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The Respiratory System Lecture 1: Organisation of the respiratory system Human form & Function - Physiology 08-09 Mikel Egaña Trinity College Dublin Copyright © 2005 Pearson Education, Inc., publishing as Benj amin Cummings. Respiration lecture series: • Mon, Jan 19 - Organization of the respiratory system • Wed, Jan 21 - Lung mechanics • Thur, Thur, Jan 22 - NO LECTURE • Mon, Jan 26 - Ventilation • Wed, Jan 28 - Gas exchange • Thur, Thur, Jan 29 - NO LECTURE • Mon, Feb 2 - Gas transport • Wed, Feb 4 - Respiratory control • Thur, Thur, Feb 5 - Effects of barometric pressure • Lecture Slides at: http://www.medicine.tcd.ie/physiology/courses/student_area/ Physiology 08-09. Respiratory System. Lecture 1. 1 Before we start… start… • The respiratory system: • Location: where? • Active - passive? • Voluntary - involuntary? • Normal ventilation: frequency, volume? Physiology 08-09. Respiratory System. Lecture 1. Lecture Outline I. Overview of Respiratory Function II. Anatomy of the Respiratory System Physiology 08-09. Respiratory System. Lecture 1. 2 I. Overview of Respiration • General function: to obtain O2 for use by the body’s cells and to eliminate the CO2 the body cells produce • Encompasses two separate but related processes: – Internal respiration • Oxidative phosphorylation – External respiration • Exchange of oxygen and carbon dioxide between atmosphere and body tissues Physiology 08-09. Respiratory System. Lecture 1. Internal Respiration • • Cellular respiration Refers to metabolic processes carried out within the mitochondria, which use O2 and produce CO2, while deriving energy from nutrient molecules Germann & Stanfield 3rd Ed., Fig 16.1 Physiology 08-09. Respiratory System. Lecture 1. 3 External Respiration (4 processes) 1. Pulmonary ventilation (movement of air into lungs and out) 2. Exchange O2 & CO2 between lungs (alveoli) and blood (pulmonary capillaries) by diffusion 3. Transportation of O2 & CO2 between lungs and tissues 4. Exchange O2 & CO2 between blood and body tissues by diffusion across systemic (tissue) capillaries Physiology 08-09. Respiratory System. Lecture 1. External & Internal Respiration Sherwood 6th Ed., Fig 13-1 Physiology 08-09. Respiratory System. Lecture 1. 4 Secondary functions (numerous) numerous) • Short term regulation of pH (acid-base balance) • Enabling speech, singing, and other vocalizations • Help in defense against pathogens in the airways • Removes, modifies, activates, or inactivates various materials passing through the pulmonary circulation • Eliminates heat and water • Assist venous return • Nose serves as the organ of smell Physiology 08-09. Respiratory System. Lecture 1. II. Anatomy of the Respiratory System • Respiratory airways leading into the lungs • Lungs • Structures of the Thoracic Cavity Physiology 08-09. Respiratory System. Lecture 1. 5 Upper Airways Air passages of the head and neck • Nasal cavity (nose) • Oral cavity • Pharynx (common passageway for respiratory and digestive systems) Germann & Stanfield 3rd Ed., Fig 16.2 Physiology 08-09. Respiratory System. Lecture 1. Respiratory Airways Conducting zone (anatomical dead space) Airways from pharynx to lungs •Larynx •Conducting zone •Respiratory zone Respiratory zone Physiology 08-09. Respiratory System. Lecture 1. Germann & Stanfield 3rd Ed., Fig 16.2 6 Conducting zone (anatomical dead space) Respiratory zone Sherwood 6th Ed., Fig 13-2 Physiology 08-09. Respiratory System. Lecture 1. Structures of the Conducting Zone • • • • • • Trachea Bronchi Secondary bronchi – Right side - 3 (to 3 lobes of right lung) – Left side - 2 (to 2 lobes of left lung) Tertiary,...Bronchi – 20-23 orders of branching Up to 8 million tubules!! Bronchioles – Less than 1 mm diameter – No cartilage, risk of collapse. To prevent: walls of elastic fibers Terminal bronchioles Physiology 08-09. Respiratory System. Lecture 1. 7 Functions of the Conducting Zone • Air passageway – 150 mL volume = dead space volume • Increase air temperature to body temperature • Humidify air Epithelium of the Conducting Zone • • • Goblet cells – secret mucus and traps foreign particles Ciliated cells – propel the mucus up the glotis to be swallowed or expelled Process: Mucus escalator Germann & Stanfield 2nd Ed., Figure 16.4a Physiology 08-09. Respiratory System. Lecture 1. Structures of the Respiratory Zone • Respiratory bronchioles • Alveolar ducts • Alveolar sacs • Alveoli Germann & Stanfield 3rd Ed., Fig 16.5 Physiology 08-09. Respiratory System. Lecture 1. 8 Function of the Respiratory Zone • Exchange of gases between air and blood by diffusion Epithelium of the Respiratory Zone • Respiratory membrane – Epithelial cells of alveoli – Endothelial cells of capillary Physiology 08-09. Respiratory System. Lecture 1. Germann & Stanfield 3rd Ed., Fig 16.3 Physiology 08-09. Respiratory System. Lecture 1. 9 Alveoli • • • • • Alveoli = site of gas exchange 300 million alveoli/lung (tennis court size):facilitate gas exchange. Rich blood supply- capillaries form sheet over alveoli Pores of Kohn permit airflow between adjacent alveoli (collateral ventilation) 3 cell types: – Type I alveolar cells – - Make up wall of alveoli, single layer epithelial cells – Type II alveolar cells – - Secrete surfactant - Reduces surface tension in alveolar walls - Helps prevent alveolar collapse – Alveolar macrophages Germann & Stanfield 3rd Ed., Fig 16.5 Removes foreign particles Physiology 08-09. Respiratory System. Lecture 1. Respiratory Membrane • • Barrier for diffusion – Alveoli: Type 1 cells + basement membrane – Capillaries: Endothelial cells + basement membrane 0.2 microns thick Germann & Stanfield 3rd Ed., Fig 16.5 Physiology 08-09. Respiratory System. Lecture 1. 10 Chest Wall and Pleural Sac Germann & Stanfield 3rd Ed., Fig 16.7 Physiology 08-09. Respiratory System. Lecture 1. Pleural Sac - Pleural sac around each lung - Side attached to chest: parietal pleura - Side attached to lung: visceral pleura - Intrapleural space filled with intrapleural fluid Volume = 15 mL Sherwood 6th Ed., Fig 13-5 Physiology 08-09. Respiratory System. Lecture 1. 11