Chapter 23 The Respiratory System Respiratory System Anatomy Structurally, the respiratory system is divided into upper and lower divisions or tracts. The upper respiratory tract consists of the nose, pharynx and associated structures. Upper respiratory tract The lower respiratory tract consists of the larynx, Lower respiratory tract trachea, bronchi and lungs. Copyright © John Wiley & Sons, Inc. All rights reserved. Respiratory System Anatomy Functionally, the respiratory system is divided into the conducting zone and the respiratory zone. The conducting zone is involved with bringing air to the site of external respiration and consists of the nose, pharynx, larynx, trachea, bronchi, bronchioles and terminal bronchioles. The respiratory zone is the main site of gas exchange and consists of the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli. Copyright © John Wiley & Sons, Inc. All rights reserved. Respiratory System Anatomy Air passing through the respiratory tract traverses the: Nasal cavity Pharynx Larynx Trachea Primary (1o) bronchi Secondary (2o) bronchi Tertiary (3o) bronchi Bronchioles Alveoli (150 million/lung) Copyright © John Wiley & Sons, Inc. All rights reserved. The Nose The external nose is visible on the face. It consists of: a supporting bony framework (frontal bone, nasal bones, and maxillae) and a cartilaginous framework of hyaline cartilage Copyright © John Wiley & Sons, Inc. All rights reserved. The Nasal cavity Lies in and posterior to the external nose Is divided by a midline nasal septum Formed by the perpedicular plate of ethmoid, & the vomer posteriorly and the septal Wikimedia Commons cartilage anteriorly It opens posteriorly into the nasopharynx Copyright © John Wiley & Sons, Inc. All rights reserved. Nasal Cavity- lateral wall Three nasal conchae (or turbinates) protrude medially from each lateral wall of nasal cavity Superior concha Middle concha Inferior concha Increase mucosal surface area & air turbulence- ensures air contacts mucosa Under each nasal concha is an opening, or meatus, for a duct that drains secretions of the sinuses and tears into the nose. Copyright © John Wiley & Sons, Inc. All rights reserved. Copyright © John Wiley & Sons, Inc. All rights reserved. The Nose Functions: Providing an airway for respiration Moistening and warming & filtering inspired air Resonation of sound Olfaction Copyright © John Wiley & Sons, Inc. All rights reserved. The Paranasal Sinuses •Mucosa-lined, air-filled spaces found in five skull bones – the frontal, sphenoid, ethmoid, and paired maxillary bones •Sinuses lighten the skull and help to warm and moisten the air Copyright © John Wiley & Sons, Inc. All rights reserved. The Paranasal Sinuses Mucosal secretions flows from the sinuses into nasal cavity Copyright © John Wiley & Sons, Inc. All rights reserved. The Phrynx The pharynx is a hollow tube that starts posterior to the internal nares and descends to the opening of the larynx in the neck. It is formed by a complex arrangement of skeletal muscles that assist in deglutition. It functions as: o a passageway for air and food o a resonating chamber o a housing for the tonsils Copyright © John Wiley & Sons, Inc. All rights reserved. The Pharynx The pharynx has 3 regions The nasopharynx is separated from the oropharynx by the hard and soft palate Nasopharynx Oropharynx Laryngopharynx Copyright © John Wiley & Sons, Inc. All rights reserved. The Nasopharynx Lies posterior to the nasal cavity and superior to the level of the soft palate Strictly an air passage Lined with psuedostratified columnar epithelium Closes during swallowing to prevent food from entering the nasal cavity The pharyngeal tonsil ( adenoids) lies high on the posterior wall Auditory tubes from middle ears open into the lateral walls Copyright © John Wiley & Sons, Inc. All rights reserved. Respiratory Lining Cilia in the upper respiratory tract move mucous and trapped particles down toward the pharynx. (Cilia in the lower respiratory tract move them up toward the larynx.) Copyright © John Wiley & Sons, Inc. All rights reserved. The Pharynx The oropharynx & laryngopharynx are both common passages for food and air & are lined by stratified squamous epithelium The oropharynx lies posterior to the oral cavity & opens into the oral cavity via the fauces The palatine