Presentation on theme: "Respiration. Overview of gas exchange Lavoisier some 200 years ago described that animal life and burning both use O 2 and produce CO 2 his reward was."— Presentation transcript:
Overview of gas exchange Lavoisier some 200 years ago described that animal life and burning both use O 2 and produce CO 2 his reward was the guillotine in 1794 at the age of 51, as he also happened to be a tax-collector oxygen is taken up by diffusion – factors: surface, gradient, distance –in multicellular organisms surface/volume ratio decreases – respiratory organs must have large surface –distance should be minimal – thin, vulnerable barrier (0,5 - 15 ) –gradient should be large – respiratory movements, circulation, blood pigments in humans the respiratory surface is 50-100 m 2, rest of the body: 2 m 2 2/12 Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-1.
Anatomy of the lung I. 2 halves, 900-1000 g together, right half is somewhat larger, 40-50 % blood airways: –trachea – bronchi – bronchioles – alveolar ducts - alveoli –branching is always fork-like, crosssectional area of the two child bronchi is always larger - 22-23 branching –trachea and large bronchi (up to 1 mm) are supported by C-shaped, or irregular plates of cartilage –below 1 mm – bronchioles, connective tissue and muscle –function: warming, saturation with water vapor (exspiration in cold, dehydration in dry air) exchange of gases occurs in alveolar duct- alveolus (300 million) - surface 50-100 m 2 during evolution more and more septum in this part – surface increase emphysema – heavy smokers, trumpet players, glass blowers barrier: endothel, epithel, fibers 3/12 Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-21, 22.
Anatomy of the lung II. lungs are covered by the parietal and visceral pleuras thin fluid layer (20 ) couples the pleuras (pleuritis, pneumothorax, treatment of tuberculosis) the lung has a collapsing tendency (surface tension + elastic fibers) surfactant in alveoli (produced by epithelial cells: dipalmitoyl-phosphatidylcholine) respiratory muscles: –inspiration active, exspiration passive normally –intercostal muscles, T1-11, external: inspiration, internal: exspiration –diaphragm, C3-5 (n. phrenicus), at rest 1-2 cm movement: 500 ml, it can be 10 cm – damage of the spinal chord – jumping into shallow water! –abdominal wall (birthday candles, trumpet, always important above 40/minute) –accessory muscles – help inspiration in case of dispnoe 4/12 Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-31.
Lung volumes lung volumes can be measured by spirometers - spirogram anatomical and physiological dead space in swans and giraffes it is huge, large tidal volume tidal volume (500 ml) – anatomical dead space (150 ml) = 350 ml dilutes functional residual volume: steady O 2 concentration total ventilation: 14 x 350 ml = 4900 ml/minute Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-23. 5/12
Gas concentrations pO 2 (mmHg) pO 2 (%) pCO 2 (mmHg) pCO 2 (%) dry air16021.00.30.30.04 wet air 15019.70.30.30.04 alveolus102*13.4405.35.3 pulmonary artery405.35.3466.16.1 pulmonary vein100**13.2405.35.3 atmospheric pressure: 760 mmHg partial pressure of water vapor: 47 mmHg * effect of O 2 consumption, and anatomical dead space ** bronchiolar veins join here 6/12
Transport of O 2 I. physical solubility of O 2 is very low – 0.3/100 ml –rainbow trout lives only in fast mountain streams –when lakes (i.e. Balaton) warm up, fish can die (decomposing organic materials also use up O 2 ) –some fish (e.g. carp) can swallow air hemoglobin increases O 2 solubility 70-fold - 20 ml/100 ml oxyhemoglobin bright red, deoxyhemoglobin dark red-purple – see difference of venous and capillary blood during blood tests some invertebrates also have hemoglobin, others copper-containing hemocyanin (gastropods, arthropods) - extracellular affinity is chracterized by half staruration: Hgb: 30 mmHg, myoglobin 5 mmHg saturation of Hgb at 100 mmHg 97.4%, at 70 mmHg 94.1% - almost no change 7/12 Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-2.Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-3.
