The Respiratory System PDF

The Respiratory System OBJECTIVES n Describe the anatomy and histology of the nose, pharynx, larynx, trachea, bronchi, and lungs. n Identify the functions of each respiratory system structure. n Describe the events that cause inhalation and exhalation. n Describe the exchange of...

The Respiratory System OBJECTIVES n Describe the anatomy and histology of the nose, pharynx, larynx, trachea, bronchi, and lungs. n Identify the functions of each respiratory system structure. n Describe the events that cause inhalation and exhalation. n Describe the exchange of oxygen and carbon dioxide in external and internal respiration. Organs of the Respiratory System n Upper respiratory system q nose, nasal cavity, pharynx, and associated structures n Lower respiratory system q Trachea, larynx, bronchi, bronchioles, and lungs n “Conducting zone” consists of q All airways that carry air to lungs: n Nose, pharynx, trachea, larynx, bronchi, bronchioles, and terminal bronchioles n “Respiratory zone” q Sites within lungs where gas exchange occurs n Respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli Organs of the Respiratory System Upper Respiratory System: Nose Root Bridge Apex External nares  Upper Respiratory System: Nose n Structure q External nares à nasal cavity à internal nares q Nasal septum divides nose into two sides q Nasal conchae covered by mucous membrane n Functions q Warm, humidify, filter/trap dust and microbes n Mucus and cilia of epithelial cells lining nose q Detect olfactory stimuli q Modify vocal sounds Upper Respiratory System: Pharynx n Known as the “throat” n Structure q Funnel-shaped tube from internal nares to larynx n Three regions (with tonsils in the upper two) q Upper: nasopharynx; posterior to nose n Contains adenoids and openings of auditory (Eustachian) tubes q Middle: oropharynx; posterior to mouth n 2 pairs of tonsils; Palatine and lingual tonsils are here q Lower: laryngopharynx n Connects with both esophagus and larynx: food and air Respiratory System: Head and Neck  Lower Respiratory System: Larynx n “Voice box” n Made largely of cartilage q Thyroid cartilage: V-shaped n “Adam's apple”: projects more anteriorly in males n Vocal cords “strung” here (and to arytenoids) q Epiglottis: leaf-shaped piece; covers airway n During swallowing, larynx moves up so epiglottis covers opening into trachea q Cricoid cartilage: inferior most portion q Arytenoids (paired, small) superior to cricoid n true vocal cords for speech n Cuneiform and Corniculate cartilages Larynx Voice Production n Mucous membrane of larynx forms two pairs of folds q Upper/superior = vertical folds or false vocal cords q Lower/inferior = vocal folds or true vocal cords n Glottis is the opening of the focal folds n Contain elastic ligaments n When muscles pull elastic ligaments tight, vocal cords vibrate à sounds in upper airways n Pitch adjusted by tension of true vocal cords n Lower pitch of male voice q Vocal cords longer and thicker; vibrate more slowly CLINICAL CONNECTION | Laryngitis and Cancer of the Larynx n Laryngitis - inflammation of the larynx that is most often caused by a respiratory infection or irritants such as cigarette smoke. n Cancer of the larynx is found almost exclusively in individuals who smoke. n The condition is characterized by hoarseness, pain on swallowing, or pain radiating to an ear. n Treatment consists of radiation therapy and/or surgery. Copyright 2010, John Wiley & Sons, Inc. Cancer & Smoking  Philippine Setting http://www.philcancer.org.ph/wp-content/uploads/2017/07/2015-PCS-Ca-Facts-Estimates_CAN090516.pdf Lower Respiratory System: Trachea n “Windpipe” n Location q Anterior to esophagus and thoracic vertebrae q Extends from end of larynx to primary bronchi n Structure q Lined with pseudostratified ciliated mucous