Bio 104Chapter 21: Respiratory System12321.1 OVERVIEW OF THERESPIRATORY SYSTEM Classified anatomically into upper and lower tracts:§ – passageways from nasal cavity to larynx§ Lower – passageways from trachea alveolio Alveoli– tiny air sacs, site of gas exchangeo –» Each is a collection of millions of alveoli andtheir blood vessels embedded in elasticconnective tissueBASIC FUNCTIONS OF THERESPIRATORY SYSTEM Classified functionally into conducting andrespiratory zones:§ - pathway air travelso Airis filtered, warmed, and moistenedstructures from nose and nasal cavity tobronchioleso Includes§ – where gas exchangeoccurs; alveoli

Bio 104Chapter 21: Respiratory System Respiration – process that provides body cells withoxygen and removes waste product carbon dioxide: Other functions – serve to maintain homeostasis:§ Speech and sound production1. Pulmonary ventilation – movement of air in and out§of lungs§ Assist with defecation, urination, and childbirth byincreasing pressure in thoracic cavity2. Pulmonary gas exchange – movement of gasesbetween lungs and blood§ Assist with flow of venous blood and lymph§ Maintaining acid-base balance3. – movement of gases through blood§4. Tissue gas exchange –THE NOSE AND NASAL CAVITY 21.2 ANATOMY OF THERESPIRATORY SYSTEMNose and nasal cavity are entryway into respiratorysystem; serve following functions:§§ Filter debris from inhaled air and secreteantibacterial substances§§ Resonates of voice Anatomy of nasal cavity:§ Nasal cavity – divided into left and right portionsby nasal septum from nostrils (anterior nares) toposterior nares§ – contain bristle-like hairs§ Superior, inferior, and middle conchae createturbulence§ Paranasal sinuses – hollow cavities found withinfrontal, ethmoid, sphenoid, and maxillary boneso Warmand humidify air; also enhance voiceresonance and reduce weight of skull124

Bio 104Chapter 21: Respiratory System THE PHARYNXHistology of nasal cavity:§ Vestibule is lined with stratified squamous125 epithelium; resists mechanical stressPharynx (throat) – three divisions:§ – posterior to nasal cavity; linedwith PSCCE§ Most of nasal cavity is lined with mucosa composedof PSCCE and goblet cells- Extends from posterior nares to soft palateforeign particles in mucus à ciliated cellsmove it toward posterior nasal cavity andpharynxo Traps§ – posterior to oral cavity- Extends from uvula to hyoid bone- stratified squamous epithelium§ – hyoid bone to esophagus- stratified squamous epitheliumTHE LARYNX Larynx or voice box – houses vocal cords§ Stratified squamous epithelium superior to vocal cords§ PSCCE found inferior to vocal cords Composed of pieces of cartilage§ –posterior tothyroid cartilage§ Thyroid cartilage – largest ofthree unpaired sections(“Adam’s apple”)§ cartilage –inferiorto thyroid cartilageRemaining six found pairs:§ Cuneiform cartilages –helpsupport epiglottis§ Arytenoid cartilages –involved in sound production§ Corniculate cartilages –involved in sound production

Bio 104Chapter 21: Respiratory System§ Vestibular folds (false vocal cords) close off glottisTHE TRACHEAduring swallowing; play no role in sound production§ True vocal cords and Vocal ligaments – elastic bands; vibrate to produce sound when air passes overthemTHE BRONCHIAL TREE § Act as irritants, increasing mucus secretion§ Partially paralyze and eventually destroy cilia lining tract As result, more mucus is present, but cilia are less able tosweep it out of airways Cough develops as only way to prevent mucus buildup Cilia will reappear within a few months after smoking stopsbronchi (enters the left or right lung at hilum)§ Right primary bronchus – wider, shorter, andnumerous adverse effects of smoke on the respiratorysystem Chemicals in smokeTrachea (windpipe) - C shape cartilage rings§SMOKER’S COUGH Deep, rattling cough of a smoker is linked directly to126straighter than left bronchi once inside each lung; three on rightand two on left bronchi continue to branch smaller and smallerBronchioles – smallest airways§ Terminal bronchioles à Respiratory bronchioles

Bio 104Chapter 21: Respiratory System As airways divide and get smaller:§ Epithelium gradually changes from PSCCE to§ Amount of smooth muscle increases§ Hyaline cartilage decreasesALVEOLI AND THE RESPIRATORYMEMBRANE Alveolar ducts à Alveolar sacs - grapelike clustersof alveoli (site of gas exchange)1. Type I alveolar cells ( )2. Type II alveolar cells (simple cuboidal cells)produce surfactant3. Alveolar macrophages are mobileTHE LUNGS AND PLEURAE Right and left lungs are separated by heart andmediastinum§§§ – where primary bronchi, blood andlymphatic vessels, and nerves enter and exit lung§ Cardiac notch§ Right lung - three lobes; left lung - two lobes127

