Presentation on theme: "The Respiratory System"— Presentation transcript:
1 The Respiratory System Biology 1612 Lecture OutlineK. Donaldson, M.S.Georgia Perimeter College
2 INTRODUCTIONThe two systems that cooperate to supply O2 and eliminate CO2 are the cardiovascular and the respiratory system.The respiratory system provides for gas exchange.The cardiovascular system transports the respiratory gases.Failure of either system has the same effect on the body: disruption of homeostasis and rapid death of cells from oxygen starvation and buildup of waste products.Respiration is the exchange of gases between the atmosphere, blood, and cells. It takes place in three basic steps: ventilation (breathing), external (pulmonary) respiration, and internal (tissue) respiration.
3 The Respiratory System Cells continually use O2 & release CO2Respiratory system designed for gas exchangeCardiovascular system is what transports gases in bloodFailure of either system leads to rapid cell death from O2 starvation
4 Respiratory System Anatomical Terms NosePharynx = throatLarynx = voice boxTrachea = windpipeBronchi = airwaysLungsTerms to indicate locations of respiratory infections:upper respiratory tract is above vocal cordslower respiratory tract is below vocal cordsThe conducting system consists of a series of cavities and tubes - nose, pharynx, larynx, trachea, bronchi, bronchiole, and terminal bronchioles - that conduct air into the lungs.The respiratory portion consists of the area where gas exchange occurs - respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.
5 External Nasal Structures Skin, nasal bones, & cartilage lined with mucous membraneOpenings are called external nares or nostrils
6 External AnatomyThe external portion of the nose is made of cartilage and skin and is lined with mucous membranes. Openings to the exterior are the external nares or nostrils.The external portion of the nose is made of cartilage and skin and is lined with mucous membranes.The bony framework of the nose is formed by the frontal bone, nasal bones, and maxillae.
7 Internal AnatomyThe interior structures of the nose are specialized for warming, moistening, and filtering incoming air; receiving olfactory stimuli; and serving as large, hollow resonating chambers to modify speech sounds.The internal portion of the nose communicates with the paranasal sinuses and nasopharynx through the internal nares.The inside of both the external and internal nose is called the nasal cavity. It is divided into right and left sides by the nasal septum. The anterior portion of the cavity is called the vestibule.
8 Nasal PolypsNasal polyps are outgrowths of the mucous membranes which are usually found around the openings of the paranasal sinuses.They are soft, noncancerous (benign) growths that develop on the lining of your nose or sinuses.Small nasal polyps usually cause few problems, but larger ones can affect your breathing and diminish your sense of smell. Sometimes they may cause dull headaches or snoring, and in rare cases, massive nasal polyps can alter the shape of your face.Nasal polyps result from chronic inflammation in the lining of your nose or sinuses, but just what triggers the inflammation isn't always clear.Although nasal polyps can affect anyone, they're more common in people older than 40 and in adults and children with conditions such as asthma, chronic sinus infections, hay fever and cystic fibrosis.
9 Nose -- Internal Structures Large chamber within the skullRoof is made up of the ethmoid bone and floor is hard palateInternal nares (choanae) are openings to pharynxIn the lateral walls of either fossa are three shell-like concavities: the superior, middle and inferior conchae. Air passages or meatuses connect the conchae.The nostrils (external nares) open anteriorly into the nasal cavity and thechoanae (posterior nares) communicate posteriorly with the nasopharynx.Nasal septum is composed of bone & cartilage.
10 Functions of the Nasal Structures Specialized columnar epithelium called olfactory epithelium lines the upper medial portion of the nasal cavity and responds to odors.Pseudostratified ciliated columnar epithelium with goblet cells lines nasal cavity. The function is to:warms air due to high its high vascularitymucous moistens air & traps dust, pollens, smoke and other airborne particlescilia move mucous towards pharynx where it can be removedParanasal sinuses open into nasal cavity:The four paranasal sinuses are the ethmoid, sphenoid, frontal & maxillary sinuses.Their function is to lighten the overall weight of the skull and to act as sound chambers for voice resonance.
11 RhinoplastyRhinoplasty (“nose job”) is a surgical procedure in which the structure of the external nose is altered for cosmetic or functional reasons (fracture or septal repair)Procedure:local and general anestheticnasal cartilage is reshaped or removed by entering through nostrilsbones fractured and repositionedinternal packing & splint while healing
12 Pharynx - OverviewThe pharynx (throat) is a muscular tube lined by a mucous membrane.The anatomic regions are the nasopharynx, oropharynx, and laryngopharynx.The nasopharynx functions in respiration.Both the oropharynx and laryngopharynx function in digestion and in respiration (serving as a passageway for both air and food).
