Human Anatomy & Physiology - Respiratory System - PDF

Marieb Human Anatomy & Physiology Twelfth Edition Chapter 22 The Respiratory System Copyright © 2025 Pearson Education, Inc. All Rights Reserved Respiratory System (1 of 2) Our bodies continuously absor...

Marieb Human Anatomy & Physiology Twelfth Edition Chapter 22 The Respiratory System Copyright © 2025 Pearson Education, Inc. All Rights Reserved Respiratory System (1 of 2) Our bodies continuously absorb oxygen and nutrients from, and excrete carbon dioxide and other wastes into, the external environment Major function of respiratory system is gas exchange: supply cells with O2 for, dispose of CO2 from, cellular respiration To do this, respiratory and cardiovascular systems work together to carry out four processes collectively called respiration – Respiratory system responsible for: 1. Pulmonary ventilation, or breathing (moving air in and out of lungs) 2. Pulmonary gas exchange (of O2 and CO2 between lungs and blood) Respiratory System (2 of 2) – Cardiovascular system responsible for: 3. Transport of respiratory gases ( O2 and CO2 in blood) 4. Tissue gas exchange (of O2 and CO2 between blood and tissues) Also functions in olfaction and speech (because it moves air) Respiration Consists of Four Processes Copyright © 2025 Pearson Education, Inc. All Rights Reserved BioFlix Video: Gas Exchange Click here to view ADA compliant Animation: Gas Exchange https://mediaplayer.pearsoncmg.com/assets/gMkhizjcFfow76d8E7_kC9ZIQ2UM8TeH Copyright © 2025 Pearson Education, Inc. All Rights Reserved The Major Respiratory Organs in Relation to Surrounding Structure Copyright © 2025 Pearson Education, Inc. All Rights Reserved The Upper Respiratory System Copyright © 2025 Pearson Education, Inc. All Rights Reserved The Lower Respiratory System Structure Description, General and Distinctive Features Function Blank Larynx Connects pharynx to trachea. Has framework of cartilage Air passageway; prevents food from and dense connective tissue. Open glottis can be closed by entering lower respiratory tract epiglottis or vocal folds. Voice production Larynx connected to the hyoid bone superiorly, in an anterior view. Houses vocal folds (true vocal cords). Trachea Flexible tube running from larynx and dividing inferiorly into Air passageway; cleans, warms, and two main bronchi. Walls contain C-shaped cartilages that moistens incoming air are incomplete posteriorly where connected by trachealis. Trachea Bronchial tree Consists of right and left main bronchi, which subdivide Air passageways connecting trachea within the lungs to form lobar and segmental bronchi and with alveoli; cleans, warms, and Left and right bronchial tree. bronchioles. Bronchiolar walls lack cartilage but contain a moistens incoming air complete layer of smooth muscle. Constriction of this muscle impedes expiration. Alveoli Microscopic chambers at termini of bronchial tree. Walls of Main sites of gas exchange simple squamous epithelium overlie thin basement membrane. External surfaces are intimately associated Surfactant reduces surface tension; Alveol with pulmonary capillaries. helps prevent alveolar collapse Special alveolar cells produce surfactant. Lungs Paired composite organs that flank mediastinum in thorax. House respiratory passages smaller Composed primarily of alveoli and respiratory than the main bronchi passageways. Stroma is elastic connective tissue, allowing Left and right lung. lungs to recoil passively during expiration. Pleurae Serous membranes. Parietal pleura lines thoracic cavity; Produce lubricating fluid and Blank visceral pleura covers external lung surfaces. compartmentalize lungs Copyright © 2025 Pearson Education, Inc. All Rights Reserved The External Nose Copyright © 2025 Pearson Education, Inc. All