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Lecture 7

PHGY 210- Lecture 7- Dr. Lauzon.docx

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Department
Physiology
Course
PHGY 210
Professor
Ann Wechsler
Semester
Winter

Description
Lecture Seven: Monday, January 18 , 2010th RESPIRATION A.-M. Lauzon, Ph.D. Class notes 2010 Reference textbooks: “Human Physiology” by Widmaier, Raff, Strang “Respiratory Physiology- the essentials” by West "The Normal Lung" by Murray STRUCTURE OF THE LUNGS AND CHEST WALL A. Function of Respiration The 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, CO2. B. The respiratory tract know the anatomy Notes from pictures: -Nasal turbinets clean air coming in. -The lung on the right hand side has 3 lobes, and 2 lobes on the left hand side. Therefore 3 lobar bronchi on the right side and 2 on the left. -Diaphragm= main muscle of respiration -Space between the lungs and the ribcage= the pleural space. Very small and containts a very small amount of water (no air). -Visceral vs. Perietal pleura (define) -Branching in the lungs even continues upwards -Pleural space feels like a fist punching into a fluid filled balloon. Air flows 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 the nasal turbinates. These surfaces clean the air of big dust particles. see picture in slides From the nose, warmed and moistened air flows through the common passages for air and food, the pharynx, and then continues through the larynx. Air finally 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 lobes). The segmental bronchi divide further into smaller branches. The smallest airways without alveoli are the terminal bronchioles (figure 2). see pictures in slides * Notes: Pleura and pleural surfaces 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 (“Human Physiology” by Widmaier, Raff, Strang). A way to visualize the apposition of the two pleural surfaces is to put a drop of water between two glass microscope slides. The two slides can easily slide over each other but are very difficult to pull apart. (“Human Physiology” by Widmaier, Raff, Strang) -Brain sends signal to the chest, makes chest expand. Due to drop of water, lungs expand as well and inspiration occurs. The pressure in the pleural space is negative. This will become clearer after the discussion of pneumothorax (figure 35).  Lungs are just like balloons.  The chest always wants to expand, while the lungs always want to collapse, therefore pressure in pleural space is negative. Pneumothorax: -Hole in chest, air goes in because the pressure inside is less than the pressure outside. -The chest expands and the lungs collapse. -Luckily we have 2 pleural spaces (one for each lung) which are not connected to each other. -Therefore if you get one pneumothorax, you won’t get it on the other side as well. see pictures in slides don’t need to know very intricate anatomy -Bronchi split into bronchioles until you get to the terminal bronchioles. C. Conducting and Respiratory Zones The airways are divided into 2 zones: the conducting zone (made up of the conducting airways) and the respiratory zone (figure 2). 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. ->alveoli everywhere in alveolar ducts, in alveolar sacs 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 lumena (figure 3). 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 acinus (figure 3). see pictures in slides D. Functions of the Conducting Airways The conducting airways have 4 main functions: 1.Defense against bacterial infection and foreign particles: the epithelial lining of the bronchi has hair-like projections called cilia. The epithelial glands secrete a thick substance, mucous, which lines the 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 system. 2.Warm and moisten inhaled air. 3.Sound and speech are produced by the movement of air passing over the vocal cords. 4.Regulation of air flow: smooth muscle around the airways may contract or relax to alter resistance to air flow-> usually negatively. E. Function of the Respiratory Zone The respiratory zone is the site of gas exchange between the air in the alveoli and the blood in the pulmonary capillaries. There are roughly 300 million alveoli in the human lungs, and each alveolus may be associated with as many as 1000 capillaries. F. Blood Supply The lungs have two circulations: the pulmonary circulation (figures 4 & 5), bringing
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