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PowerPoint® Lecture Slides prepared by Janice Meeking, Mount Royal College CHAPTER 22 The Respiratory System: Part A – anatomy and histology Copyright © 2010 Pearson Education, Inc. Major Functions of the Respiratory System • To supply the body with oxygen and dispose of carbon dioxide • Respiration – four distinct processes must happen • Pulmonary ventilation (breathing): movement of air into and out of the lungs • External respiration: O2 and CO2 exchange between the lungs and the blood • Transport: O2 and CO2 in the blood • Internal respiration: O2 and CO2 exchange between systemic blood vessels and tissues Copyright © 2010 Pearson Education, Inc. Respiratory system Circulatory system Respiratory System – conducting and respiratory zone • Consists of the respiratory and conducting zones • Respiratory zone: • Site of gas exchange • Consists of respiratory bronchioles, alveolar ducts, and alveoli • Conducting zone: • Conduits for air to reach the sites of gas exchange • Includes all other respiratory structures (e.g., nose, nasal cavity, pharynx, trachea) • Respiratory muscles – diaphragm and other muscles that promote ventilation Copyright © 2010 Pearson Education, Inc. Respiratory System – conducting and respiratory zone • Conducting passageways carrying air to and from the alveoli • Upper respiratory passages filter and humidify incoming air • Lower passageways include delicate conduction passages and alveolar exchange surfaces • The conducting passageways of the respiratory system (nasal cavity, trachea, bronchi and bronchioles) are lined by ciliated pseudostratified columnar ET, which includes mucus-secreting goblet cells. • Because the passage of air depends on wide open passageways, the larger respiratory passages (trachea and bronchi) are supported by rings of cartilage. • The respiratory regions are lined with simple squamous ET Copyright © 2010 Pearson Education, Inc. Function of the Nose • The only externally visible part of the respiratory system that functions by: • Providing an airway for respiration • Moistening and warming the entering air • Filtering inspired air and cleaning it of foreign matter • Serving as a resonating chamber for speech • Housing the olfactory receptors Copyright © 2010 Pearson Education, Inc. Paranasal Sinuses • Sinuses in bones that surround the nasal cavity • Sinuses lighten the skull and help to warm and moisten the air http://sinusitis.upmc.com/Images/Sub/PhotoSinusitis.jpg Copyright © 2010 Pearson Education, Inc. Larynx (Voice Box) • Attaches to the hyoid bone and opens into the laryngopharynx superiorly • Continuous with the trachea posteriorly • The functions of the larynx are: • Air passage • To act as a switching mechanism to route air and food into the proper channels • To function in voice production Copyright © 2010 Pearson Education, Inc. Framework of the Larynx • Cartilages (hyaline) of the larynx • Shield-shaped anterosuperior thyroid cartilage with a midline laryngeal prominence (Adam’s apple) • Signet ring–shaped anteroinferior cricoid cartilage • Three pairs of small arytenoid, cuneiform, and corniculate cartilages • Epiglottis – elastic cartilage that covers the laryngeal inlet during swallowing • Glottis is the superior opening of the larynx. It is guarded by the epiglottis (cartilage) Copyright © 2010 Pearson Education, Inc. Vocal Ligaments • Attach the arytenoid cartilages to the thyroid cartilage • Composed of elastic fibers that form mucosal folds called true vocal cords • The medial opening between them is the glottis • They vibrate to produce sound as air rushes up from the lungs • False vocal cords • Mucosal folds superior to the true vocal cords • Have no part in sound production Copyright © 2010 Pearson Education, Inc. Voice Production • Speech: release of expired air while opening and closing the glottis • Pitch is determined by the length and tension of the vocal cords • Loudness depends upon the force of air • Chambers of pharynx, oral, nasal, and sinus cavities amplify and enhance sound quality • Sound is “shaped” into language by muscles of the pharynx, tongue, soft palate, and lips Copyright © 2010 Pearson