Rights Reserved The Nasal Cavity Copyright © 2025 Pearson Education, Inc. All Rights Reserved Clinical—Homeostatic Imbalance: Rhinitis Copyright © 2025 Pearson Education, Inc. All Rights Reserved The Pharynx, Larynx, and Upper Trachea Copyright © 2025 Pearson Education, Inc. All Rights Reserved Clinical—Homeostatic Imbalance: Swollen Adenoids Copyright © 2025 Pearson Education, Inc. All Rights Reserved The Pharynx, Larynx, and Upper Trachea Copyright © 2025 Pearson Education, Inc. All Rights Reserved The Lower Respiratory System Consists of Conducting and Respiratory Zone Structures Anatomically, lower respiratory system divided into: – Larynx, trachea, bronchi, and lungs Functionally, respiratory system divided into: – Respiratory zone ▪ Sites of gas exchange (all microscopic structures) ▪ Consists of respiratory bronchioles, alveolar ducts, and alveoli – Conducting zone ▪ Consists of all other airways, from nose to respiratory bronchioles ▪ Functions: – Conduits that transport air to and from sites of gas exchange – Cleanse, warm, and humify incoming air Copyright © 2025 Pearson Education, Inc. All Rights Reserved The Larynx Figure 22.6 The larynx. Copyright © 2025 Pearson Education, Inc. All Rights Reserved The Larynx Figure 22.6 The larynx. Copyright © 2025 Pearson Education, Inc. All Rights Reserved Movements of the Vocal Folds Copyright © 2025 Pearson Education, Inc. All Rights Reserved Clinical—Homeostatic Imbalance: Laryngitis Copyright © 2025 Pearson Education, Inc. All Rights Reserved Tissue Composition of the Tracheal Wall Figure 22.8 Tissue composition of the tracheal wall. Copyright © 2025 Pearson Education, Inc. All Rights Reserved Tissue Composition of the Tracheal Wall Figure 22.8c Tissue composition of the tracheal wall. Copyright © 2025 Pearson Education, Inc. All Rights Reserved Clinical—Homeostatic Imbalance: Smoker’s cough Copyright © 2025 Pearson Education, Inc. All Rights Reserved Clinical— Homeostatic Imbalance Heimlich maneuver Copyright © 2025 Pearson Education, Inc. All Rights Reserved Conducting Zone Passages Copyright © 2025 Pearson Education, Inc. All Rights Reserved Respiratory Zone Structures (1 of 2) Figure 22.10a Respiratory zone structures. Copyright © 2025 Pearson Education, Inc. All Rights Reserved Respiratory Zone Structures (2 of 2) Figure 22.10b Respiratory zone structures. Copyright © 2025 Pearson Education, Inc. All Rights Reserved Alveoli and the Respiratory Membrane (1 of 2) Figure 22.11 Alveoli and the respiratory membrane. Copyright © 2025 Pearson Education, Inc. All Rights Reserved Alveoli and the Respiratory Membrane (2 of 2) Figure 22.11c Alveoli and the respiratory membrane. Copyright © 2025 Pearson Education, Inc. All Rights Reserved IP Anatomy Review Animation: Respiratory Click here to view ADA compliant Animation: IP Anatomy Review Animation: Respiratory https://mediaplayer.pearsoncmg.com/assets/secs-ipweb-respiratory-anat-rev Copyright © 2025 Pearson Education, Inc. All Rights Reserved Anatomical Relationships of Organs in the Thoracic Cavity (1 of 3) Figure 22.12 Anatomical relationships of organs in the thoracic cavity. Copyright © 2025 Pearson Education, Inc. All Rights Reserved Anatomical Relationships of Organs in the Thoracic Cavity (2 of 3) Figure 22.12c Anatomical relationships of organs in the thoracic cavity. Copyright © 2025 Pearson Education, Inc. All Rights Reserved Clinical—Homeostatic Imbalance: Pleurisy Copyright © 2025 Pearson Education, Inc. All Rights Reserved A Cast of the Bronchial Tree Copyright © 2025 Pearson Education, Inc. All Rights Reserved The Lower Respiratory System Copyright © 2025 Pearson Education, Inc. All Rights Reserved Volume Changes Cause Pressure Changes, Which Cause Air to Move Pulmonary ventilation (breathing) consists of two phases: – Inspiration: period of air (gas) flow into lungs – Expiration: period of air (gas) flow out of lungs Copyright © 2025 Pearson Education, Inc. All Rights Reserved Pressure Relationships in the Thoracic Cavity (1 of 4) Atmospheric pressure (Patm ) – Pressure exerted by air (gases) surrounding the body – At sea level, Patm 760 mm Hg (or 1 atmosphere) ▪ Pressure exerted by column of mercury 760 mm high Respiratory pressures always described relative to Patm – Negative respiratory pressures are less than Patm ▪ E.g.,  4 mm Hg 756 mm Hg at sea level – Positive respiratory pressures are greater than Patm – Zero respiratory pressure Patm Copyright © 2025 Pearson Education, Inc. All Rights Reserved Pressure Relationships in the Thoracic Cavity (2 of 4) Intrapulmonary pressure (Ppul ), also called intra-alveolar, is the pressure in the alveoli – Fluctuates during breathing, but equalizes with Patm to end each phase of breathing—inspiration and expiration Copyright © 2025 Pearson Education, Inc. All Rights Reserved Pressure Relationships in the Thoracic Cavity (3 of 4) Intrapleural pressure (Pip ) is the pressure in pleural cavity – Fluctuates with breathing, but always negative ( Patm ); 4 mm Hg less than Ppul ▪ Kept negative as opposing forces try to pull visceral and parietal pleurae apart – Two inward directed (collapsing) forces tend to shrink the lungs as they (visceral pleura) are pulled away from walls of thorax (parietal pleura) ▪ The lungs’ elasticity (tendency to recoil and assume smallest size possible) ▪ The surface tension of the alveolar fluid – Attraction between water molecules draws alveolar walls inward, acting to shrink alveoli to smallest size possible – One outward directed (expanding) force tends to enlarge the lungs as they (visceral pleura) are pulled outward by the thoracic wall (parietal pleura) ▪ The elasticity of the chest wall pulls the thoracic wall (parietal pleura) outward Copyright © 2025 Pearson Education, Inc. All Rights Reserved Pressure Relationships in the Thoracic Cavity (4 of 4) Intrapleural pressure (Pip ) (cont.) inued – Surface tension of pleural fluid helps secure layers of pleura together ▪ Fluid level must be kept at a minimum, excess removed by lymphatic system – If fluid accumulates, positive Pip pressure develops Transpulmonary pressure is the difference between the intrapulmonary and intrapleural pressures (Ppul  Pip ) – Pressure that keeps lung spaces open (prevents collapsing) ▪ Size of transpulmonary pressure determines size of lungs (more pressure causes greater lung expansion) – Any condition allowing P to equalize with Ppul (or Patm ) will cause ip lung collapse ▪ Negative Pip must be maintained to keep lungs inflated Copyright © 2025 Pearson Education, Inc. All Rights Reserved Intrapulmonary and Intrapleural Pressure Relationships Copyright © 2025 Pearson Education, Inc. All Rights Reserved Pneumothorax Copyright © 2025 Pearson Education, Inc. All Rights Reserved Pulmonary Ventilation Consists of inspiration and expiration; mechanical process that requires volume changes – Volume changes lead to pressure changes, and pressure changes lead to the flow of gases to equalize the pressure Boyle’s law: relationship between pressure and volume of a gas – Gases always fill their container ▪ If container volume is reduced, gas molecules will be forced closer together and the pressure rises (if volume is increased, pressure falls) – So pressure (P) varies inversely with volume (V) ▪ Mathematically: PV 1 1 P2V2 Copyright © 2025 Pearson Education, Inc. All Rights Reserved Pulmonary Ventilation – During normal quiet inspiration, as lungs stretch, thoracic cavity (and so lung) volume increases by 500 ml ▪ Ppul decreases to  1 mm Hg (Ppul  Patm ) – 500 ml of air flows into lungs, down its