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Respiration .pdf

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McGill University
PHGY 210
Anne- Marie Lauzon

Respiration Function of RespirationThe primary function of respiration is gas exchange In mammals gas exchange occurs in the lungs During inspiration air rich in O2 is inhaled in the lungs During expiration CO2 produced during the oxidative processes of the body is exhaled from the lungs Both gases are transported by the blood Therefore both the cardiovascular system and the respiratory system are involved with supplying body cells with O2 and eliminating their waste product CO2The Respiratory TractAir ows through a series of air passages that connect the lungs to the nose and mouth Inhaled air passes over a complex series of surfaces when it goes through the nose the nasal septum and theThese surfaces clean the air of big dust particles nasal turbinatesFrom the nose warmed and moistened air ows through the common passages for air and food the pharynx and then continues through the larynx Air nally reaches the periphery of the lungs via the trachea and bronchi The lungs and the airways share the chest cavity with the heart the great vessels and the esophagus The airways consist of a series of tubes that branch and become narrower shorter and more numerous as they penetrate into the lungs The trachea divides into 2 main bronchi each of which divides into lobar and segmental bronchi The right main bronchus has 3 lobar bronchi the right lung has 3 lobes while the left main bronchus divides into only 2 bronchi the left lung has only 2 lobesThe segmental bronchi divide further into smaller branches The smallest airways without alveoli are the terminal bronchiolesis the main muscle of respiration It splits the chest from the abdomen When the Diaphragmintercostal muscle contract the diaphragm pulls down and enlarges the size of the chest visceral pleura The layer inside the chest is the parietal pleura The layer on top of the lungs is the These are the extremities of the pleural space pleural space is located between the outside of the lungs and the inside of The small space called the the chest wall The pleural space can be thought of as a uid lled balloon There exists a small amount of uid in this space Pleura Thin cellular sheet attached to the thoracic cage interior parietal pleura and folding back upon itself attached to the lung surface visceral pleura forms two enclosed pleural sacs in thoracic cage There are two distinct non connected pleural spaces The pleural space couples the lungs to the chest Upon breathing the chest muscles contract they pull out the chest and the lungs which are attached are pulled upon This creates a pressure difference The pressure in the lungs drops as compared to the outside environment creating a pressure gradient which allows air to rush inside The pressure inside the pleural space is negative as compared to the atmosphere At rest the pressure in the lungs is 0 Pneumothorax occurs upon puncturing of the chest The lung collapses and the chest increases The respiratory system is coupled by the pleural space Model below demonstrates the method of contraction by way of a mechanical pump Due to pleural space the lungs are inated and their volume increases creating a negative pressure Conducting and Respiratory ZonesThe airways are divided into 2 zones the conducting zone made up of the conducting airways and the respiratory zone The conducting airways consist of the airways from the mouth and nose openings all the way down to the terminal bronchioles These airways conduct air from the atmosphere to the respiratory part of the lungs The conductive airways do not contribute to gas exchange and are thus said to compose the anatomical dead space Conducting zone is made up of the trachea the left and right main bronchi the bronchioles and terminal bronchioles Upon the presence of alveoli the tubular structures are part of the respiratory zone not conducting The respiratory part of the lungs the respiratory zone begins where the terminal bronchioles divide into respiratory bronchioles which have some alveoli opening into their lumenal Beyond the respiratory bronchioles are the alveolar ducts lined with alveoli The alveolated region of the lungs is the site of gas exchange and is called the respiratory zone Because of such abundant branching of the airways the respiratory zone makes up most of the lungs The smallest physiological unit of the lungs distal to the terminal bronchioles is the acinusSmooth muscle is represented as red in the gure above These are involuntary muscles upon contraction reduce the area of their tubules This can be asthma problematic for respiratory muscles a distinct type of muscleThere are also Functions of the Conducting ZoneThe conducting airways have 4 main functions1Defense against bacterial infection and foreign particles the epithelial lining of the bronchi has hairlike cilia The epithelial glands secrete a thick substance mucous which lines the projections called respiratory passages as far down as the bronchioles Foreign particles stick to the mucous and the cilia constantly sweep the mucous up into the pharynx This is called the mucociliary defense system2Warm and moisten inhaled air3Sound and speech are produced by the movement of air passing over the vocal cords
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