Lecture 25 Introduction to the Respiratory System 2023 PDF

to respiratory system Written by: Kelly Roballo DMV, PhD. Presented by: Jim Mahaney, PhD Learning Objectives Lecture 25: Introduction of Respiratory System 1. Identify the major structures of the respiratory system such as: lobes, blood vessels, and airway regions. 2. Recall the difference betw...

to respiratory system Written by: Kelly Roballo DMV, PhD. Presented by: Jim Mahaney, PhD Learning Objectives Lecture 25: Introduction of Respiratory System 1. Identify the major structures of the respiratory system such as: lobes, blood vessels, and airway regions. 2. Recall the difference between conducting zone and respiratory zone. 3. Define what are the major respiratory system protective mechanisms. 4. Define the sources of blood perfusing the lungs and their different roles in respiration. 5. Identify the major lung volumes and capacities (TLC, RV, FRV, ERV, VC, TV, IC, and IRV) 6. Define the factors that determine total lung capacity, functional residual capacity, and residual volume. 7. Describe the mechanisms responsible for the changes in those volumes that occur in patients with emphysema and pulmonary fibrosis and relate with respective pulmonary changes graphs. 8. Discuss the abnormalities associated with restrictive and obstructive lung disorders seen on spirometry. • Chapter 5 Costanzo physiology book 2 Obj. 1 Thoracic cavity Pleura: serous membrane that forms a twolayered membranous pleural sac. Visceral pleura: contact with lungs Parietal pleura: contact with ribs / muscles Pleural cavity: filled with fluid that allows visceral and parietal pleura to slide over each other. Diaphragm: main muscle for respiration Intercostal muscles: secondary system for respiration 3 Obj. 1 Anatomy • Lungs and series of airways that connect the lungs to the external airways. • Respiratory system is divided in: • Conducting zones and respiratory zones 4 Obj. 2 Structure: airways • The respiratory system includes the lungs and a series of airways that connect the lungs to the external environment. • The structures of the respiratory system are subdivided into: • a conducting zone which brings air into and out of the lungs, and … • a respiratory zone lined with alveoli where gas exchange occurs. 5 Obj. 2 Conducting zones • Nose, Nasopharynx, Larynx • Bronchi, Bronchioles, And terminal bronchioles • Smooth muscle: • Beta2 receptors (Sympathetic System)dilatation (asthma: Beta 2-adrenergic agonists) • Muscarinic receptor (Parasympathetic)constriction • Cartilage zeroth to 10th • After 10th favorable transmural pressure 6 Obj. 2 Respiratory zones • Gas exchange zone: respiratory bronchioles alveolar ducts and alveolar sac • Each lung has 300 million alveoli= large surface area • Alveolar walls: epithelial cells called type I an type II PNEUMOCYTES. •Thermoregulation: breathing causes you to lose heat (you breathe out warm, moist air). 7 Respiratory system cells: Protective Systems Obj. 3 • Ciliated: most abundant, primary defense mechanism to remove debris. Cilia beat to move material toward pharynx to swallow or cough out. • Basal: provide attachment layer for ciliated and goblet cells • Secretory: progenitor cells, also called “club” cells, secrete surfactants for fluid lining the airway • Neuroendocrine: secrete factors like catecholamine and hormones • Goblet: provide mucous to trap inhaled particles • Aveolar type 1: primary gas exchange • Aveolar type 2: surfactant, xenobiotic metabolism, movement of water, regeneration of aveolar epithelium following lung injury • Aveolar Macrophage: defense • Fibroblast: extracellular membrane, effector cells during injury repair 8 Obj. 3 Cellular crosstalk in the development and regeneration of the respiratory system 9 Mucocilliary Escalataor or Mucocilliary Clearance Mechanism for removal of pollution, dust and foreign particles Mucosal layer covers airway cells. Sticky mucous surface catches particles, rides on an aqueous layer which allows ciliated cells move the mucous upward to pharynx where they can be swallowed or coughed out. 10 Obj. 3 Respiratory System protection Foreign particles can: (1) move into the aqueous layer…OR (2) get trapped in the mucous layer and transported to the pharynx… OR (3) Get captured by macrophages that will embed in the mucous for removal from the system….OR (4) can be taken in through the epithelial cells (transcellular transport) for removal. 