pressure gradient, until Ppul Patm ▪ Also, Pip falls to about  6 mm Hg relative to Patm – During deep or forced inspirations (e.g., during exercise or in people with COPD), accessory muscles are used to further increase volume (and thus pressure) ▪ Scalenes, sternocleidomastoid, and pectoralis minor ▪ Also, erector spinae muscles help to straighten thoracic curvature Copyright © 2025 Pearson Education, Inc. All Rights Reserved The Mechanics of Breathing at Rest Copyright © 2025 Pearson Education, Inc. All Rights Reserved IP2: Breathing Cycles and Muscles Click here to view ADA compliant Animation: Breathing Cycles and Muscles https://mediaplayer.pearsoncmg.com/assets/sci-ip2-pv-breathing-cycle-and-muscles Copyright © 2025 Pearson Education, Inc. All Rights Reserved Pulmonary Ventilation Expiration – During quiet expiration (a passive process), inspiratory muscles relax and thoracic cavity volume decreases ( 500 ml) as the lungs recoil ▪ Ppul increases to 1 mm Hg (Ppul  Patm ) – Air ( 500 ml) flows out of lungs down its pressure gradient until Ppul Patm – Forced expiration is an active process that uses: ▪ Abdominal wall muscles to increase intra-abdominal pressure (forcing the diaphragm up) and pull the ribs in (depressing the rib cage) ▪ Internal intercostal muscles to assist in depressing the rib cage Nonrespiratory air movements – Many other processes move air into or out of lungs, altering respiratory rhythm – Some are voluntary, and some are reflexive (like sneezing and hiccups) Copyright © 2025 Pearson Education, Inc. All Rights Reserved The Mechanics of Breathing at Rest Copyright © 2025 Pearson Education, Inc. All Rights Reserved Changes in Intrapulmonary and Intrapleural Pressures During Inspiration and Expiration Copyright © 2025 Pearson Education, Inc. All Rights Reserved Physical Factors Influencing Pulmonary Ventilation Airway resistance, alveolar surface tension, and lung compliance influence the ease (or work) of ventilation, and therefore the amount of energy required Airway resistance – Friction is the major nonelastic source of resistance to gas flow in airways – Flow (F) is directly proportional to the difference in pressures (Ppul  Patm ), or pressure gradient ( P), and inversely proportional to airway resistance (R): P F R ▪ P ~ 1– 2 mm Hg during normal quiet breathing, enough to move 500 ml of air Copyright © 2025 Pearson Education, Inc. All Rights Reserved Physical Factors Influencing Pulmonary Ventilation – Resistance in respiratory tree usually insignificant for two reasons: 1. Conducting zone airways have huge diameters (relative to low air viscosity) 2. All the bronchioles running in parallel (creates huge cross-sectional area) – Greatest resistance in medium-sized bronchi – At terminal bronchioles flow stops and diffusion of gases takes over Copyright © 2025 Pearson Education, Inc. All Rights Reserved Resistance in Respiratory Passageways Copyright © 2025 Pearson Education, Inc. All Rights Reserved Clinical—Homeostatic Imbalance: Asthma Copyright © 2025 Pearson Education, Inc. All Rights Reserved Label the regions of expiration and inspiration. Copyright © 2025 Pearson Education, Inc. All Rights Reserved Where would these pressures be measured? Atmospheric pressure Interpulmonary pressure Interpleural pressure Transpulmonary pressure Copyright © 2025 Pearson Education, Inc. All Rights Reserved Pulmonary Volumes and Capacities Copyright © 2025 Pearson Education, Inc. All Rights Reserved IP2: Lung Volumes and Capacities Click here to view ADA compliant Animation: Lung Volumes and Capacities https://mediaplayer.pearsoncmg.com/assets/sci-ip2-pv-lung-volumes-and-capacities Copyright © 2025 Pearson Education, Inc. All Rights Reserved Effects of Breathing Rate and Depth on Alveolar Ventilation of Three Hypothetical