Functions of the Respiratory System

81
Functions of the Respiratory Functions of the Respiratory System System 1. Gas Exchange 2. Regulation of blood pH 3. Voice production 4. Olfaction 5. Protection

description

Functions of the Respiratory System. Gas Exchange Regulation of blood pH Voice production Olfaction Protection. Tracheobronchial Tree. Conducting Zone Respiratory Zone Alveoli Type I pneumocytes Type II pneumocytes. Thoracic Wall & Muscles of Respiration. Thoracic wall - PowerPoint PPT Presentation

Transcript of Functions of the Respiratory System

Page 1: Functions of the Respiratory System

Functions of the Respiratory SystemFunctions of the Respiratory System

1. Gas Exchange

2. Regulation of blood pH

3. Voice production

4. Olfaction

5. Protection

Page 2: Functions of the Respiratory System

Tracheobronchial TreeTracheobronchial Tree

• Conducting Zone

• Respiratory Zone– Alveoli– Type I pneumocytes– Type II pneumocytes

Page 3: Functions of the Respiratory System
Page 4: Functions of the Respiratory System

Thoracic Wall & Muscles of RespirationThoracic Wall & Muscles of Respiration

• Thoracic wall– Thoracic vertebrae– Ribs– Sternum– Muscles

• Thoracic cavity– Thoracic wall & Diaphragm

Page 5: Functions of the Respiratory System

Thoracic Wall & Muscles of RespirationThoracic Wall & Muscles of Respiration

• Muscles of Respiration– Muscles of Inspiration

• Diaphragm• External intercostals• Pectoralis minor• Scalenes

– Muscles of Expiration• Abdominal muscles• Internal intercostals

Page 6: Functions of the Respiratory System

PleuraPleura

• Each lung is surrounded by a separate pleural cavity.

• Parietal pleura– Covers the inner layer of the throacic wall.

• Visceral pleura– Covers the surface of the lung.

• Pleural Cavity– Filled with pleural fluid.

Page 7: Functions of the Respiratory System
Page 8: Functions of the Respiratory System

Pleural FluidPleural Fluid

• Acts as lubricant allowing parietal and visceral

• Helps hold the parietal and visceral pleural membranes together.

Page 9: Functions of the Respiratory System

Blood SupplyBlood Supply

• Blood that has passed through the lungs and picked up oxygen is called oxygenated blood.

• Blood that has passed through the tissues and released some of its oxygen is called deoxygenated blood.

Page 10: Functions of the Respiratory System

VentilationVentilation

• Moving air in & out of the lungs.

• Flow of air into the lungs requires a pressure gradient from the outside of the body to the alveoli.

• If air needs the flow out of the lungs, a pressure gradient needs to exist in the other direction.

• F = (P1 – P2) / R

Page 11: Functions of the Respiratory System

Pressure & VolumePressure & Volume

• General gas law– P = nRT / V– n, R, and T are all constants, therefore pressure is

inversly proportional to volume.– Called Boyle’s Law.

Page 12: Functions of the Respiratory System

Airflow into & out of AlveoliAirflow into & out of Alveoli

• Inspiration– Initiated by contraction of diaphragm & external

intercostal muscles.– Result: increase in the size of the thorax.– Leads to a drop in alveolar pressure (Boyle’s

Law).

– Palv < PB

– Lung will expand.

Page 13: Functions of the Respiratory System
Page 14: Functions of the Respiratory System

Airflow into & out of AlveoliAirflow into & out of Alveoli

• Expiration– At the end of inspiration, the nerves to the

diaphragm and external intercostals stop firing.– These muscles relax.– Lungs & chest wall passively return to their

original dimensions.

Page 15: Functions of the Respiratory System

Airflow into & out of AlveoliAirflow into & out of Alveoli

• Expiration– As lungs decrease in size, the pressure increases

(Boyle’s Law).

– Palv > PB

– Air will flow from the alveoli to the atmosphere.

Page 16: Functions of the Respiratory System
Page 17: Functions of the Respiratory System

Forced ExpirationForced Expiration

• During exercise, the expiration of larger volumes is achieved by the contraction of the internal intercostals and the abdominal muscles.

Page 18: Functions of the Respiratory System
Page 19: Functions of the Respiratory System

Lung ComplianceLung Compliance

• Compliance = “stretchability”.

