Presentation on theme: "Why oxygen is import Most animals satisfy their energy requirement by oxidation of food, in the processes forming carbon dioxide and water Oxygen is most."— Presentation transcript:
1 Why oxygen is importMost animals satisfy their energy requirement by oxidation of food, in the processes forming carbon dioxide and waterOxygen is most abundant element in the earth’s crust (49.2%)In atmosphere Per liter water (150C, 1 atm)O % mlCO % mlN % mlArgon %Total 100%
2 Vacuum760 mmPressure exerted byatmospheric air aboveEarth’s surfacePressure atsea levelMercury (Hg)
3 Oxygen and carbon dioxide in physical environment Oxygen is added to atmosphere:Photosynthesis (dominant)Photodissociation of water vaporOxygen is removed from atmosphere:Living organism respirationOxidizing of organic matter, rocks, gases and fossil fuels
4 "Global warming" is a real phenomenon: Earth's temperature is increasing. TrueFalse
9 Oxygen and carbon dioxide in physical environment Solubility of oxygen decreases with increasing water temperature and salinityTemperature Fresh water Sea waterml O2/L water ml O2/L waterNormoxic water: 100% saturated with oxygenHypoxic water contains less oxygen than normoxic waterAnoxic water contains no dissolved oxygen
12 Transport O2 and CO2 in living systems Diffusion is common mechanism for transport both O2 and CO2 across the body surfaceTo maximize the rate of gas transferLarge respiratory surface areaSmall diffusion distance
14 The lungs contain many branching airways which collectively are known as the bronchial tree
15 • The trachea and all the bronchi have supporting cartilage which keeps the airways open. • Bronchioles lack cartilage and contain more smooth muscle in their walls than the bronchi, for airflow regulation• The airways from the nasal cavity through the terminal bronchioles are called the conducting zone.The air is moistened, warmed, and filtered as it flows through these passageways.
17 The pulmonary arteries carry blood which is low in oxygen from the heart to the lungs. • These blood vessels branch repeatedly, eventually forming dense networks of capillaries that completely surround each alveolus.• oxygen and carbon dioxide are exchanged between the air in the alveoli and the blood in the pulmonary capillaries.• Blood leaves the capillaries via the pulmonary veins, which transports the oxygenated blood out of the lungs and back to the heart.
18 Alveoli ~ 300 million air sacs. Large surface area (60 – 80 m2). Each alveolus is 1 cell layer thick.Total air barrier is 2 cells across (0.5 mm).3 types of cells:Alveolar type I:Structural cells.Alveolar type II:Secrete surfactant.
19 Ventilation Mechanical process to move air in and out of the lungs. O2 of air is higher in the lungs than in the blood, O2 diffuses from air to the blood.C02 moves from the blood to the air by diffusing down its concentration gradient.Gas exchange occurs entirely by diffusion.Diffusion is rapid because of the large surface area and the small diffusion distance.
20 1. simple epithelium cells 2. alveolar macrophages Three types of cells:1. simple epithelium cells2. alveolar macrophages3. surfactant-secreting cells• The wall of an alveolus is primarily composed of simple epithelium, or Type I cells. Gas exchange occurs easily across this very thin epithelium.• The alveolar macrophages, or dust cells, creep along the inner surface of the alveoli, removing debris and microbes.• The alveolus also contains scattered surfactant-secreting, or Type II, cells.
21 • Water in the fluid creates a surface tension. Surface tension is due to the strong attraction between water molecules at the surface of a liquid, which draws the water molecules closer together.• Surfactant, which is a mixture of phospholipids and lipoproteins, lowers the surface tension of the fluid by interfering with the attraction between the water molecules, preventing alveolar collapse.• Without surfactant, alveoli would have to be completely reinflated between breaths, which would take an enormous amount of energy.
22 • The wall of an alveolus and the wall of a capillary form the respiratory membrane, where gas exchange occurs.
24 Summary• The lungs contain the bronchial tree, the branching airways from the primary bronchi through the terminal bronchioles.• The respiratory zone of the lungs is the region containing alveoli, tiny thin-walled sacs where gas exchange occurs.• Oxygen and carbon dioxide diffuse between the alveoli and the pulmonary capillaries across the very thin respiratory membrane.
25 Three main factors:1.The surface area and structure of the respiratory membrane.2. Partial pressure gradients3. Matching alveolar airflow to pulmonary capillary blood flow
26 Atmosphere760 mm HgAtmospheric pressure (the pressureexerted by the weight of the gas in theatmosphere on objects on the Earth’ssurface—760 mm Hg at sea level)Airways (represents all airways collectively)Thoracic wall(represents entire thoracic cage)Intra-alveolar pressure (the pressure withinthe alveoli—760 mm Hg when equilibratedwith atmospheric pressure)760 mm HgPleural sac(space represents pleural cavity)756 mm HgLungs (represents all alveoli collectively)Intrapleural pressure (the pressure withinthe pleural sac—the pressure exertedoutside the lungs within the thoraciccavity, usually less than atmosphericpressure at 756 mm Hg)Fig , p.480
29 Accessory muscles of inspiration (contract only during forceful InternalintercostalmusclesSternocleidomastoidScalenusSternumRibsMusclesof activeexpiration(contract onlyduring activeexpiration)ExternalintercostalmusclesDiaphragmMajormuscles ofinspiration(contract everyinspiration;relaxationcauses passiveexpiration)AbdominalmusclesFig , p.482
30 Externalintercostalmuscles(relaxed)Elevatedrib cageElevation of ribs causes sternumto move upward and outward, whichincreases front-to-back dimensionof thoracic cavityContractionof externalintercostalmusclesSternumContraction ofdiaphragmDiaphragm(relaxed)Before inspirationInspirationLowering of diaphragm oncontraction increases verticaldimension of thoracic cavityContraction of external intercostalmuscles causes elevation of ribs,which increases side-to-sidedimension of thoracic cavity(a)Fig a, p.483
31 Contraction of internal intercostal muscles flattens ribs and sternum, further reducingside-to-side and front-to-back dimensionsof thoracic cavityRelaxationof externalintercostalmusclesContractionof internalintercostalmusclesRelaxation ofdiaphragmContraction ofabdominalmusclesPosition ofrelaxedabdominalmusclesPassive expirationActive expirationReturn of diaphragm, ribs, and sternumto resting position on relaxation ofinspiratory muscles restores thoraciccavity to preinspiratory sizeContraction of abdominal musclescauses diaphragm to be pushedupward, further reducing verticaldimension of thoracic cavity(b)(c)Fig bc, p.483
40 Factors affecting the exchange of oxygen and carbon dioxide during internal respiration: 1.The available surface area2. Partial pressure gradients.3. The rate of blood flow in a specific tissue.