Patients Copyright © 2025 Pearson Education, Inc. All Rights Reserved Pulmonary Gas Exchange Three factors influence pulmonary gas exchange (diffusion of O2 and CO2 across respiratory membrane): – Partial pressure gradients and gas solubilities – Thickness and surface area of the respiratory membrane – Ventilation-perfusion coupling: matching alveolar ventilation with pulmonary blood perfusion Partial pressure gradients and gas solubilities – Steep partial pressure gradient for O ( P ) exists between blood 2 O2 and lungs ▪ Venous blood PO  40 mm Hg 2 ▪ Alveolar PO 104 mm Hg 2 Copyright © 2025 Pearson Education, Inc. All Rights Reserved Comparison of Gas Partial Pressures and Approximate Percentages in the Atmosphere and in the Alveoli Copyright © 2025 Pearson Education, Inc. All Rights Reserved Pulmonary Gas Exchange – Large PO (64 mm Hg) drives diffusion of oxygen into blood 2 ▪ Equilibrium is reached across respiratory membrane in 0.25 seconds ▪ RBC has 0.75 seconds to travel from start to end of pulmonary capillary – Ensures full oxygenation even if velocity of blood flow increases 3 Copyright © 2025 Pearson Education, Inc. All Rights Reserved Pulmonary Gas Exchange Partial pressure gradients and gas solubilities (cont.) inued – Partial pressure gradient for CO2 ( PCO ) much smaller, only 5 mm Hg 2 ▪ Venous blood PCO  45 mm Hg 2 ▪ Alveolar PCO  40 mm Hg 2 – Though its P is much weaker, CO2 diffuses at nearly the same rate as oxygen because CO2 is 20  more soluble in plasma and alveolar fluid than O2 Thickness and surface area of the respiratory membrane – Respiratory membranes are very thin, only 0.5 to 1 m thick – Alveoli provide a huge total surface area, about 60  the surface area of the skin Copyright © 2025 Pearson Education, Inc. All Rights Reserved Partial Pressure Gradients Promoting Gas Movements in the Body Copyright © 2025 Pearson Education, Inc. All Rights Reserved Oxygenation of Blood in the Pulmonary Capillaries at Rest Copyright © 2025 Pearson Education, Inc. All Rights Reserved Clinical—Homeostatic Imbalance emphysema. Copyright © 2025 Pearson Education, Inc. All Rights Reserved Pulmonary Gas Exchange Ventilation-perfusion coupling – Ventilation (amount of gas reaching alveoli) and perfusion (amount of blood flowing through pulmonary capillaries) must be coupled for optimal, efficient gas exchange – Both controlled by local autoregulatory mechanisms ▪ Alveolar PO controls perfusion by changing arteriolar diameter 2 ▪ Alveolar PCO controls ventilation by changing bronchiolar 2 diameter Copyright © 2025 Pearson Education, Inc. All Rights Reserved Pulmonary Gas Exchange – Influence of local PO on perfusion 2 ▪ Changes in local alveolar PO cause changes in diameters 2 of local arterioles – If PO is high (from good ventilation), arterioles dilate to 2 increase perfusion – If PO is low (from poor ventilation), arterioles constrict 2 to decrease perfusion ▪ Directs blood to go to well ventilated alveoli, where O2 is high (and CO2 is low), so blood can pick up more oxygen (and remove more CO2 ) ▪ Opposite mechanism seen in systemic arterioles that dilate when oxygen is low and constrict when high Copyright © 2025 Pearson Education, Inc. All Rights Reserved Pulmonary Gas Exchange – Influence of local PCO on perfusion 2 ▪ Changes in local alveolar PCO cause changes in diameters 2 of local bronchioles – Where alveolar PCO is high, bronchioles dilate to 2 increase alveolar ventilation (allows elimination of CO2 more rapidly) – Where alveolar PCO is low, bronchioles constrict 2 – Balancing ventilation and perfusion ▪ Poor alveolar ventilation results in low alveolar PO (high PCO ), 2 2 causing pulmonary arterioles serving these alveoli to constrict (bronchioles dilate) Copyright © 2025 Pearson Education, Inc. All