• Two determinants:– Compliance (stretchability of lung tissue)– Surface tension at the air-water interface of the

alveoli.

• Surfactant

Page 20: Functions of the Respiratory System

Respiratory Distress SyndromeRespiratory Distress Syndrome

• 2nd leading cause of death in premature infants.

• Normal maturation of surfactant-synthesizing cells is facilitated by hormones (particularly cortisol).

• Secretion of cortisol increases late in pregnancy (7th month).

Page 21: Functions of the Respiratory System

Respiratory Distress SyndromeRespiratory Distress Syndrome

• Premature babies lack mature type II alveolar cells due to low levels of cortisol.

• Treatment:– Administration of cortisol to mother.– Administer high pressure, oxygen-rich air to infant.– Exogenous source of surfactant to infant.

Page 22: Functions of the Respiratory System

Pleural PressurePleural Pressure

• Normally lower than the alveolar pressure.

• This helps keep the alveoli expanded.

• If this difference is lost the alveoli will collapse.

• e.g. Pneumothorax

Page 23: Functions of the Respiratory System
Page 24: Functions of the Respiratory System

Airway ResistanceAirway Resistance

• F = ΔP / R

• Factors that affect R:– Viscosity– Length– Radius

Page 25: Functions of the Respiratory System

Airway ResistanceAirway Resistance

• Factors that affect radius:– Transpulmonary pressure:

• Exerts a distending force.• Increases during inspiration.

– Lateral traction:• Connective tissue fibers pulling outwards.

– Mucus Accumulation

Page 26: Functions of the Respiratory System

Airway ResistanceAirway Resistance

• Factors that affect radius:– Parasympathetic nerves

• Constriction (ACh)

– Epinephrine• Dilates

– Histamine• Constricts

Page 27: Functions of the Respiratory System

AsthmaAsthma

• Attacks are characterized by smooth muscle contraction.

• Increases resistance impairing ventilation.

• More mucus may also be secreted.

• Main defect is inflammation of the airways.

• Cause of inflammation varies from person to person (virus, allergy, etc.).

Page 28: Functions of the Respiratory System

AsthmaAsthma

• Smooth muscle can be hyperresponsive to:– Exercise– Emotional stress– Cold air– Cigarette smoke– Irritants– Certain drugs

Page 29: Functions of the Respiratory System

AsthmaAsthma

• Therapy:– Anti-inflammatory drugs– Bronchodilators

Page 30: Functions of the Respiratory System

Chronic ObstructiveChronic ObstructivePulmonary DiseasePulmonary Disease

• Examples:– Emphysema & Chronic Bronchitis

• Emphysema– Destruction of alveolar walls.– Impairs gas exchange.– Destruction of elastic tissue also contributes to

airway collapse (obstruction).

Page 31: Functions of the Respiratory System

Chronic ObstructiveChronic ObstructivePulmonary DiseasePulmonary Disease

• Examples:– Emphysema & Chronic Bronchitis

• Chronic Bronchitis– Characterized by excessive mucus production in

bronchi.– Results in obstruction.

Page 32: Functions of the Respiratory System

Pulmonary Volumes & CapacitiesPulmonary Volumes & Capacities

• Spirometry is the process of measuring volumes of air moving in & out of the lungs.

• Important volumes– Tidal volume– Inspiratory reserve volume– Expiratory reserve volume– Residual volume

Page 33: Functions of the Respiratory System

Pulmonary Volumes & CapacitiesPulmonary Volumes & Capacities

• Spirometry is the process of measuring volumes of air moving in & out of the lungs.

• Important capacities (= sum of two or more lung volumes)

– Inspiratory capacity– Functional residual capacity– Vital capacity– Total lung capacity

Page 34: Functions of the Respiratory System
Page 35: Functions of the Respiratory System
Page 36: Functions of the Respiratory System

Pulmonary Volumes & CapacitiesPulmonary Volumes & Capacities

• Forced expiratory vital capacity is a simple clinical pulmonary test.

• Forced expiratory volume in one second(FEV1) is also an important diagnostic value.

• Airway obstructions (asthma, emphysema, chronic bronchitis, etc) cause a decreased FEV1.