14 PharynxMuscular tube (5 inch long) hanging from skull composed of skeletal muscle and mucous membranes.Extends from internal nares to cricoid cartilageFunctions:passageway for food and airresonating chamber for speech productiontonsil (lymphatic tissue) in the walls protects entryway into bodyDistinct regions -- nasopharynx, oropharynx and laryngopharynx
15 Nasopharynx From choanae to soft palate Passageway for air only openings of auditory (Eustachian) tubes from middle ear cavityadenoids or pharyngeal tonsil in roofPassageway for air onlypseudostratified ciliated columnar epithelium with goblet
16 Oropharynx From soft palate to epiglottis fauces is opening from mouth into oropharynxpalatine tonsils found in side walls, lingual tonsil in tongueCommon passageway for food & airstratified squamous epithelium
17 Laryngopharynx Extends from epiglottis to cricoid cartilage Common passageway for food & air & ends as esophagus inferiorlystratified squamous epithelium
18 Larynx - OverviewThe larynx (voice box) is a passageway that connects the pharynx with the trachea.It contains the thyroid cartilage (Adam’s apple); the epiglottis, which prevents food from entering the larynx; the cricoid cartilage, which connects the larynx and trachea; and the paired arytenoid, corniculate, and cuneiform cartilages.Voice Production:The larynx contains vocal folds (true vocal cords), which produce sound.Taunt vocal folds produce high pitches, and relaxed vocal folds produce low pitches. Other structures modify the sound.
19 Cartilages of the Larynx Thyroid cartilage forms Adam’s appleEpiglottis---leaf-shaped piece of elastic cartilageduring swallowing, larynx moves upwardepiglottis bends to cover glottisCricoid cartilage---ring of cartilage attached to top of tracheaPair of arytenoid cartilages sit upon cricoidmany muscles responsible for their movementpartially buried in vocal folds (true vocal cords)
20 Larynx Cartilage & connective tissue tube Anterior to C4 to C6 Constructed of 3 single & 3 paired cartilages
21 Vocal CordsFalse vocal cords (ventricular folds) found above vocal folds (true vocal cords)True vocal cords attach to arytenoid cartilages
22 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, it moves the cartilages & stretches the vocal cord tightWhen 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 pitchTo increase volume of sound, push air harder.
23 Movement of Vocal Cords Opening and closing of the vocal folds occurs during breathing and speech
24 Speech and Whispering Speech is modified sound made by the larynx. Speech requires pharynx, mouth, nasal cavity & sinuses to resonate that soundTongue & lips form wordsPitch is controlled by tension on vocal foldspulled tight produces higher pitchmale vocal folds are thicker & longer so vibrate more slowly producing a lower pitchWhispering is forcing air through almost closed rima glottidis -- oral cavity alone forms speech
25 LaryngitisLaryngitis is an inflammation of the larynx that is usually caused by respiratory infection or irritants.
26 TracheaThe trachea (windpipe) extends from the larynx to the primary bronchi.It is composed of smooth muscle and C-shaped rings of cartilage and is lined with pseudostratified ciliated columnar epithelium.The cartilage rings keep the airway open.The cilia of the epithelium sweep debris away from the lungs and back to the throat to be swallowed.
27 Trachea Size is 5 in long & 1in diameter Extends from larynx to T5 anterior to the esophagus and then splits into bronchiLayersmucosa = pseudostratified columnar with cilia & gobletsubmucosa = loose connective tissue & seromucous glandshyaline cartilage = 16 to 20 incomplete ringsopen side facing esophagus contains trachealis m. (smooth)internal ridge on last ring called carinaadventitia binds it to other organs
28 Trachea and Bronchial Tree Full extent of airways is visible starting at the larynx and trachea
29 Histology of the Trachea Ciliated pseudostratified columnar epitheliumHyaline cartilage as C-shaped structure closed by trachealis muscle
30 Airway EpitheliumCiliated pseudostratified columnar epithelium with goblet cells produce a moving mass of mucus.
31 Tracheostomy and Intubation Reestablishing airflow past an airway obstructioncrushing injury to larynx or chestswelling that closes airwayvomit or foreign objectTracheostomy is incision in trachea below cricoid cartilage if larynx is obstructedIntubation is passing a tube from mouth or nose through larynx and trachea
32 Bronchi The trachea divides into the right and left pulmonary bronchi. The bronchial tree consists of the trachea, primary bronchi, secondary bronchi, tertiary bronchi, bronchioles, and terminal bronchioles.Walls of bronchi contain rings of cartilage.Walls of bronchioles contain smooth muscle.