tonsils lie in the lateral walls of the fauces (those usually taken in a tonsillectomy) and small lingual tonsil at the base of the tongue The laryngopharynx lies posterior to the upright epiglottis Leads into the larynx & the esophagus Copyright © John Wiley & Sons, Inc. All rights reserved. The Pharynx Copyright © John Wiley & Sons, Inc. All rights reserved. The Larynx The larynx, composed of 9 pieces of cartilage, forms a short passageway connecting the laryngopharynx with the trachea (the “windpipe”). The thyroid cartilage (the large “Adam’s apple”) and the one below it (the cricoid cartilage) are landmarks for making an emergency airway (called a cricothyrotomy). Anterior view of the larynx Copyright © John Wiley & Sons, Inc. All rights reserved. The Larynx 9 Cartilages of the larynx Epiglottis – elastic cartilage that covers the glottis during swallowing Thyroid cartilage- hyaline cartilage with a midline laryngeal prominence (Adam’s apple) Cricoid cartilage - hyaline cartilage Three pairs of small arytenoid, corniculate, & cuneiform cartilages Copyright © John Wiley & Sons, Inc. All rights reserved. Copyright © John Wiley & Sons, Inc. All rights reserved. Copyright © John Wiley & Sons, Inc. All rights reserved. The Larynx The epiglottis is a flap of elastic cartilage covered with a mucus membrane, attached to the root of the tongue. The epiglottis guards the entrance of the glottis, the opening between the vocal folds. o For breathing, it is held anteriorly, then pulled backward to close off the glottic opening during swallowing. Copyright © John Wiley & Sons, Inc. All rights reserved. The Larynx The mucous membrane of the larynx forms two pairs of folds: The superior pair are the Ventricular folds ( false vocal cords) also called vestibular folds The space between the ventricular folds is the rima vestibuli The inferior pair are the vocal folds ( true vocal cords) The space between the vocal folds ( true vocal cords) is the rima glottidis True vocal cords & the opening between them form the glottis Copyright © John Wiley & Sons, Inc. All rights reserved. Copyright © John Wiley & Sons, Inc. All rights reserved. The Larynx The functions of the larynx are: To provide an airway To route air and food into the proper channels To function in voice production- True vocal cords vibrate to produce sound as air passes False vocal cords have no part in sound production; help close glottis during swallowing Valsalva’s maneuver- by closing the glottis the larynx is closed during certain abdominal straining conditions to prevent exhalation Copyright © John Wiley & Sons, Inc. All rights reserved. Lower Respiratory Tract As air passes from the laryngopharynx into the larynx, it leaves the upper respiratory tract and enters the lower respiratory tract. Air passing through the respiratory tract Nasal cavity Upper respiratory tract Pharynx Larynx Trachea Primary bronchi Lower respiratory tract Secondary bronchi Tertiary bronchi Bronchioles Alveoli (150 million/lung) Copyright © John Wiley & Sons, Inc. All rights reserved. The Trachea The trachea is a semi-rigid pipe made of semi-circular cartilaginous rings, and located anterior to the esophagus. It is about 12 cm long and extends inferior to larynx into the mediastinum At the level of carina ( an internal ridge of last tracheal cartiage) it divides into right and left primary (1o, “mainstem”) bronchi. It is composed of 4 layers: the mucosa ( lined by ciliated respiratory epithelium), submucosa, hyaline cartilage, and adventitia Copyright © John Wiley & Sons, Inc. All rights reserved. The Trachea The tracheal cartilage rings are incomplete posteriorly, facing the esophagus. Esophageal masses can press into this soft part of the trachea and make it difficult to breath, or even totally obstruct the airway. Copyright © John Wiley & Sons, Inc. All rights reserved. The Bronchi The right and left primary (1o or “mainstem”) bronchi emerge from the inferior trachea to go to the lungs Right primary bronchus is more vertical compared to left primary bronchus Copyright © John Wiley & Sons, Inc. All rights reserved. The Bronchi Primary bronchi- subdivide into: Secondary bronchi (lobar bronchi), each supplying a lobe of the lungs –two on the left side and three on the right Subdivide into tertiary bronchi (segmental bronchi)- each