Most of the anatomy will be covered on the next lab practical, but for this exam
ID: 77947 • Letter: M
Question
Most of the anatomy will be covered on the next lab practical, but for this exam, to lung development, bronchopulmonary segments, epithelial lining, and the alveoli - specifically the make-up of the respiratory membrane and types of cells Understand the mechanics of ventilation, including pleural membranes, pressures, actions, expiration actions. Understand tidal volume (TV) and anatomical dead space. Other lung volumes capacities will be covered in the Respiratory Physiology Lab exercise. Understand partial pressures, pressure gradients, external respiration, perfusion coupling, internal respiration. Understand O_2 transport via plasma and more importantly, via hemoglobin. Understand the three ways in which CO_2 is transported in the blood. Know that respiration is controlled centrally by the medulla and pons, but can also influenced by the hypothalamus and cerebral cortex. Understand that CO_2 is the most influential of the chemical factors affectingExplanation / Answer
Answer 5: O2 is transported through the blood in two ways, namely, through plasma and hemoglobin. The diffusion of oxygen in plasma depends on the partial pressure of oxygen (PO2) at the site within the body. In the alveolar air, PO2 is almost 100 mm Hg and so diffusion of oxygen is very high. In the venous blood PO2 is low, around 40mm Hg, and so the diffusion of oxygen is poor.
Most of the oxygen is transported by binding to the heme sites of hemoglobin. This binding is also dependent on various factors like the PO2 and pH due to H+ and CO2. There are total four heme sites on hemoglobin and when all four are bound to oxygen atoms they are said to be saturated. The saturation of hemoglobin is maximum in the lungs where the PO2 is high. When it reaches the tissues and muscles that have increased levels of H+ due to physical activity, lower levels of PO2 and higher levels of PCO2, the affinity of hemoglobin for oxygen decreases and it leaves the oxygen, which is taken up by the the tissues and muscles.
Answer 6: CO2 is transported through the blood in three ways, namely, through direct dissolution into the blood, binding to hemoglobin and as bicarbonate ion.
As compared to oxygen, CO2 is more soluble in blood and around 5-7% of it is dissolved directly in the plasma. Another 10% of CO2 is transported by binding to plasma proteins or hemoglobin by forming carbaminohemoglobin. This binding is reversible; so, when CO2 rich blood reaches the lungs the CO2 dissociates from the blood and leaves the body. The rest, that is 85% of CO2 and a majority of it, is transported by the bicarbonate buffer system. The enzyme carbonic anhydrase (CA) converts CO2 to carbonic acid, H2CO3. However, H2CO3 is an unstable molecule and so dissociates into HCO3- and H+. The H+ ions bind to the hemoglobin and the HCO3- move into the liquid component of blood in exchange of Cl- ions. When the blood reaches the lungs, all these steps reverse. HCO3- leaves Cl- and enters the red blood cells, H+ leaves hemoglobin and combines with HCO3- to form carbonic acid and carbonic acid is reconverted to CO2 by carbon anhydrase. CO2 formed is then expelled at exhalation.
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