membrane: traps and moves dust upward q C-shaped rings of cartilage support trachea, keep lumen open during exhalation n Tracheostomy: opening in trachea for tube Lower Respiratory System: Bronchi, Bronchioles n Structure of bronchial tree q Bronchi contain cartilage rings q Primary bronchi enter the lungs medially q In lungs, branchingà secondary bronchi n One for each lobe of lung: 3 in right, 2 in left q Tertiary bronchi à à à terminal bronchioles n These smaller airways q Have less cartilage, more smooth muscle. q In asthma, these airways can close. q Can be bronchodilated by sympathetic nerves, epinephrine, or related medications. Branching of airways from the trachea: the bronchial tree. Lower Respiratory System: Lungs n Two lungs: left and right q Right lung has 3 lobes q Left lung has 2 lobes and cardiac notch n Lungs surrounded by pleural membrane q Parietal pleura attached to diaphragm and lining thoracic wall q Visceral pleura attached to lungs q Pleural cavity contains lubricating fluid q Broad bottom of lungs = base; pointy top = apex Lung Lobes n Divided into lobules fed by tertiary bronchi n Further divisions à terminal bronchioles n à Respiratory bronchioles q Lined with nonciliated epithelium n à Alveolar ducts n à Alveolar sacs n à Surrounded by alveoli Microscopic anatomy of a lobule of the lungs. Copyright 2010, John Wiley & Sons, Inc. Lower Respiratory System: Alveoli n Cup-shaped outpouchings of alveolar sacs n Alveoli: two types of alveolar epithelial cells q Type I alveolar cells are the main sites of gas exchange. q Type II alveolar cells, containing microvilli, secrete alveolar fluid, which keeps the surface between the cells and the air moist q In the alveolar fluid are scattered surfactant- secreting cells. n Lowers surface tension (keeps alveoli from collapsing) n Humidifies (keeps alveoli from drying out) Alveoli n The exchange of O2 and CO2 between the air spaces in the lungs and the blood takes place by diffusion across the alveolar and capillary walls, which together form the respiratory membrane. n Respiratory membrane: alveoli + capillary q Gases diffuse across these thin epithelial layers: air ßà blood Structure of an Alveolus  Pathophysiology of COVID-19 n Several researchers have identified human angiotensin converting enzyme 2 (ACE2) as an entry receptor for SARS- CoV-2. n SARSCoV-2 is mostly transmissible through large respiratory droplets, directly infecting cells of the upper and lower respiratory tract, especially nasal ciliated and alveolar epithelial cells. Respiration: Three Major Steps 1. Pulmonary ventilation (breathing) q Moving air in and out of lungs 2. External respiration q Gas exchange between alveoli and blood 3. Internal respiration q Gas exchange between blood and cells Respiration Step: 1. Pulmonary Ventilation n Air flows: atmosphere ß à lungs due to difference in pressure related to lung volume q Lung volume changes due to respiratory muscles n Inhalation: diaphragm + external intercostals q Diaphragm contracts (moves downward) à ↑ lung volume n Cohesion between parietal-visceral pleura à ↑ lung volume as thorax volume ↑. Exhalation n Exhalation is normally passive process due to muscle relaxation q Diaphragm relaxes and rises à ↓ lung volume q External intercostals relax à ↓ lung volume n Active exhalation: exhale forcefully q Example: playing wind instrument q Uses additional muscles: internal intercostals, abdominal muscles Muscles of Inhalation and Exhalation Copyright 2010, John Wiley & Sons, Inc. Volume-Pressure Changes in Lungs n Volume and pressure are inversely related q As ↑ lung volumeà ↓ alveolar pressure q As ↓ lung volumeà ↑ alveolar pressure n Contraction of diaphragm à lowers diaphragm à ↑ lung volumeà ↓ alveolar pressure so it is < atmospheric pressure à air enters lungs = inhalation n Relaxation