33 Bronchi and Bronchioles Primary bronchi supply each lungSecondary bronchi supply each lobe of the lungs (3 right + 2 left)Tertiary bronchi supply each bronchopulmonary segmentRepeated branchings called bronchioles form a bronchial tree
34 Histology of Bronchial Tree Epithelium changes from pseudostratified ciliated columnar to nonciliated simple cuboidal as pass deeper into lungsIncomplete rings of cartilage replaced by rings of smooth muscle & then connective tissuesympathetic NS & adrenal gland release epinephrine that relaxes smooth muscle & dilates airwaysasthma attack or allergic reactions constrict distal bronchiole smooth musclenebulization therapy = inhale mist with chemicals that relax muscle & reduce thickness of mucus.
35 Pleural Membranes & Pleural Cavity Visceral pleura covers lungs --- parietal pleura lines ribcage & covers upper surface of diaphragmPleural cavity is potential space between ribs & lungs
36 Lungs - OverviewLungs are paired organs in the thoracic cavity; they are enclosed and protected by the pleural membrane .The parietal pleura is the outer layer which is attached to the wall of the thoracic cavity.The visceral pleura is the inner layer, covering the lungs themselves.Between the pleurae is a small potential space, the pleural cavity, which contains a lubricating fluid secreted by the membranes.The pleural cavities may fill with air (pneumothorax) or blood (hemothorax).A pneumorthorax may cause a partial or complete collapse of the lung.The lungs extend from the diaphragm to just slightly superior to the clavicles and lie against the ribs anteriorly and posteriorly.
37 Lungs - Overview The lungs almost totally fill the thorax. The right lung has three lobes separated by two fissures; the left lung has two lobes separated by one fissure and a depression, the cardiac notch.The secondary bronchi give rise to branches called tertiary (segmental) bronchi, which supply segments of lung tissue called bronchopulmonary segments.Each bronchopulmonary segment consists of many small compartments called lobules, which contain lymphatics, arterioles, venules, terminal bronchioles, respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.
38 Gross Anatomy of LungsBase, apex (cupula), costal surface, cardiac notchOblique & horizontal fissure in right lung results in 3 lobesOblique fissure only in left lung produces 2 lobes
39 Mediastinal Surface of Lungs Blood vessels & airways enter lungs at hilusForms root of lungsCovered with pleura (parietal becomes visceral)
40 Structures within a Lobule of Lung Branchings of single arteriole, venule & bronchiole are wrapped by elastic CTRespiratory bronchiolesimple squamousAlveolar ducts surrounded by alveolar sacs & alveolisac is 2 or more alveoli sharing a common opening
41 AlveoliAlveolar walls consist of type I alveolar (squamous pulmonary epithelial) cells, type II alveolar (septal) cells, and alveolar macrophages (dust cells).Type II alveolar cells secrete alveolar fluid, which keeps the alveolar cells moist and which contains a component called surfactant. Surfactant lowers the surface tension of alveolar fluid, preventing the collapse of alveoli with each expiration.Respiratory Distress Syndrome is a disorder of premature infants in which the alveoli do not have sufficient surfactant to remain open.Gas exchange occurs across the alveolar-capillary membrane.
42 Histology of Lung Tissue Photomicrograph of lung tissue showing bronchioles, alveoli and alveolar ducts.
44 Cells Types of the Alveoli Type I alveolar cellssimple squamous cells where gas exchange occursType II alveolar cells (septal cells)free surface has microvillisecrete alveolar fluid containing surfactantAlveolar dust cellswandering macrophages remove debris
45 Alveolar-Capillary Membrane Respiratory membrane = 1/2 micron thickExchange of gas from alveoli to blood4 Layers of membrane to crossalveolar epithelial wall of type I cellsalveolar epithelial basement membranecapillary basement membraneendothelial cells of capillaryVast surface area = handball court
46 Details of Respiratory Membrane Find the 4 layers that comprise the respiratory membrane
47 Double Blood Supply to the Lungs Deoxygenated blood arrives through pulmonary trunk from the right ventricleBronchial arteries branch off of the aorta to supply oxygenated blood to lung tissueVenous drainage returns all blood to heartLess pressure in venous systemPulmonary blood vessels constrict in response to low O2 levels so as not to pick up CO2 on there way through the lungs
48 Clinical Applications Nebulization, a procedure for administering medication as small droplets suspended in air into the respiratory tract, is used to treat many different types of respiratory disorders.In the lungs vasoconstriction in response to hypoxia diverts pulmonary blood from poorly ventilated areas to well ventilated areas. This phenomenon is known as ventilation – perfusion coupling.
