A&P1, Chapter 10 Tutor: Eleshia Howell RESPIRATORY SYSTEM (c)Eleshia Howell, 2012. All rights reserved. 1 As we have previously learned in our study of the digestive system, the cells of the body need energy for all of their metabolic activities. Most of this is derived from chemical reactions which can only take place in the presence of Oxygen (aerobic catabolism). The main waste product produced is carbon dioxide. The respiratory system provides the route of supply of oxygen, and excretion of carbon dioxide. (c)Eleshia Howell, 2012. All rights reserved. 2 The respiratory system, organised into Upper and Lower respiratory systems, is composed of structures involved in ventilation and gas exchange. Upper = nose, nasal cavity, paranasal sinuses, pharynx. Purpose: filter, warm, humidify the air. Lower = Larynx, trachea, bronchi, bronchioles and alveoli of the lungs. The term respiratory tract refers to the passageways that carry air to and from the exchange surfaces of the lungs. (c)Eleshia Howell, 2012. All rights reserved. 3 The condition of the atmospheric air varies according the to external environment. Air breathed in through the passageways is warmed / cooled to body temperature, moistened and ‘cleaned’ and distributed throughout the body via the blood. Exchange of gases between the lungs and the blood is called external respiration Exchange between the blood and cells is called internal respiration. (c)Eleshia Howell, 2012. All rights reserved. 4 The organs / structures of the resp. system are: Nose Pharynx Larynx Trachea Two bronchi Bronchioles & smaller air passages Two lungs & their pleura Muscles of respiration (intercostals & diaphragm) (c)Eleshia Howell, 2012. All rights reserved. 5 p234 (c)Eleshia Howell, 2012. All rights reserved. 6 Functions of Respiratory System 1. Provide extensive surface area for gas exchange between air & circulating blood 2. Movement of air to & from exchange surfaces 3. Protecting respiratory surfaces from dehydration, temperature changes & other environmental variations; defence against pathogens. (c)Eleshia Howell, 2012. All rights reserved. 7 4. Producing sounds involved in speaking, singing and other forms of communication 5. Facilitating detection of olfactory stimuli (olfactory receptors in nasal cavity). (c)Eleshia Howell, 2012. All rights reserved. 8 Nose / Nasal cavity The main route of air entry. Nose is a large irregular cavity divided into two equal sections by the septum. The anterior nares, or nostrils, are the openings into the nasal cavity; nasal hairs and sticky mucous serve to trap foreign particles and pathogens as part of non-specific defence. (c)Eleshia Howell, 2012. All rights reserved. 9 p235 (c)Eleshia Howell, 2012. All rights reserved. 10 The nose is lined with highly vascular ciliated columnar epithelium which contains mucous secreting goblet cells. the conchae, within the nasal cavity, increase the surface area and cause turbulence, spreading the air across the nasal surfaces, maximising the warming, filtering and humidifying functions. Warming ~ occurs due to the immense vascularity of the mucosal lining. (c)Eleshia Howell, 2012. All rights reserved. 11 Filtering & cleaning ~ hairs trap larger particles, mucous traps smaller ones such as dust & microbes. Mucous also protects the underlying epithelium from irritation & prevents drying. The cilia move the trapped particles towards the throat, to be either swallowed or coughed up (expectorated). Humidification ~ as air travels over the moist mucosa it becomes saturated with water vapour. Irritation of the mucosa = sneezing, a reflex action that forcibly expels an irritant. (c)Eleshia Howell, 2012. All rights reserved. 12 Smell ~ the nose is the organ for our sense of smell (olfaction). As we have already discovered during our study of Special Senses there are millions of specialised sensory nerve endings in the roof of the nose which, when stimulated by airborne odours, carry signals via the olfactory nerves to the brain where the smell is perceived. (c)Eleshia Howell, 2012. All rights reserved. 