Transport of O 2 II. O 2 affinity of Hgb controls plasma concentration in the lung, high affinity is advantageous to keep plasma concentration low in the tissues, low affinity is advantageous to keep plasma concentration high affinity is decreased by: –increased temperature – active tissues are warmer –decrease of pH, increase of CO 2 - applies to active tissues and organs Bohrs-effect: H + uptake - affinity decreases, on the other hand uptake of O 2 increases acidity Haldanes-effect –organic phosphate ligands, e.g. ATP, GTP, 2,3- bisphosphoglycerate (BPG) BPG increases when O 2 decreases, or pH increases – in high mountains hyperventilation because of the low O 2 - pH increases, O 2 affinity increases, release of O 2 (desaturation) in the tissues is difficult - BPG restores affinity in stored blood, BPG is low – large volume transfusion of such blood – release of O 2 insufficient 8/12 Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-4.
Transport of O 2 III. O 2 affinity depends on the chain composition of the Hgb (4 peptid chains): in the fetus chain instead of - higher affinity methemoglobin contains Fe +++ ion instead of Fe ++ - cannot bind oxygen enzyme in red blood cells reduces iron back - nitrite and other inorganic ions increase Fe +++ amount either directly or by enzyme inhibition carboxyhemoglobin - CO binds to hemoglobin, affinity 200-fold, half-saturation at 0.1 mmHg – very dangerous (car exhaust) sickle cell anemia - valine/glutamate change in the chain – sickle shape, cannot pass through small capillaries - O 2 supply deteriorates – but defends against malaria 70-200 ml blood in the lung capillaries spread on 70 m 2 – fast gas exchange red blood cell stays for 750 ms in the capillary – saturated in 250 ms with O 2 – spare time! 9/12
Transport of CO 2 CO 2 is more soluble physically, but it also reacts with water transport mainly in the form of HCO 3 - (88- 90%), some as CO 2, H 2 CO 3, or CO 3 2-, some attached to proteins (carbamino) most of the released CO 2 from HCO 3 - (80%) CO 2 - H 2 CO 3 transformation is slow (several seconds) – carbonic anhydrase enzyme inside the red blood cell – speeds up reaction H+ ion is taken up by the deoxyhemoglobin that is weaker acid than the oxyhemoglobin HCO 3 - is exchanged for Cl - - facilitated diffusion with antiporter - Hamburger-shift opposite process in the lungs 10/12 Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-9. Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-11.
Regulation of breathing I. mammals use 5-10% of all energy consumption for the perfusion and ventilation of the lung closely matched processes to avoid wasted perfusion or ventilation alveolar hypoxia - local vasoconstriction in high mountains low O 2, general constriction – increased resistance – higher blood pressure in pulmonary artery – lung edema central regulation: inspiratory and expiratory neurons in the medulla – other functions as well, thus not a center –dorsomedial neurons, close to the nucl. tractus solitarius: inspiratory neurons –ventrolateral expiratory neurons in the pons pneumotaxic center: role is less clear descending effects: talking, singing, crying, laughing, etc. 11/12
Regulation of breathing II. output: motoneurons innervating the diaphragm and the intercostal muscles trigger for inspiration: –increase of CO 2 and H + - central receptors; no breathing below a certain CO 2 threshold –decrease of O 2, increase of CO 2 and H + - glomus caroticum and aorticum –in terrestrial animals CO 2 is regulated, in aquatic animals O 2 – its concentration changes more; if O 2 exchange is sufficient, than that of the more soluble CO 2 should be also OK trigger for expiration: stretch receptors in the lungs - Hering-Breuer reflex these information serve not only gas exchange and pH regulation, but such reflexes as swallowing, coughing, etc. 12/12 Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-49.