Rights Reserved Pulmonary Gas Exchange – Brings blood flow and air flow into closer physiological match ▪ Likewise, low alveolar PCO (high PO ) cause bronchioles 2 2 serving these alveoli to constrict (pulmonary arterioles dilate) ▪ Autoregulation synchronizes ventilation-perfusion; but it is never balanced for all alveoli because of: 1. Regional variations, due to effect of gravity on blood and air flow 2. Occasional (mucus) plugged alveolar ducts cause unventilated areas Copyright © 2025 Pearson Education, Inc. All Rights Reserved Ventilation-Perfusion Coupling Copyright © 2025 Pearson Education, Inc. All Rights Reserved Tissue Gas Exchange Involves capillary gas exchange in body tissues, where partial pressures and diffusion gradients are reversed compared to pulmonary gas exchange – Tissue PO is always lower than in arterial blood PO 2 2 (40 v s 100 mm Hg) er us ▪ O2 diffuses from blood to tissues until equilibrium is reached – Tissue PCO is always higher than arterial blood PCO 2 2 (45 v s 40 mm Hg) er us ▪ CO2 diffuses from tissues into blood until equilibrium is reached – Venous blood returning to heart has: ▪ PO of 40 mm Hg (after equilibrating with tissue PO ) 2 2 ▪ PCO2 of 45 mm Hg (after equilibrating with tissue PCO ) 2 Copyright © 2025 Pearson Education, Inc. All Rights Reserved Oxygen Transport (1 of 5) Molecular O is carried in blood in two ways: 2 – 1.5% is dissolved in plasma – 98.5% is loosely bound to hemoglobin (Hb) in RBCs Association of oxygen and hemoglobin – Each Hb composed of four polypeptide chains, each with an iron-containing heme group, so each Hb can transport four O2 molecules ▪ Binding (loading) of O2 to Hb forms oxyhemoglobin (HbO2 ) ▪ Release (unloading) of O2 from Hb forms reduced hemoglobin (HHb), or deoxyhemoglobin Copyright © 2025 Pearson Education, Inc. All Rights Reserved Oxygen Transport (2 of 5) Association of oxygen and hemoglobin (cont.) inued – Loading and unloading of O2 is facilitated by a change in shape of H b ▪ As O2 binds, Hb changes shape, increasing its affinity for O 2 ▪ As O is released, Hb shape change decreases its affinity for O2 2 – Hb fully saturated when all four heme groups carry O2 , partially saturated when one to three heme groups carry O2 – To ensure adequate oxygenation of blood and delivery of O2 to cells, rate of loading and unloading of O2 is influenced by the following factors:  PO 2  Temperature  Blood pH ▪ PCO2 ▪ Concentration of BPG Copyright © 2025 Pearson Education, Inc. All Rights Reserved Oxygen Transport (3 of 5) Influence of PO on hemoglobin saturation 2 – Local PO controls O2 loading and unloading from Hb 2 – Percent Hb saturation can be plotted against PO ,2 producing an S-shaped curve called the oxygen-hemoglobin dissociation curve – Arterial blood contains 20 ml of O2 per 100 ml blood (20 volume %) ▪ PO 100 mm Hg and Hb is 98% saturated 2 ▪ A larger PO (as in deep breathing) produces minimal increase in H b 2 saturation – Venous blood contains 15 ml of O2 per 100 ml blood (15 volume %) ▪ PO  40 mm Hg and Hb is still 75% saturated 2 ▪ Venous reserve: oxygen remaining in venous blood that can still be used Copyright © 2025 Pearson Education, Inc. All Rights Reserved The Oxygen-hemoglobin Dissociation Curve Copyright © 2025 Pearson Education, Inc. All Rights Reserved IP2: Tissue Oxygen Exchange Click here to view ADA compliant Animation: Tissue Oxygen Exchange https://mediaplayer.pearsoncmg.com/assets/sci-ip2-ote-systemic-oxygen-exchange Copyright © 2025 Pearson Education, Inc. All Rights Reserved The Oxygen-Hemoglobin Dissociation Curve (1 of 2) Focus Figure 22.2 The Oxygen-Hemoglobin Dissociation Curve. Copyright © 2025 Pearson Education, Inc. All Rights Reserved The Oxygen-Hemoglobin Dissociation Curve (2 of 2) Focus Figure 22.2 The Oxygen-Hemoglobin