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Chapter 21 The Respiratory System • Cells continually use O2 & release CO2 • Respiratory system designed for gas exchange • Cardiovascular system transports gases in blood • Failure of either system – rapid cell death from O2 starvation Respiratory System Anatomy • Nose • Pharynx • Larynx • Trachea • Bronchi • Lungs *Locations of infections – upper respiratory tract is above vocal cords – lower respiratory tract is below vocal cords External Nasal Structures • Skin, nasal bones, & cartilage lined with mucous membrane • Openings called external nares or nostrils Tortora & Grabowski 9/e 2000 JWS 23-4 Nose -- Internal Structures • • • • • Large chamber within the skull Roof is made up of ethmoid and floor is hard palate Internal nares (choanae) are openings to pharynx Nasal septum is composed of bone & cartilage Bony swelling or conchae on lateral walls Functions of the Nasal Structures • Olfactory epithelium for sense of smell • Pseudostratified ciliated columnar with goblet cells lines nasal cavity – warms air due to high vascularity – mucous moistens air & traps dust – cilia move mucous towards pharynx • Paranasal sinuses open into nasal cavity – found in ethmoid, sphenoid, frontal & maxillary – lighten skull & resonate voice Pharynx • Muscular tube (5 inch long) hanging from skull – skeletal muscle & mucous membrane • Extends from internal nares to cricoid cartilage • Functions – passageway for food and air – resonating chamber for speech production – tonsil (lymphatic tissue) in the walls protects entryway into body • Distinct regions -- nasopharynx, oropharynx and laryngopharynx Nasopharynx • From choanae to soft palate – openings of auditory (Eustachian) tubes from middle ear cavity – adenoids or pharyngeal tonsil in roof • Passageway for air only Oropharynx • From soft palate to epiglottis – fauces is opening from mouth into oropharynx – palatine tonsils found in side walls, lingual tonsil in tongue • Common passageway for food & air Laryngopharynx • Extends from epiglottis to cricoid cartilage • Common passageway for food & air & ends as esophagus inferiorly Cartilages of the Larynx • Thyroid cartilage forms Adam’s apple • Epiglottis---leaf-shaped piece of elastic cartilage – during swallowing, larynx moves upward – epiglottis bends to cover glottis • Cricoid cartilage---ring of cartilage attached to top of trachea • Pair of arytenoid cartilages sit upon cricoid – many muscles responsible for their movement – partially buried in vocal folds (true vocal cords) Larynx • Cartilage & connective tissue tube • Anterior to C4 to C6 • Constructed of 3 single & 3 paired cartilages Vocal Cords • False vocal cords (ventricular folds) found above vocal folds (true vocal cords) • True vocal cords attach to arytenoid cartilages The Structures of Voice Production • True vocal cord contains both skeletal muscle and an elastic ligament (vocal ligament) • When 10 intrinsic muscles of the larynx contract, move cartilages & stretch vocal cord tight • When air is pushed past tight ligament, sound is produced (the longer & thicker vocal cord in male produces a lower pitch of sound) • The tighter the ligament, the higher the pitch • To increase volume of sound, push air harder Movement of Vocal Cords • Opening and closing of the vocal folds occurs during breathing and speech Speech and Whispering • Speech is modified sound made by the larynx. • Speech requires pharynx, mouth, nasal cavity & sinuses to resonate that sound • Tongue & lips form words • Pitch is controlled by tension on vocal folds – pulled tight produces higher pitch – male vocal folds are thicker & longer so vibrate more slowly producing a lower pitch • Whispering is forcing air through almost closed rima glottidis -- oral cavity alone forms speech Trachea • Size is 5 in long & 1in diameter • Extends from larynx to T5 anterior to the esophagus and then splits into bronchi • Layers – mucosa = pseudostratified columnar with cilia & goblet – submucosa = loose connective tissue & seromucous glands – hyaline cartilage = 16 to 20 incomplete rings • open side facing esophagus contains trachealis m. (smooth) • internal ridge on last ring called carina – adventitia binds it to other organs Trachea and Bronchial Tree • Full extent of airways is visible starting at the larynx and trachea Chest x Ray Tortora & Grabowski 9/e 2000 JWS 23-19 Tracheostomy and Intubation • Reestablishing airflow past an airway obstruction – crushing injury to larynx or chest – swelling that closes airway – vomit or foreign object • Tracheostomy is incision in trachea below cricoid cartilage if larynx is obstructed • Intubation is passing a tube from mouth or nose through larynx and trachea Tortora & Grabowski 9/e 2000 JWS 23-20 Bronchi and Bronchioles • • • • Primary bronchi supply each lung Secondary bronchi supply each lobe of the lungs (3 right + 2 left) Tertiary bronchi supply each bronchopulmonary segment Repeated branchings called bronchioles form a bronchial tree Pleural Membranes & Pleural Cavity • Visceral pleura covers lungs --- parietal pleura lines ribcage & covers upper surface of diaphragm • Pleural cavity is potential space between ribs & lungs Gross Anatomy of Lungs • Base, apex (cupula), costal surface, cardiac notch • Oblique & horizontal fissure in right lung results in 3 lobes • Oblique fissure only in left lung produces 2 lobes Mediastinal Surface of Lungs • Blood vessels & airways enter lungs at hilus • Forms root of lungs • Covered with pleura (parietal becomes visceral) Structures within a Lobule of Lung • Branchings of single arteriole, venule & bronchiole are wrapped by elastic CT • Respiratory bronchiole – simple squamous • Alveolar ducts surrounded by alveolar sacs & alveoli – sac is 2 or more alveoli sharing a common opening Cells Types of the Alveoli • Type I alveolar cells – simple squamous cells where gas exchange occurs • Type II alveolar cells (septal cells) – free surface has microvilli – secrete alveolar fluid containing surfactant • Alveolar dust cells – wandering macrophages remove debris Alveolar-Capillary Membrane • Respiratory membrane = 1/2 micron thick • Exchange of gas from alveoli to blood • 4 Layers of membrane to cross – – – – alveolar epithelial wall of type I cells alveolar epithelial basement membrane capillary basement membrane endothelial cells of capillary • Vast surface area = handball court Details of Respiratory Membrane • Find the 4 layers that comprise the respiratory membrane Breathing or Pulmonary Ventilation • Air moves into lungs when pressure inside lungs is less than atmospheric pressure – How is this accomplished? • Air moves out of the lungs when pressure inside lungs is greater than atmospheric pressure – How is this accomplished? • Atmospheric pressure = 1 atm or 760mm Hg Boyle’s Law • As the size of closed container decreases, pressure inside is increased • The molecules have less wall area to strike so the pressure on each inch of area increases. Dimensions of the Chest Cavity • Breathing in requires muscular activity & chest size changes • Contraction of the diaphragm flattens the dome and increases the vertical dimension of the chest Quiet Inspiration • Diaphragm moves 1 cm & ribs lifted by muscles • Intrathoracic pressure falls and 2-3 liters inhaled Quiet Expiration • Passive process with no muscle action • Elastic recoil & surface tension in alveoli pulls inward • Alveolar pressure increases & air is pushed out Labored Breathing • Forced expiration – abdominal mm force diaphragm up – internal intercostals depress ribs • Forced inspiration – sternocleidomastoid, scalenes & pectoralis minor lift chest upwards as you gasp for air Intrathoracic Pressures • Always subatmospheric (756 mm Hg) • As diaphragm contracts intrathoracic pressure decreases even more (754 mm Hg) • Helps keep parietal & visceral pleura stick together Summary