49 PULMONARY VENTILATION Respiration occurs in three basic steps: pulmonary ventilation, external respiration, and internal respiration.Inspiration (inhalation) is the process of bringing air into the lungs.The movement of air into and out of the lungs depends on pressure changes governed in part by Boyle’s law, which states that the volume of a gas varies inversely with pressure, assuming that temperature is constant.
50 Breathing or Pulmonary Ventilation Air moves into lungs when pressure inside lungs is less than atmospheric pressureHow is this accomplished?Air moves out of the lungs when pressure inside lungs is greater than atmospheric pressureAtmospheric pressure = 1 atm or 760mm Hg
51 Boyle’s LawAs the size of closed container decreases, pressure inside is increasedThe molecules have less wall area to strike so the pressure on each inch of area increases.
52 Dimensions of the Chest Cavity Breathing in requires muscular activity & chest size changesContraction of the diaphragm flattens the dome and increases the vertical dimension of the chest
53 InspirationThe first step in expanding the lungs involves contraction of the main inspiratory muscle, the diaphragm.Inhalation occurs when alveolar (intrapulmonic) pressure falls below atmospheric pressure. Contraction of the diaphragm and external intercostal muscles increases the size of the thorax, thus decreasing the intrapleural (intrathoracic) pressure so that the lungs expand. Expansion of the lungs decreases alveolar pressure so that air moves along the pressure gradient from the atmosphere into the lungs.During forced inhalation, accessory muscles of inspiration (sternocleidomastoids, scalenes, and pectoralis minor) are also used.
54 Quiet Inspiration Diaphragm moves 1 cm & ribs lifted by muscles Intrathoracic pressure falls and 2-3 liters inhaled
55 ExpirationExpiration (exhalation) is the movement of air out of the lungs.Exhalation occurs when alveolar pressure is higher than atmospheric pressure. Relaxation of the diaphragm and external intercostal muscles results in elastic recoil of the chest wall and lungs, which increases intrapleural pressure, decreases lung volume, and increases alveolar pressure so that air moves from the lungs to the atmosphere. There is also an inward pull of surface tension due to the film of alveolar fluid.Exhalation becomes active during labored breathing and when air movement out of the lungs is impeded. Forced expiration employs contraction of the internal intercostals and abdominal muscles.
56 Quiet Expiration Passive process with no muscle action Elastic recoil & surface tension in alveoli pulls inwardAlveolar pressure increases & air is pushed out
57 Labored Breathing Forced expiration Forced inspiration abdominal mm force diaphragm upinternal intercostals depress ribsForced inspirationsternocleidomastoid, scalenes & pectoralis minor lift chest upwards as you gasp for air
58 Intrapleural Pressures Always subatmospheric (756 mm Hg)As diaphragm contracts intrathoracic pressure decreases even more (754 mm Hg)Helps keep parietal & visceral pleura stick together
59 Summary of Breathing Alveolar pressure decreases & air rushes in Alveolar pressure increases & air rushes out
60 Alveolar Surface Tension Thin layer of fluid in alveoli causes inwardly directed force = surface tensionwater molecules strongly attracted to each otherCauses alveoli to remain as small as possibleDetergent-like substance called surfactant produced by Type II alveolar cellslowers alveolar surface tensioninsufficient in premature babies so that alveoli collapse at end of each exhalation
61 Compliance of the Lungs Ease with which lungs & chest wall expand depends upon elasticity of lungs & surface tensionSome diseases reduce compliancetuberculosis forms scar tissuepulmonary edema --- fluid in lungs & reduced surfactantparalysis
62 Airway Resistance Resistance to airflow depends upon airway size increase size of chestairways increase in diametercontract smooth muscles in airwaysdecreases in diameter
63 Breathing PatternsEupnea is normal variation in breathing rate and depth.Apnea refers to breath holding.Dyspnea relates to painful or difficult breathing.Tachypnea involves rapid breathing rate.Costal breathing requires combinations of various patterns of intercostal and extracostal muscles, usually during need for increased ventilation, as with exercise.Diaphragmatic breathing is the usual mode of operation to move air by contracting and relaxing the diaphragm to change the lung volume.Modified respiratory movements are used to express emotions and to clear air passageways.