13 Pharynx Encompasses the nasopharynx, oropharynx and laryngopharynx. Dual purpose – passageway for food and air. Is also responsible for warming & humidifying the air as it is inhaled Assists hearing – air from nasopharynx enters the auditory tubes to establish the atmospheric pressure required for tympanic membranes to detect sound waves. (c)Eleshia Howell, 2012. All rights reserved. 14 Larynx Aka ‘voice box’...links the laryngopharynx and the trachea at the level of 3rd- 6th Cervical vertebrae. During puberty, in males the larynx enlarges and becomes more prominent (adam’s apple) creating a deeper voice. It is composed of several sections of cartilage attached by ligaments & membranes. (c)Eleshia Howell, 2012. All rights reserved. 15 Anterior view of Larynx, p238 (c)Eleshia Howell, 2012. All rights reserved. 16 Thyroid cartilage – most prominent, lays at the anterior throat, visible adam’s apple part. Bound by ligaments to hyoid bone; site of numerous attachments for anterior neck muscles. Cricoid cartilage – lies below the thyroid cartilage, completely encircling the larnyx. The lower border marks the end of the upper respiratory tract. Arytenoid cartilages – paired pieces of cartilage situated on top of cricoid. Provide attachment for vocal cords. Epiglottis – flexible stalk of cartilage emanating from the anterior thyroid cartilage ; rises obliquely upwards to behind the tongue & hyoid bone, acting as a lid, to close off larynx during swallowing. (c)Eleshia Howell, 2012. All rights reserved. 17 VOCAL CORDS: Comprise of two folds of mucous membrane with cord-like free edges, extending from the inner wall of the thyroid prominence anteriorly, and the arytenoid cartilages posteriorly. When the muscles controlling the vocal cords are relaxed, the vocal cords open and the passageway for air arising from the larynx is clear cords abducted. When the muscles contract, the cords are stretched tightly across the larynx – adducted (c)Eleshia Howell, 2012. All rights reserved. 18 (c)Eleshia Howell, 2012. All rights reserved. 19 p239 (c)Eleshia Howell, 2012. All rights reserved. 20 FUNCTIONS OF THE LARYNX: Production of sound ~ Pitch: length & tightness of cords Volume: depends upon force of vibration Resonance/ Tone: determined by shape of the mouth, position of tongue & lips, facial muscles & air in paranasal sinuses. Speech – when sounds produced by vocal cords are manipulated by the tongue, cheeks & lips (c)Eleshia Howell, 2012. All rights reserved. 21 Protection of lower respiratory tract – during swallowing the larynx moves upwards to block the opening to the trachea, ensuring food passes into the oesophagus. Airway – passageway for air to enter trachea Humidifying, filtering & warming . (c)Eleshia Howell, 2012. All rights reserved. 22 Trachea Aka ‘windpipe’ extends down from larynx, dividing into right & left bronchi at approx T5 A series of C-shaped rings of hyaline cartilage are embedded into the anterior surface of the trachea to help stabilise & protect the airway. Parasympathetic stimulation (via branches of Vagus nerve) constricts the trachea; Sympathetic stimulation (via sympathetic ganglia) dilates it. (c)Eleshia Howell, 2012. All rights reserved. 23 (c)Eleshia Howell, 2012. All rights reserved. 24 FUNCTIONS OF TRACHEA: Support & Patency: tracheal cartilage holds it permanently open (patent) but the soft tissue at the posterior of the bands allows flexibility so that the trunk can move freely without obstructing or kinking . The absence of cartilage posteriorly also allows the trachea to dilate & constrict in response to nerve stimulation, and to allow indentation as bolus is swallowed down oesophagus. (c)Eleshia Howell, 2012. All rights reserved. 25 (c)Eleshia Howell, 2012. All rights reserved. 26 Cough reflex: nerve endings in the larynx, trachea and bronchi are sensitive to irritation, generating impulses conducted along the Vagus nerve to the respiratory centre of the brain stem, initiating a motor reflex response to expel the irritant. The ciliated mucous membrane cells assist the movement of captured particles upwards towards the larynx to be either swallowed or coughed out. (c)Eleshia Howell, 2012. All rights reserved. 