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respiratory system.docx

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Biological Sciences
Kenneth Welch

The Respiratory System The Respiratory System: An Introduction Functions of the respiratory system •Gas exchange between air and circulating blood •Moving air from the exchange surface of the lungs •Protection of respiratory surfaces •Production of sound •Provision for olfactory sensations Organization of the respiratory system •Upper respiratory system •Nose, nasal cavity, paranasal sinuses, pharynx •Lower respiratory system •Larynx, trachea, bronchi, bronchioles, alveoli The Respiratory tract •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 Respiratory Mucosa •Respiratory epithelium and underlying connective tissue •Respiratory membrane, supported by lamina propria, changes along tract •Lines conducting portion of respiratory tract •Protected from contamination by respiratory defense system The Upper Respiratory System The nose and nasal cavity consists of: •External nares •Nasal cavity •Vestibule •Superior, middle and inferior meatuses •Hard and soft palates •Internal nares •Nasal mucosa The pharynx •Shared by the digestive and respiratory systems •Divided into three sections: •Nasopharynx – superior portion •Oropharynx – continuous with the oral cavity •Laryngopharynx – between the hyoid bone and the esophagus The Larynx The larynx •Air passes through the glottis on the way to the lungs •Larynx protects the glottis •Cartilages of the larynx •Three large cartilages •Thyroid, cricoid, and epiglottis •Paired cartilages •Arytenoids, corniculate, and cuneiform Folds of the larynx •Inelastic vestibular folds •Delicate vocal folds Sound production •Air passing through the glottis vibrates the vocal folds producing sound waves •Pitch depends on conditions of vocal folds •Diameter •Length •Tension The laryngeal musculature •Muscles of the neck and pharynx position and stabilize the larynx •When swallowing,these muscles •Elevate the larynx •Bend the epiglottis over the glottis •Intrinsic muscles control tension on the vocal folds and open the glottis The Trachea and Primary Bronchi The trachea •Extends from the sixth cervical vertebra to the fifth thoracic vertebra •A tough, flexible tube running from the larynx to the bronchi •Held open by C-shaped tracheal cartilages in submucosa •Mucosa is similar to the nasopharynx The primary bronchi •Trachea branches in the mediastinum into right and left bronchi •Bronchi enter the lungs at the hilus •Root = the connective tissue mass including: •Bronchus •Pulmonary vessels •Nerves The Lungs Lobes and surfaces of the lungs •Lobes of the lung are separated by fissures •Right lung has three lobes •Left lung has two lobes •Concavity on medial surface = cardiac notch 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 bronchi •Tertiary bronchi supply air to a single bronchopulmonary segment •Cartilage in walls decrease and smooth muscle increase with branching The bronchioles •Ultimately branch into terminal bronchioles •Delivers air to a single pulmonary lobule •Terminal bronchiole becomes respiratory bronchioles •Connective tissue of root branches to form interlobar septa Alveolar ducts and alveoli •Respiratory bronchioles end in ducts and sacs •Respiratory exchange surfaces connected to circulatory system via pulmonary circuit Respiratory Membrane •Simple squamous epithelium •Endothelial cell lining an adjacent capillary •Fused basal laminae Cells of the respiratory membrane include •Septal cells •Scattered in respiratory membrane •Produce surfactant •Alveolar Macrophage •Patrol epithelium and engulf foreign particles The blood supply to the lungs •Conducting portions •Receive blood from external carotids, thyrocervical, bronchial arteries •Respiratory exchange surfaces •receive blood from the arteries of the pulmonary circuit •are the source of angiotensin-converting enzyme (ACE) •Pulmonary veins return blood to the left atrium The pleural cavities and pleural membranes •Each lung covered by one pleura •Pleura – serous membranes lining the pleural cavity •Parietal - attaches to
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