64 Modified Respiratory Movements Coughingdeep inspiration, closure of rima glottidis & strong expiration blasts air out to clear respiratory passagesHiccupingspasmodic contraction of diaphragm & quick closure of rima glottidis produce sharp inspiratory sound
65 LUNG VOLUMES AND CAPACITIES Air volumes exchanged during breathing and rate of ventilation are measured with a spiromometer, or respirometer, and the record is called a spirogram.Among the pulmonary air volumes exchanged in ventilation are tidal (500 ml), inspiratory reserve (3100 ml), expiratory reserve (1200 ml), residual (1200 ml) and minimal volumes. Only about 350 ml of the tidal volume actually reaches the alveoli, the other 150 ml remains in the airways as anatomic dead space.Pulmonary lung capacities, the sum of two or more volumes, include inspiratory (3600 ml), functional residual (2400 ml), vital (4800 ml), and total lung (6000 ml) capacities.The minute volume of respiration is the total volume of air taken in during one minute (tidal volume x 12 respirations per minute = 6000 ml/min).
66 Lung Volumes and Capacities Tidal volume = amount air moved during quiet breathingMVR= minute ventilation is amount of air moved in a minuteReserve volumes ---- amount you can breathe either in or out above that amount of tidal volumeResidual volume = 1200 mL permanently trapped air in systemVital capacity & total lung capacity are sums of the other volumes
67 EXCHANGE OF OXYGEN AND CARBON DIOXIDE To understand the exchange of oxygen and carbon dioxide between the blood and alveoli, it is useful to know some gas laws.According to Dalton’s law, each gas in a mixture of gases exerts its own pressure as if all the other gases were not present.
68 Dalton’s Law Each gas in a mixture of gases exerts its own pressure as if all other gases were not presentpartial pressures denoted as pTotal pressure is sum of all partial pressuresatmospheric pressure (760 mm Hg) = pO2 + pCO2 + pN2 + pH2Oto determine partial pressure of O2-- multiply 760 by % of air that is O2 (21%) = 160 mm Hg
69 What is Composition of Air? Air = 21% O2, 79% N2 and .04% CO2Alveolar air = 14% O2, 79% N2 and 5.2% CO2Expired air = 16% O2, 79% N2 and 4.5% CO2Observationsalveolar air has less O2 since absorbed by bloodmystery-----expired air has more O2 & less CO2 than alveolar air?Anatomical dead space = 150 ml of 500 ml of tidal volume
70 EXCHANGE OF OXYGEN AND CARBON DIOXIDE The partial pressure of a gas is the pressure exerted by that gas in a mixture of gases. The total pressure of a mixture is calculated by simply adding all the partial pressures. It is symbolized by P.The partial pressures of the respiratory gases in the atmosphere, alveoli, blood, and tissues cells are shown in the text.The amounts of O2 and CO2 vary in inspired (atmospheric), alveolar, and expired air.
71 Henry’s LawHenry’s law states that the quantity of a gas that will dissolve in a liquid is proportional to the partial pressure of the gas and its solubility coefficient (its physical or chemical attraction for water), when the temperature remains constant.Nitrogen narcosis and decompression sickness (caisson disease, or bends) are conditions explained by Henry’s law.