Dissociation Curve. Copyright © 2025 Pearson Education, Inc. All Rights Reserved Oxygen Transport (4 of 5) Influence of other factors on hemoglobin saturation – Temperature, H concentration, PCO , and BPG levels affect the shape and 2 therefore affinity of Hb for O2 – Increases in these factors reduce affinity of Hb for O2 ▪ Occurs in systemic capillaries (tissues) ▪ Enhances O2 unloading, shifting the O2 -Hb dissociation curve to the right – Note the lower saturation (higher dissociation) at any PO 2 – Decreases in these factors increase the affinity of Hb for O2 ▪ Occurs in pulmonary capillaries (lungs) ▪ Enhances O2 loading, shifting the O -Hb dissociation curve to the left 2 – Note the higher saturation at any PO 2 Copyright © 2025 Pearson Education, Inc. All Rights Reserved Effect of Temperature, PCO2 , and Blood pH on P sub C O 2, the Oxygen-Hemoglobin Dissociation Curve Figure 22.23 Effect of temperature, PCO2 , and blood pH on the oxygen-hemoglobin dissociation curve. Copyright © 2025 Pearson Education, Inc. All Rights Reserved Oxygen Transport (5 of 5) – Influence of other factors on hemoglobin saturation (cont.) inued ▪ RBCs produce BPG during glycolysis – Levels rise as temperature rises (and O2 levels fall) ▪ The more glucose and O2 cells consume to make ATP, the more heat and CO2 they release, increasing PCO and H in local capillary blood 2 – Increasing temperature directly and indirectly decreases H b affinity for O2 – Reduced affinity of Hb for O2 resulting from falling blood pH and rising PCO2 called the Bohr effect – These factors enhanced O2 unloading occurs where it is needed most Copyright © 2025 Pearson Education, Inc. All Rights Reserved Carbon Dioxide Transport (1 of 4) CO2 transported in blood in three forms: 1. Dissolved in plasma (7 to 10%), thus responsible for PCO2 2. Chemically bound to hemoglobin (just over 20%) ▪ CO2 binds to globin (not heme) of Hb, forming carbaminohemoglobin 3. As bicarbonate ions in plasma (about 70%) ▪ Formation of HCO3  in plasma involves CO2 combining with water to form carbonic acid (H2CO3 ), which quickly dissociates into HCO3 and H   ▪ Occurs primarily in RBCs, where enzyme carbonic anhydrase reversibly and rapidly catalyzes this reaction Copyright © 2025 Pearson Education, Inc. All Rights Reserved Carbon Dioxide Transport (2 of 4) In systemic capillaries, after HCO3  is created, it quickly diffuses from R BCs into plasma – Outrush of HCO3  from RBCs is balanced as Cl moves into RBCs from plasma ▪ Referred to as chloride shift In pulmonary capillaries, the processes occur in reverse – HCO3  moves into RBCs while Cl moves out of RBCs back into plasma – HCO3  binds with H to form H2CO3 – H2CO3 is split by carbonic anhydrase into CO2 and water – CO2 diffuses into alveoli Copyright © 2025 Pearson Education, Inc. All Rights Reserved Carbon Dioxide Transport (3 of 4) Haldane effect – Amount of CO2 transported in blood is affected by PO 2 – The lower the PO and Hb saturation, the more CO2 can be carried in 2 blood, called the Haldane effect – Reduced hemoglobin buffers H+ and forms carbaminohemoglobin more easily – Process encourages CO2 exchange at tissues and at lungs ▪ At tissues: – As CO2 enters blood, causes more O2 to dissociate from Hb (Bohr effect) – As Hb releases O2 , it more readily binds to CO (Haldane effect) 2 ▪ At lungs, situation is reversed Copyright © 2025 Pearson Education, Inc. All Rights Reserved Transport and Exchange of CO2 and O2 C O sub 2 and O sub 2 Copyright © 2025 Pearson Education, Inc. All Rights Reserved IP2: Carbon Dioxide Transport and Exchange: Summary Click here to view ADA compliant Animation: Carbon Dioxide Transport and Exchange: Summary https://mediaplayer.pearsoncmg.com/assets/sci-ip2-cdte-summary Copyright © 2025 Pearson Education, Inc. All