Education, Inc. Trachea • Flexible and mobile tube extending from the larynx into the mediastinum • Composed of three layers • Mucosa – ciliated pseudostratified columnar epithelium with goblet cells • Submucosa – connective tissue with mucous glands, lymph nodes • Adventitia – fibrous CT that contains C-shaped rings of hyaline cartilage Copyright © 2010 Pearson Education, Inc. The primary bronchi • Trachea branches in the mediastinum into right and left primary bronchi • Bronchi enter the lungs at the hilus • Have C-shaped cartilaginous supporting rings Copyright © 2010 Pearson Education, Inc. The bronchial tree • System of tubes formed from the primary bronchi and their branches • Primary bronchi branch into secondary or lobar bronchi • Secondary bronchus goes to each lobe of the lungs • Secondary bronchi branch into tertiary (segmental) bronchi • Both secondary and tertiary bronchi are covered by overlapping plates of cartilage and not rings • Cartilage in walls decrease and smooth muscle increase with branching Copyright © 2010 Pearson Education, Inc. The bronchioles • Branching of the bronchi that are 1 mm or less in diameter and lack cartilage. Bronchioles are surrounded by smooth muscle that allows the change of diameter. • Ultimately bronchioles branch into the final branch of the conducting division - terminal bronchioles with a diameter of 0.3-0.5 mm • Terminal bronchiole becomes respiratory bronchioles – the beginning of the respiratory division Copyright © 2010 Pearson Education, Inc. Respiratory Zone • Defined by the presence of alveoli; begins as terminal bronchioles feed into respiratory bronchioles • Respiratory bronchioles lead to alveolar ducts, then to terminal clusters of alveolar sacs composed of alveoli • Approximately 300 million alveoli: • Account for most of the lungs’ volume • Provide tremendous surface area for gas exchange Copyright © 2010 Pearson Education, Inc. Respiratory Membrane • This air-blood barrier is composed of: • Alveolar and capillary walls • Their fused basal laminas • Simple squamous ET (type I) – most of the cells in the alveolus wall and are part of the respiratory membrane (allow gas exchange) • Septal cells (type II ) – about 5% of the alveolar wall. The septal cells secret surfactant – a lipoprotein secretion that reduces the surface tension in the alveolus • Alveolar Macrophage (dust cells) - patrol epithelium and engulf foreign particles Copyright © 2010 Pearson Education, Inc. Pleurae • Thin, double-layered serosa • Parietal pleura • Covers the thoracic wall and superior face of the diaphragm • Continues around heart and between lungs • Visceral, or pulmonary, pleura • Covers the external lung surface • Divides the thoracic cavity into three chambers • The central mediastinum • Two lateral compartments, each containing a lung Copyright © 2010 Pearson Education, Inc. Dead Space • Some of the inspired air does not contribute to the gas exchange in the alveoli • Anatomical dead space – volume of the conducting respiratory passages (150 ml) • Alveolar dead space – alveoli that cease to act in gas exchange due to collapse or obstruction • Total dead space – sum of alveolar and anatomical dead spaces Copyright © 2010 Pearson Education, Inc. Pulmonary Function Tests • Spirometer – an instrument consisting of a hollow bell inverted over water, used to evaluate respiratory function • Spirometry can distinguish between: • Obstructive pulmonary disease – increased airway resistance • Restrictive disorders – reduction in total lung capacity from structural or functional lung changes • Total/minute ventilation – total amount of gas flow into or out of the respiratory tract in one minute • Forced vital capacity (FVC) – gas forcibly expelled after taking a deep breath • Forced expiratory volume (FEV) – the amount of gas expelled • Increases in TLC, FRC, and RV may occur as a result of obstructive disease • Reduction in VC, TLC, FRC, and RV result from restrictive disease Copyright © 2010 Pearson Education, Inc. Nonrespiratory Air Movements • Most result from reflex action • Examples include: coughing, sneezing, crying, laughing, hiccupping, and yawning Copyright © 2010 Pearson Education, Inc.