27 Lungs Two lungs, one each on either side of the midline in the thoracic cavity. Cone shaped with an apex, base, tip; costal & medial surfaces. The concave medial surface of the lung has a hilum (indented area) where structures enter/ exit the lung, eg primary bronchus, pulmonary artery, pulmonary veins (2), bronchial artery & vein, lymphatics & nerves. (c)Eleshia Howell, 2012. All rights reserved. 28 p242 (c)Eleshia Howell, 2012. All rights reserved. 29 p243 (c)Eleshia Howell, 2012. All rights reserved. 30 The area between the lungs (mediastinum) is occupied by the heart, great vessels, trachea, right & left bronchi, oesophagus, lymph nodes/vessels and nerves. The right lung is divided into 3 lobes (superior, middle, inferior). The left lung is smaller due to the heart occupying space just left of the midline. It is divided into only two lobes (superior & inferior). The divisions between lobes are called fissures. (c)Eleshia Howell, 2012. All rights reserved. 31 PLEURA & PLEURAL CAVITY: The pleura consists of a closed sac of serous membrane (one for each lung) containing a small amount of serous fluid. The lung is invaginated into this sac so that it forms two layers: Visceral pleura – adherent to the lung, covering each lobe & passing into the fissures Parietal layer – adherent to the inside of the chest wall & thoracic surface of diaphragm. (c)Eleshia Howell, 2012. All rights reserved. 32 The pleural cavity is only a potential space & contains no air. The two layers of pleura are separated by a thin layer of serous fluid, allowing them to glide over each other, preventing friction during breathing. The serous fluid is excreted by the epithelial cells of the pleural membrane. If either layer of pleura is punctured, the underlying lung collapses. (c)Eleshia Howell, 2012. All rights reserved. 33 (c)Eleshia Howell, 2012. All rights reserved. 34 The interior of the lungs are composed of The bronchi Alveoli Connective tissue Blood vessels Lymph vessels Nerves ...all embedded in an elastic connective tissue matrix. Each lobe consists of a large number of lobules. (c)Eleshia Howell, 2012. All rights reserved. 35 Pulmonary blood supply The pulmonary trunk divides into left and right pulmonary arteries, transporting deoxygenated blood to each lung. Inside the lungs, each artery divides into numerous branches, eventually ending in a dense capillary network around the walls of the alveoli. (c)Eleshia Howell, 2012. All rights reserved. 36 The walls of the alveoli and capillaries are just a single layer of epithelial cells, allowing the rapid diffusion of gases across the membranes. The pulmonary capillaries join to form two pulmonary veins in each lung, leaving the lung at the hilum to carry oxygenated blood to the left atrium of the heart. The innumerable capillaries and blood vessels are supported by connective tissue. (c)Eleshia Howell, 2012. All rights reserved. 37 p244 (c)Eleshia Howell, 2012. All rights reserved. 38 Bronchi & Bronchioles Two primary bronchi are formed when the trachea divides at T5. The right bronchus is wider, shorter & more vertical than the left and is more prone to obstruction by an inhaled foreign body. It sub-divides into 3 branches, one to each lobe, before dividing further into numerous smaller branches. (c)Eleshia Howell, 2012. All rights reserved. 39 The left bronchus is shorter and narrower, dividing into only 2 branches (one to each lobe) before subdividing into progressively smaller branches as it infiltrates further into the lung tissue. The bronchial walls are composed of the same tissue as the trachea (ciliated columnar epithelium). (c)Eleshia Howell, 2012. All rights reserved. 40 p244 (c)Eleshia Howell, 2012. All rights reserved. 41 As the bronchi divide and become progressively smaller, their structure also changes to match their function: Cartilage – rigid cartilage would interfere with the expansion of the lung tissue, hindering gas exchange, so it is present only in the larger airways. The cartilage rings gradually become much smaller plates until, at the bronchiole level, become non-existent. (c)Eleshia Howell, 2012. All rights reserved. 