Respiratory Physiology and Pathophysiology Lecture Notes PDF

F A C U L T Y O F P h a r m a c y F A L L 2 0 2 3 Faculty of Pharmacy 1 Respiratory Physiology and Pathophysiology Dr. Ramadan Saad From this study you should be able to: Describe the n...

F A C U L T Y O F P h a r m a c y F A L L 2 0 2 3 Faculty of Pharmacy 1 Respiratory Physiology and Pathophysiology Dr. Ramadan Saad From this study you should be able to: Describe the need to breath as a part of a metabolic process Describe the function of the respiratory conducting zone Describe pulmonary ventilation Briefly explain how surface tension arises & is stabilized Define lung volumes & lung capacities Briefly describe neurological control of breathing with description of the stimulation of central chemoreceptor State the role of Haemoglobin in gas movement Explain how O2 & CO2 are carried in the blood  Functions of the Respiratory System Primary functions: Supply oxygen and eliminate carbon dioxide Other Functions of the Respiratory System: BEHAVIORAL: talking, laughing, singing, reading DEFENSE: humidification, particle expulsion (coughing, sneezing), particle trapping (clots), immunoglobulins from tonsils and adenoids. SECRETIONS: mucus. 4 Faculty of Pharmacy Other Functions: METABOLIC- forms angiotensin II, prostacyclin, bradykinin, serotonin and histamine ACID - BASE BALANCE- changes in ventilation e.g., acute acidosis of exercise MISCELLANAEOUS- lose heat and water, liquid reservoir for blood, defecation and childbirth. 5 Faculty of Pharmacy Respiration It is the process by which the body takes in oxygen and utilizes and removes CO2 from the tissues into the expired air It comprises of Ventilation by the lungs inspiration and expiration Gas exchange across alveolar membrane Diffusion in the alveoli. Transport of gases by blood (haemoglobin) Uptake of O2 and release of CO2 by tissues Diffusion at the cellular level 6 7 Respiratory tract is made up of two zones Conducting zone: Includes all the structures that air passes through before reaching the respiratory zone. Mouth, nose, pharynx, larynx, trachea, bronchi. Major functions Warms and humidifies until inspired air becomes: 37 degrees Saturated with water vapor Filters and cleans: Mucus secreted to trap particles Mucus/particles moved by cilia to be expectorated. 8 Faculty of Pharmacy Respiratory zone Region of gas exchange between air and blood - Respiratory bronchioles - Alveolar ducts, Alveolar Sacs and - Alveoli Primary sites of gas exchange, have huge surface area Type I cells- simple squamous epithelia Type II cells- secrete surfactant, helps keep alveoli open Alveolar macrophages- “dust cells” help keep lungs clean Alveoli are surrounded by pulmonary capillaries, exchange gas with blood 9 10 Faculty of Pharmacy Mechanics of breathing Inspiration: Active process- Diaphragm contracts → increased thoracic volume vertically. External Intercostal muscle contract, expanding rib cage → increased thoracic volume laterally. More volume → lowered pressure → air in. Expiration Passive process at rest- diaphragm only relaxes and air flows out Active during exercise. Mechanism When contraction of inspiratory muscles stops and due to recoil of elastic lungs. Less volume -> pressure within alveoli is just above atmospheric pressure -> air leaves lungs. 12  Surface Tension and Surfactant Surface Tension - results from forces between water molecules at air-water interface - contributes to inward recoil force in lungs, tends to collapse alveoli inward. - greater effect on small alveoli than large alveoli. Pulmonary surfactant - secreted by type II alveolar cells → reduces surface tension and decreases work of breathing  Clinical Application Respiratory Distress Syndrome of the New Born ❑Developing fetal lungs are unable to synthesize surfactant until late in pregnancy ❑Premature babies may not have enough pulmonary surfactant ❑This causes respiratory distress syndrome of the new born ❑The baby makes very strenuous inspiratory efforts in an attempt to overcome the high surface tension and inflate the lungs. Faculty of Pharmacy Bronchial Asthma Pathogenesis Spasmodic contraction of smooth muscles in walls of smaller bronchi and bronchioles (Bronchospasm). Associated with increased secretions from bronchial mucous glands Attacks precipitated by allergens Interact with mast cells which Release chemical mediators as histamine that induce bronchospasm. Clinical manifestations Shortness of breath Wheezing respirations Air flow impeded more on expiration than on inspiration Air trapped in lungs Lungs become overinflated Treated with drugs such as epinephrine or theophylline that relax bronchospasms and block the release of mediators from mast cells Faculty of Pharmacy  O₂ Transport in blood O₂ is transported in blood in two forms:- 1. Physically dissolved O₂. It represent a small fraction ( 1.5%). 2. Chemically bound to hemoglobin. It is the most important form (98.5%). Hemoglobin is formed of 4 subunits, each subunit contains a ferrous ion that binds reversibly with O₂, so the reaction is called oxygenation and not oxidation. HbO₂ O₂+ Hb Faculty of Pharmacy CO2 Transport CO2 transported in the blood: - most as bicarbonate ion (HCO3-) - dissolved CO2 - CO2 attached to hemoglobin and plasma proteins 18 Faculty of Pharmacy Faculty of Pharmacy The control of respiration is tied to the principle of homeostasis (image right). The basic rhythm of breathing is set by the inspiratory center, located in the medulla. The inspiratory center sets the rhythm by automatically initiating inspiration (image below). Faculty of Pharmacy  CHEMICAL CONTROL OF RESPIRATION ⚫The ultimate goal of respiration is to maintain the PO2, PCO2 & pH in tissues constant. ⚫ O2,  CO2 or  pH in arterial blood increases the activity of the respiratory center → pulmonary ventilation, while  O2,  CO2 or pH has the opposite effect. ⚫In this way, the respiratory rate is adjusted according to the body’s metabolic needs. ⚫The effect of changes in PO2, PCO2 & pH on ventilation is mediated through chemoreceptors to the respiratory center. 22 Faculty of Pharmacy Location of Chemoreceptors The basic rhythm of breathing is modified by input from the central and peripheral chemoreceptors. They respond to changes in the PCO2, pH, and PO2 of arterial blood. These are the most important factors that alter ventilation.  Changes in PCO2, pH, and PO2. Faculty of Pharmacy  Changes in PCO2, pH, and PO2. Faculty of Pharmacy  Changes in PCO2, pH, and PO2. Faculty of Pharmacy Faculty of Pharmacy Hypoxia decreased O2 delivery to the tissues 1. HYPOXIC HYPOXIA ❑ Most common ❑ In high altitudes and lung disease. ❑ Inadequate O2 delivery to body tissues → hypoxia. Inadequate O2 delivery to body tissues → hypoxia Faculty of Pharmacy 2. ANAEMIC HYPOXIA ❑ Can be brought about by: o  [Hb] or circulating red blood cells → anemia. Inadequate O2 delivery to body tissues → hypoxia Faculty of Pharmacy 3. STAGNANT HYPOXIA ❑ Arises when there is a decrease in blood flow to the tissues ❑ in severe haemorrhage ❑ Heart failure. Inadequate O2 delivery to body tissues → hypoxia Faculty of Pharmacy 4. HISTOTOXIC HYPOXIA ❑ O2 delivery to the tissues is normal but the cells are unable to use the O2 eg. Cyanide poisoning Inadequate O2 delivery to body tissues → hypoxia  Thank you! 31 NOMAD:RESPIPHYS: Intro