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Supply oxygen and dispose of carbon dioxide Enable speech production To accomplish this, 4 independent processes, collectively called respiration must occur: 1. Pulmonary ventilation 2. External respiration 3. Transport of respiratory gases 4. Internal respiration (gas exchange between blood & tissue cells) Only the first two processes are the direct responsibility of the respiratory system. However, the other two must occur in order for oxygen to be obtained and for carbon dioxide to be removed. Movement of air into an out of the lungs so that gases in the air sacs (alveoli) of the lungs are continuously changed and refreshed. This air movement is known as ventilation or, more commonly, breathing. Ventilation exchange of air between lungs and atmosphere Gas Exchange in pulmonary capillaries Oxygen and Carbon Dioxide Diffusion, based on concentration gradient Breathing largely involuntary activity Transport of O2 and CO2 between lungs and tissue cells of the body Accomplished by cardiovascular system Blood is the transporting fluid All cells require oxygen for metabolism All cells require means to remove carbon dioxide Gas exchange occurs at cellular level Also simple diffusion, based on concentration gradient Upper respiratory tract Nose/Mouth Pharynx Epiglottis Lower respiratory tract Larynx Trachea Bronchi Lungs Bronchioles Alveoli Nose is the only externally visible part of the respiratory system Numerous functions: Airway for respiration Moistens and warms entering air Filters inspired air and cleanses it of foreign matter Resonating chamber for speech Houses olfactory receptors Mouth can be used in lieu of the nose as an airway for respiration. Air will be less “treated” Nasopharynx adenoids or pharyngeal tonsils oropharynx palatine tonsils laryngopharynx larynx Oropharynx and laryngopharynx serve as a common passageway for both food and air Epiglottis acts as a lid or flap that covers the larynx and trachea (airway) so food does not enter the lungs. “voice box” Three main functions: Patent (open) airway Switching mechanism to route food and air into proper channels Voice production (houses vocal cords) Windpipe or airway Mucous membrane lining with cilia Smooth muscle with c-shaped cartilage rings divides into two branches: bronchi no gaseous exchange Bronchus = singular c-shaped cartilage rings with smooth muscle Each bronchi divides into bronchioles Terminate in air sacs called alveoli Two circulations Pulmonary circulation Bronchial circulation Innervated by parasympathetic and (rare) sympathetic motor fibers Each lung enclosed in pleura parietal pleura (outer) visceral pleura (inner) Lubricating pleura fluid “air sacs” Alveolar wall membranes one cell thick and surrounded by capillaries Location of gaseous exchange