42 Smooth muscle – as the cartilage disappears it is replaced by smooth muscle, allowing the diameter of the airways to be increased or decreased (via ANS control) to regulate respiration. Epithelial lining – ciliated epithelium is gradually replaced with non-ciliated epithelium and goblet cells disappear. (c)Eleshia Howell, 2012. All rights reserved. 43 The Vagus nerve supplies the lungs... Parasympathetic stimulation causes contraction of the smooth muscle in the bronchial tree (bronchoconstriction) while sympathetic stimulation causes bronchodilation. Lymph is drained from the walls of the air passes in a network of lymph vessels through nodes situated around the trachea and bronchial tree, then into the thoracic duct on the left, right lymphatic duct on the other side. (c)Eleshia Howell, 2012. All rights reserved. 44 FUNCTION of BRONCHI: Control of airway – diameter is altered according to ANS stimulation Warming & humidifying Support & patency Removal of particulate matter Cough reflex (c)Eleshia Howell, 2012. All rights reserved. 45 Bronchioles & Alveoli The bronchioles subdivide into respiratory bronchioles, alveolar ducts and large numbers of air sacs known as alveoli (approx 150million in an adult lung). It is in these structures that gas exchange occurs. As the airways progressively divide and get smaller, their walls gradually become thinner until muscle & connective tissue disappear, leaving a single layer of squamous epithelial cells in the alveolar ducts & alveoli. (c)Eleshia Howell, 2012. All rights reserved. 46 These distal respiratory passages are supported by loose, elastic connective tissue in which macrophages, fibroblasts, nerves & blood / lymph vessels are embedded. The alveoli are surrounded by a dense network of capillaries. In healthy lung tissue the extensive air spaces are clearly seen as a honeycomb-like appearance. (c)Eleshia Howell, 2012. All rights reserved. 47 (c)Eleshia Howell, 2012. All rights reserved. 48 (c)Eleshia Howell, 2012. All rights reserved. 49 Lying between the squamous cells are septal cells that secrete surfactant, a phospholipid fluid which prevents the alveoli from drying out. It also helps to reduce surface tension & prevent the alveoli from collapsing during expiration. Secretion of surfactant begins at 35wks gestation. (c)Eleshia Howell, 2012. All rights reserved. 50 p246 (c)Eleshia Howell, 2012. All rights reserved. 51 p246 (c)Eleshia Howell, 2012. All rights reserved. 52 Respiration The exchange of gases between body cells and the environment. Involves 2 processes: Breathing – movement of air into and out of the lungs Exchange of gases – in the lungs (external respiration) and in the tissues (internal respiration). (c)Eleshia Howell, 2012. All rights reserved. 53 BREATHING: Supplies oxygen to the alveoli and eliminates carbon dioxide Expansion of the chest during inspiration occurs due to muscular activity ~ partly voluntary & partly involuntary. The main muscles used in normal, quiet breathing are the external intercostal muscles and the diaphragm. (c)Eleshia Howell, 2012. All rights reserved. 54 Intercostal Muscles – 11 pairs of muscles that occupy the spaces between the 12 pairs of ribs. Arranged in 2 layers – external (used during inspiration) & internal (used during active expiration, eg exercise). The 1st rib is fixed, so when the external intercostal muscles contract they pull all the other ribs upwards towards it. The size & shape of the ribs encourages an outward movement of the ribcage, enlarging the thoracic cavity. (c)Eleshia Howell, 2012. All rights reserved. 55 p247 (c)Eleshia Howell, 2012. All rights reserved. 56 Diaphragm – A dome shaped muscular structure separating the thoracic cavity & the roof of the abdominal cavity. It consists of a central tendon from which muscle fibres radiate to attach to the lower ribs and sternum, and to the vertebral column When the diaphragm is relaxed, the central tendon is at level of T8; when it contracts, the tendon is pulled downwards to T9, lengthening the thoracic cavity. (c)Eleshia Howell, 2012. All rights reserved. 