Chapter 6 Respiratory System PDF

Chapter 6 Respiratory System Porcari, John. “Chapter 6: Respiratory System.” Exercise Physiology, F.A. Davis Company, 2015. Anatomy of the Respirator y System Consists of: + Airways + Lungs + Respiratory muscles + Epiglottis: Tips to protect the airwa...

Chapter 6 Respiratory System Porcari, John. “Chapter 6: Respiratory System.” Exercise Physiology, F.A. Davis Company, 2015. Anatomy of the Respirator y System Consists of: + Airways + Lungs + Respiratory muscles + Epiglottis: Tips to protect the airway in swallowing  Breathing Cycle +Fresh, oxygen-rich air contained in the atmosphere is brought into the lungs through inhalation, also called inspiration. +Oxygen-depleted air that is rich in CO2 is removed from the lungs by exhalation, or expiration. +In the lung tissue, gas is exchanged between the atmosphere and blood; this exchange is referred to as external respiration, or pulmonary respiration. +Internal respiration occurs between the blood and all other cells of the body. Thoracic Cavity + AKA Chest Cavity + Space located above the diaphragm that houses the lungs and heart + Protected by thoracic cage (ribs, spine, sternum, and muscles involved in respiration) + Internal and external intercostals Lungs + Two lungs in the body (right and left), each located in the thoracic cavity + Right Lung is divided into 3 lobes (upper, middle, and lower) + Left Lung is divided into 2 lobes (upper and lower) + Cone-Shaped + Comprised of light, spongy tissue that contains hundreds of millions of microscopic air- filled sacs called alveoli Pleura and Pleural Cavity + Pleura: Very thin set of moist membranes that enclose the lungs + Inner layer of pleura: Visceral Pleura + Lines the thoracic walls and diaphragm + Parietal Pleura: Fused to outer surface of each lung + Between the two membranes is a small space called the pleural cavity. Conducting Zone + Contains the air passages that transport air from the external environment to the areas of the respiratory system where gas exchange occurs. + Nose, nasal cavity, mouth, pharynx, larynx, trachea, bronchial tree, and terminal bronchioles + Pharynx: AKA throat, contains 3 regions + Trachea: AKA windpipe + Goblet Cells: Produce Mucus + Larynx: Contains folds that produce sound + Main function: Conditioning and clean the air that enters the body + Warming + Humidification + Filtration Trachea + AKA Windpipe + Passageway that moves air into the lungs + Semi-Flexible tube supported by 15-20 rings of cartilage + 2.5 cm in diameter and 12 cm long + Branches into right and left primary bronchi, initiating the bronchial tree. + Largest cartilage of larynx: Thyroid Cartilage Bronchial Tree + The bronchial tree is a progressively dividing network of airway passages that originates from the first branching of the trachea (generation 1) into the right and left primary bronchi. + The bronchial tree contains approximately 23 generations of airways. + Primary Bronchus: Projects from trachea, supplies each lung + The secondary bronchus supplies each lobe of the lung. + Tertiary bronchus: supplies each lung segment + Respiratory Bronchiole: Air sacs branch from these structures + Eventually, the bronchi lose all cartilage and reach a diameter of less than 1 millimeter at which point they become bronchioles. + The bronchioles continue to diverge before they end with the terminal bronchioles deep in the lungs. (Last part of the conducting zone). Respiratory Zone + Site of gas exchange in the lungs + Structures Include: Respiratory bronchioles, alveolar ducts, and alveolar sacs + Exercise-Induced Asthma- Constriction of bronchioles Respiratory Membrane + Very thin wall separating the alveolar surface and blood + Type 2 alveolar cells produce and secrete surfactant + Type 1 alveolar cells are the most prominent cell type of the alveoli. Alveolar Interdependence + Each alveolus is mechanically tethered to one another to establish a degree of structural support called alveolar interdependence. + Alveolar interdependence is important during the respiratory cycle, as it helps to