of Breathing • Alveolar pressure decreases & air rushes in • Alveolar pressure increases & air rushes out Alveolar Surface Tension • Thin layer of fluid in alveoli causes inwardly directed force = surface tension – water molecules strongly attracted to each other • Causes alveoli to remain as small as possible • Detergent-like substance called surfactant produced by Type II alveolar cells – lowers alveolar surface tension – insufficient in premature babies so that alveoli collapse at end of each exhalation Pneumothorax • Pleural cavities are sealed cavities not open to the outside • Injuries to the chest wall that let air enter the intrapleural space – causes a pneumothorax – collapsed lung on same side as injury – surface tension and recoil of elastic fibers causes the lung to collapse Tortora & Grabowski 9/e 2000 JWS 23-38 Compliance of the Lungs • Ease with which lungs & chest wall expand depends upon elasticity of lungs & surface tension • Some diseases reduce compliance – tuberculosis forms scar tissue – pulmonary edema --- fluid in lungs & reduced surfactant – paralysis Tortora & Grabowski 9/e 2000 JWS 23-39 Airway Resistance • Resistance to airflow depends upon airway size – increase size of chest • airways increase in diameter – contract smooth muscles in airways • decreases in diameter Breathing Patterns • • • • • Eupnea = normal quiet breathing Apnea = temporary cessation of breathing Dyspnea =difficult or labored breathing Tachypnea = rapid breathing Diaphragmatic breathing = descent of diaphragm causes stomach to bulge during inspiration • Costal breathing = just rib activity involved Modified Respiratory Movements • Coughing – deep inspiration, closure of rima glottidis & strong expiration blasts air out to clear respiratory passages • Hiccuping – spasmodic contraction of diaphragm & quick closure of rima glottidis produce sharp inspiratory sound Lung Volumes and Capacities • Tidal volume = amount air moved during quiet breathing • MVR= minute ventilation is amount of air moved in a minute • Reserve volumes ---- amount you can breathe either in or out above that amount of tidal volume • Residual volume = 1200 mL permanently trapped air in system • Vital capacity & total lung capacity are sums of the other volumes Dalton’s Law • Each gas in a mixture of gases exerts its own pressure – as if all other gases were not present – partial pressures denoted as p • Total pressure is sum of all partial pressures – atmospheric pressure (760 mm Hg) = pO2 + pCO2 + pN2 + pH2O – to determine partial pressure of O2-- multiply 760 by % of air that is O2 (21%) = 160 mm Hg What is Composition of Air? • • • • Air = 21% O2, 79% N2 and .04% CO2 Alveolar air = 14% O2, 79% N2 and 5.2% CO2 Expired air = 16% O2, 79% N2 and 4.5% CO2 Observations – alveolar air has less O2 since absorbed by blood – mystery-----expired air has more O2 & less CO2 than alveolar air? – Anatomical dead space = 150 ml of 500 ml of tidal volume Henry’s Law • Quantity of a gas that will dissolve in a liquid depends upon the amount of gas present and its solubility coefficient – explains why you can breathe compressed air while scuba diving despite 79% Nitrogen • N2 has very low solubility unlike CO2 (soda cans) • dive deep & increased pressure forces more N2 to dissolve in the blood (nitrogen narcosis) • decompression sickness if come back to surface too fast or stay deep too long • Breathing O2 under pressure dissolves more O2 in blood Hyperbaric Oxygenation • Clinical application of Henry’s law • Use of pressure to dissolve more O2 in the blood – treatment for patients with anaerobic bacterial infections (tetanus and gangrene) – anaerobic bacteria die in the presence of O2 • Hyperbaric chamber pressure raised to 3 to 4 atmospheres so that tissues absorb more O2 • Used to treat heart disorders, carbon monoxide poisoning, cerebral edema, bone infections, gas embolisms & crush injuries Tortora & Grabowski 9/e 2000 JWS 23-47 