3 Gas Exchange Respiratory Systems alveoli elephant seals gills
4 Why do we need a respiratory system? Need O2 infor aerobic cellular respirationmake ATPNeed CO2 outwaste product from Krebs cyclefoodATPO2CO2
5 Gas exchange O2 & CO2 exchange between environment & cells need moist membraneneed high surface area
6 Optimizing gas exchange Why high surface area?maximizing rate of gas exchangeCO2 & O2 move across cell membrane by diffusionrate of diffusion proportional to surface areaWhy moist membranes?moisture maintains cell membrane structuregases diffuse only dissolved in watersmall intestineslarge intestinescapillariesmitochondriaHigh surface area? High surface area! Where have we heard that before?
7 Evolution of gas exchange structures Aquatic organismsexternal systems with lots of surface area exposed to aquatic environmentTerrestrialConstantly passing water across gillsCrayfish & lobsterspaddle-like appendages that drive a current of water over their gillsFishcreates current by taking water in through mouth, passes it through slits in pharynx, flows over the gills & exits the bodymoist internal respiratory tissues with lots of surface area
8 LungsExchange tissue: spongy texture, honeycombed with moist epitheliumWhy is this exchange with the environment RISKY?Lungs, like digestive system, are an entry point into the bodylungs are not in direct contact with other parts of the bodycirculatory system transports gases between lungs & rest of body
9 Mammalian respiratory systems Larynx (upper part of respiratory tract)Vocal cords (sound production)Trachea (windpipe)Bronchi (tube to lungs)BronchiolesAlveoli (air sacs)Diaphragm (breathing muscle)
10 Alveoli Gas exchange across thin epithelium of millions of alveoli total surface area in humans ~100 m2
11 Negative pressure breathing Breathing due to changing pressures in lungsair flows from higher pressure to lower pressurepulling air instead of pushing it
12 Take out April calendar Share plan with tablemates to get A or B on all April quizzes2) Change Sat, April 21 to Sat, April 14th3) Come up with a structure is ties to function example
13 Counter current exchange system Water carrying gas flows in one direction, blood flows in opposite directionLiving in water has both advantages & disadvantages as respiratory mediumkeep surface moistO2 concentrations in water are low, especially in warmer & saltier environmentsgills have to be very efficientventilationcounter current exchangeWhy does it work counter current? Adaptation!just keep swimming….
14 How counter current exchange works frontback70%40%100%15%water60%30%90%counter-current5%bloodwaterblood50%70%100%50%30%5%concurrentBlood & water flow in opposite directionsmaintains diffusion gradient over whole length of gill capillarymaximizing O2 transfer from water to blood
15 Gas Exchange on Land Advantages of terrestrial life Disadvantages air has many advantages over waterhigher concentration of O2O2 & CO2 diffuse much faster through airrespiratory surfaces exposed to air do not have to be ventilated as thoroughly as gillsair is much lighter than water & therefore much easier to pumpexpend less energy moving air in & outDisadvantageskeeping large respiratory surface moist causes high water lossreduce water loss by keeping lungs internalWhy don’t land animals use gills?
16 Terrestrial adaptations Tracheaeair tubes branching throughout bodygas exchanged by diffusion across moist cells lining terminal ends, not through open circulatory systemHow is this adaptive?No longer tied to living in or near water.Can support the metabolic demand of flightCan grow to larger sizes.
17 Mechanics of breathing Air enters nostrilsfiltered by hairs, warmed & humidifiedsampled for odorsPharynx glottis larynx (vocal cords) trachea (windpipe) bronchi bronchioles air sacs (alveoli)Epithelial lining covered by cilia & thin film of mucusmucus traps dust, pollen, particulatesbeating cilia move mucus upward to pharynx, where it is swallowed
18 Breathing and Homeostasis ATPHomeostasiskeeping the internal environment of the body balancedneed to balance O2 in and CO2 outneed to balance energy (ATP) productionExercisebreathe fasterneed more ATPbring in more O2 & remove more CO2Diseasepoor lung or heart function = breathe fasterneed to work harder to bring in O2 & remove CO2CO2O2
19 Hemoglobin Why use a carrier molecule? Reversibly binds O2 O2 not soluble enough in H2O for animal needsblood alone could not provide enough O2 to animal cellshemocyanin in insects = copper (bluish/greenish)hemoglobin in vertebrates = iron (reddish)Reversibly binds O2loading O2 at lungs or gills & unloading at cellsheme groupThe low solubility of oxygen in water is a fundamental problem for animals that rely on the circulatory systems for oxygen delivery.For example, a person exercising consumes almost 2 L of O2 per minute, but at normal body temperature and air pressure, only 4.5 mL of O2 can dissolve in a liter of blood in the lungs.If 80% of the dissolved O2 were delivered to the tissues (an unrealistically high percentage), the heart would need to pump 500 L of blood per minute — a ton every 2 minutes.cooperativity