11 Physiological Anatomy of the Pulmonary Circulatory System Obj. 4 Pulmonary Vessels • The pulmonary artery extends from the right ventricle and then divides into right and left main branches that supply blood to the two respective lungs. The pulmonary arterial branches are short and have larger diameters than their counterpart systemic arteries. The vessels are thin and distensible, giving them a large compliance. This large compliance allows the pulmonary arteries to accommodate the stroke volume output of the right ventricle. • The pulmonary veins, like the pulmonary arteries, are also short. They immediately empty their effluent blood into the left atrium. Bronchial Vessels • Blood also flows to the lungs through small bronchial arteries that originate from the systemic circulation, amounting to 1% to 2% of the total cardiac output. This bronchial arterial blood is oxygenated blood, in contrast to the partially deoxygenated blood in the pulmonary arteries. It supplies the tissues of the lungs. This blood empties into the pulmonary veins and enters the left atrium, rather than passing back to the right atrium. Therefore, the flow into the left atrium and left ventricular output are about 1% to 2% greater than that of the right ventricular output. Lymphatics • Lymph vessels are present in all the supportive tissues of the lung, beginning in the connective tissue spaces that surround the terminal bronchioles, coursing to the hilum of the lung, and then mainly into the right thoracic lymph duct. Particulate matter entering the alveoli is partly removed by these lymph vessels, and plasma protein leaking from the lung capillaries is also removed from the lung tissues, thereby helping to prevent pulmonary edema. 12 Physiological Anatomy of the Pulmonary Circulatory System Right subclavian vein Obj. 4 Left subclavian vein Pulmonary Arteries / Veins (in picture): Carry oxygen poor blood from right ventricle to alveoli for oxygenation. Blood returns to the left atrium via pulmonary veins Bronchial Arteries / Veins (not shown): Carries oxygen rich blood to the lung tissue to support function. Blood returns to the heart via the pulmonary veins Lymphatics: Removes excess interstitial fluid from the lungs to help prevent edema. Drains into subclavian veins to the superior vena cava into the right atrium 13 Muscles That Cause Lung Expansion and Contraction Obj. 5 The lungs can be expanded and contracted in two ways: (1) by downward or upward movement of the diaphragm to lengthen or shorten the chest cavity; and (2) by elevation or depression of the ribs to increase or decrease the anteroposterior diameter of the chest cavity. 1. Diaphram: The dominant normal quiet breathing is accomplished almost entirely by movement of the diaphragm. During inspiration, contraction of the diaphragm pulls the lower surfaces of the lungs downward. Then, during expiration, the diaphragm simply relaxes, and the elastic recoil of the lungs, chest wall, and abdominal structures compresses the lungs and expels the air. 2. Raise the rib cage: Raising the rib cage expands the lungs because, in the natural resting position, the ribs slant downward, as shown on the left side of Figure. The most important muscles that raise the rib cage are the external intercostals, but others that help are the following: (1) sternocleidomastoid muscles, which lift upward on the sternum; (2) anterior serrati, which lift many of the ribs; and (3) scaleni, which lift the first two ribs. 14 Obj. 5 Lung Volumes Know these terms: • Tidal Volume (VT , 500 ml): the volume of the air that fills the alveoli plus the airways during normal quiet breathing. • Inspiratory Reserve Volume (IRV, 3000 ml): Breathe in as much air as possible. • Expiratory Volume (EV, 1200 ml): Breathe out as much air as possible. • Residual Volume (RV, 12000 ml): Air that remains in lungs after maximal exhalation. 