Pulmonary - Structure & Function of the Pulmonary System PDF

Structure & Function of the Pulmonary System Chapter 26 Learning Objectives 1. Discuss common disorders related to altered respiratory functioning 2. Discuss the pathophysiology of the upper, lower, restrictive and obstructive respiratory disease. 3. Identify clinical manifestat...

Structure & Function of the Pulmonary System Chapter 26 Learning Objectives 1. Discuss common disorders related to altered respiratory functioning 2. Discuss the pathophysiology of the upper, lower, restrictive and obstructive respiratory disease. 3. Identify clinical manifestations of respiratory disease. 4. Discuss environmental factors that influence the development of respiratory disease. 5. Discuss differences between restrictive, obstructive, and vascular disorders of the respiratory system. 6. Describe long term effects of a respiratory disease. 7. Describe medical treatment for common respiratory disorders. Function of the Pulmonary System PRIMARY FUNCTION is the exchange of gases between the environmental air and the blood. There are 3 steps in this process: 1. VENTILATION: the movement of air into and out of the lungs 2. DIFFUSION: the movement of gases between air spaces in the lungs and the bloodstream 3. PERFUSION: the movement of blood into and out of the capillary beds of the lungs to the body organs and tissues Let's talk about what we know… What is the primary organ in the respiratory system? How many lobes per lung? Can anyone name more structures of the pulmonary system? What is the mediastinum? Structures of the Pulmonary System Conducting Airways: allows air into and out of the gas-exchange structures of the lungs Gas Exchange Airways: participate in gas exchange Pulmonary and Bronchial Circulation: gas exchange, delivering nutrients to lung tissues and providing oxygen-rich blood to the heart Control of the Pulmonary Circulation: important for matching ventilation and perfusion Chest Wall and Pleura: protects the lungs from injury Conducting Airways Upper Airway: - Nasopharynx & oropharynx: lined with mucosa that warms and humidifies air and removes foreign particles from it Larynx: - Connects the upper and lower airways - “Voicebox”; supported by cartilage, contains vocal cords Lower Airway: - Trachea: connects larynx to bronchi, supported by U-shaped cartilage - Bronchi: brings air into the lung at the hilum, then further branch - The lining of the bronchi contains exocrine glands called goblet cells (mucous secretion) Gas-Exchange Airways trachea → bronchi → bronchioles → alveolar ducts →alveoli ALVEOLI - Primary gas-exchange units of the lung, where oxygen (O2) enters the blood and carbon dioxide (CO2) is removed - Epithelial cells - Type I maintain structure - Type II secrete surfactant - Alveolar Macrophages immune protection; ingests foreign material that reaches the alveolus Pulmonary & Bronchial Circulation Pulmonary circulation carries deoxygenated blood away from the heart, to the lungs, and returns oxygenated blood back to the heart. Pulmonary & Bronchial Circulation Alveolocapillary membrane - Formed by the shared alveolar and capillary walls - Gas exchange occurs across this membrane Pulmonary artery - Divides and enters the lung at the hilus - Deoxygenated blood from the heart Pulmonary veins - Drains several pulmonary capillaries & dispersed randomly throughout the lung - Leave the lung at the hila and enter the left atrium - Oxygenated blood to the heart Control of the Pulmonary Circulation Calibre (internal diameter) of pulmonary artery decreases as smooth muscle in the arterial walls contracts. Contraction (vasoconstriction) and relaxation (vasodilation) occur in response to local humoral (hormone) conditions & acidemia - Most important cause of pulmonary artery constriction is a low alveolar partial pressure of oxygen (PO2) - Constriction can affect only one portion of the lung (ex. one lobe is obstructed, decreasing its partial pressure of oxygen) - The arterioles to the segment constrict, shunting blood to other well-ventilated portions of the lung (improves the lung efficiency by matching ventilation and perfusion) - If all segments of the lung are affected, pulmonary hypertension can occur; and if not treated can lead to right-sided heart failure (cor pulmonale) Chest Wall & Pleura Chest Wall: skin, ribs, and intercostal muscles - The intercostal muscles, as well as the diaphragm, accessory muscles and