5Why do we need a respiratory system? respiration for respirationWhy do we need a respiratory system?foodATPO2CO2
6Gas exchange O2 & CO2 exchange between environment & cells Atmospheric Gases:Oxygen -- 21%Nitrogen -- 78%CO %Diffusion from area of [High partialpressure] to [Low partial pressure]
7Optimizing gas exchange Why high surface area?maximizing rate of gas exchangeCO2 & O2 move across cell membrane by diffusion [High concentration] to [Low concentration]rate 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?
8Gas exchange in many forms… one-celledamphibiansechinodermsciliainsectsfishmammalssize•water vs. land•endotherm vs. ectotherm
9Large & Thin Surface Area Respiratory Surfaces:Lung alveoli in mammalsGill lamellae in fishLeaf in PlantsCell membrane in ProtozoaSkin in Amphibians
10Evolution of gas exchange structures Aquatic organismsexternal systems with lots of surface area exposed to aquatic environmentConstantly 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 bodyTerrestrialmoist internal respiratory tissues with lots of surface area
11Gas Exchange in Water: Gills In fish, blood must pass through two capillary beds, the gill capillaries & systemic capillaries.When blood flows through a capillary bed, blood pressure — the motive force for circulation — drops substantially.Therefore, oxygen-rich blood leaving the gills flows to the systemic circulation quite slowly (although the process is aided by body movements during swimming).This constrains the delivery of oxygen to body tissues, and hence the maximum aerobic metabolic rate of fishes.
12Counter 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….
13How counter current exchange works frontback70%40%100%15%watercounter-currentbloodwaterconcurrentbloodBlood & water flow in opposite directionsmaintains diffusion gradient over whole length of gill capillarymaximizing O2 transfer from water to blood
14Gas 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?
15Terrestrial 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.
16Exchange tissue: spongy texture, honeycombed with moist epithelium LungsWhy 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
21oxygenated bloodair inair outair sac in lungsbody cellsdeoxygenated blood
22Features of Alveoli for efficient gas exchange large surface area to absorb oxygen.moist surface to allow oxygen to dissolve.thin lining to allow easy diffusion of gases.dense network of blood capillaries for easy gas exchange.
23Features of capillaries for efficient gas exchange dense network to carry CO2 and O2Large surface area to transport gasesLining is one cell thick so gases can pass through quickly and easily.
24AlveoliGas exchange across thin epithelium of millions of _________________total surface area in humans ~100 m2
25Negative pressure breathing Breathing due to changing pressures in lungsair flows from higher pressure to lower pressurepulling air instead of pushing it
27Mechanics 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
28Autonomic breathing control don’t want to have to think to breathe!Medulla sets rhythm & pons moderates itcoordinate respiratory, cardiovascular systems & metabolic demandsNerve sensors in walls of aorta & carotid arteries in neck detect O2 & CO2 in blood
29Medulla monitors blood Monitors CO2 level of blood & cerebrospinal fluid bathing the brainCO2 + H2O H2CO3 (carbonic acid) H+ + CO3-Higher CO2 concentration, increase in H+, lowering pHif pH decreases then increase depth & rate of breathing & excess CO2 is eliminated in exhaled air
30Breathing and Homeostasis ATPHomeostasiskeeping the internal environment of the body balancedExerciseneed more ATPbring in more O2 & remove more CO2Diseaseneed to work harder to bring in O2 & remove CO2CO2O2
31Diffusion of gasesConcentration gradient & pressure drives movement of gases into & out of blood at both lungs & body tissuecapillaries in lungscapillaries in muscleO2O2O2O2CO2CO2CO2CO2bloodlungsbloodbody
33Hemoglobin 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
35Cooperativity 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
36O2 dissociation curve for hemoglobin Bohr Shiftdrop in pH lowers affinity of Hb for O2active tissue (producing CO2) lowers blood pH & induces Hb to release more O2“Right Shift”Decreased Oxygen AffinityEffect of pH (CO2 concentration)PO2 (mm Hg)102030405060708090100120140More O2 delivered to tissuespH 7.60pH 7.20pH 7.40% oxyhemoglobin saturation
37O2 dissociation curve for hemoglobin Effect of TemperatureBohr Shiftincrease in temperature lowers affinity of Hb for O2active muscle produces heat“Right Shift”Decreased Oxygen AffinityPO2 (mm Hg)102030405060708090100120140More O2 delivered to tissues20°C43°C37°C% oxyhemoglobin saturation
38Transporting CO2 in blood Dissolved in blood plasma as “bicarbonate ion”Tissue cellsPlasmaCO2 dissolvesin plasmaCO2 combineswith HbCO2 + H2OH2CO3H+ + HCO3–HCO3–CO2CarbonicanhydraseCl–carbonic acidCO2 + H2O H2CO3bicarbonateH2CO3 H+ + HCO3–carbonic anhydrase
39Releasing 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+
40Adaptations for pregnancy Mother & fetus exchange O2 & CO2 across placental tissueWhy would mother’s Hb give up its O2 to baby’s Hb?
41Fetal hemoglobin (HbF) HbF has greater attraction to O2 than HbAlow % O2 by time blood reaches placentafetal Hb must be able to bind O2 with greater attraction than maternal Hb“Left Shift” Greater Oxygen AffinityBoth mother and fetus share a common blood supply. In particular, the fetus's blood supply is delivered via the umbilical vein from the placenta, which is anchored to the wall of the mother's uterus. As blood courses through the mother, oxygen is delivered to capillary beds for gas exchange, and by the time blood reaches the capillaries of the placenta, its oxygen saturation has decreased considerably. In order to recover enough oxygen to sustain itself, the fetus must be able to bind oxygen with a greater affinity than the mother.Fetal hemoglobin's affinity for oxygen is substantially greater than that of adult hemoglobin. Notably, the P50 value for fetal hemoglobin (i.e., the partial pressure of oxygen at which the protein is 50% saturated; lower values indicate greater affinity) is roughly 19 mmHg, whereas adult hemoglobin has a value of approximately 26.8 mmHg. As a result, the so-called "oxygen saturation curve", which plots percent saturation vs. pO2, is left-shifted for fetal hemoglobin in comparison to the same curve in adult hemoglobin.Hydroxyurea, used also as an anti-cancer drug, is a viable treatment for sickle cell anemia, as it promotes the production of fetal hemoglobin while inhibiting sickling.What is the adaptive advantage?2 alpha & 2 gamma units
42Tidal Volume = Amount of air inhaled and exhaled with each breath = 500ml Vital Capacity = Tidal volume during maximum inhalation and exhalation = 3.4 L (women) & 4.8 L (men)Residual Volume = Air that remains after a forced exhalation
43Lungs Can you? Label the internal structures of the lungs State the features of the alveoli which allow efficient gas exchangeExplain the role of diffusion in gas exchangeState the features of the capillary network that allow efficient gas exchange
44Smoking Cilia: Hair-like extensions lining the trachea Traps dust and particlesTraps microorganismsMucus secretionCigarette smoking prevents cilia from beating in wave-like pattern, moving the microorganisms upwardEffects ---- Bronchitis, Emphysema
45BronchitisInflammation of the lung airwaysMucus accumulation
46Emphysema Damage to alveoli in lungs, lose elasticity Reduced surface area for gas exchange