20 Cooperativity in Hemoglobin Binding O2binding of O2 to 1st subunit causes shape change to other subunitsconformational changeincreasing attraction to O2Releasing O2when 1st subunit releases O2, causes shape change to other subunitslowers attraction to O2
21 Transporting CO2 in blood Dissolved in blood plasma as bicarbonate ionTissue cellsPlasmaCO2 dissolvesin plasmaCO2 combineswith HbCO2 + H2OH2CO3H+ + HCO3–HCO3–CO2CarbonicanhydraseCl–carbonic acidCO2 + H2O H2CO3bicarbonateH2CO3 H+ + HCO3–carbonic anhydrase
22 Releasing CO2 from blood at lungs Lower CO2 pressure at lungs allows CO2 to diffuse out of blood into lungsPlasmaLungs: AlveoliCO2 dissolvedin plasmaHCO3–Cl–CO2H2CO3Hemoglobin + CO2CO2 + H2OHCO3 – + H+
24 Exchange of materialsAnimal cells exchange material across their cell membranefuels for energynutrientsoxygenwaste (urea, CO2)If you are a 1-cell organism that’s easy!diffusionIf you are many-celled that’s harder
25 In circulation… What needs to be transported nutrients & fuels from digestive systemrespiratory gasesO2 & CO2 from & to gas exchange systems: lungs, gillsintracellular wastewaste products from cellswater, salts, nitrogenous wastes (urea)protective agentsimmune defenseswhite blood cells & antibodiesblood clotting agentsregulatory moleculeshormones
26 Circulatory systems All animals have: open closed circulatory fluid = “blood”tubes = blood vesselsmuscular pump = heartopenclosedhemolymphblood
27 Open circulatory system Taxonomyinvertebratesinsects, arthropods, mollusksStructureno separation between blood & interstitial fluidhemolymphThe fact that open and closed circulatory systems are each widespread among animals suggests that both offer advantages. For example, the lower hydrostatic pressures associated with open circulatory systems make them less costly than closed systems in terms of energy expenditure. Furthermore, because they lack an extensive system of blood vessels, open systems require less energy to build and maintain. And in some invertebrates, open circulatory systems serve a variety of other functions. For example, in molluscs and freshly molted aquatic arthropods, the open circulatory system functions as a hydrostatic skeleton in supporting the body.
28 Closed circulatory system closed system = higher pressuresTaxonomyinvertebratesearthworms, squid, octopusesvertebratesStructureblood confined to vessels & separate from interstitial fluid1 or more heartslarge vessels to smaller vesselsmaterial diffuses between blood vessels & interstitial fluidWhat advantages might be associated with closed circulatory systems? Closed systems, with their higher blood pressure, are more effective at transporting circulatory fluids to meet the high metabolic demands of the tissues and cells of larger and more active animals. For instance, among the molluscs, only the large and active squids and octopuses have closed circulatory systems. And although all arthropods have open circulatory systems, the larger crustaceans, such as the lobsters and crabs, have a more developed system of arteries and veins as well as an accessory pumping organ that helps maintain blood pressure. Closed circulatory systems are most highly developed in the vertebrates.
29 Vertebrate circulatory system Adaptations in closed systemnumber of heart chambers differs234high pressure & high O2 to bodylow pressure to bodylow O2 to bodyWhat’s the adaptive value of a 4 chamber heart?4 chamber heart is double pump = separates oxygen-rich & oxygen-poor blood; maintains high pressure
30 Circulation system evolution Fish: 2-chambered heart; single circuit of blood flowAmphibians: 3-chambered heart; 2 circuits of blood flow- pulmocutaneous (lungs and skin); systemic (some mixing)Mammals: 4-chambered heart; double circulation; complete separation between oxygen-rich and oxygen poor blood
31 Evolution of 4-chambered heart Selective forcesincrease body sizeprotection from predationbigger body = bigger stomach for herbivoresendothermycan colonize more habitatsflightdecrease predation & increase prey captureEffect of higher metabolic rategreater need for energy, fuels, O2, waste removalendothermic animals need 10x energyneed to deliver 10x fuel & O2 to cellsconvergent evolution
32 Vertebrate cardiovascular system Chambered heartatrium = receive bloodventricle = pump blood outBlood vesselsarteries = carry blood away from heartarteriolesveins = return blood to heartvenulescapillaries = thin wall, exchange / diffusioncapillary beds = networks of capillariesArteries, veins, and capillaries are the three main kinds of blood vessels, which in the human body have a total length of about 100,000 km.Notice that arteries and veins are distinguished by the direction in which they carry blood, not by the characteristics of the blood they contain. All arteries carry blood from the heart toward capillaries, and veins return blood to the heart from capillaries. A significant exception is the hepatic portal vein that carries blood from capillary beds in the digestive system to capillary beds in the liver. Blood flowing from the liver passes into the hepatic vein, which conducts blood to the heart.