Page 37: Functions of the Respiratory System

Alveolar VentilationAlveolar Ventilation

• Pulmonary Ventilation

• VP = f (VT)

• During inspiration, a portion of the inspired air fills the anatomic dead space before reaching the alveoli.

• This air is not available for gas exchange.

• VA = f (VT – VD)

Page 38: Functions of the Respiratory System

Principles of Gas ExchangePrinciples of Gas Exchange

• Dalton’s Law

• Partial Pressure

• Nitrogen (78.62%)

• Oxygen (20.84%)

• Sea level– Total atmospheric pressure = 760 mmHg– Partial pressure of nitrogen = 597.5 mmHg– Partial pressure of oxygen = 158.4 mmHg

Page 39: Functions of the Respiratory System

Inspired air vs. Alveolar airInspired air vs. Alveolar air

• Inspired air and alveolar air are different.– Air entering repiratory system is humidified.– Oxygen diffuses from alveoli into the blood.– Carbon dioxide diffuses from pulmonary

capillaries into the alveoli.– Air in the alveoli is only partially replaced with

atmospheric air during each inspiration.

Page 40: Functions of the Respiratory System

Diffusion of GasesDiffusion of GasesThrough Respiratory MembraneThrough Respiratory Membrane

• Influenced by:– Thickness of the membrane.– Diffusion coefficient of the gas.– Surface area of the membrane (70 m2).– Difference of the partial pressures of the gas on

either side of the membrane.

Page 41: Functions of the Respiratory System

Oxygen & Carbon DioxideOxygen & Carbon DioxideTransport in the BloodTransport in the Blood

• Oxygen– Po2 in alveoli is approx. 104 mmHg.

– Po2 in blood in pulmonary capillaries is approx.40 mmHg.

– Therefore, O2 diffuses from the alveoli to the pulmonary capillaries.

Page 42: Functions of the Respiratory System

Oxygen & Carbon DioxideOxygen & Carbon DioxideTransport in the BloodTransport in the Blood

• Oxygen– Equilibrium is achieved during the first third of the

pulmonary capillary beds.– Blood leaving the lungs in the pulmonary veins

has a Po2 of approx. 95 mmHg due to mixing with bronchial veins.

– At the tissues, the Po2 is close to 40 mmHg in the interstitial space and approx. 20 mmHg in the individual cells.

Page 43: Functions of the Respiratory System

Oxygen & Carbon DioxideOxygen & Carbon DioxideTransport in the BloodTransport in the Blood

• Carbon Dioxide– CO2 is continually produced during cellular

respiration.

– The intracellular Pco2 is approx. 46 mmHg

– Interstitial Pco2 is approx. 45 mmHg

– Arterial Pco2 is close to 40 mmHg

– Venous Pco2 is approx. 45 mmHg

– Because the Pco2 is approx. 40 mmHg in the alveoli, CO2 will diffuse into the alveoli.

Page 44: Functions of the Respiratory System
Page 45: Functions of the Respiratory System

Hemoglobin & Oxygen TransportHemoglobin & Oxygen Transport

• Approx. 98.5% of oxygen transported in the blood is combined with hemoglobin.

• The other 1.5% is dissolved in the plasma.

• Effect of Po2 on oxygen transport.

– Oxygen-hemoglobin dissociation curve

Page 46: Functions of the Respiratory System
Page 47: Functions of the Respiratory System
Page 48: Functions of the Respiratory System

Hemoglobin & Oxygen TransportHemoglobin & Oxygen Transport

• Effect of pH, Pco2, & temperature on oxygen transport.

– pH• Bohr Effect: Decreases in blood pH results in an

decreased ability of Hb to bind to oxygen (decreased affinity) and vice versa.

– Pco2

• Increases in Pco2 decreases the ability of Hb to bind to oxygen (decreased affinity) because of the effect of CO2 on pH and vice versa.

Page 49: Functions of the Respiratory System

Hemoglobin & Oxygen TransportHemoglobin & Oxygen Transport

• Effect of pH, Pco2, & temperature on oxygen transport.

– Temperature• Increases in temperature decreases the tendency for

oxygen to remain bound to Hb (decreased affinity).

