Fundamentals of Anatomy & Physiology Chapter 23: The Respiratory System PDF

Chapter 23 The Respiratory System Lecture Presentation by Lee Ann Frederick University of Texas at Arlington  Learning outcomes List the functions of the respiratory system Understand the organization of the respiratory system Describe the integrated process of r...

Chapter 23 The Respiratory System Lecture Presentation by Lee Ann Frederick University of Texas at Arlington  Learning outcomes List the functions of the respiratory system Understand the organization of the respiratory system Describe the integrated process of respiration Understand the mechanics of breathing Describe the various lung measurements Understand the process of gas exchange and transport Able to describe the control of respiration  Respiratory system Five functions of the respiratory system 1. Provides extensive gas exchange surface area between air and circulating blood 2. Moves air to and from exchange surfaces of lungs 3. Protects respiratory surfaces from outside environment 4. Produce sounds 5. Participates in olfactory sense  Respiratory system Organization of the respiratory system – The respiratory system is divided into: Upper respiratory system – above the larynx Lower respiratory system – below the larynx  Upper Respiratory System Nose Nasal cavity Sinuses Tongue Pharynx Esophagus Lower Respiratory System Clavicle Larynx Trachea Bronchus Bronchioles Smallest bronchioles Ribs Right Left lung lung Alveoli Diaphragm  Respiratory system The respiratory tract – Consists of a conducting portion From nasal cavity to terminal bronchioles – Consists of a respiratory portion The respiratory bronchioles and alveoli  Trachea Cartilage plates Left primary bronchus Visceral pleura Secondary bronchus Conducting portion Tertiary bronchi Smaller bronchi Bronchioles Terminal bronchiole Alveoli in a Respiratory pulmonary lobule bronchiole Respiratory portion Bronchopulmonary segment  Respiratory bronchiole Alveolar duct Smooth muscle Alveolus Alveolar Elastic sac fibers Capillaries The basic structure of the distal end of a single lobule: A network of capillaries supported by elastic fibers that surrounds each alveolus. Respiratory bronchioles are wrapped by smooth muscle cells that can change the diameter of these airways.  Respiratory portion Alveoli – Are air-filled pockets within the lungs Where all gas exchange takes place Large surface area to increase diffusion rate Pulmonary venule Pulmonary arteriole Red: Oxygenated blood Blue: Deoxygenated blood 10  Respiratory portion Alveolar epithelium – Consists of simple squamous epithelium – Consists of thin, delicate type I pneumocytes patrolled by alveolar macrophages (dust cells) – Majority of gas exchange occurs in type I pneumocytes – Contains type II pneumocytes (septal cells) that produce surfactant Respiratory portion Image from Wikipedia  Type II Type I pneumocyte pneumocyte Alveolar macrophage Elastic fibers Alveolar macrophage Capillary Endothelial cell of capillary A diagrammatic view of alveolar structure. A single capillary may be involved in gas exchange with several alveoli simultaneously  Respiratory portion Surfactant – Is an oily secretion – Contains phospholipids and proteins – Coats alveolar surfaces and reduces surface tension – Prevents collapse of the lung What is alveolar surface tension? Attraction force between water molecules at liquid air interface, which resists the stretching of the lungs When the water surface is attempting to contract, it tends to force air out of the alveoli and causes collapse of alveoli. 15 16  Respiration Respiration – Refers to two integrated processes 1. External respiration –Includes all processes involved in exchanging O2 and CO2 with the environment 2. Internal respiration –Result of cellular respiration –Involves the uptake of O2 and production of CO2 within individual cells  External respiration Three processes of external respiration 1. Pulmonary ventilation (breathing) 2. Gas diffusion Across membranes and capillaries 3. Transport of O2 and CO2 Between alveolar capillaries Between capillary beds in other tissues  External respiration Respiration External Respiration Internal Respiration Pulmonary ventilation O2 transport Tissues Gas Gas diffusion diffusion Lungs Gas Gas diffusion diffusion CO2 transport  Pulmonary ventilation Pulmonary ventilation ▪ Is the physical movement of air in and out of respiratory tract ▪ Provides alveolar ventilation ▪ The movement of air into and out of the lungs o major mechanism - Atmospheric pressure (Pa) o The weight of air o Has several important physiological effects  Pulmonary ventilation Gas pressure and volume – Boyle’s Law Defines the relationship between gas pressure (P) and volume (V) P = 1/V In a contained gas: –External pressure forces molecules closer together –Movement of gas molecules exerts pressure on container Boyle’s law  Pulmonary ventilation Pressure and airflow to the lungs – Air flows from area of higher pressure to area of lower pressure – A respiratory cycle Consists of: –An inspiration (inhalation) –An expiration (exhalation)  Pulmonary ventilation Pulmonary ventilation – Causes volume changes that create changes in pressure – Volume of thoracic cavity changes With expansion or contraction of diaphragm or rib cage – Summary video  Ribs and sternum elevate Diaphragm contracts As the rib cage is elevated or the diaphragm is depressed, the volume of the thoracic cavity increases.  Thoracic wall Parietal pleura Pleural fluid Visceral pleura Lung Poutside=Pinside Pressure outside and inside are equal, so no air movement occurs At rest, prior to inhalation  Volume increases Poutside>Pinside Pressure inside decreases, so air flows in Inhalation. Elevation of the rib cage and contraction of the diaphragm increase the size of the thoracic cavity. Pressure within the thoracic cavity decreases, and air flows into the lungs  Volume decreases Poutside