Rights Reserved Which Shift in the oxygen-hemoglobin dissociation cure would allow more oxygen delivery to tissues? Reasons: Reasons: Copyright © 2025 Pearson Education, Inc. All Rights Reserved Respiratory Centers in the Brain Stem Copyright © 2025 Pearson Education, Inc. All Rights Reserved Neural and Chemical Influences on Brain Stem Respiratory Centers Copyright © 2025 Pearson Education, Inc. All Rights Reserved Factors Influencing Breathing Rate and Depth Chemical factors – Arterial blood PCO , PO , and pH are most important factors affecting ventilation 2 2 – Fluctuations detected by chemoreceptors ▪ Central chemoreceptors located throughout brain stem, including medulla ▪ Peripheral chemoreceptors found in aortic arch and carotid arteries – Influence of PCO 2 ▪ Strongest influence on ventilation, most closely controlled ▪ If arterial PCO rises (hypercapnia), CO2 accumulates in CSF of brain and 2 joins with water to become carbonic acid, which releases H – Increased H (drop in pH) stimulates central chemoreceptors, which synapse with respiratory centers – VRG increases depth and rate of breathing, causing decrease in blood PCO 2 , causing reduction in H (rise in pH) back to normal levels Copyright © 2025 Pearson Education, Inc. All Rights Reserved Changes in PCO , Regulate Ventilation by a Negative P sub c o sub 2 2 Feedback Mechanism Copyright © 2025 Pearson Education, Inc. All Rights Reserved Factors Influencing Breathing Rate and Depth – Influence of PCO (cont.) 2 inued ▪ If arterial PCO falls abnormally low, respiration becomes slow and shallow 2 – Periods of apnea (breathing cessation) can occur until arterial PCO 2 rises again (stimulating respiratory centers) – Swimmers sometimes voluntarily hyperventilate so they can hold their breath longer Causes rapid/large drop in PCO , delaying stimulation of respiratory 2 centers until PCO levels build back up 2 Can cause dangerous drops in PO levels, leading to “black out” 2 Copyright © 2025 Pearson Education, Inc. All Rights Reserved Factors Influencing Breathing Rate and Depth (4 of 7) Chemical factors (cont.)inued – Influence of PO 2 ▪ Peripheral chemoreceptors detect fluctuations in arterial blood O2 levels ▪ Declining arterial PO normally has only slight effect on ventilation because of 2 huge O2 reservoir bound to Hb – Arterial PO must drop substantially (60 mm Hg or less) before it 2 becomes a major stimulus for ventilation – Influence of arterial pH ▪ pH can influence ventilation even with normal arterial PCO and PO 2 2 – Mediated by peripheral chemoreceptors ▪ Decreased pH may reflect CO2 retention, accumulation of lactic acid, or excess ketone bodies ▪ Respiratory centers attempt to raise pH by increasing ventilation, which increases CO2 removal from blood, lowering H levels Copyright © 2025 Pearson Education, Inc. All Rights Reserved Location and Innervation of the Peripheral Chemoreceptors in the Carotid and Aortic Bodies Copyright © 2025 Pearson Education, Inc. All Rights Reserved The Pathogenesis of COPD Copyright © 2025 Pearson Education, Inc. All Rights Reserved Copyright This work is protected by United States copyright laws and is provided solely for the use of instructors in teaching their courses and assessing student learning. Dissemination or sale of any part of this work (including on the World Wide Web) will destroy the integrity of the work and is not permitted. The work and materials from it should never be made available to students except by instructors using the accompanying text in their classes. All recipients of this work are expected to abide by these restrictions and to honor the intended pedagogical purposes and the needs of other instructors who rely on these materials. Copyright © 2025 Pearson Education, Inc. All Rights Reserved