Bio 104Chapter 21: Respiratory System Each lung is found within a pleural cavity§ pleura – outer layer of serous membrane§ pleura continuous with surface of lungs§ Pleural membranes secrete a thin layer of serous fluid tolubricate surfaces of lungs as they expand and contractPLEURITIS AND PLEURALFRICTION RUB Many conditions (heart failure to pneumonia) cancause inflammation of the visceral and parietal pleura(pleuritis) Pleuritic pain – one of most common symptoms; chestpain with inhalation; results from inflamed pleurarubbing together as lungs expand and contract Rubbing can sometimes be heard with stethoscope;termed pleural friction rub; resembles sandpaperrubbing against itselfTHE PRESSURE-VOLUMERELATIONSHIP 21.3 PULMONARY VENTILATION – pressure and volume of a gas areinversely relatedFirst process of respiration is pulmonary ventilationThe pressure-volume relationship provides drivingforce for pulmonary ventilation§ Gas molecules move from areas of pressureto areas of pressureAs volumePressure(and vise versa)128

Bio 104Chapter 21: Respiratory SystemTHE PROCESS OF PULMONARYVENTILATION Inspiration:Process of pulmonary ventilation consists of inspirationand expiration§ – main inspiratory muscleVolume changes in thoracic cavity and lungs leads topressure changes and air tomove into or out of the lungsThese muscles increase thoracic cavity volume alongwith lung volume § External – muscles found between ribs Maximal inspiration aided by contraction ofsternocleidomastoid , pectoralis minor, and scalenesmuscles Nonrespiratory movements, not intended forventilation, include yawns, coughs, sighs, sneeze,laughing, hiccups, crying, etc.Expiration is a mostly passive process that does notutilize muscle contraction§ Diaphragm returns to its original dome shape thatpushes up on lungs§ decrease lung volume and raiseintrapulmonary pressure above atmosphericpressure so air flows out of lungs Maximum expiration muscles include internalintercostals and abdominal muscles§ Forcefully decrease size of thoracic cavity; why yourabdominal and back muscles are often sore after havinga cough§ Heimlich maneuver – delivering abdominal thrusts thatpush up on diaphragm129

Bio 104Chapter 21: Respiratory System 130Pressures at work during ventilation :§ Atmospheric pressure – at sea level atmosphericpressure is about 760 mm Hg§ pressure – rises and falls withinspiration and expiration§ Intrapleural pressure – rises and falls withinspiration and expiration; always belowintrapulmonary pressureINFANT RESPIRATORYDISTRESS SYNDROMEPULMONARY VOLUMES ANDCAPACITIES Inadequate surfactant makes alveolar inflation betweenbreaths very difficult – amount of air inspired or expired duringnormal quiet ventilation Surfactant is not produced significantly until last10–12 weeks of gestation; premature newborns maytherefore suffer from infant respiratory distresssyndrome (RDS) – volume of air that can be forciblyinspired after a normal TV inspiration – amount of air that can be forcibly expiredafter a normal tidal expiration (700–1200 ml)Treatment – delivery of surfactant by inhalation; alsopositive airway pressure (CPAP); slightly pressurizedair prevents alveoli from collapsing during expiration – air remaining in lungs after forcefulexpiration

Bio 104Chapter 21: Respiratory System13121.4 GAS EXCHANGEGAS EXCHANGE Pulmonary ventilation only brings new air into andremoves oxygen-poor air from alveoli Two processes are involved in gas exchange:THE BEHAVIOR OF GASES 1.§ gasexchange involves exchange ofgases between alveoli and blood2. Surface area of respiratory membrane3.§ gasexchange involves exchange of gasesbetween blood in systemic capillaries and body’s cellsof partial pressures – each gas in amixture exerts its own pressure, called its partial pressure(Pgas); total pressure of a gas mixture is sum of partialpressures of all its component gasesGas behavior – important factor that affects gasexchange4. Ventilation-perfusion matching§ lawPULMONARY GAS EXCHANGE PN2 PO2 PO2 Pothers Atmospheric pressure (760 mm Hg)Pulmonary gas exchange (external respiration) isdiffusion of gases between alveoli and blood;PN2 0.78 760 593 mm Hg§ Oxygen diffuses from intoPO2 0.21 760 160 mm HgPartial pressure of a gas in a mixture determines where gas diffuses§ Carbon dioxide simultaneously diffuses in oppositedirectionooBlood has a low PO2 (40 mm Hg) while PO2 in air is 104 mmHgBlood has a high CO2 (45 mm Hg) compared to alveoli air (40mm Hg)