establish uniformity in ventilation across the lung tissue and to maximize gas exchange. Emphysema + Destruction of alveoli + Causes alveoli to rupture and create big air sacs COPD Lung Volumes + Tidal volume (VT)—the volume of air exchanged with each breath + Inspiratory reserve volume (IRV)— at the end of a quiet inspiration, the amount of air that a person can maximally inhale + Expiratory reserve volume (ERV)— at the end of a quiet expiration, the amount of air a person can maximally exhale + Residual volume (RV)—volume of air remaining in the lungs after a forced maximal expiration  Lung Volumes & Capacities +Spirometry measures lung volumes throughout the various stages of the respiratory cycle and can assess airflow. +Provides important data that may indicate depressed lung function or pulmonary disease Lung Capacities + Four lung capacities can be estimated from various combinations of lung volumes: + Vital capacity (VC)—the maximum amount of air that can be expired following a maximal inspiration VC = IRV + VT + ERV + Inspiratory capacity (IC)—the maximum amount of air that can be inspired following a normal expiration IC = VT + IRV + Functional residual capacity (FRC)—the amount of air left in the lungs after a quiet normal resting expiration FRC = ERV + RV + Total lung capacity (TLC)—total volume of air the lungs can accommodate TLC = IRV + TV + ERV = RV Ventilation + Minute ventilation (V̇ E) is the air that is transported into and out of the lungs each minute. + Product of the volume of air exchanged with each breath (tidal volume; VT) and the respiratory rate (RR) + V̇ E = VT × RR + Alveolar ventilation (V̇ A) is the volume of inspired fresh air that reaches the alveoli for gas exchange in one minute. + To calculate V̇ A, we must first subtract the anatomical dead space AKA dead space ventilation (V D) from tidal volume (VT). + V̇ A = (VT - anatomical dead space volume) × RR + Anatomical Dead Space= Air that is trapped in the conducting airways and does not reach alveoli  Let's Practice! + A 35-year-old woman comes to your facility for a pulmonary assessment at rest and during exercise. + Calculate VE at rest and during exercise. + Calculate VA at rest and during exercise. + VE = VT × RR + V̇ A = (VT - 150 mL) × RR (Remember to convert L to mL in this equation when plugging in VT- THEN convert back to L for final answer). Variable Resting Condition Exercise Condition RR 14 breaths/min 30 breaths/min VT 0.4 L/breath 1.2 L/breath FEV1/FVC Ratio + The maximal volume of air that can be expired over a specified time is a good indicator of respiratory function and is particularly useful for diagnosing obstructive lung diseases that increase airway resistance (e.g., asthma, chronic obstructive pulmonary disease). + The volume of air that is forced out of the lungs in the first second of expiration (FEV1) is a good indicator of airway resistance and can be used to diagnose lung disease. + The FEV1 is expressed as a proportion of the forced vital capacity (FVC; FEV1/FVC ratio). + Forced vital capacity (FVC) simply means that a person forces all air out of the lungs as fast as possible during expiration. + Normally, FEV1/FVC is greater than 0.80, meaning that 80% of the air in the lungs is exhaled in the first second of expiration.  Respiratory Control Center CONTROLS RATE AND DEPTH OF HAPPENS IN COORDINATION WITH CONTROLLED BY SPECIALIZED AREAS IN BREATHING TO PROVIDE TISSUES WITH SENSORY INFORMATION RECEIVED FROM THE BRAINSTEM ADEQUATE OXYGEN TO MEET THEIR PERIPHERAL AND CENTRAL AREAS METABOLIC NEEDS Respiratory Control Center + The medulla oblongata contains most of the respiratory control center. + Dorsal respiratory group (DRG) + Ventral respiratory group (VRG) + Pons + Apneustic area (controls depth of breath by promoting prolonged inspiration) + Pneumotaxic area (limits length of inhalation) Humoral Control + The respiratory control center adjusts ventilation in response to changes in the chemical composition of the peripheral and central internal environments. + Alterations in the arterial PCO2 and PO2 as well as