57 This decreases pressure in the thoracic cavity and increases the pressure in the abdominal and pelvic cavities. The diaphragm is innervated by the Phrenic nerves (branching from C3-5). Quiet, restful breathing is often referred to as diaphragmatic breathing as 75% of the work is done by the diaphragm. The external intercostals & the diaphragm contract simultaneously, enlarging the thoracic cavity in all directions. (c)Eleshia Howell, 2012. All rights reserved. 58 (c)Eleshia Howell, 2012. All rights reserved. 59 (c)Eleshia Howell, 2012. All rights reserved. 60 ACCESSORY MUSCLES OF RESPIRATION: When extra respiratory effort is required, additional muscles are used. Forced inspiration ~ sternocleidomastoid (SCM) and scalene muscles of the neck, help to increase ribcage expansion. Forced expiration ~ internal intercostal muscles and abdominal muscles (mainly transverse & oblique) help to increase the pressure in the thorax by applying a squeezing action. (c)Eleshia Howell, 2012. All rights reserved. 61 Other muscles which can aid respiration are: Serratus posterior superior (inspiration) Pectoralis Minor (forced inspiration) Quadratus Lumborum (forced expiration) Transversus Thoracis & Subcostales (forced expiration) Latissimus Dorsi (accessory) (c)Eleshia Howell, 2012. All rights reserved. 62 CYCLE OF BREATHING: The average respiratory rate is 12-15 breaths per minute Each breath consists of 3 phases Inspiration Expiration Pause Breathing is dependent upon changes in pressure and volume in the thoracic cavity (c)Eleshia Howell, 2012. All rights reserved. 63 The underlying physical principal is that increasing the volume of a container decreases the pressure inside it, and that decreasing the volume of a container increases the pressure inside it. Since air flows from an area of high pressure to one of low pressure, changing the pressure inside the lungs determines the direction of airflow. (c)Eleshia Howell, 2012. All rights reserved. 64 Diaphragm + external intercostal muscles contract, expanding the thoracic cavity... Pressure in the pleural cavity decreases in relation to the pulmonary cavity, causing the lungs to expand... The resultant decrease in pulmonary cavity pressure (compared to the atmospheric pressure outside the body) causes air to be drawn into the lungs. This active process also aids venous return to the heart ~ respiratory pump. (c)Eleshia Howell, 2012. All rights reserved. 65 p243 (c)Eleshia Howell, 2012. All rights reserved. 66 When the diaphragm & external intercostals relax, the build up of pressure in the abdominal cavity increases the pressure in thoracic & pulmonary cavities, pushing the air out of the lungs. This is a passive process. (c)Eleshia Howell, 2012. All rights reserved. 67 Variables Affecting Breathing: Elasticity – the ability of the lung to return to its normal shape after each breath. Loss of elasticity necessitates forced expiration & increased effort on inspiration. Compliance – the measure of stretchability of the lungs (effort required to inflate alveoli). Little effort is required to inflate healthy lungs. (c)Eleshia Howell, 2012. All rights reserved. 68 Airway resistance – bronchoconstriction means more respiratory effort is required to inflate the lungs. The lungs and air passages are never empty, but gas exchange only occurs at the site of the alveoli, so the remaining capacity of the respiratory passages is known as anatomical dead space. (c)Eleshia Howell, 2012. All rights reserved. 69 Lung function testing is carried out to determine respiratory function and are based on the following parameters: Tidal Volume (TV) – the amount of air passing in & out of the lungs during each breath cycle (about 500ml at rest) Inspiratory Reserve Volume (IRV) – the extra volume of air that can be inhaled during max inspiration Inspiratory Capacity (IC) – the amount of air that can be inspired with maximum effort TV + IRV = IC (c)Eleshia Howell, 2012. All rights reserved. 