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Respiratory System Lecture Notes

by: Claire Neville

Respiratory System Lecture Notes BMS 251-20

Marketplace > Grand Valley State University > Biomedical Sciences > BMS 251-20 > Respiratory System Lecture Notes
Claire Neville
GPA 3.209

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Respiratory System
Anatomy & Physiology II
Dr. Tara Alger
Class Notes
BMS 251, anatomy, Physiology, Respiratory system, Lungs, bronchial, oxygen
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This 12 page Class Notes was uploaded by Claire Neville on Thursday March 10, 2016. The Class Notes belongs to BMS 251-20 at Grand Valley State University taught by Dr. Tara Alger in Winter 2016. Since its upload, it has received 42 views. For similar materials see Anatomy & Physiology II in Biomedical Sciences at Grand Valley State University.

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Date Created: 03/10/16
Chapter 23 Respiratory System The Respiratory System  Respiration is gas exchange: O for CO 2 2 o Occurs between atmosphere and body cells  ATP production through aerobic respiration requires oxygen, and Carbon dioxide is a biproduct  The respiratory system provides the means for gas exchange o Consists of  respiratory passageways in head, neck, and trunk  The lungs 23.1a General Functions of the Respiratory System  Air passageway o Inspiration: movement of air from atmosphere into the lungs o Expiration: Air moves from lungs to atmosphere  Site for oxygen and carbon dioxide exchange o Oxygen diffuses from alveoli into blood o Carbon dioxide diffuses from blood into alveoli  Odor detection o Olfactory receptors in superior nasal cavity o Sensory input is relayed to the brain  Sound production o Air moves across vocal cords of the larynx (voice box) o Vocal cords vibrate, producing sound o Sounds resonate in the upper respiratory structures  Rate and depth of breathing influ+nce o Blood levels of O ,2CO ,2H o Venous return of blood; lymphatic return of fluid to blood 23.1b General Organization of the Respiratory System  Structural organization o Upper respiratory tract  Larynx and above o Lower respiratory tract  Trachea and below  Functional organization o The conducting zone transports air  Nose to terminal bronchioles o The respiratory zone participates in gas exchange  Respiratory bronchioles to alveoli 23.1c Respiratory Mucosa  Mucosa = mucous membrane: respiratory lining o Epithelium resting on a basement membrane o Lamina Propria: Connective tissue layer beneath  Respiratory epithelium o Becomes thinner from the nose to the alveoli  pseudostratified ciliated columnar  simple ciliated columnar  simple cuboidal  simple squamous  Mucous secretions o Produced from secretions of  Goblet cells of epithelial lining  Mucous and serous glands of the lamina propria o Contain mucin protein  Increases mucus viscosity and serves to trap dust, dirt, pollen, etc. o Contains defenses against microbes  Lysozyme (antibacterial enzyme)  Defensins (antibacterial proteins)  Immunoglobulin A (antibody) 23.2a Nose and Nasal Cavity  Nose: external structure including bone, cartilage and skin  Choanae: o Floor formed by palate o Nasal septum divides left and right sides  Posterior part is bony perpendicular plate of ethmoid plate and vomer bone  The Nasal Cavity o Three paired, bony projections on lateral walls of nasal cavity  Superior, middle, and inferior conchae o Produce turbulence in inhaled air o Partition the nasal cavity into separate passages  Each passage called a Nasal meatus  Nasal cavity parts o Nasal vestibule: just inside nostrils  Lined by skin and particle-trapping hairs (vibrissae) o Olfactory region  Superior part of nasal cavity containing olfactory epithelium  Airborne molecules stimulate receptors for odor detection o Respiratory region  Lined by pseudostratified ciliated columnar epithelium  Has an extensive vascular network  Nosebleeds common due to large numbers of superficial vessels  Nasal cavity warms, cleanses, and humidifies o Air is warmed by extensive blood vessels o Mucus traps dust, microbes, and foreign material o Cilia sweep mucous toward the pharynx to be swallowed o Moist environment humidifies o Air turbulence created by conchae enhances all three processes 