34 Arteries: Built for high pressure pump thicker wallsprovide strength for high pressure pumping of bloodnarrower diameterelasticityelastic recoil helps maintain blood pressure even when heart relaxes
35 Veins: Built for low pressure flow thinner-walledwider diameterblood travels back to heart at low velocity & pressurelower pressuredistant from heartblood must flow by skeletal muscle contractions when we movesqueeze blood through veinsvalvesin larger veins one-way valves allow blood to flow only toward heartBlood flowstoward heartOpen valveClosed valve
36 Capillaries: Built for exchange very thin wallslack 2 outer wall layersonly endotheliumenhances exchange across capillarydiffusionexchange between blood & cells
37 Controlling blood flow to tissues Blood flow in capillaries controlled by pre-capillary sphincterssupply varies as blood is neededafter a meal, blood supply to digestive tract increasesduring strenuous exercise, blood is diverted from digestive tract to skeletal musclescapillaries in brain, heart, kidneys & liver usually filled to capacitysphincters opensphincters closed
38 Exchange across capillary walls LymphaticcapillaryFluid & solutes flows out of capillaries to tissues due to blood pressure“bulk flow”Interstitial fluid flows back into capillaries due to osmosisplasma proteins osmotic pressure in capillaryBP > OPBP < OPInterstitialfluidWhat about edema?About 85% of the fluid that leaves the blood at the arterial end of a capillary bed reenters from the interstitial fluid at the venous end, and the remaining 15% is eventually returned to the blood by the vessels of the lymphatic system.Bloodflow85% fluid returns to capillariesCapillary15% fluid returns via lymphArterioleVenule
39 BloodPlasma: liquid matrix of blood in which cells are suspended (90% water)Erythrocytes (RBCs): transport O2 via hemoglobinLeukocytes (WBCs): defense and immunityPlatelets: clottingStem cells: pluripotent cells in the red marrow of bonesBlood clotting: fibrinogen (inactive)/ fibrin (active); hemophilia; thrombus (clot)
40 Lymphatic system Parallel circulatory system transports white blood cellsdefending against infectioncollects interstitial fluid & returns to bloodmaintains volume & protein concentration of blooddrains into circulatory system near junction of vena cava & right atrium
41 Lymph system Production & transport of WBCs Traps foreign invaders lymph vessels(intertwined amongst blood vessels)lymph node
42 Mammalian heartto neck & head & armsCoronary arteries
43 Mammalian circulation systemicpulmonarysystemicWhat do blue vs. red areas represent?
46 Heart valves 4 valves in the heart Atrioventricular (AV) valve SL4 valves in the heartflaps of connective tissueprevent backflowAtrioventricular (AV) valvebetween atrium & ventriclekeeps blood from flowing back into atria when ventricles contract“lub”Semilunar valvesbetween ventricle & arteriesprevent backflow from arteries into ventricles while they are relaxing“dub”The heart sounds heard with a stethoscope are caused by the closing of the valves. (Even without a stethoscope, you can hear these sounds by pressing your ear tightly against the chest of a friend—a close friend.) The sound pattern is “lub–dup, lub–dup, lub–dup.” The first heart sound (“lub”) is created by the recoil of blood against the closed AV valves. The second sound (“dup”) is the recoil of blood against the semilunar valves.
47 Lub-dub, lub-dub Heart sounds Heart murmur closing of valves “Lub” recoil of blood against closed AV valves“Dub”recoil of blood against semilunar valvesHeart murmurdefect in valves causes hissing sound when stream of blood squirts backward through valveSLAVAV
49 Measurement of blood pressure High Blood Pressure (hypertension)if top number (systolic pumping) > 150if bottom number (diastolic filling) > 90
50 Cardiovascular disease Cardiovascular disease (>50% of all deaths)Heart attack- death of cardiac tissue due to coronary blockageStroke- death of nervous tissue in brain due to arterial blockageAtherosclerosis: arterial plaques depositsArteriosclerosis: plaque hardening by calcium depositsHypertension: high blood pressureHypercholesterolemia: LDL, HDL
51 DemonstrationsDemonstrate the path of an O2 molecule from the air to a knee cell as it travels through the respiration system and the circulatory system (travelling on a red blood cell). Make sure to include arteries, capillaries and/or veins.Demonstrate the path of an CO2 molecule from a knee cell to the air as it travels through the respiration system and the circulatory system (travelling on a red blood cell). Make sure to include arteries, capillaries and/or veins.
52 All members verbally involved 8 or more different props Creativity Scoring guideAll members verbally involved8 or more different propsCreativityAccurate descriptionKinesthetic