abdominal muscles do the muscular work of breathing Thoracic Cavity: contained by the chest wall and encases the lungs Pleura: adheres to the lungs (visceral), folds over itself, and attaches to chest wall (parietal) - The area between the two pleura is called the pleural space (cavity) - Normally, a thin layer of fluid is secreted by the pleura called pleural fluid, which lubricates the surfaces Quick Review Which is TRUE regarding the pulmonary system? A. Each lobe is divided into bronchi. B. Left lobe is divided into three lobes. C. Mediastinum contains the lungs and heart. D. Larynx connects the upper and lower airways. Function of the Pulmonary System PRIMARY FUNCTION is the exchange of gases between the environmental air and the blood. There are 3 steps in this process: 1. VENTILATION: of the alveoli 2. DIFFUSION: of gases into and out of the blood 3. PERFUSION: of the lungs so that organs and tissues of the body receive blood that is rich in oxygen Ventilation The mechanical movement of gas into and out of the lungs - “Respiratory rate” is actually the ventilatory rate, or the # of times gas is inspired and expired per minute… what is our normal range for this? Neurochemical Control → the respiratory center in the brainstem controls respirations by sending impulses to the respiratory muscles, causing them to contract and relax → the lung is innervated by the autonomic nervous system (ANS), and the sympathetic & parasympathetic divisions control the calibre of the airway - Parasympathetic contracts smooth muscle (ex. when there is an irritant) - Sympathetic relaxes Chemoreceptors monitor the pH, PaCO2, and PaO2 of arterial blood & sends signals to maintain homeostasis Mechanics of Breathing 1/3 Major muscles: - Diaphragm - External intercostals Accessory muscles: - Sternocleidomastoid muscle - Scalene muscles - Abdominal muscles - Internal intercostals Mechanics of Breathing 2/3 Alveolar Surface Tension & Ventilation: - Function of surfactant; decreases surface tension on the alveoli, allowing the alveoli to ventilate effectively - If surfactant is not produced, surface tension increases causing alveolar collapse (↑WOB, ↓lung expansion, severe gas-exchange abnormalities) Elastic Properties of the Lung and Chest Wall: - Elastic recoil: return to resting state after inspiration - Compliance: opposite of elasticity; see how much they can be stretched - INCREASED compliance indicates that the lungs or chest wall is abnormally easy to inflate and has LOST some elastic recoil (ex. aging, emphysema) - DECREASED compliance indicates that the lungs or chest wall is abnormally stiff or difficult to inflate (ex. pneumonia, pulmonary fibrosis) Mechanics of Breathing 3/3 Airway Resistance: - Determined by length, diameter, and airway obstructions (mucus, tumors, or foreign bodies) - Pulmonary Function Tests (PFTs) measure lung volumes and flow rates and can be used to diagnose lung disease Work of Breathing: - Determined by muscular effort required for ventilation - WOB may increase in diseases that disrupt the equilibrium between forces exerted by the lung and chest wall - More muscular effort is required when compliance decreases, or airways are obstructed Quick Review A patient has a history of emphysema and has hyperinflated lungs. Which would be TRUE regarding this patient? A. Increased compliance B. Decreased surfactant C. Increased elastic recoil D. Increased airway resistance Gas Transport 1. Ventilation of the lungs 2. Diffusion of oxygen from the alveoli into the capillary blood 3. Perfusion of systemic capillaries with oxygenated blood 4. Diffusion of oxygen from systemic capillaries into the cells *Diffusion of CO2 occurs in reverse order Ventilation-Perfusion Ratio (V/Q) & V/Q mismatch https://www.youtube.com/watch?v=UKsOLb5XWa0&ab_channel=RespiratoryTher apyZone Oxygen & Carbon Dioxide Transport Oxygen Transport - Diffusion across the alveolocapillary membrane - Determinants of arterial oxygenation: Hemoglobin binding & Oxygen saturation - Oxygen saturation (SaO2) id the percentage of the hemoglobin that is bound to oxygen, and can be measured using an oximeter Carbon Dioxide Transport Carried in 3 ways - Dissolved in plasma - As bicarbonate (HCO3) - Carbamino compounds Geriatric Considerations Decreased chest wall compliance and elastic recoil of the lungs - Reduces ventilatory reserve Decreased surface area for gas exchange as well as capillary perfusion Decreased exercise capacity