Respiration • 4 distinct processes collectively called respiration must occur: Pulmonary Ventilation, External Respiration, Transport of Respiratory Gases, and Internal Respiration Tortora & Grabowski 9/e 2000 JWS 23-48 1. Pulmonary Ventilation • Movement of air into and out of the lungs so that the gases in the air sacs (alveoli) of the lungs are continuously changed and refreshed • The air movement is called ventilation Tortora & Grabowski 9/e 2000 JWS 23-49 2. External Respiration • Gas exchange (oxygen loading and carbon dioxide unloading) between the blood and the air-filled chambers of the lungs Tortora & Grabowski 9/e 2000 JWS 23-50 External Respiration • Gases diffuse from areas of high partial pressure to areas of low partial pressure • Exchange of gas between air & blood • Deoxygenated blood becomes saturated • Compare gas movements in pulmonary capillaries to tissue capillaries Rate of Diffusion of Gases • Depends upon partial pressure of gases in air – p O2 at sea level is 160 mm Hg – 10,000 feet is 110 mm Hg / 50,000 feet is 18 mm Hg • Large surface area of our alveoli • Diffusion distance is very small • Solubility & molecular weight of gases – O2 smaller molecule diffuses somewhat faster – CO2 dissolves 24X more easily in water so net outward diffusion of CO2 is much faster – disease produces hypoxia before hypercapnia – lack of O2 before too much CO2 3. Transport of Respiratory Gases • Transport of oxygen and carbon dioxide between the lungs and tissue cells of the body • Accomplished by the cardiovascular system, which uses blood as the transporting fluid Tortora & Grabowski 9/e 2000 JWS 23-53 4. Internal Respiration • Gas exchanges (oxygen unloading and carbon dioxide loading) between the systemic blood and tissue cells Tortora & Grabowski 9/e 2000 JWS 23-54 Internal Respiration • Exchange of gases between blood & tissues • Conversion of oxygenated blood into deoxygenated • Observe diffusion of O2 inward – at rest 25% of available O2 enters cells – during exercise more O2 is absorbed • Observe diffusion of CO2 outward Oxygen Transport in the Blood • Oxyhemoglobin contains 98.5% chemically combined oxygen and hemoglobin – inside red blood cells • Does not dissolve easily in water – only 1.5% transported dissolved in blood • Only the dissolved O2 can diffuse into tissues • Factors affecting dissociation of O2 from hemoglobin are important • Oxygen dissociation curve shows levels of saturation and oxygen partial pressures Hemoglobin and Oxygen Partial Pressure • Blood is almost fully saturated at pO2 of 60mm – people OK at high altitudes & with some disease • Between 40 & 20 mm Hg, large amounts of O2 are released as in areas of need like contracting muscle Acidity & Oxygen Affinity for Hb • As acidity increases, O2 affinity for Hb decreases • Bohr effect • H+ binds to hemoglobin & alters it • O2 left behind in needy tissues pCO2 & Oxygen Release • As pCO2 rises with exercise, O2 is released more easily • CO2 converts to carbonic acid & becomes H+ and bicarbonate ions & lowers pH. Temperature & Oxygen Release • As temperature increases, more O2 is released • Metabolic activity & heat • More BPG, more O2 released – RBC activity – hormones like thyroxine & growth hormone Oxygen Affinity & Fetal Hemoglobin • Differs from adult in structure & affinity for O2 • When pO2 is low, can carry more O2 • Maternal blood in placenta has less O2 Carbon Monoxide Poisoning • CO from car exhaust & tobacco smoke • Binds to Hb heme group more successfully than O2 • CO poisoning • Treat by administering pure O2 Carbon Dioxide Transport • 100 ml of blood carries 55 ml of CO2 • Is carried by the blood in 3 ways – dissolved in plasma – combined with the globin part of Hb molecule forming carbaminohemoglobin – as part of bicarbonate ion • CO2 + H2O combine to form carbonic acid that dissociates into H+ and bicarbonate ion Summary of Gas Exchange & Transport Role of the Respiratory Center • Respiratory