23.2b Paranasal Sinuses  Paranasal Sinuses: spaces within skull bones o Named for specific bone in which they are housed o All connected by ducts to nasal cavity 23.2c Pharynx  Pharynx (throat) o Funnel-shaped passageway posterior to nasal cavity, oral cavity, and larynx o Lateral walls composed of skeletal muscles o Partitioned into  Nasopharynx  Oropharynx  Laryngopharynx  Nasopharynx most superior part of pharynx o Posterior to nasal cavity, superior to soft palate o Lined by pseudostratified ciliated columnar epithelium o An air passage—not for food  Soft palate elevates during swallowing, blocking food or drink o Connects to middle ear via auditory tubes  Opening tubes allows equalization of pressure on each side of tympanic membrane o Contains tonsils—infection-fighting lymphatic tissue 23.3a Larynx  Larynx (voice box) o Cylindrical airway between laryngopharynx and trachea o Several functions  Air passageway (usually open)  Prevents ingested materials from entering respiratory tract  epiglottis covers superior opening during swallowing  Produces sound for speech  Vocal cords (ligaments) vibrate during expiration  Participates in sneeze and cough reflexes  Abdominal muscles contract increasing thoracic pressure  Vocal cords are forcibly opened by pressure from below  Explosive blast of exhaled air is a cough or sneeze 23.3a Larynx anatomy  Vocal: o Composed primarily of elastic connective tissue o Covered with mucosa to form the vocal folds (true vocal cords) o Produce sound when air passes between them o rima glottides: space between the vocal ligaments  Vestibular folds: superior to vocal folds o Covered with mucosa to form the vestibular folds (false vocal cords) o Play no role in sound production o Protect vocal cords o Extrinsic skeletal muscles  Stabilize larynx and help it move during swallowing o Intrinsic skeletal muscles  Located within larynx  Contraction results in change in size of rima glottidis  Involved in voice production and swallowing  Sound production: vocal cord vibration  Intrinsic laryngeal muscles narrow opening of rima glottidis  Air is forced past vocal cords during expiration o Range of voice determined by length, thickness of vocal cords  Males have longer and thicker folds, and so deeper voices o Pitch (frequency) determined by tension on vocal cords  Increased tension = folds vibrate more = higher pitch  Regulated by intrinsic laryngeal muscles o Loudness depends on force of air passing across vocal cords  More air = louder sound o Other structures are also necessary for speech  Pharynx, nasal and oral cavities, and paranasal sinuses serve as resonating chambers  Lips, teeth, and tongue help form speech sounds 23.3b Trachea  Gross anatomy of trachea (windpipe) o Flexible, slightly rigid, tubular organ o Goes from larynx to main bronchi o Tracheal cartilages support anterior and lateral walls  C-shaped rings of hyaline cartilages  Ensure trachea is always open o Carina: internal ridge at inferior end of trachea (where it splits) containing many sensory receptors  Initiates cough reflex when irritants are present o Trachealis muscle on trachea’s posterior surface  Connects open ends of C-shaped cartilages  Allow accommodation for esophagus when bulge of food passes  Trachealis contracts during coughing 23.3c Bronchial Tree  Bronchial tree: system of highly branched air passages o Originates at main bronchi, branches to more narrow tubes o Ends in small bronchiole passageways  Gross anatomy of bronchial tree o Trachea splits into right and left main bronchi (primary bronchi) at level of sternal angle  Each bronchus enters a lung on its medial surface  Right bronchus shorter, wider, and more vertically oriented  Foreign particles more likely to lodge here o Each main bronchus branches into smaller tubes, from primary to secondary, to tertiary bronchi o Eventually leading to bronchioles o Tree continues to divide into smaller passageways  Leads to terminal bronchioles (last part of conducting zone)  Leads to respiratory bronchioles (first part of respiratory zone) o Bronchioles have no cartilage  Have proportionally thicker layer of smooth muscle  Muscle contraction narrows bronchiole diameter  bronchoconstriction = less air through bronchial tree (less entry of potentially harmful substances)  