of diaphragm à raises diaphragm à ↓ lung volume à ↑ alveolar pressure so it is > atmospheric pressure à air leaves lungs = exhalation Copyright 2010, John Wiley & Sons, Inc. Volume-Pressure Changes in Lungs Copyright 2010, John Wiley & Sons, Inc. CLINICAL CONNECTION | Respiratory Distress Syndrome n breathing disorder of premature newborns in which the alveoli do not remain open due to a lack of surfactant. n symptoms include labored and irregular breathing, flaring of the nostrils during inhalation, grunting during exhalation, and perhaps a blue skin color. n In mild RDS may require only supplemental oxygen n In severe cases oxygen may be delivered by nasal continuous positive airway pressure (NCPAP) through tubes in the nostrils or a mask on the face. In such cases surfactant may be administered directly into the lungs. Copyright 2010, John Wiley & Sons, Inc. Air Flow Terms n Frequency = breaths/min; normal: 12/min n Tidal volume (TV) = volume of one breath. Normal ~ 500 ml q About 70% of TV reaches alveoli (350 ml) q Only this amount is involved in gas exchange q 30% in airways = anatomic dead space n Minute ventilation (MV) = f x TV = 6000 mL/min Copyright 2010, John Wiley & Sons, Inc. Lung Volumes n Measured by spirometer q Inspiratory reserve volume (IRV) = volume of air that can be inhaled beyond tidal volume (TV) q Expiratory reserve volume (ERV) = volume of air that can be exhaled beyond TV q Air remaining in lungs after a maximum expiration = residual volume (RV) Copyright 2010, John Wiley & Sons, Inc. Lung Capacities n Inspiratory capacity = TV + IRV n Functional residual capacity (FRC) = RV + ERV n Vital capacity (VC) = IRV + TV + ERV n Total lung capacity (TLC) = VC + RV Copyright 2010, John Wiley & Sons, Inc. Lung Capacities Copyright 2010, John Wiley & Sons, Inc. Breathing Patterns n Eupnea = normal breathing q Highly variable in pattern q Costal breathing: shallow with rib movements q Diaphragmatic breathing: deep breathing Copyright 2010, John Wiley & Sons, Inc. Nature of Air n Mixture of gases (N2, O2,, CO2, H2O, and others) n Each gas has own partial pressure, such as PO2 or PN2 n Sum of all partial pressures = atmospheric pressure n Each gas diffuses down its partial pressure gradient Copyright 2010, John Wiley & Sons, Inc.  Respiration Step 2: Pulmonary Gas Exchange: External Respiration n Diffusion across alveolar to capillary membrane q O2 diffuses from air (PO2 ~105 mm Hg) to pulmonary artery (“blue”) blood (PO2 ~40 mm Hg). (Partial pressure gradient = 65 mm Hg) n Continues until equilibrium (PO2 ~100-105 mm Hg) q Meanwhile “blue” blood (PCO2 ~45) diffuses to alveolar air (PCO2 ~40) (Partial pressure gradient = 5 mm Hg) Copyright 2010, John Wiley & Sons, Inc. Respiration Step 3: Systemic Gas Exchange: Internal Respiration n Occurs throughout body n O2 diffuses from blood to cells: down partial pressure gradient n PO2 lower in cells than in blood because O2 is used in cellular metabolism n Meanwhile CO2 diffuses in opposite direction: cells à blood Copyright 2010, John Wiley & Sons, Inc. Internal and External Respiration Copyright 2010, John Wiley & Sons, Inc. Transport of Oxygen within Blood n 98.5% of O2 is transported bound to hemoglobin in RBCs q Binding depends on PO2 q High PO2 in lung and lower in tissues q O2 dissolves poorly in plasma so only 1.5% is transported in plasma n Tissue release of O2 to cells is increased by factors present during exercise: q High CO2 (from active muscles) q Acidity (lactic acid from active muscles) q Higher temperatures (during exercise) Copyright 2010, John Wiley & Sons, Inc. Transport of Carbon Dioxide n CO2 diffuses from tissues into blood à n CO2 carried in blood: q Some dissolved in plasma (7%) q Bound to proteins including hemoglobin (23%) q Mostly as part of bicarbonate ions (70%) n CO2 + H2O