mm. controlled by neurons in pons & medulla • 3 groups of neurons – medullary rhythmicity – pneumotaxic – apneustic centers Medullary Rhythmicity Area • • • • Controls basic rhythm of respiration Inspiration for 2 seconds, expiration for 3 Autorhythmic cells active for 2 seconds then inactive Expiratory neurons inactive during most quiet breathing only active during high ventilation rates Regulation of Respiratory Center • Cortical Influences – voluntarily alter breathing patterns – limitations are buildup of CO2 & H+ in blood – inspiratory center is stimulated by increase in either – if you hold breathe until you faint----breathing will resume Chemical Regulation of Respiration • Central chemoreceptors in medulla – respond to changes in H+ or pCO2 – hypercapnia = slight increase in pCO2 is noticed • Peripheral chemoreceptors – respond to changes in H+ , pO2 or PCO2 – aortic body---in wall of aorta • nerves join vagus – carotid bodies--in walls of common carotid arteries • nerves join glossopharyngeal nerve Negative Feedback Regulation of Breathing • Negative feedback control of breathing • Increase in arterial pCO2 • Stimulates receptors • Inspiratory center • Muscles of respiration contract more frequently & forcefully • pCO2 Decreases Regulation of Ventilation Rate and Depth Types of Hypoxia • Deficiency of O2 at tissue level • Types of hypoxia – hypoxic hypoxia--low pO2 in arterial blood • high altitude, fluid in lungs & obstructions – anemic hypoxia--too little functioning Hb • hemorrhage or anemia – ischemic hypoxia--blood flow is too low – histotoxic hypoxia--cyanide poisoning • blocks metabolic stages & O2 usage Respiratory Influences & Reflex Behaviors • Quick breathing rate response to exercise – input from proprioceptors • Inflation Reflex (Hering-Breurer reflex) – big deep breath stretching receptors produces urge to exhale • Factors increasing breathing rate – emotional anxiety, temperature increase or drop in blood pressure • Apnea or cessation of breathing – by sudden plunge into cold water, sudden pain, Tortora & Grabowski 9/e 2000 JWS 23-72 irritation of airway Exercise and the Respiratory System • During exercise, muscles consume large amounts of O2 & produce large amounts CO2 • Pulmonary ventilation must increase – moderate exercise increases depth of breathing, – strenuous exercise also increases rate of breathing • Abrupt changes at start of exercise are neural – anticipation & sensory signals from proprioceptors – impulses from motor cortex • Chemical & physical changes are important – decrease in pO2, increase in pCO2 & increased 23-73 temperature Tortora & Grabowski 9/e 2000 JWS Smokers Lowered Respiratory Efficiency • Smoker is easily “winded” with moderate exercise – – – – – nicotine constricts terminal bronchioles carbon monoxide in smoke binds to hemoglobin irritants in smoke cause excess mucus secretion irritants inhibit movements of cilia in time destroys elastic fibers in lungs & leads to emphysema • trapping of air in alveoli & reduced gas exchange Tortora & Grabowski 9/e 2000 JWS 23-74 Developmental Anatomy of Respiratory System • 4 weeks endoderm of foregut gives rise to lung bud • Differentiates into epithelial lining of airways • 6 months closed-tubes swell into alveoli of lungs Tortora & Grabowski 9/e 2000 JWS 23-75 Aging & the Respiratory System • Respiratory tissues & chest wall become more rigid • Vital capacity decreases to 35% by age 70. • Decreases in macrophage activity • Diminished ciliary action • Decrease in blood levels of O2 • Result is an age-related susceptibility to pneumonia or bronchitis Disorders of the Respiratory System • Asthma • Chronic obstructive pulmonary disease – Emphysema – Chronic bronchitis – Lung cancer • Pneumonia • Tuberculosis • Coryza and Influenza • Pulmonary Edema & Grabowski 9/e 2000 JWS •Tortora Cystic fibrosis 23-77 Homework • A1, A2, A5, A6, B4, B8, B10, C2, C3, C10, D1 Tortora & Grabowski 9/e 2000 JWS 23-78