Muscle relaxation increases bronchiole diameter  bronchodilation = more air through the bronchial tree 23.3d Respiratory Zone: Respiratory Bronchioles, Alveolar Ducts, and Alveoli  Respiratory zone structures are microscopic o Respiratory bronchioles subdivide to alveolar ducts o Alveolar ducts lead to alveolar sacs, clusters of alveoli o Alveoli = spherical organization of squamous cells  Epithelium o Respiratory bronchioles lined with simple cuboidal epithelium o Alveoli and alveolar ducts lined by simple squamous o Thinness facilitates gas exchange  Cell types of alveolar wall o Simple squamous alveolar type I cells  95% of alveolar surface area  Part of thin barrier separating air from blood o Alveolar type II ceIIs  Secrete oily pulmonary surfactant  Coats inside of alveolus and opposes collapse during expiration o Alveolar macrophages (dust cells)  Leukocytes that engulf microorganisms  Either fixed in alveolar wall or free to migrate 23.3e Respiratory Membrane  The respiratory membrane o Thin barrier between alveoli and pulmonary capillaries o Consists of  Alveolar epithelium and its basement membrane  Capillary epithelium and its basement membrane o Oxygen diffuses from alveolus into capillaries  Erythrocytes become oxygenated o Carbon dioxide diffuses from blood to alveolus  Expired to external environment 23.4a Gross Anatomy of the Lung  Lungs are in thorax on either side of mediastinum o House bronchial tree and all respiratory portions of respiratory system  hilum o Indented region on lung’s mediastinal side o Bronchi, pulmonary vessels, autonomic nerves, lymph vessels pass through here  These structures collectively termed the root of the lung  Right lung is larger and wider than left lung o Has three lobes divided by two fissures  Left lung is smaller than right due to heart’s position o Has two lobes divided by one fissure o surface indentations accommodate heart and aorta  Cardiac impression on medial surface  Cardiac notch on anterior surface 23.4b Circulation to and Innervation of the Lungs  Blood supply  Two types of circulation in the lungs o Pulmonary circulation o Bronchial circulation  Pulmonary circulation replenishes O , eli2inates CO 2 o Pulmonary arteries carry deoxygenated blood to pulmonary capillaries o Blood is reoxygenated o Blood enters pulmonary venules and veins, returns to left atrium  Bronchial ciruclation transports oxygenated blood to tissues of lungs o Bronchial arteries branch off descending aorta o Bronchial veins collect venous blood  Lymph drainage o Lymph vessels and nodes located:  Within lung’s connective tissue  Around bronchi  In pleura o Important in removing excess fluid from the lungs  Innervation of the respiratory system o Autonomic nervous system innervates smooth muscles and glands of respiratory structures  Sympathetic input generally causes bronchodilation  Parasympathetic causes bronchoconstriction  Sends signals to larynx 23.4c Pleura Membranes and Pleural Cavity  Pleura: serous membrane o Outer lining of lung surfaces and adjacent thoracic wall o Composed of simple squamous epithelium o Visceral pleura adheres to lung surface o Parietal Pleura lines  Internal thoracic walls  Lateral surface of mediastinum  Superior surface of diaphragm  Pleural Cavity o Located between visceral and parietal serous membranes o When lungs are inflated, considered a potential space  Visceral and parietal layers almost touching  Serous fluid produced by serous membranes o Covers pleural cavity surface o Lubricates, allowing pleural surfaces to slide by easily 23.4d How Lungs Remain Inflated  Intrapleural pressure (between membranes) is low o Chest wall configured to expand outward  Lungs cling to chest wall due to serous fluid’s surface tension  Because intrapulmonary pressure (in alveoli) is greater than intrapleural pressure, lungs remain inflated  Processes of Respiration  Respiration (exchange of gases between atmosphere and body’s cells) involves four processes o Pulmonary ventilation: movement of gases between atmosphere and alveoli o Alveolar gas exchange: external respiration): exchange of gases between alveoli and blood o Gas transport: transport of gases in blood between lungs and systemic cells o Systemic gas exchange: internal respiration): exchange of respiratory gases