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Unformatted text preview: Lecture 22 Lecture Respiration Respiration 29 November 2010 29 Ventilation Ventilation Transition from Aquatic to Aerial Ventilation Ventilation Ventilation Ventilation Cycle in Hoplerythrinus Hoplerythrinus Ventilation Ventilation Ventilation Cycle in Hoplerythrinus Hoplerythrinus Ventilation Ventilation Advanced Lung in South American Lungfish (Protopterus) Ventilation Ventilation Ventilation Cycle in Frogs Lithobates catesbeianus Cycle Lithobates
After filling its buccal cavity with air, the bullfrog uses positive pressure to force the air into its lungs. Ventilation Ventilation Development of Respiration in L. catesbeianus Development catesbeianus
Note the difference in proportions of O2 and CO2 exchanged across the lungs versus the skin in adults. This difference is due to the different solubilities of O2 and CO2 in H2O. Ventilation Ventilation Ventilation in Birds Ventilation Ventilation Ventilation in Crocodilian Reptiles Reptiles (including birds) and mammals draw air into their lungs via a negative pressure pump (in contrast to the positive pressure pump of amphibians). Breathing in Mammals Breathing Breathing in Mammals Breathing Enormous total alveolar surface area provides adequate diffusion area for the exchange of respiratory gases between alveolar air and pulmonary capillary blood. Breathing in Mammals Breathing Breathing in Mammals Breathing
Inspiration: Contraction of respiratory muscles → → Increase in thoracic volume → → Decrease in IntraAlveolar Pressure → → Air flow into of the lung This is the causal sequence in pulmonary ventilation. Inspiration requires contraction of the diaphragm and external intercostal muscles. Expiration at rest does not require muscle not contraction. Forced expiration requires contraction of the internal intercostal muscles. Airflow (F) is a function of the pressure Airflow differences between the atmosphere (Patm) and the alveoli (Palv), divided by resistance to airflow (R). Air flows into the lungs when Palv < Patm Air flows out of the lungs when Palv > Patm Breathing in Mammals Breathing FRC > 4VT Alveolar Ventilation Alveolar
• Minute ventilation (ml/min) = VT x f
– f = frequency of respiration (~ 10-12 breaths/min) – At rest, minute ventilation = 5000 – 6000 ml/min At • Anatomic dead space is the volume of the Anatomic conducting airways conducting
– Anatomic dead space volume = 150 ml • Alveolar ventilation = (VT – Vd) x f – ml/min = (ml/breath) x (breaths/min) – Alveolar ventilation = 3500 – 4200 ml/min Alveolar Slow rate of replacement; Stabilization of the composition of alveolar air; Constant diffusion gradient for exchange of O2 and and diffusion CO2. Constant partial pressures of O2 CO and CO2 in pulmonary capillary blood. in Equilibration occurs in first Equilibration 1/3 of pulmonary capillary. Transport of Oxygen and Carbon Dioxide Transport The volumes of respiratory gases exchanged across the respiratory membrane in the lungs is equal to the volumes exchanged across the systemic capillaries. Transport of Transport Oxygen and Carbon Dioxide
Partial pressures of respiratory gases equilibrate between alveolar air and pulmonary capillary blood, and between cells of the body and systemic capillary blood. Partial pressures do not change within the arteries and within the veins. Oxygen-Hemoglobin Dissociation Curve Oxygen Transport of Oxygen Transport
0.3 ml of O2 is dissolved in 100 ml of arterial blood Dissolved O2 is a function of PO2 19.7 ml of O2 is covalently bound to hemoglobin in 100 ml of arterial blood Oxygen-Hemoglobin Dissociation Curve Oxygen (Oxyhemoglobin Dissociation Curve)
Deoxyhemoglobin Hb + O2 Hb.O2 Hb
Oxyhemoglobin (See Figure 23.5, page 589) Changes in Affinity of Hemoglobin For Oxygen Changes
Factors that cause right shift: ↑Temperature ↓ pH (Bohr effect) ↑CO2 (carbamino effect) In the transition from rest to exercise, temperature and CO2 production increase, and pH decreases. All of these changes facilitate delivery of O2 from blood into tissues. 50% Saturation 50% P50 Hb > P50 Mb Mb has higher O2 affinity than Hb P50 of hemoglobin Carbon Dioxide Transport Carbon Dissolved in plasma: 5-6% Bound to Hb: 6-8% Bound Hb Bicarbonate: 86-90%
Chloride shift Most bicarbonate transported in plasma Carbon Dioxide Transport Carbon Effect of Oxygen on Carbon Dioxide Transport: Haldane Effect Dioxide Oxygen decreases affinity of hemoglobin for carbon dioxide Summary of Oxygen Unloading and Summary Carbon Dioxide Loading in Tissue ...
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