Pharmacy Lecture: Respiratory Physiology & Pathophysiology PDF

Physiology & Pathophysiology of Respiratory System Dr. Mohamed Shebl Amer PhD in Human Physiology, Leeds Uni, UK Faculty of Pharmacy 2024-2025  Objectives  At the end of...

Physiology & Pathophysiology of Respiratory System Dr. Mohamed Shebl Amer PhD in Human Physiology, Leeds Uni, UK Faculty of Pharmacy 2024-2025  Objectives  At the end of this lecture, the student should be able to discuss the:  Physiology of respiration  Lung volumes and capacities.  Regulation of respiration.  Pathophysiology of Pneumonia.  Pathophysiology of bronchial asthma.  Respiratory System Functionally: The respiratory system consists of: 1. Lungs: The gas exchange organ. Both lungs present within the thoracic cavity, each of them covered by pleura (bilayer membrane, inner visceral & outer parietal pleural surfaces with a pleural cavity between them filled with a small amount of fluid) to protect the lungs from friction with the chest wall and create a surface tension helping the lungs stay expanded. 2. Thoracic wall: It is the pump that ventilates the lungs. It contains the respiratory muscles (diaphragm and intercostal muscles). Respiratory System  Functions of Respiratory System Respiratory functions: 1. Supplies O2 and excretes CO2 Non respiratory functions: 1. Regulation of pH (acid base balance) through controlling the amount of CO2 wash. 2. Excretion of volatile waste product (e.g. CO2 – Acetone). 3. Helping venous return (thoracic pump). 4. Voice production. 5. Defensive reflexes (cough, sneezing)  The air passages consist of: 1. Nose 2. Pharynx 3. Larynx 4. Trachea 5. Primary Bronchi 6. Bronchioles 7. Several divisions 8. Alveoli The airways divide 23 times between the trachea and Alveoli  The Respiratory lobule It is the functional unit of the lungs. It is composed of one respiratory bronchiole and its generations (alveolar ducts, alveolar sacs and alveoli with their blood vessels).  Process of Respiration The process of respiration divided into: 1. External respiration 2. Transport of O2 and CO2 by the blood 3. Internal respiration  1. External respiration External respiration occurs in the lungs and it consists of: a) Pulmonary ventilation: Exchange of air between the lungs and atmosphere. b) Pulmonary perfusion: Cardiac output from the right ventricle of the heart to the pulmonary artery then to the pulmonary capillaries. c) Pulmonary respiration: Exchange of gases between air in the alveoli and blood in the pulmonary capillaries.  Pulmonary ventilation It means exchange of air between the lungs and atmosphere. It occurs by respiratory movements or cycles in a rate of: a) 12 – 16 cycles/min in adults b) 17 – 35 cycles/min in children c) 30 – 60 cycles/min in newborns Each cycle consists of inspiration and expiration. Pulmonary ventilation depends mainly on the difference between atmospheric pressure and the pressure of air in the alveoli of the lungs.  Mechanism of inspiration (Inhalation) Impulses from the inspiratory center in the medulla oblongata. Contraction of diaphragm and intercostal muscles so, the diaphragm moves downward and the ribs move upward and forward. Increases the volume of the lungs. Decreasing the pressure within the lungs. Atmospheric air rushes into the lungs.  Mechanism of expiration (Exhalation) Expiration or exhaling is the exact opposite of inhaling. Impulses from the expiratory center in the medulla oblongata. Both the diaphragm and intercostal muscles relax so, the diaphragm moves upward and the ribs move downward and backward. Decreasing the volume of the lungs. Increasing the pressure within the lungs. The air within the lungs forces to the atmosphere.  2. Transport of O2 and CO2 O2 is transported by blood in two forms: 1. Physical: Free oxygen molecules dissolved in plasma (small amount). 2. Chemical: Oxygen molecules combine with the hemoglobin of RBCs (oxyhemoglobin) (large amount). CO2 is transported by blood in two forms: 1. Physical: Free CO2 dissolved in plasma (small amount). 2. Chemical: As bicarbonate (HCO3) (large amount) or combined with hemoglobin of RBCs (carbamino- hemoglobin).  3. Internal respiration It means gas exchange between blood and tissues through the capillaries to generate energy (ATP) inside the cells using O2 molecules.  Lungs Volumes and capacities Volume Definition Average value (cc) Tidal volume - The amount of air moved into or out of the 500 lungs in quiet, relaxed breathing. Vital capacity - The volume of air that can be expelled from 4800 the lungs by maximum exhalation following maximum inhalation. Residual volume - The volume of air that remains in the lungs 1200 after maximum exhalation. Total lung - The total volume of air that can be contained 6000 capacity in the lungs after maximum inhalation. Functional - The amount of air remaining in the lungs 2400 residual capacity after normal exhalation. Lungs Volumes and capacities Regulation of respiration: A complex process that must keep pace with moment-to-moment changes in cellular oxygen requirements and carbon dioxide production. 