Page 50: Functions of the Respiratory System
Page 51: Functions of the Respiratory System

Transport of Carbon DioxideTransport of Carbon Dioxide

• CO2 is transported in the blood in three different ways.

1. Dissolved in the plasma (7%)

2. Combined with hemoglobin (23%)

3. As bicarbonate ions (70%)

Page 52: Functions of the Respiratory System

Transport of Carbon DioxideTransport of Carbon Dioxide

• Dissolved in the plasma (7%)– CO2 simply dissolves in the plasma.

Page 53: Functions of the Respiratory System

Transport of Carbon DioxideTransport of Carbon Dioxide

• Combined with hemoglobin (23%)– CO2 combines with Hb in a reversible fashion.

– Many CO2 molecules can combine with one Hb molecule.

– Deoxyhemoglobin binds more readily to CO2 than oxyhemoglobin (Haldane effect).

Page 54: Functions of the Respiratory System

Transport of Carbon DioxideTransport of Carbon Dioxide

• As bicarbonate ions (70%)– More than half of the CO2 molecules react with

water (H2O) molecules inside the red blood cell.

CO2 + H20 H2CO3 HCO3- + H+

– As HCO3- accumulates it is exchanged for chloride

ions (Cl-) (chloride shift).

Page 55: Functions of the Respiratory System

Transport of Carbon DioxideTransport of Carbon Dioxide

• As bicarbonate ions (70%)

CO2 + H20 H2CO3 HCO3- + H+

– Hb binds to H+ ions which decreases the H+ concentration and therefore increases pH.

– Therefore Hb acts as a buffer.

Page 56: Functions of the Respiratory System

Transport of Carbon DioxideTransport of Carbon Dioxide

• As bicarbonate ions (70%)

CO2 + H20 H2CO3 HCO3- + H+

– The reverse occurs in the lungs.

Page 57: Functions of the Respiratory System
Page 58: Functions of the Respiratory System

Carbon Dioxide & Blood pHCarbon Dioxide & Blood pH

• CO2 can also bind with H2O in the plasma.

• Therefore, as plasma CO2 levels increase, hydrogen ion levels increase, and blood pH decreases.

• The respiratory system can regulate the pH of the blood by changing plasma CO2 levels.

• Hyperventilation decreases CO2 levels and hypoventilation increases CO2 levels.

Page 59: Functions of the Respiratory System

Rhythmic VentilationRhythmic Ventilation

• The basic rhythm of ventilation is generated and controlled by the medulla oblongata.

• Medullary respiratory center.– Two dorsal groups

• Primarily responsible for stimulating the contraction of the diaphragm.

– Two ventral groups• Primarily responsible for stimulating the external &

internal intercostals, and abdominal muscles.

Page 60: Functions of the Respiratory System
Page 61: Functions of the Respiratory System

Chemical Control of VentilationChemical Control of Ventilation

• Respiratory system maintains O2 & CO2 concentrations, and blood pH in their normal range.

• If these get out of their normal range they will have an effect on respiratory movements.

Page 62: Functions of the Respiratory System

ChemoreceptorsChemoreceptors

• Respond to hydrogen ion concentration (pH) or changes in Po2.

• Central chemoreceptors– Located in medulla oblongata

• Peripheral chemoreceptors– Located in aortic and carotid bodies

Page 63: Functions of the Respiratory System

Effect of pHEffect of pH

• Blood pH is closely linked to Pco2.

• Pco2 levels are monitored by medullary chemoreceptors.

• If Pco2 levels rise, blood pH decreases.

• Decreased blood pH values stimulates the respiratory center resulting in elimination of CO2.

• And vice versa…

Page 64: Functions of the Respiratory System
Page 65: Functions of the Respiratory System

Effect of COEffect of CO22

• Major regulator of respiration during rest and intense exercise.

• An increase in Pco2 of only 5 mmHg can increase ventilation by 100%!

• Hypercapnia = elevated Pco2

• Hypocapnia = lowered Pco2

• Hypercapnia and hypocapnia affect blood pH and thereby ventilation.

Page 66: Functions of the Respiratory System

Effect of OEffect of O22

• Affects respiration at a relatively minor level.

• Hypoxia = reduced Po2 levels

• Ventilation will increase, but only after a marked decrease (50% or more) in Po2.

• This is due to the oxygen-Hb saturation curve.

