Transcript Document
Anatomy & Physiology Lecture 23: The Respiratory System Lecturer: Dr. Barjis Room: P307 Phone: (718) 260-5285 E-Mail: [email protected] Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Frederic H. Martini Fundamentals of Learning Objectives • Describe the primary functions of the respiratory system • Identify the organs of the respiratory system and describe their functions • Define and compare the processes of external and internal respiration Learning Objectives • Summarize the physical principles governing the movement of air into the lungs and the diffusion of gases into the blood • Explain the important structural features of the respiratory membrane • Describe how oxygen and carbon dioxide are picked up, transported and released in the blood Functions of the respiratory system • Gas exchange between air and circulating blood • Moving air from the exchange surface of the lungs • Protection of respiratory surfaces • Production of sound • Provision for olfactory sensations Organization of the respiratory system • Respiratory system is divided into upper and lower respiratory systems. • Upper respiratory system • Nose, nasal cavity, paranasal sinuses, pharynx • Lower respiratory system • Larynx, trachea, bronchi, bronchioles, alveoli The Components of the Respiratory System • The hard palate separates the nasal cavity from the oral cavity The Respiratory tract • Conducting passageways carrying air to and from the alveoli • Upper respiratory passages filter, warm and humidify incoming air • Lower passageways include delicate conduction passages and alveolar exchange surfaces The Nose, Nasal Cavity, and Pharynx • Nasal conchae creates turbulence as air passes through the nasal cavity. • Turbulence makes the air bounce, thus small microorganisms will be trapped in the mucus The pharynx • Shared by the digestive and respiratory systems • Divided into three sections: • Nasopharynx – superior portion • Oropharynx – continuous with the oral cavity • The portion of pharynx that receives oth air and food • Laryngopharynx The larynx • Receives inhaled air from pharynx through glottis • Larynx protects the glottis • Food/drink that touch the vestibular or vocal folds trigger coughing reflex • Larynx consist of 3 large cartilages • Thyroid – is largest laryngeal cartilage • Cricoid – ring shaped cartilage • Epiglottis – is an elastic cartilage that prevents food and water from entering the larynx The Larynx The Larynx Sound production • Air passing through the glottis vibrates the vocal folds producing sound waves • Pitch depends on conditions of vocal folds • Diameter • Length • Tension The Glottis The Larynx The laryngeal musculature • Muscles of the neck and pharynx position and stabilize the larynx • When swallowing these muscles • Elevate the larynx • Bend the epiglottis over the glottis • Intrinsic muscles control tension on the vocal folds and open the glottis The trachea • A tough, flexible tube running from the larynx to the bronchi • Held open by C-shaped tracheal cartilages The Anatomy of the Trachea The bronchi • Trachea branches in the mediastinum into right and left bronchi • Bronchi enter the lungs at the hilus • The two primary bronchi branches further to secondary bronchi as they enter the lungs • Secondary bronchi branches into tertiary bronchi and tertiary bronchi branches into brancheoles within the lung • As they branch, amount of cartilage in their wall reduces and amount of smooth muscle increases The Lungs Lobes and surfaces of the lungs • Lobes of the lung are separated by fissures • Right lung has three lobes • Left lung has two lobes The Gross Anatomy of the Lungs The bronchial tree • System of tubes formed from the primary bronchi and their branches • Primary bronchi branch into secondary bronchi • Secondary bronchus goes to each lobe of the lungs • Secondary bronchi branch into tertiary bronchi • Tertiary bronchi supply air to a single bronchopulmonary segment The Bronchi and Lobules of the Lung The Bronchi and Lobules of the Lung The bronchioles • Each tertiary bronchus branches several times and give rise to bronchioles • Bronchioles branches into terminal bronchioles where each terminal brancheole: • Delivers air to a single pulmonary lobule • Terminal bronchiole becomes respiratory bronchioles Summary of air flow • Nasal cavity • Pharynx • Nasopharynx • Oropharynx • Laryngopharynx • Larynx • Trachea • Bronchi • Primary Bronchi • Secondary Bronchi • Tertiary Bronchi • Broncheoles • Terminal Broncheoles • Respiratory Broncheoles • Alveoli –is the only site of gas exchange Cells of the respiratory membrane include • Septal cells • Scattered in respiratory membrane • Septal cells produce surfactant • Surfacant prevents the alveoli from colapsing • Alveolar Macrophage • Macrophages patrol epithelium and engulf foreign particles Animation: Respiratory Structures (see