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Mikel Egaña Trinity College Dublin Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings. Respiratory System. Lecture 1. 1 Respiratory System. Lecture 1. • 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 Respiratory System. Lecture 1. 2 • • Cellular respiration Refers to metabolic processes carried out within the mitochondria, which use O2 and produce CO2, while deriving energy from nutrient molecules Respiratory System. Lecture 1. 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 Respiratory System. Lecture 1. 3 Respiratory System. Lecture 1. • 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 Respiratory System. Lecture 1. 4 Respiratory System. Lecture 1. Air passages of the head and neck • Nasal cavity (nose) • Oral cavity • Pharynx (common passageway for respiratory and digestive systems) Respiratory System. Lecture 1. 5 Conducting zone (anatomical dead space) Airways from pharynx to lungs • Larynx • Conducting zone • Respiratory zone Respiratory zone Respiratory System. Lecture 1. Conducting zone (anatomical dead space) Respiratory zone Respiratory System. Lecture 1. 6 • 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 Respiratory System. Lecture 1. • Air passageway – 150 mL volume = dead space volume • Increase air temperature to body temperature • Humidify air • • • Goblet cells – secret mucus and traps foreign particles Ciliated cells – propel the mucus up the glotis to be swallowed or expelled Process: Mucus escalator Respiratory System. Lecture 1. 7 • Respiratory bronchioles • Alveolar ducts • Alveolar sacs • Alveoli Respiratory System. Lecture 1. • Exchange of gases between air and blood by diffusion • Respiratory membrane – Epithelial cells of alveoli – Endothelial cells of capillary Respiratory System. Lecture 1. 8 Respiratory System. Lecture 1. • • • • • 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 Removes foreign particles Respiratory System. Lecture 1. 9 • Barrier for diffusion – Alveoli: Type 1 cells + basement membrane – Capillaries: Endothelial cells + basement membrane • 0.2 microns thick Respiratory System. Lecture 1. Respiratory System. Lecture 1. 10 - 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 Respiratory System. Lecture 1. 11