72 Henry’s LawQuantity of a gas that will dissolve in a liquid depends upon the amount of gas present and its solubility coefficientexplains why you can breathe compressed air while scuba diving despite 79% NitrogenN2 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 longBreathing O2 under pressure dissolves more O2 in blood
73 Hyperbaric Oxygenation A major clinical application of Henry’s law is hyperbaric oxygenation.Use of pressure to dissolve more O2 in the bloodtreatment for patients with anaerobic bacterial infections (tetanus and gangrene)anaerobic bacteria die in the presence of O2Hyperbaric chamber pressure raised to 3 to 4 atmospheres so that tissues absorb more O2Used to treat heart disorders, carbon monoxide poisoning, cerebral edema, bone infections, gas embolisms & crush injuries
75 External RespirationO2 and CO2 diffuse from areas of their higher partial pressures to areas of their lower partial pressures.Diffusion depends on partial pressure differencesCompare gas movements in pulmonary capillaries to tissue capillaries
76 Rate of Diffusion of Gases Depends upon partial pressure of gases in airp O2 at sea level is 160 mm Hg10,000 feet is 110 mm Hg / 50,000 feet is 18 mm HgLarge surface area of our alveoliDiffusion distance (membrane thickness) is very smallSolubility & molecular weight of gasesO2 smaller molecule diffuses somewhat fasterCO2 dissolves 24X more easily in water so net outward diffusion of CO2 is much fasterdisease produces hypoxia before hypercapnialack of O2 before too much CO2
77 Internal Respiration Exchange of gases between blood & tissues Conversion of oxygenated blood into deoxygenatedObserve diffusion of O2 inwardat rest 25% of available O2 enters cellsduring exercise more O2 is absorbedObserve diffusion of CO2 outward
78 Oxygen TransportIn each 100 ml of oxygenated blood, 1.5% of the O2 is dissolved in the plasma and 98.5% is carried with hemoglobin (Hb) inside red blood cells as oxyhemglobin (HbO2).Hemoglobin consists of a protein portion called globin and a pigment called heme.The heme portion contains 4 atoms of iron, each capable of combining with a molecule of oxygen.
79 Hemoglobin and Oxygen Partial Pressure The most important factor that determines how much oxygen combines with hemoglobin is PO2.The greater the PO2, the more oxygen will combine with hemoglobin, until the available hemoglobin molecules are saturated.
80 Hemoglobin and Oxygen Partial Pressure Blood is almost fully saturated at pO2 of 60mmpeople OK at high altitudes & with some diseaseBetween 40 & 20 mm Hg, large amounts of O2 are released as in areas of need like contracting muscle
81 Oxygen Transport in the Blood Oxyhemoglobin contains 98.5% chemically combined oxygen and hemoglobininside red blood cellsDoes not dissolve easily in wateronly 1.5% transported dissolved in bloodOnly the dissolved O2 can diffuse into tissuesFactors affecting dissociation of O2 from hemoglobin are importantOxygen dissociation curve shows levels of saturation and oxygen partial pressures
82 Hemoglobin and Oxygen Partial Pressure Blood is almost fully saturated at pO2 of 60mmpeople OK at high altitudes & with some diseaseBetween 40 & 20 mm Hg, large amounts of O2 are released as in areas of need like contracting muscle
83 Other Factors Affecting Hemoglobin Affinity for Oxygen In an acid (low pH) environment, O2 splits more readily from hemoglobin. This is referred to as the Bohr effect.Low blood pH (acidic conditions) results from high PCO2.Within limits, as temperature increases, so does the amount of oxygen released from hemoglobin. Active cells require more oxygen, and active cells (such as contracting muscle cells) liberate more acid and heat. The acid and heat, in turn, stimulate the oxyhemoglobin to release its oxygen.BPG (2, 3-biphosphoglycerate) is a substance formed in red blood cells during glycolysis. The greater the level of BPG, the more oxygen is released from hemoglobin.
84 Acidity & Oxygen Affinity for Hb As acidity increases, O2 affinity for Hb decreasesBohr effectH+ binds to hemoglobin & alters itO2 left behind in needy tissues
85 pCO2 & Oxygen ReleaseAs pCO2 rises with exercise, O2 is released more easilyCO2 converts to carbonic acid & becomes H+ and bicarbonate ions & lowers pH.
86 Temperature & Oxygen Release As temperature increases, more O2 is releasedMetabolic activity & heatMore BPG, more O2 releasedRBC activityhormones like thyroxine & growth hormone
87 Oxygen Affinity & Fetal Hemoglobin Differs from adult in structure & affinity for O2When pO2 is low, can carry more O2Maternal blood in placenta has less O2
89 Fetal HemoglobinFetal hemoglobin has a higher affinity for oxygen because it binds BPG less strongly and can carry more oxygen to offset the low oxygen saturation in maternal blood in the placenta.Because of the strong attraction of carbon monoxide (CO) to hemoglobin, even small concentrations of CO will reduce the oxygen carrying capacity leading to hypoxia and carbon monoxide poisoning.
90 Carbon Monoxide Poisoning CO from car exhaust & tobacco smokeBinds to Hb heme group more successfully than O2CO poisoningTreat by administering pure O2
91 Carbon Dioxide Transport CO2 is carried in blood in the form of dissolved CO2 (7%), carbaminohemoglobin (23%), and bicarbonate ions (70%).The conversion of CO2 to bicarbonate ions and the related chloride shift maintains the ionic balance between plasma and red blood cells.