1. Respiratory control centers: Location: medulla and pons of the brain stem. Function: regulate the rate, depth, and rhythm of respiration. Mechanism: Respiratory center in the medulla → motor nerve fibers extend into the spinal cord (cervical segments) → fibers continue through the phrenic nerve to the diaphragm. Nature of the process: involuntary, but the diaphragm and the other muscles of respiration can be voluntary regulated by messages from the higher brain centers (cortex) to breath more rapidly or more slowly or to hold his breath and not breath at all for a time. 2. Chemoreceptors: Location: carotid and aortic bodies (peripheral), as well as in the medulla oblongata (central). Stimulator: sensitive to: ↓O2, ↑ CO2, and ↑H+ Peripheral chemoreceptors are sensitive to reduction in the partial pressure of oxygen. Central chemoreceptors are sensitive to changes in H+ in CSF as determined by changes in the partial pressure of CO2 in the blood. Mechanism: Impulses are sent from the receptors to the center.  Some signs and symptoms of respiratory diseases 1. Cyanosis: Bluish coloration of the skin and mucus membrane due to increased level of reduced hemoglobin (hemoglobin released its bound O2) more than 5 gm/dl. 2. Hypoxia: Oxygen deficiency at tissue level. 3. Dyspnea: Difficulty in breathing. 4. Orthopnea: Dyspnea on lying down that relieved or partially relieved by sitting. 5. Sneezing: Deep inspiration followed by forced expiration against opened glottis. It occurs due to irritation of nasal mucosa. 6. Cough: Deep inspiration followed by forced expiration against closed glottis. It occurs due to irritation of tracheal mucosa. Cyanosis  Lung diseases 1. Restrictive lung diseases: Cause a decrease in the lungs ability to fully expand so, the total lung capacity and vital capacity are decreased. Causes and pathophysiology: a) Brain cause: direct depression of the respiratory center. b) Chest wall abnormalities: 1. Thoracic deformity: Deformity of chest compress lung tissues. 2. Traumatic chest wall instability: e.g., Fracture of groups of ribs. 3. Neuromuscular disorders: paralysis of intercostal muscles and diaphragm. c) Pleural disorders: Accumulation of fluid, air, blood or pus in the pleural cavity: 1. Pleural effusion (Accumulation of fluid). 2. Pneumothorax (Accumulation of air). 3. Hemothorax (Accumulation blood). 4. Empyema (Accumulation of pus). 5. Pleural thickening (Due to fibrosis). d) Disorders of lung parenchyma: pneumonia, pulmonary edema, and pulmonary fibrosis. 2. Obstructive pulmonary disease: Obstruct airflow within the lungs. Classification based on durations as: a) Acute obstructive airway disease: 1. Acute Bronchitis. 2. Bronchial Asthma. b) Chronic obstructive pulmonary disease (COPD): 1. Chronic bronchitis 2. Emphysema  Pneumonia Definition: It is inflammation of the lung parenchyma. It is one of the common causes of restrictive lung disease. Pathophysiologic changes on the lung: When the lung parenchyma is inflamed → the inflammatory cells and exudative fluids accumulate in the lung tissues → result in solidification of the spongy elastic lung → the lung loses its normal expansion capacity (restrictive lung disease). Example: Covid-19 Pneumonia (Ground glass appearance). Treatment: Antibiotics and plenty fluids and protein diet with bed rest and good ventilation.  Bronchial Asthma It is a common obstructive inflammatory disease of the airways. The pathological features: 1. Bronchospasm 2. Mucosal edema 3. Mucus plugs. Symptoms: Wheezing, coughing, chest tightness, and shortness of breath (dyspnea). Pathophysiology of bronchial asthma It is thought to be caused by a combination of genetic and environmental factors called allergens or irritants such as viral or bacterial infection, exposure to dust, smoke, severe exercise, cold air, pets, pollens or drugs. The exposure to these allergens results in an IgE-dependent release of the inflammatory mediators from mast cells such as histamine, tryptase, leukotrienes, and prostaglandins that directly contract the airway smooth muscles causing bronchoconstriction and inflammation of the bronchial mucosa. Treatment of acute symptoms is usually with an inhaled bronchodilator, corticosteroids, oxygen therapy and fluid for dehydration. In very severe cases, intravenous corticosteroids and hospitalization may be required. Symptoms can be prevented by: 1. Avoiding triggers, such as allergens and irritants. 2. Use of inhaled corticosteroids.  Thank You Faculty of Pharmacy 2024 - 2025