70 Functional Residual Capacity (FRC) – the amount of air remaining in the passageways and alveoli at end of quiet expiration. Expiratory Reserve Volume (ERV) – the largest volume of air that can be expelled during maximum expiration. Residual Volume (RV) – the volume of air remaining in the lungs after forced expiration (cannot be directly measured). Vital Capacity (VC) – maximum volume of air able to move in and out of lungs VC = TV + IRV + ERV (c)Eleshia Howell, 2012. All rights reserved. 71 Total Lung Capacity (TLC) – maximum amount of air the lungs can hold. In adult, approx 6L. Alveolar Ventilation – is the volume of air that moves into and out of the alveoli per minute. It is equal to the tidal volume – anatomical dead space x respiratory rate. (c)Eleshia Howell, 2012. All rights reserved. 72 EXCHANGE OF GASES: Is a continuous and ongoing process across the respiratory membranes. Diffusion of oxygen and carbon dioxide depends on pressure differences, eg between atmospheric air and blood, or between blood and the tissues. Atmospheric Air is a mixture of gases: oxygen, carbon dioxide, nitrogen, water vapour and small quantities of inert gases (eg Argon, Helium, Hydrogen, Methane). (c)Eleshia Howell, 2012. All rights reserved. 73 Each gas in the mixture exerts a part of the total pressure, proportional to its concentration. Known as partial pressure (PO2) Composition of inspired & expired air. p250 (c)Eleshia Howell, 2012. All rights reserved. 74 Alveolar air is different from atmospheric air; it is saturated with water vapour and contains more CO2 and less O2. The saturation of water vapour reduces the partial pressure of all the other gases present. Exchange of gases occurs when a difference in partial pressure exists across a semipermeable membrane. Gases move by diffusion from higher concentration to lower until equilibrium is established. (c)Eleshia Howell, 2012. All rights reserved. 75 External respiration – the exchange of gases between the alveoli and the blood in the capillaries, across the respiratory membrane. Internal respiration – the exchange of gases between the blood in the capillaries and the body cells. O2 and CO2 are transported in the blood in different ways... (c)Eleshia Howell, 2012. All rights reserved. 76 Oxygen is carried in the blood in chemical combination with haemoglobin (as oxyhaemoglobin) as well as in plasma water solution. Carbon dioxide, a waste product of metabolism, is excreted by the lungs and is transported by 3 mechanisms: As bicarbonate ions in the plasma Some carried in RBC’s Some dissolved in the plasma (c)Eleshia Howell, 2012. All rights reserved. 77 Control of Respiration Effective control of respiration enables the body to regulate blood gas levels over a wide range of physiological, environmental and pathological conditions, and is normally involuntary. Voluntary control is exerted during activities such as speaking and singing, but is overridden if blood CO2 rises. (c)Eleshia Howell, 2012. All rights reserved. 78 Respiratory Centre – Is formed by groups of nerves in the medulla, the respiratory rhythmicity centre, which controls the respiratory pattern (rate & depth of breathing). Regular discharge of inspiratory neurones within this centre set the rate and depth of breathing. Activity in the respiratory centre is adjusted by nerves in the pons (pneumotaxic & apneustic centres) in response to input from other parts of the brain. (c)Eleshia Howell, 2012. All rights reserved. 79 Motor impulses from the respiratory centre pass in the Phrenic and Intercostal nerves to the diaphragm & intercostal muscles. Chemoreceptors – Respond to changes in the partial pressures of O2 and CO2 in the blood and CSF. They are located centrally and peripherally. (c)Eleshia Howell, 2012. All rights reserved. 80 Central chemoreceptors are located on the surface of the medulla oblongata and are bathed in CSF. When arterial CO2 rises even slightly, these receptors respond by stimulating an increase in respiration. A small reduction in O2 has the same but less pronounced effect, but a substantial reduction depresses breathing. (c)Eleshia Howell, 2012. All rights reserved. 