92 Carbon Dioxide Transport 100 ml of blood carries 55 ml of CO2Is carried by the blood in 3 waysdissolved in plasmacombined with the globin part of Hb molecule forming carbaminohemoglobinas part of bicarbonate ionCO2 + H2O combine to form carbonic acid that dissociates into H+ and bicarbonate ion
93 Summary of Gas Exchange and Transport in Lungs and Tissues CO2 in blood causes O2 to split from hemoglobin.Similarly, the binding of O2 to hemoglobin causes a release of CO2 from blood.
95 Respiratory CenterThe area of the brain from which nerve impulses are sent to respiratory muscles is located bilaterally in the reticular formation of the brain stem. This respiratory center consists of a medullary rhythmicity area (inspiratory and expiratory areas), pneumotaxic area, and apneustic area.
96 Role of the Respiratory Center Respiratory mm. controlled by neurons in pons & medulla3 groups of neuronsmedullary rhythmicitypneumotaxicapneustic centers
97 Medullary Rhythmicity Area The function of the medullary rhythmicity area is to control the basic rhythm of respiration.The inspiratory area has an intrinsic excitability of autorhythmic neurons that sets the basic rhythm of respiration.The expiratory area neurons remain inactive during most quiet respiration but are probably activated during high levels of ventilation to cause contraction of muscles used in forced (labored) expiration.
98 Medullary Rhythmicity Area Controls basic rhythm of respirationInspiration for 2 seconds, expiration for 3Autorhythmic cells active for 2 seconds then inactiveExpiratory neurons inactive during most quiet breathing only active during high ventilation rates
99 Pneumotaxic AreaThe pneumotaxic area in the upper pons helps coordinate the transition between inspiration and expiration.The apneustic area sends impulses to the inspiratory area that activate it and prolong inspiration, inhibiting expiration.
100 Regulation of Respiratory Center Cortical Influencesvoluntarily alter breathing patternsCortical influences allow conscious control of respiration that may be needed to avoid inhaling noxious gasses or water.Voluntary breath holding is limited by the overriding stimuli of increased [H+] and [CO2].inspiratory center is stimulated by increase in eitherif you hold breathe until you faint----breathing will resume
101 Chemoreceptor Regulation of Respiration A slight increase in PCO2 (and thus H+), a condition called hypercapnia, stimulates central chemoreceptors.As a response to increased PCO2, increased H+ and decreased PO2, the inspiratory area is activated and hyperventilation, rapid and deep breathing, occurs.If arterial PCO2 is lower than 40 mm Hg, a condition called hypocapnia, the chemoreceptors are not stimulated and the inspiratory area sets its own pace until CO2 accumulates and PCO2 rises to 40 mm Hg.Severe deficiency of O2 depresses activity of the central chemoreceptors and respiratory center.
102 Chemical Regulation of Respiration Central chemoreceptors in medullarespond to changes in H+ or pCO2hypercapnia = slight increase in pCO2 is noticedPeripheral chemoreceptorsrespond to changes in H+ , pO2 or PCO2aortic body---in wall of aortanerves join vaguscarotid bodies--in walls of common carotid arteriesnerves join glossopharyngeal nerve
103 Negative Feedback Regulation of Breathing Negative feedback control of breathingIncrease in arterial pCO2Stimulates receptorsInspiratory centerMuscles of respiration contract more frequently & forcefullypCO2 Decreases
104 Control of Respiratory Rate Proprioceptors of joints and muscles activate the inspiratory center to increase ventilation prior to exercise induced oxygen need.The inflation (Hering-Breuer) reflex detects lung expansion with stretch receptors and limits it depending on ventilatory need and prevention of damage.Other influences include blood pressure, limbic system, temperature, pain, stretching the anal sphincter, and irritation to the respiratory mucosa.Table 23.2 summarizes the changes that increase or decrease ventilation rate and depth.
106 HypoxiaHypoxia refers to oxygen deficiency at the tissue level and is classified in several ways.Hypoxic hypoxia is caused by a low PO2 in arterial blood (high altitude, airway obstruction, fluid in lungs).In anemic hypoxia, there is too little functioning hemoglobin in the blood (hemorrhage, anemia, carbon monoxide poisoning).Stagnant hypoxia results from the inability of blood to carry oxygen to tissues fast enough to sustain their needs (heart failure, circulatory shock).In histotoxic hypoxia, the blood delivers adequate oxygen to the tissues, but the tissues are unable to use it properly (cyanide poisoning).