tutorial) Alveolar Organization The pleural cavities and pleural membranes • Each lung is covered by one pleura • Pleura is a serous membrane lining the pleural cavity • Parietal pleura - covers the inner surface of thoracic wall • Visceral Pleura - covers the surface of the lungs • Pleural fluid – fills and lubricates the space between the pleura Respiratory physiology is a series of integrated processes • Internal respiration • Exchange of gases between interstitial fluid and cells or between the blood and interstitial fluid or capillaries and interstitial fluid. • Oxygen diffuses from the capillaries to the interstitial fluid and from the interstitial fluid to the cell • Carbon dioxide diffuses from the cell to the interstitial fluid and from the interstitial fluid to the capillaries. • External respiration • Exchange of gases between interstitial fluid and the external environment i.e. gas exchange between circulating blood and alveoli. • Oxygen diffuses from the alveoli to the capillaries • Carbon dioxide diffuses from the capillaries to the alveoli. Respiratory physiology is a series of integrated processes • The steps of external respiration include: • Pulmonary ventilation • Gas diffusion • Transport of oxygen and carbon dioxide • Oxygen bounds to hemoglobin and is transported from the lungs to the cells. • Carbon dioxide is transported in the form of bicarbonate ions from the cell to the lungs • Reactions are completely reversible An Overview of Respiratory Processes and Partial Pressures in Respiration Animation: Respiratory Processes and Partial Pressures in Respiration (see tutorial) An Overview of Key Steps in Respiration Pulmonary Ventilation • The physical movement of air into and out of the lungs • Movement of air • Relationship between intrapulmonary pressure and atmospheric pressure determines direction of air flow • Boyle’s Law • Boyle’s law state that pressure and volume has inverse relationship i.e. the higher the volume the lower the pressure, and the lesser the volume the higher the pressure • Volume depends on movement of diaphragm and ribs Mechanisms of Pulmonary Ventilation Respiratory cycle • Respiratory cycle is single cycle of inhalation and exhalation • Amount of air moved in one cycle is called tidal volume Animation: Pulmonary Ventilation (see tutorial) Mechanisms of breathing • Quiet breathing (eupnea) • In quite breathing diaphragm and external and internal intercostals muscles are required (work) • Forced breathing (hyperpnea) • In forced breathing in addition to the diaphragm and intercostals muscles accessory muscles are needed Respiratory volumes • Tidal Volume (VT) • Amount of air inhaled or exhaled with each breath • Vital capacity • Tidal volume plus expiratory and inspiratory reserve volumes • Residual volume • Air left in lungs after maximum exhalation Respiratory Volumes and Capacities Gas Exchange The gas laws • Daltons Law and partial pressure • Individual gases in a mixture exert pressure proportional to their abundance • In a mixture of gases like air the total pressure is the sum of pressure by the individual gas • Diffusion between liquid and gases (Henry’s law) • The amount of gas in solution is directly proportional to their partial pressure Henry’s Law and the Relationship between Solubility and Pressure Henry’s Law and the Relationship between Solubility and Pressure Diffusion and respiratory function • Gas exchange across respiratory membrane is efficient due to: • Differences in partial pressure • Small diffusion distance • Lipid-soluble gases • Large surface area of all alveoli • Coordination of blood flow and airflow Oxygen transport • Carried mainly by RBCs, bound to hemoglobin • The amount of oxygen carried by hemoglobin depends upon: • PO2 • pH • temperature • BPG • Fetal hemoglobin has a higher O2 affinity than adult hemoglobin The Oxygen-Hemoglobin Saturation Curve The Effect of pH and Temperature on Hemoglobin Saturation A Functional Comparison of Fetal and Adult Hemoglobin Carbon dioxide transport • 7% dissolved in plasma • 70% carried as carbonic acid • 23% bound to hemoglobin • carbaminohemoglobin Carbon Dioxide Transport in Blood A Summary of the Primary Gas Transport Mechanisms Respiratory reflexes • Respiratory centers are modified by sensory information including • Chemoreceptor reflexes • Level of carbon dioxide • Baroreceptors reflexes • Hering-Breuer reflexes • Prevents overinflation • Protective reflexes You should now be familiar with: • The primary functions of the respiratory system • The organs of the respiratory system and their functions • The processes of external and internal respiration • The physical principles governing the movement of air into the lungs and the diffusion of gases into the blood • The important structural features of the respiratory membrane • How oxygen and carbon dioxide are picked up, transported and released in the blood