41 • These gases are carried in several different forms: Oxygen and Carbon Dioxide Transportation• The blood transports oxygen and carbon dioxide between the lungs and other tissues throughout the body.• These gases are carried in several different forms:1. dissolved in the plasma2. chemically combined with hemoglobin3. converted into a different molecule
43 Hemoglobin and 02 Transport 280 million hemoglobin/ RBC.Each hemoglobin has 4 polypeptide chains and 4 hemes.Each heme has 1 atom iron that can combine with 1 molecule O2Each hemoglobin can combine with 4 molecule O2Combine reversibly with O2 depend on PO2
44 Hemoglobin's affinity for oxygen increases as its saturation increases the affinity of hemoglobin for oxygen decreases as its saturation decreases
45 Hemoglobin Oxyhemoglobin: Deoxyhemoglobin: Normal heme contains iron in the reduced form. Reduced form of iron can share electrons and bond with oxygen.Deoxyhemoglobin:When oxyhemoglobin dissociates to release oxygen, the heme iron is still in the reduced form.
46 Hemoglobin Hemoglobin production controlled by erythropoietin. Production stimulated by P02 delivery to kidneys.Loading/unloading depends:P02 of environment.Affinity between hemoglobin and 02.
47 Oxyhemoglobin Dissociation Curve Oxygen dissociation curve describes the relation between percent of saturation and the partial pressure of oxygen (S-shape, sigmoid)At high PO2, a large amount of O2 is boundAt low PO2, only small amount of O2 is bound
48 Hemoglobin saturation is determined by the partial pressure of oxygen S-shaped curve
51 Oxyhemoglobin Dissociation Curve Loading and unloading of 02.Steep portion of the curve, small changes in P02 produce large differences in % saturation (unload more 02).Decreased pH, increased temp., and increased 2,3 DPG, increase CO2 affinity of Hb for 02 decreases.Shift to the right greater unloading.Bohr effect
53 Muscle MyoglobinSlow-twitch skeletal fibers and cardiac muscle cells are rich in myoglobin.Has a higher affinity for 02 than hemoglobin.Acts as a “go-between” in the transfer of 02 from blood to the mitochondria within muscle cells.May also have an 02 storage function in cardiac muscles.
54 Human fetal hemoglobin contains g chains, which has a high O2 affinity than adult b hemoglobin In humans, the oxygen affinity of blood decrease for about 3 months after the birth
57 This reaction is catalyzed by the enzyme carbonic anhydrase.
58 C02 Transport C02 transported in the blood: HC03- (70%). Dissolved C02 (7%).Carbaminohemoglobin (23%).HCO3- is high in plasma than in erythrocytesCO2 enters and leaves the blood as molecular CO2 rather than HCO3-
59 Chloride Shift at Systemic Capillaries H20 + C H2C H+ + HC03-At the tissues, C02 diffuses into the RBC, reaction shifts to the right.Increased [HC03-] in RBC, HC03- diffuses into the plasma with assistance of band III protein.RBC becomes more +.Cl- diffuses in (Cl- shift).HbC02 formed, give off 02.
60 At Pulmonary Capillaries H20 + C H2C H+ + HC03-At the alveoli, C02 diffuses into the alveoli, reaction shifts to the left.Decreased [HC03-] in RBC, HC03- diffuses into the RBC.RBC becomes more -.Cl- diffuses out (Cl- shift).Hb02 formed, give off HbC02.
63 Summary• O2 is transported in two ways:• dissolved in plasma, and• bound to hemoglobin as oxyhemoglobin• The O2 saturation of hemoglobin is affected by:• PO2, pH , temperature, PCO2, and DPGCO2 is transported in three ways:• dissolved in plasma, bound to hemoglobin as carbaminohemoglobin, and converted to bicarbonate ionsOxygen loading facilitates carbon dioxide unloading from hemoglobin. This is known as the Haldane effect.• When the pH decreases, carbon dioxide loading facilitates oxygen unloading. The interaction between hemoglobin's affinity for oxygen and its affinity for hydrogen ions is called the Bohr effect.
64 Pons Pons Pneumotaxic center respiratory centers Apneustic center Pre-BötzingercomplexRespiratorycontrolcenters inbrain stemDorsal respiratorygroupMedullaryrespiratorycenterMedullaVentral respiratorygroupFig , p.513
65 + + Input from other areas–– some excitatory, some inhibitory Inspiratory neuronsin DRG(rhythmically firing)Medulla+Spinal cordPhrenic nerve+DiaphragmNot shown are intercostal nerves to external intercostal muscles.Fig , p.513