supplies one bronchopulmonary segment There are upto 10 bronchopulmonary segments in each lung http://pblnotes.wordpress.com/2011/ Copyright © John Wiley & Sons, Inc. All rights reserved. Bronchioles Air passages undergo 23 orders of branchings Bronchioles- smaller than 1mm in diameter- lack cartilage Bronchioles divide into terminal bronchioles A branch of the terminal bronchioles supplies air to a lobule Terminal bronchioles branch into respiratory bronchioles which now have alveoli Respiratory bronchioles lead to the alveolar ducts which have alveoli The respiratory bronchioles, alveolar ducts and alveoli form the 'respiratory zone' Copyright © John Wiley & Sons, Inc. All rights reserved. Lung lobule Pulmonary lobule: Wrapped in elastic C.T., each pulmonary lobule contains a lymphatic vessel, an arteriole, a venule and a branch of terminal bronchiole. Copyright © John Wiley & Sons, Inc. All rights reserved. The bronchi and bronchioles go through structural changes as they branch and become smaller. The mucous membrane changes The cartilaginous rings become more sparse, and eventually disappear altogether. As cartilage decreases, smooth muscle (under the control of the Autonomic Nervous System) increases. o Sympathetic stimulation causes airway dilation, while parasympathetic stimulation causes airway constriction. Copyright © John Wiley & Sons, Inc. All rights reserved. All the branches from the trachea to the terminal bronchioles are conducting airways – they do not participate in gas exchange. Copyright © John Wiley & Sons, Inc. All rights reserved. Alveoli Alveoli are the cup-shaped outpouchings which participate in gas exchange Alveoli make up a large surface area (750 ft2). They are lined chiefly by type I alveolar cells, simple squamous epithelium)which allow for exchange of gases with the pulmonary capillaries. Copyright © John Wiley & Sons, Inc. All rights reserved. Alveoli Type II cells in the alveoli secrete a substance called surfactant that prevents collapse of the alveoli Alveoli macrophages (also called “dust cells”) engulf and remove pathogens & debris Copyright © John Wiley & Sons, Inc. All rights reserved. Respiratory Membrane The Respiratory membrane across which diffusion of gases occurs is composed of: Alveolar lining epithelium Capillary endothelium Their fused basement membranes Copyright © John Wiley & Sons, Inc. All rights reserved. Blood Supply to the Lungs The lungs receive blood via two sets of arteries Pulmonary arteries carry deoxygenated blood from the right heart to the lungs for oxygenation Bronchial arteries branch from the aorta and deliver oxygenated blood to the lungs primarily perfusing the muscular walls of the bronchi and bronchioles ( not the alveoli) Copyright © John Wiley & Sons, Inc. All rights reserved. The Lungs The lungs are divided into lobes by fissures. The right lung is divided by the oblique fissure and the horizontal fissure into 3 lobes . The left lung is divided into 2 lobes by the oblique fissure. Each lobe receives it own 2o bronchus that branches into 3o segmental bronchi (which continue to further divide). Copyright © John Wiley & Sons, Inc. All rights reserved. Copyright © John Wiley & Sons, Inc. All rights reserved. Respiratory System Anatomy The apex of the lung is superior, and extends slightly above the clavicles. The base of the lungs rests on the diaphragm. The cardiac notch – in the left lung (the indentation for the heart) • The medial mediastinal surface has the hilus – an indentation Copyright © John Wiley & Sons, Inc. All rights reserved. Respiratory System Anatomy The lungs are separated from each other by the heart and other structures in the mediastinum. Each lung is enclosed by a double-layered pleural membrane. The parietal pleura line the walls of the thoracic cavity. The visceral pleura adhere tightly to the surface of the lungs themselves. Copyright © John Wiley & Sons, Inc. All rights reserved. Respiratory System Anatomy On each side of the thorax, a pleural cavity is formed. The pleural cavity contains pleural fluid -reduces friction The pleura, adherent to the chest wall and to the lung, produces a mechanical coupling for the two layers to move together. Copyright © John Wiley & Sons, Inc. All rights reserved. Copyright © John Wiley & Sons, Inc. All rights reserved.