between the blood and the systemic cells 23.5a Introduction to Pulmonary Ventilation  Pulmonary ventilation (breathing): air movement o Consists of two cyclic phases  Inspiration brings air into the lungs (inhalation)  Expiration forces air out of the lungs (exhalation) o Quiet, rhythmic breathing occurs at rest o Forced, vigorous breathing accompanies exercise o Volume changes result in changes in pressure gradient between lungs and atmosphere o Air moves down its pressure gradient 23.5b Mechanics of Breathing  Volume changes in the thoracic cavity o Thoracic volume changes vertically, laterally, and anterior-posteriorly o Vertical changes result from diaphragm movement  Flattens (by moving inferiorly) when contracted  When relaxed, returns to original position, vertical dimensions decrease  Boyle’s gas law Relationship of volume and pressure o At constant temperature, pressure (P) of a gas decreases if volume (V) of the container increases, and vice versa o Inverse relationship between gas pressure and volume  An air pressure gradient exists when force per unit area is greater in one place than another o If the two places are interconnected, air flows from high to low pressure until pressure is equal  Volumes and pressures associated with breathing  Atmospheric pressure: pressure of air in environment o Changes with altitude  Increased altitude = “thinner air” = lower pressure  Sea level value is 760 mm Hg  Unchanged in process of breathing  Alveolar volume: collective volume of alveoli  Intrapulmonary pressure: pressure in alveoli o Fluctuates with breathing  Volume changes create pressure changes and air flows down its pressure gradient o During inspiration: thoracic volume increases, thoracic pressure decreases, so air flows in o During expiration: thoracic volume decreases, thoracic pressure increases, so air flows out  Forced breathing o Involves steps similar to quiet breathing o Requires contraction of additional muscles o Causes greater changes in thoracic cavity volume and intrapulmonary pressure o More air moves into and out of lungs o Significant chest volume changes are apparent 23.5c Nervous Control of Breathing  Autonomic nuclei within the brain coordinate breathing o Respiratory center of the brainstem  Medullary respiratory center contains two groups  Pontine respiratory center in pons  Brainstem neurons influence respiratory muscles +  Chemoreceptors monitor changes in concentrations of H , PCO and PO 2 2 o Central chemoreceptors in medulla monitor pH of CSF  CSF pH changes are caused by changes in blood PCO 2  carbonic acid is built from CO a2d water o Peripheral chemoreceptors are in aortic and carotid bodies  Stimulated by changes in H or respiratory gases in blood  Aortic and carotid bodies send signals to respiratory center  Other receptors also influence respiration o Proprioceptors of muscles and joints are stimulated by body movements o Baroreceptors in pleurae and bronchioles respond to stretch o Irritant receptors in air passageways stimulated by particulate matter  Physiology of quiet breathing o Inspiration begins when medullary group inspiratory neurons fire spontaneously o Signals are sent from VRG to nerve pathways exciting skeletal muscles  Diaphragm and external intercostals contract causing air to flow in o Quiet expiration occurs when VRG is inhibited  Signals from inspiratory neurons are relayed to VRG expiratory neurons  Expiratory neurons send inhibitory signals back (negative feedback) o Signals no longer sent to inspiratory muscles (for about 3 sec)  Diaphragm and external intercostals relax causing air to flow out o Respiration rate for normal, quiet breathing is eupnea o Pontine respiratory center facilitates smooth transitions between inspiration and expiration  Reflexes that alter breathing rate and depth  Rate changes by altering amount of time in inspiration and expiration  Depth changes by stimulation of accessory muscles o Ventilation increases in response to  Central chemoreceptors detecting increase in H concentration of CSF +  Peripheral chemoreceptors detecting increase in blood H or PCO 2 o Increased ventilation expels more CO retu2ning conditions to normal o Ventilation decreases if chemoreceptors detect decreases in H or PCO + 2 o Blood PCO is2most important stimulus