Bio 104Chapter 21: Respiratory System132REVIEWOxygen diffusion during gas exchange isa.b.from the pulmonary blood into the alveolar airc.driven by the gradient between inspired air andalveolar bloodd.less efficient than diffusion of carbon dioxideREVIEWso slow that equilibrium is never reachedREVIEWThe efficiency of pulmonary gas exchange isimpacted by all of the following EXCEPTThe efficiency of pulmonary gas exchange isincreased bya.Degree of match between air and blood flowa.A mismatch between air and blood flowb.c.d.Surface area of respiratory membraneb.c.d.An increase in respiratory membrane surface areaThickness of the respiratory membraneBlood pressure in the pulmonary capillariesHYPERBARIC OXYGENTHERAPY Person placed in chamber and exposed to higher than normalpartial pressures of oxygen; increases oxygen levels dissolved inplasma; in turn increases delivery to tissues Used to treat conditions benefiting from increased oxygendelivery: severe blood loss, crush injuries, anemia (decreased O2carrying capacity of blood), chronic wounds, certain infections,burns Also used for decompression sickness (“bends”); seen indivers who ascended too rapidly; caused by dissolved gases inblood coming out of solution and forming bubbles inbloodstream; therapy forces gases back into solution,eliminating bubblesThickening of the respiratory membraneA decrease in respiratory membrane surface areaFACTORS AFFECTING EFFICIENCYOF PULMONARY GAS EXCHANGE Surface area of respiratory membrane of both lungsis extremely large (approximately 1000 square feet)§ Any factor that reduces surface area decreasesefficiency of pulmonary gas exchange§ – low blood oxygen level; sign ofseverely impaired pulmonary gas exchange§ – high blood carbon dioxide level; signof severely impaired pulmonary gas exchange

Bio 104Chapter 21: Respiratory System Thickness of respiratory membrane – distance that agas must diffuse133Ventilation-perfusion matching – degree of matchbetween amount of air reaching alveoli ( )and amount of blood flow ( ) in pulmonarycapillaries§ Ventilation/perfusion ratio (V/Q) – measurement that§describes this match; when affected by disease, called amismatch§ Thickening of the membrane reduces exhange efficiency(inflammation)TISSUE GAS EXCHANGE Tissue gas exchange (internal respiration) is oxygenand carbon dioxide between blood and tissues§ Cells use oxygen constantly for cellular respiration soin tissue is low§ Tissues produce large quantities of so partialpressure is high Factors affecting efficiency of tissue gas exchangeinclude:§ Surface area available for gas exchange (of branchedsystemic capillaries); large enough to allow for gasexchange efficiency§ Distance over which diffusion must occur; lessdistance to diffuse results in more efficient gas exchange§ Perfusion of tissue –

Bio 104Chapter 21: Respiratory System134GAS TRANSPORT21.5 GAS TRANSPORT THROUGHTHE BLOOD Only 1.5% of inspired oxygen is dissolved in bloodplasma due to its poor solubility; majority of oxygen istransported in blood plasma by There are three ways that carbon dioxide is transported Hemoglobin binds and releases oxygenOXYGEN TRANSPORT Oxygen transport is facilitated by hemoglobin (Hb)§ carriedby Hb§ Oxygen from alveoli binds to hemoglobin in pulmonarycapillaries; oxyhemoglobin (HbO2)§ Hemoglobin is a protein found in§ Hb in systemic capillaries releases oxygen to cells of§ Consists of four subunits, each including a heme group;tissueseach heme contains one iron atom that can bind to onemolecule of oxygen§ Effect of affinity on hemoglobin saturation isdetermined by four factors:1.Lower blood PO2; unloading reaction is favored asfewer O2 molecules are available to bind to Hb2.PCO2 increase, Hb binds oxygen less strongly somore oxygen is unloaded

Bio 104Chapter 21: Respiratory System3.When pH decreases, Hb binds oxygen less stronglyso more oxygen is unloaded4.Increasing temperature decreases Hb’s affinity foroxygen; facilitates unloading reaction of oxygen intotissues; reverse also trueCARBON DIOXIDE TRANSPORT Carbon dioxide is transported from tissues to lungs inblood three ways:1. Dissolved in plasma ( )2. (23%) - CO2 binds to Hb’s proteincomponent (not heme group that oxygen binds) carbaminohemoglobin3. Bicarbonate ions (70%)§ CO2 quickly diffuses into erythrocytes§ Carbonic anhydrase (CA) catalyz