Page 67: Functions of the Respiratory System
Page 68: Functions of the Respiratory System

Hering-Breuer ReflexHering-Breuer Reflex

• Limits inspiration and prevents overinflation of lungs.

• Initiated by stretch receptors in the walls of bronchi and bronchioles.

• Inhibitory influence on the respiratory center.

Page 69: Functions of the Respiratory System

Effect of Exercise on VentilationEffect of Exercise on Ventilation

• Two phases– Abrupt increase in ventilation

• As much as 50%.• Primarily due to nervous system.

– Gradual increase in ventilation• Arterial Po2, Pco2, and pH values play a minor role.

• Nervous system also plays a role.• pH changes at anaerobic threshold.

Page 70: Functions of the Respiratory System

Respiratory Adaptations to ExerciseRespiratory Adaptations to Exercise

• Training:– Lead to more efficient cardiovascular and

respiratory systems.– Slight decrease in residual volume– Slight increase in vital capacity– Slight decrease in respiratory rate– Therefore, little change in minute ventilation.

Page 71: Functions of the Respiratory System

Respiratory Adaptations to ExerciseRespiratory Adaptations to Exercise

• Training:– However, minute ventilation is greatly increased

during exercise.• Untrained 120 l/min• Trained 150 l/min• Highly trained 180 l/min

Page 72: Functions of the Respiratory System

Ventilation in Steady-Rate ExerciseVentilation in Steady-Rate Exercise

• Light to moderate exercise, ventilation increases linearly with O2 consumption and CO2 production.

• Averages about 20 - 25 liters of air for every liter of oxygen consumed.

• Also known as ventilatory equivalent (VE/VO2)

Page 73: Functions of the Respiratory System

Ventilation in Steady-Rate ExerciseVentilation in Steady-Rate Exercise

• Healthy young adults maintain VE/VO2 of 25 during submax exercise up to approx 55% VO2max

• Children’s values average around 32.

Page 74: Functions of the Respiratory System

Pulmonary Ventilation During Graded Exercise

0

20

40

60

80

100

120

140

160

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Oxygen Consumption (l/min)

VE

(l/

min

)

Page 75: Functions of the Respiratory System

Ventilation in Non-Steady-Rate Ventilation in Non-Steady-Rate ExerciseExercise

• At progressively more intense levels of exercise beyond 55% VO2max, minute ventilation increases sharply.

• Ventilation increases more quickly than O2 consumption.

• Therefore, the ventilatory equivalent increases to values as high as 35 or 40 liters of air per liter of O2 consumed!

Page 76: Functions of the Respiratory System

Ventilatory Threshold (VVentilatory Threshold (VTT))

• VT describes the point at which pulmonary ventilation increases disproportionately with O2 consumption.

• Ventilation is no longer linked with O2 consumption.

• Increased ventilation is a result of increases in CO2 levels.

Page 77: Functions of the Respiratory System

Ventilatory Threshold (VVentilatory Threshold (VTT))

• Increased CO2 levels come from the buffering of lactate that accumulates from anaerobic glycolysis.

• Sodium bicarbonate is the buffer in the blood that buffers almost all of the lactate generated.

Lactic acid + NaHCO3 Na Lactate + H2CO3 H2O + CO2

Page 78: Functions of the Respiratory System

Respiratory Exchange Ratio (R)Respiratory Exchange Ratio (R)

• R is the ratio of CO2 produced and O2 consumed (VCO2/VO2).

• In steady-rate exercise the R value remains less than 1.00.

• Excessive CO2 production due to the buffering of lactate increases R to a value greater than 1.00.

Page 79: Functions of the Respiratory System

Pulmonary Ventilation During Graded Exercise

0

20

40

60

80

100

120

140

160

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Oxygen Consumption (l/min)

VE

(l/

min

)

Page 80: Functions of the Respiratory System

Pulmonary Ventilation During Graded Exercise

0

20

40

60

80

100

120

140

160

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Oxygen Consumption (l/min)

VE

(l/

min

)

Page 81: Functions of the Respiratory System

0

20

40

60

80

100

120

140

160

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Oxygen Consumption (l/min)

VE

(l/

min

)

Point of ventilatory threshold

Pulmonary Ventilation During Graded Exercise