affecting breathing  CO f2uctuations influence sensitive central chemoreceptors  CO 2ombines with water to form carbonic acid in CSF  CSF lacks protein buffers and so its pH change triggers reflexes  Blood PO i2 not a sensitive regulator of breathing  When PO dr2ps it causes peripheral chemoreceptors to be more sensitive to blood PCO 2 o Altering breathing through other receptors  Joint and muscle proprioceptors are stimulated by body movement  Signal respiratory center to increase breathing depth  Baroreceptors within visceral pleura and bronchiole smooth muscle  Send signals to respiratory center when overstretched  shut off inspiration and protect against overinflation  Irritant receptors initiate sneezing and coughing  Exaggerated intake of breath followed by closure of larynx  Abrupt opening of vocal cords and explosive blast of exhaled air o Action of higher brain centers  Hypothalamus increases breathing rate if body is warm  Limbic system alters breathing rate in response to emotions  Frontal lobe of cerebral cortex controls voluntary changes in breathing patterns 23.5d Airflow, Pressure Gradients, and Resistance  Airflow: amount of air moving in and out of lungs with each breath o Depends on  The pressure gradient established between atmospheric pressure and intrapulmonary pressure  The resistance that occurs due to conditions within the airways, lungs, and chest wall  F = ∆P/R o F = flow o ∆P = difference in pressure between atmosphere and intrapulmonary pressure = pressure gradient = P atm– Palv o R = resistance o Flow directly related to pressure gradient and inversely related to resistance  If pressure gradient increases, airflow to lungs increases  If resistance increases, airflow lessens  Resistance: greater difficulty moving air o May be altered by  Change in elasticity of chest wall and lungs  Change in bronchiole diameter (size of air passageway)  Collapse of alveoli o Decreases in chest wall elasticity increase resistance  Chest wall elasticity decreases with aging and disease  Vertebral malformations (scoliosis) can decrease elasticity  Arthritis in thoracic cage  Replacement of elastic tissue with scar tissue o Bronchiole diameter varies inversely with resistance  Bronchoconstriction or occlusion increase resistance  Constriction caused by parasympathetic activity or cold  Occlusion by excess mucus or inflammation  Bronchodilation decreases resistance  Caused by sympathetic stimulation, epinephrine o Collapsed alveoli increase resistance  Can occur if alveolar type II cells are not producing surfactant (high surface tension of alveoli is not overcome)  An important factor for premature infants  ___________________ o Ease with which lungs and chest wall expand o Determined by surface tension and elasticity of chest and lung o The easier the lung expands, the greater the compliance  Several conditions can increase resistance to airflow o Decreases in size of bronchiole lumen (asthma) o Decrease in compliance (pulmonary fibrosis) o The result is a need for more forceful inspirations o More forceful inspirations of respiratory disorders require high amount of energy  Can cause four-fold to six-fold increase in energy need 23.5e Pulmonary and Alveolar Ventilation  Pulmonary ventilation o Process of moving air into and out of the lungs o Amount of air moved between atmosphere and alveoli in 1 minute  Tidal volume = amount of air per breath  Respiration rate = number of breaths per minute  Tidal volume × Respiration rate = Pulmonary ventilation  500 mL × 12 breaths/min = 6 L/ minute (typical amount) 23.6a Chemical Principles of Gas Exchange  Partial pressure and Dalton’s law  __________________ : pressure exerted by each gas within a mixture of gases, measured in mm Hg o Written with P followed by gas symbol (i.e., PO ) 2 o Each gas moves independently down its partial pressure gradient during gas exchange  Atmospheric pressure = 760 mm Hg at sea level o Total pressure all gases collectively exert in the environment o Includes N ,2O ,2CO ,2H O2 and other minor gases  Total pressure × % of gas = Partial pressure of that gas o Nitrogen is 78.6% of the gas in air o 760 mm HG × 78.6% = 597 mm Hg = partial pressure of nitrogen  Partial pressure __________________  Gradient exists when partial pressure for a gas is