ßà H+ + HCO3- n Process reverses in lungs as CO2 diffuses from blood into alveolar air à exhaled Copyright 2010, John Wiley & Sons, Inc. Transport of Oxygen and Carbon Dioxide Copyright 2010, John Wiley & Sons, Inc. CLINICAL CONNECTION | Carbon Monoxide Poisoning n Carbon monoxide (CO) is a colorless and odorless gas found in exhaust fumes from automobiles, gas furnaces, and space heaters and in tobacco smoke. n CO binds to the heme group of hemoglobin, just as O2 does, except CO binds to hemoglobin is over 200x as strong as the binding of O2 to hemoglobin. n CO reduce the oxygen-carrying capacity of the blood by 50%. n Tx- administering pure oxygen, which speeds up the separation of carbon monoxide from hemoglobin Copyright 2010, John Wiley & Sons, Inc. Pulmonary function tests n a group of tests that measure how well the lungs take in and release air n how well they move gases such from the atmosphere into the body's circulation. n FVC, FEV1 & FEV1/ FVC ratio n Normal result n A value is usually considered abnormal if it is less than 80% of your predicted value. Pulmonary Function Tests Copyright 2010, John Wiley & Sons, Inc. Why the Test is Performed? n Diagnose certain types of lung disease (e.g. asthma, bronchitis, and emphysema) n Find the cause of SOB n Measure whether exposure to chemicals at work affects lung function n Check lung function before someone has surgery n Assess the effect of medication n Measure progress in disease treatment Copyright 2010, John Wiley & Sons, Inc.  Control of Respiration n Medullary rhythmicity area in medulla q Contains both inspiratory and expiratory areas, q Control the basic rhythm of respiration n Quiet breathing q Inspiratory area à nerve signals to inspiratory muscles for ~2 sec à q Inspiration à q Inspiration ends and muscles relax à q Expiration à q Expiratory center active only during forceful breathing n Two areas in pons adjust length of inspiratory stimulation q Pneumotaxic area and apneustic area Copyright 2010, John Wiley & Sons, Inc. Regulation of Respiratory Center n Cortical input: voluntary adjustment of patterns q For talking or cessation of breathing while swimming q Chemoreceptor input will override breath-holding Copyright 2010, John Wiley & Sons, Inc. Regulation of Respiratory Center n Chemoreceptor input to à increase ventilation q Central receptors in medulla: sensitive to ↑ H+ or PCO2 in CSF q Peripheral receptors in arch of aorta + common carotids: respond to ↓ PO2 as well as ↑ H+ or PCO2 in blood n Blood and brain pH can be maintained by these negative feedback mechanisms Copyright 2010, John Wiley & Sons, Inc. Regulation of Respiratory Center Copyright 2010, John Wiley & Sons, Inc. Other Regulatory Factors of Respiration n Respiration can be stimulated by q Limbic system: anticipation of activity, emotion q Proprioception as activity is started q Increase of body temperature n Sudden pain can à apnea: stop breathing q Prolonged somatic pain can increase rate n Airway irritationà cough or sneeze n Inflation reflex q Bronchi wall stretch receptors inhibit inspiration q Prevents overinflation Copyright 2010, John Wiley & Sons, Inc. Obstructive and Restrictive Lung Disease n obstructive pattern exists when air moves out of the lungs at a slower rate than that of a healthy person. n airway obstruction causes an increase in resistance. n restrictive lung disease - compliance of the lung is reduced, which increases the stiffness of the lung and limits expansion. Aging and the Respiratory System n Lungs lose elasticity/ability to recoil à more rigid; leads to q Decrease in vital capacity q Decreased blood PO2 level q Decreased exercise capacity n Decreased macrophage activity and ciliary action à q Increased susceptibility to pneumonia, bronchitis and other disorders Copyright 2010, John Wiley & Sons, Inc.