107 EXERCISE AND THE RESPIRATORY SYSTEM The respiratory system works with the cardiovascular system to make appropriate adjustments for different exercise intensities and durations.As blood flow increases with a lower O2 and higher CO2 content, the amount passing through the lung (pulmonary perfusion) increases and is matched by increased ventilation and oxygen diffusion capacity as more pulmonary capillaries open.Ventilatory modifications can increase 30 times above resting levels, in an initial rapid rate due to neural influences and then more gradually due to chemical stimulation from changes in cell metabolism. A similar, but reversed, effect occurs with cessation of exercise.Smokers have difficulty breathing for a number of reasons, including nicotine, mucous, irritants, and that fact that scar tissue replaces elastic fibers.
108 Smokers Lowered Respiratory Efficiency Smoker is easily “winded” with moderate exercisenicotine constricts terminal bronchiolescarbon monoxide in smoke binds to hemoglobinirritants in smoke cause excess mucus secretionirritants inhibit movements of ciliain time destroys elastic fibers in lungs & leads to emphysematrapping of air in alveoli & reduced gas exchange
109 The time line for development of the respiratory system 6 – 16 weeks the basic structures are formed16 – 26 weeks vascularization and the development of respiratory bronchioles, alveolar ducts and some alveoli begins26 weeks to birth many more alveoli developBy 26 – 28 weeks there is sufficient surfactant for survival.
110 Aging & the Respiratory System Respiratory tissues & chest wall become more rigidVital capacity decreases to 35% by age 70.Decreases in macrophage activityDiminished ciliary actionDecrease in blood levels of O2Result is an age-related susceptibility to pneumonia or bronchitis
111 Disorders of the Respiratory System AsthmaChronic obstructive pulmonary diseaseEmphysemaChronic bronchitisLung cancerPneumoniaTuberculosisCoryza and InfluenzaPulmonary EdemaCystic fibrosis
112 PneumothoraxPleural cavities are sealed cavities not open to the outsideInjuries to the chest wall that let air enter the intrapleural spacecauses a pneumothoraxcollapsed lung on same side as injurysurface tension and recoil of elastic fibers causes the lung to collapse
113 DISORDERS OF THE RESPIRATORY SYSTEM Asthma is characterized by the following: spasms of smooth muscle in bronchial tubes that result in partial or complete closure of air passageways; inflammation; inflated alveoli; and excess mucus production. A common triggering factor is allergy, but other factors include emotional upset, aspirin, exercise, and breathing cold air or cigarette smoke.Chronic obstructive pulmonary disease (COPD) is a type of respiratory disorder characterized by chronic and recurrent obstruction of air flow, which increases airway resistance.The principal types of COPD are emphysema and chronic bronchitis.Bronchitis is an inflammation of the bronchial tubes, the main symptom of which is a productive (raising mucus or sputum) cough.
114 DISORDERS OF THE RESPIRATORY SYSTEM In bronchogenic carcinoma (lung cancer), bronchial epithelial cells are replaced by cancer cells after constant irritation has disrupted the normal growth, division, and function of the epithelial cells. Airways are often blocked and metastasis is very common. It is most commonly associated with smoking.Pneumonia is an acute infection of the alveoli. The most common cause in the pneumococcal bacteria but other microbes may be involved. Treatment involves antibiotics, bronchodilators, oxygen therapy, and chest physiotherapy.Tuberculosis (TB) is an inflammation of pleurae and lungs produced by the organism Mycobacterium tuberculosis. It is communicable and destroys lung tissue, leaving nonfunctional fibrous tissue behind.Coryza (common cold) is caused by viruses and usually is not accompanied by a fever, whereas influenza (flu) is usually accompanied by a fever greater than 101oF.
115 DISORDERS OF THE RESPIRATORY SYSTEM Pulmonary edema refers to an abnormal accumulation of interstitial fluid in the interstitial spaces and alveoli of the lungs. It may be pulmonary or cardiac in origin.Cystic fibrosis is an inherited disease of secretory epithelia that affects the respiratory passageways, pancreas, salivary glands, and sweat glands.Asbestos related diseases develop as a result of inhaling asbestos particles. Diseases such as asbestosis, diffuse pleural thickening, and mesothelioma may result.Sudden infant death syndrome (SIDS) is the sudden unexpected death of an apparently healthy infant. Peak incidence is ages two to four months. The exact cause is unknown.Severe acute respiratory syndrome (SARS) is an emerging infectious disease.