. ### Notes * **Dyspnea:** Difficulty in breathing. * **Eupnea:** Normal breathing. * **Pleurisy:** Inflammation of the pleural membranes. * **Respiratory Distress Syndrome (RDS):** A disorder in newborns, where the alveoli collapse due to the deficiency of surfactant. ### Bronchitis * Inflammation of the bronchi, leading to increased mucus production and difficulty in breathing. * The Hb + O₂ bond is stronger than the Hb + CO bond. This is significant for carbon monoxide poisoning, which prevents the binding of oxygen to hemoglobin. ### Disorders of Gas Transport: * **Hypocapnea:** Decreased carbon dioxide concentration in the blood. * **Hypercapnea:** Increased carbon dioxide concentration in the blood. * **Hypoxia:** Reduced oxygenation of the tissues. * **Anoxia:** Complete lack of oxygen supply to the tissues.