81 Peripheral chemoreceptors are situated in the arch of the aorta & in the carotid bodies. They are more sensitive to rises in blood CO2 than to small decreases in blood O2 levels. Nerve impulses generated here are conveyed by the Glossopharyngeal & Vagus nerves to the medulla and stimulate the respiratory centre. An increase in blood acidity stimulates the chemoreceptors, resulting in increased ventilation, increased CO2 output and increased blood pH. (c)Eleshia Howell, 2012. All rights reserved. 82 p252 (c)Eleshia Howell, 2012. All rights reserved. 83 Exercise and respiration – Physical exercise increases both the rate and depth of respiration to supply the increased oxygen requirements of the muscles. The increased respiratory effort persists even after exercise stops in order to repay the oxygen debt (to rid the cells of waste, lactic acid etc) (c)Eleshia Howell, 2012. All rights reserved. 84 Other factors that influence respiration include: Speech, singing Emotional displays, eg crying, laughter, fear Drugs, eg sedatives, alcohol Sleep Temperature, eg fever, hypothermia. Breathing may be modified by the higher brain centres during these activities. (c)Eleshia Howell, 2012. All rights reserved. 85 Respiratory Changes at Birth The respiratory system of foetuses and newborns differ in several important ways. Before delivery, pulmonary arterial resistance is high because the pulmonary vessels are collapsed. The ribcage is compressed and the lungs & airways contain only small amounts of fluid but no air. During delivery the lungs are compressed further; as placental connection is lost, blood O2 levels fall and CO2 increases rapidly... (c)Eleshia Howell, 2012. All rights reserved. 86 At birth, the newborn takes its first breath through powerful contractions of the diaphragm and external intercostal muscles. The inhaled air must enter the respiratory passages with enough force to overcomes surface tension and inflate the bronchial tree and most of the alveoli. The same drop in pressure that pulls air into the lungs pulls blood into the pulmonary circulation. (c)Eleshia Howell, 2012. All rights reserved. 87 The changes in blood flow and rise in O2 levels lead to the closure of the foramen ovale and the ductus arteriosus. The exhalation that follows that first breath fails to empty the lungs completely, keeping the airways open; surfactant is secreted to prevent alveolar collapse. Subsequent breaths complete the inflation of all of the alveoli. (c)Eleshia Howell, 2012. All rights reserved. 88 Age & respiratory performance Many factors interact to reduce the efficiency of the respiratory system in elderly individuals. Three noteworthy examples are: Deterioration of elastic tissue, altering the compliance of the lungs and their vital capacity. Arthritic changes can limit chest movement, limiting respiratory volume. (c)Eleshia Howell, 2012. All rights reserved. 89 Some degree of emphysema is normal in individuals over 50, however, the extent increases considerably with exposure to cigarette smoke and other respiratory irritants. (c)Eleshia Howell, 2012. All rights reserved. 90 Pathologies of the Respiratory System Infectious & inflammatory disorders of the upper respiratory tract can be caused by inhaling irritants and pathogens. Infections are usually caused by viruses that lower the resistance to other pathogens, allowing bacteria to invade the tissues, producing inflammation & exudate. (c)Eleshia Howell, 2012. All rights reserved. 91 Common cold (Coryza) is usually caused by the rhinoviruses and is highly infectious. Symptoms include runny nose (rhinorrhoea) sneezing, sore throat and slight fever. Influenza is caused by a different group of viruses and produced far worse symptoms, including very high fever and muscle pain. Complete recovery can take weeks and secondary bacterial infections are common. (c)Eleshia Howell, 2012. All rights reserved. 92 Sinusitis – usually spread by microbes from the nose and pharynx to the mucous membrane lining of the paranasal sinuses. Congested mucous blocks the openings between the nose and the sinuses, preventing drainage of mucopurulent discharge. Symptoms include facial pain and headache. Hayfever (allergic rhinitis) – hypersensitivity to foreign antigens develops into acute inflammation of the mucosa and conjunctiva. (c)Eleshia Howell, 2012. All rights reserved. 