changes in blood pH exert the most important influences on ventilation. + Ventilation is increased because specialized bodies of neuronal cells, termed chemoreceptors, sense mild changes in blood gases and H+ concentrations. The Work of Breathing + The oxygen cost to perform the work of breathing at rest is approximately 5% of total oxygen consumption or 6 ml O2/min. + During exercise, the oxygen cost may increase up to 30% of total oxygen consumption as overall pulmonary ventilation increases and more muscles are recruited for this work. + In individuals who live with chronic obstructive pulmonary diseases, such as asthma, the oxygen cost of breathing can be much greater—so great that their ability to exercise or perform activities of daily living is severely limited. Mechanics of Inspiration and Expiration at Rest Inspiration—flow of air into the lungs Inspiration is controlled by the contraction of the diaphragm Phrenic nerve innervates the diaphragm. Chest expansion causes a decrease in intrapulmonic pressure below that of atmospheric pressure, and air will flow inward from an area of high to lower pressure. Expiration—air flow out of the lungs Expiration is elicited by the relaxation of the diaphragm immediately following inhalation. This movement causes an increase in intrapulmonic pressure above that of atmospheric pressure, and air will flow outward from an area of higher pressure to lower pressure. Muscles of Ventilation During Exercise + Diaphragm + Accessory muscles of ventilation + Scalenes + Sternocleidomastoid + External intercostals + Internal intercostals + Abdominal wall muscles Gas Diffusion + The ability of the body to diffuse gases in and out of the alveoli and the tissues (muscle in particular) quickly and efficiently is an essential physiological process at rest and during exercise performance.  Gases diffuse along their individual pressure gradient from areas of high concentration to areas of low concentration. Fick’s law for diffusion establishes Factors the directly proportional relationship between the rate of gas diffusion and Affecting Gas gas solubility, pressure gradient, and Diffusion surface area. Fick Equation: ̇VO2 = Q̇ × (a-v)O2 diff Sites for Gas Diffusion + Diffusion at the Alveoli: External Respiration + A significant pressure gradient facilitates appropriate gas exchange from alveoli (higher pressure) to capillary (lower pressure) for oxygen and capillary (higher pressure) to alveoli (lower pressure) for carbon dioxide. + Diffusion at the Tissues: Internal Respiration + A considerable pressure gradient exists to facilitate appropriate gas exchange from capillary (higher pressure) to tissue (lower pressure) for oxygen and from tissue (higher pressure) to capillary (lower pressure) for carbon dioxide. Oxygen Transport in the Blood The two means of oxygen transport in the blood are: 1.Dissolved in the plasma + Accounts for approximately 1.5% of total oxygen in the blood 2.Bound to hemoglobin + Hemoglobin is an oxygen binding protein found on the red blood cell. + Roughly 98.5% of oxygen in the blood is bound to and transported by hemoglobin, and the presence of this protein increases the total blood oxygen capacity 70 times. Hemoglobin-Oxygen Saturation: Oxy- Hemoglobin Dissociation Curve + The dissociation curve demonstrates the relationship between hemoglobin-oxygen saturation (y-axis) and the partial pressure of oxygen (x-axis). + Eventually, the curve will reach a plateau as hemoglobin binds its maximum four oxygen molecules to become fully saturated. + Factors that affect the curve and oxygen saturation: + Blood pH + Temperature + 2,3-Biphosphoglycerate + Partial Pressure of CO2 Carbon Dioxide Transport in the Blood + During rest, bioenergetic pathways in cells, such as the TCA cycle, will produce approximately 200 to 220 mL of carbon dioxide per minute, which eventually requires removal by the lungs. + Unlike oxygen transport, carbon dioxide can be transported through the blood in three ways: 1.Dissolved in plasma 2.Bound to the protein hemoglobin 3.Formed as the bicarbonate ion (HCO3)