higher in one region of the respiratory system than another  Gas moves from region of higher partial pressure to region of lower partial pressure until pressures become equal o In lungs:  O2 moves from alveoli to the blood  CO2 moves from blood to alveoli o In body tissues:  O2 moves from blood to tissue  CO2 moves from tissue to blood  Gas solubility and Henry’s law   Henry’s Law at a given temperature, the solubility of a gas in liquid is dependent upon the o Partial pressure of the gas in the air o Solubility coefficient of the gas in the liquid (a constant)  volume of gas that dissolves in a specified volume of liquid at a given temperature and pressure  Gases vary in their solubility in water o Carbon dioxide about 24 times as soluble as oxygen o Nitrogen about half as soluble as oxygen  It does not normally dissolve in blood in significant amounts o Gases with low solubility require larger pressure gradients to “push” the gas into the liquid 23.6b Alveolar Gas Exchange (External Respiration)  Efficiency of gas exchange at respiratory membrane  Anatomical features of membrane contributing to efficiency o Large surface area o Minimal thickness  Physiologic adjustments: ventilation-perfusion coupling o Ability of bronchioles to regulate airflow and arterioles to regulate blood flow  Ventilation changes by bronchodilation or bronchoconstriction  _______________ changes by pulmonary arteriole dilation or constriction 23.6c Systemic Gas Exchange (Internal Respiration)  Oxygen diffuses out of systemic capillaries to enter systemic cells o Partial pressure gradient drives the process  PO 2n systemic cells 40 mm Hg  PO 2n systemic capillaries is 95 mm Hg o Continues until blood PO is 20 mm Hg o Systemic cell PO st2ys fairly constant  Oxygen delivered at same rate it is used unless engaging in strenuous activity  Carbon dioxide o Diffuses from systemic cells to blood o Partial pressure gradient driving process  PCO in systemic cells 45mm Hg 2  PCO i2 systemic capillaries 40 mm Hg o Diffusion continuing until blood PCO is 25 mm Hg 23.7a Oxygen Transport  Blood’s ability to transport oxygen depends on o Solubility coefficient of oxygen  This is very low, and so very little oxygen dissolves in plasma o Presence of hemoglobin  The iron of hemoglobin attaches oxygen  About 98% of O in2blood is bound to hemoglobin  HbO is oxyhemoglobin (with oxygen bound) 2  Hb is deoxyhemoglobin (without bound oxygen) 23.7b Carbon Dioxide Transport  Carbon dioxide has three means of transport o As CO di2solved in plasma (7%) o As CO at2ached to amine group of globin portion of hemoglobin (23%)  HbCO i2 carbaminohemoglobin o As bicarbonate dissolved in plasma (70%) 23.7c Hemoglobin as a Transport Molecule  Binding of one substance causes a change in shape of the hemoglobin molecule o Influences the ability of hemoglobin to bind or release the other two substances o Saturation increases as PO inc2eases  __________________________: each O th2t binds causes a change in hemoglobin making it easier for next O to 2ind 23.8a Effects of Hyperventilation and Hypoventilation on Cardiovascular Function  __________________: breathing rate or depth above body’s demand o Caused by anxiety, ascending to high altitude, or voluntarily o PO r2ses and PCO fall2in the air of alveoli o Additional oxygen does not enter blood because hemoglobin is already saturated o There is greater loss of CO fr2m blood  ____________________: breathing too slow or too shallow o Causes include: airway obstruction, pneumonia, brainstem injury, other respiratory conditions o O l2vels down, CO leve2s up in alveoli o Blood PO de2reases and can lead to low oxygen in tissues o Blood PCO increases 2 o Clinical View: Asthma  Episodes of bronchoconstriction, wheezing, coughing, shortness of breath, and excess mucus  Asthmatic with sensitivity to airborne agent  Localized immune reaction occurs in bronchi and bronchioles  Walls of the bronchi becoming permanently thickened Clinical View: Measuring Blood Oxygen Levels with a Pulse Oximeter  Noninvasive and indirect way to measure oxygen ̶ Applied to finger or earlobe  Measure hemoglobin saturation by determining the ratio of oxyhemoglobin to deoxyhemoglobin  Normal reading hemoglobin saturation >95%


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