15 Obj. 5 Lung Capacities Know these terms: • Inspiratory Capacity (IC): TV + IRV = 3,500 ml • Functional Residual Capacity (FRC): ERV + RV = 2400 ml • Vital Capacity (VC): IC + ERV = 4700 ml Total Lung Capacity (TLC) = 5900 ml 16 Obj. 5, 6 17 Other Volumes: Anatomic and Physiologic Dead Space Obj. 5 • Anatomic Dead Space: volume of the airways and lungs that that does not participate in gas exchange • Nose, mouth, trachea, bronchi and bronchioles • Physiologic Dead Space: total volume of the lungs that does not participate in gas exchange. Includes anatomic dead space and *functional* dead space = ventilated alveoli that do not participate in gas exchange. One third of each tidal volume (VT) fills the anatomic dead space Green is fresh inspired air that does not participate in gas exchange Purple is fresh air that does participate in exchange Yellow is the expired air that remains after previous breath 18 Obj. 5 Ventilation * Rates Ventilation Rate = volume of air moved into and out of the lungs per unit time. Minute Ventilation = rate of air movement into and out of the lungs Minute Ventilation = VT x Breaths/min Alveolar Ventilation = minute ventilation corrected for the physiologic dead space • VA = (VT – VD) x Breaths / min *Note: the dot above the V indicates this is a time derivative or a rate. 19 Obj. 5 Alveolar Ventilation Recall that O2 and CO2 pass readily between air and cells / interstitium / blood. There is NO difference in the amount (pressure) of CO2 and O2 in the alveolar space (PA) and arterial blood (Pa) in contact with the alveoli. Inspired air has virtually no CO2 and a high percentage of O2 whereas exhaled air has significant CO2 and some residual O2 (low level). Alveolar ventilation is the FUNDAMENTAL relationship of respiratory physiology that describes the inverse relationship between alveolar ventilation (VA) and alveolar P-CO2 or PACO2. Each curve is the relationship at a constant level of CO2 production…i.e., at rest or when exercising, etc. 20 chronic obstructive pulmonary disease (COPD) Obj. 7 A group of diseases that cause airflow blockage and breathing-related problems. Chronic bronchitis and emphysema are the two main forms, and usually occur together. Progressive diseases that get worse over time. Smoking is usually the main cause for both conditions. Rare condition is α-1 antitrypsin deficiency, which can cause emphysema without having a history of smoking. https://www.biophysics.org/blog/molecular-mechanisms-of-inflammatory-signaling-in-copd 21 Obj. 7 Chronic Bronchitis Decreased airway flow, decreased capacitance, increased and thicker mucous lining Caused by overproduction and hypersecretion of mucous by goblet cells. Epithelial cells respond to toxic or infectious stimuli b releasing inflammatory mediators and proinflammatory cytokines. Smoking is most common cause, but also chronic poor air quality (pollution, dust). More prone to lung infections since clearance mechanisms impaired. 22 Obj. 7 Emphysema Abnormal permanent enlargement of lung air spaces with destruction of their walls and destruction of lung parenchyma with loss of elasticity. Irritants from smoking or air pollution cause inflammation, which results in degradation of the elastic fibers of and septa between alveoli. The spaces become large and less elastic, preventing efficient air intake and gas exchange. 23 Obj. 7 Restrictive Lung Disease and COPD Restrictive lung diseases decrease total volume of air lung can hold often due to a loss of elasticity of lung tissue. All capacities decreased. COPD lungs can hold more air but the functional (physiological) volumes are perturbed. 24 Obj. 7 pulmonary fibrosis • Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive lung disease. • Characterized by progressive lung scarring and usual interstitial pneumonia (UIP). • Fibrosis greatly decreases the elasticity of lung tissue, hampering intake of breath. 25 Obj. 7 Changes in Airway Resistance: Histamine and ASthma • Histamine and several leukotrienes are potent bronchoconstrictors that increase airway resistance. • Lung volume: changes in lung volume alter airway resistance. Persons with asthma breathe at higher lung volumes which partially offset the high airway resistance of their disease (i.e., the volume mechanism helps to reduce airway resistance as a compensatory mechanism). • Compensatory bronchoconstriction: an adaptive mechanism involving airway resistance is utilized when ventilated alveoli are not perfused with pulmonary capillary blood. 26 COPD and Exertion / Exercise Intolerance Obj. 7 Normal: Lungs dynamic, elastic respond to changes needed for exercise / exertion. COPD: Greater RV decreases VC, obstructed limits air exchange, 27 pressure Bring it all together: The LUNg Pressure-Volume Loop 28 Obj. 8 How Disease Affects the PV Loop 29 Thank you