93 Obstructive Lung Disorders: Bronchitis – acute is usually secondary to a bacterial infection of the bronchi (eg cold, flu). Chronic is usually a progressive inflammatory disease resulting from prolonged irritation of the bronchial epithelium. Emphysema – a chronic, progressive condition where the destruction of alveolar surfaces results in decreased surface area for gas exchange. Characterised by shortness of breath, unable to tolerate physical exertion. (c)Eleshia Howell, 2012. All rights reserved. 94 Asthma – a common inflammatory disease of the airways, associated with episodes of reversible over-activity of the smooth muscle in the airways. The mucous membrane & muscle layers of the bronchi become thickened and the mucous glands enlarge, reducing airflow in the lower respiratory tract. The walls swell and thicken with inflammatory exudate and an influx of inflammatory cells, especially eosinophils. During an attack, spasmodic contraction of bronchial muscle constricts the airway; excessive secretion of thick, sticky mucous further narrows the airway. (c)Eleshia Howell, 2012. All rights reserved. 95 (asthma cont’d) Inspiration is normal but only partial expiration is achieved, so the lungs become hyperinflated; there is severe dyspnoea and wheezing. The duration of attacks varies from minutes to hours. In severe cases the bronchi may be obstructed by mucous plugs, leading to acute respiratory failure, hypoxia and possibly death. (c)Eleshia Howell, 2012. All rights reserved. 96 Cystic Fibrosis – a common genetic disorder affecting 1 in 2500 babies. An estimated 5% of people carry the recessive gene, which must be present in both parents to cause the disease. The secretions of all exocrine glands have abnormally high viscosity, the most severely affected are those of the lungs, pancreas, intestines, biliary tract and reproductive system (males). In less acute stages there may be impairment of protein & fat digestion. (c)Eleshia Howell, 2012. All rights reserved. 97 Restrictive Disorders: Are characterised by increasing stiffness of lung tissue, making it harder to inflate the lung and increasing the work of breathing. Chronic restrictive disease is often associated with progressive fibrosis caused by repeated inflammation of the lungs. Pneumoconioses – a group of lung diseases caused by inhaling dusts / work related pollutants. Frequently affects people working in coal / mineral mines, quarries, stone masonry, sand blasting, glass / pottery. (c)Eleshia Howell, 2012. All rights reserved. 98 Lung Infections: Pneumonia – infection of the alveoli occurring when protective processes fail to prevent inhaled or blood-borne microbes from reaching and colonising the lungs. Numerous causes. Tuberculosis – caused by mycobacterium; highly infectious air-borne disease spread by coughing, sneezing or droplet transmission. Characterised by tubercles in lungs (walled off infection sites), coughing of blood tinged sputum, night sweats, fever & weight loss. (c)Eleshia Howell, 2012. All rights reserved. 99 Tumours: Bronchial carcinoma – a very common malignancy, with 90% occurring in smokers (or passive smokers). Usually not detected early, prognosis often poor. Tumour fragments are spread by blood and lymph producing metastases elsewhere in the body. Pleural mesothelioma – linked with exposure to asbestos (particularly ‘blue’ asbestos). Tumour involves both layers of the pleura and as it grows obliterates the pleural cavity, compressing the lung. (c)Eleshia Howell, 2012. All rights reserved. 100 Lung Collapse: The clinical effects of all or part of a lung depend on how much of the lung is affected. The four main causes of a collapsed lung: Obstruction of airway Impaired surfactant function Pressure collapse – when air or fluid enters the pleural cavity, altering the pressure and preventing lung expansion. Alveolar hypoventilation – may be due to pain experienced on inspiration, post-operative, chest infections. (c)Eleshia Howell, 2012. All rights reserved. 101 (c)Eleshia Howell, 2012. All rights reserved. 102