l>Chapter 17

Chapter 17 - respiratory System: GasExchange and also Regulation that Breathing

Pulmonary Circulation The cell of the human body consume an median 250 ml of oxygen per minute and produce about 200 ml of carbon dioxide per minute. The proportion of the carbon dioxide produced over the oxygen spend is called the respiratory quotient. Hence, the median respiratory quotient is 0.8.

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The figure below illustrates the motions of oxygen and also carbon dioxide into and out that the lungs and tissue under relaxing conditions.
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The figure above illustrates just how oxygen and also carbon dioxide goes in between alveolar air and also blood throughout the respiratory membrane created of type I epithelial cells of the alveolar walls, endothelial cells of capillaries and the basement membranes sandwiched between them.
Diffusion the Gases Partial push of Gases The partial press of a gas is the relationship of pressure contributed by an separation, personal, instance gas to the full pressure of a mixture the gases. Partial push is discovered by multiplying: 1. Fractional concentration of a gas in a mixture by,
2. Total pressure exerted by a gas mixture.
The full pressure the air can be defined as the sum of the major gases uncovered in air
top top a molar basis air is 79% nitrogen and also 21% oxygen assuming zero humidity. Any humidity (water vapor) subtracts native the proportions that nitrogen and also oxygen. Carbon dioxide account for just 0.03% of the air molecules. at zero humidity and at sea level in air:
Pnitrogen
= 0.79 x 760 mm Hg = 600 mm Hg
Poxygen = 0.21 x 760 mm Hg = 160 mm Hg
Pcarbon dioxide = 0.0003 x 760 mm Hg = 0.23 mm Hg

Solubility that Gases in Liquids Gas molecules liquified in water have actually a specific partial pressure. As soon as a liquid and gas come right into contact, the concentration that gas molecule in the fluid is proportional to the partial press of the gas. In ~ a provided partial press the loved one concentration of different dissolved gases will differ based upon there various solubility in the liquid. For instance carbon dioxide is 20 times an ext soluble in blood 보다 oxygen.
Henry"s law describes this partnership with :
c
= Molar concentration the gas
P = Partial press of gas in atmosphere
k = Henry"s law constant (based top top gas and temperature)

as soon as containers of water space exposed to 100 mm Hg of pure oxygen or carbon dioxide, overtime the gas in the waiting equilibrates v the gas liquified in the fluid till they are both at 100 mm Hg. However, due to the fact that carbon dioxide dissolves much more readily in water, the concentration the the gas in the water is lot higher because that carbon dioxide 보다 for oxygen. This i do not care clear as soon as the calculations room made:
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Pressure at 37o C Concentration in Air Concentration in Water
Oxygen 100 mm Hg 5.2 mmole/liter 0.15 mmole/liter
Carbon dioxide 100 mm Hg 5.2 mmole/liter 3.0 mmole/liter

Exchange that Oxygen and also Carbon Dioxide Gases will certainly diffuse down their partial push gradients.
Gas Exchange in the lung return partial pressure of oxygen and also carbon dioxide in the environment are 160 mm Hg and also 0.23 mm Hg, respectively, in the alveoli the pressures space 100 mm Hg for oxygen and 40 mm Hg for carbon dioxide. This is because: 1. Exchanges the gas in between alveoli and also capillaries.
2. Mixing of atmospheric air v air of anatomic dead spaces.
3. Saturation that alveoli air v water vapor.
Deoxygenated blood beginning the pulmonary capillaries has a PO2 the 40 mm Hg and also PCO2 of 46 mm Hg. The gases diffuse under their concentration gradients and leave at the very same partial pressures as the gases in the alveoli (PO2 = 100 mm Hg and also PCO2 = 40 mm Hg).
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Diffusion is a an extremely rapid procedure taking about 0.25 seconds or in ~ the very first 33% of the capillary length in the alveoli. The rapidness that the rate of diffusion is because of the loved one thinness that the respiratory tract membrane.
Gas Exchange in Respiring Tissue when oxygenated blood enters the organization the PO2 is 100 mm Hg and also that of PCO2 is 40 mm Hg. The tissues have a reduced partial push of oxygen since of oxygen utilization and a greater carbon dioxide concentration because of carbon dioxide production.
The amount of PO2 and PCO2 in the venous blood counts on the metabolic activity that the tissue with the greater activity resulting in lower PO2 and higher PCO2.
The venous blood indigenous all parts of the human body returns to the appropriate side of the heart and mixes. The venous blood in the right atrium is therefore called mixed venous blood.At rest, the usual values are a PO2 of 40 mm Hg and PCO2 of 46 mm Hg.
components of Alveolar PO2 and PCO2 Alveolar PO2 and also PCO2 are identified by: 1. PO2 and PCO2 that motivated air.
2. Minute alveolar ventilation.
3. Prices of oxygen consumption and also carbon dioxide production.
usually PO2 and PCO2 of inspired air remains continuous and the alveolar partial pressures count on the last 2 factors. This is reflect by the fact that:
1. As soon as alveolar ventilation increases family member to oxygen consumption alveolar PO2 increases and also PCO2 decreases.
2. As soon as alveolar ventilation decreases loved one to oxygen consumption alveolar PO2 decreases and also PCO2 increases.
typical alveolar ventilation is readjusted to satisfy tissue demands. This proper increase in ventilation is referred to as hyperpnea. Hypoventilation occurs once alveolar ventilation is insufficient to meet tissue demand. Together a an effect PCO2 rises and PO2 decreases. Hyperventilation occurs when alveolar ventilation exceeds the needs of the tissue so that PO2 increases and also PCO2 decreases.
Transport of Gases in Blood Oxygen transport by Hemoglobin about 1.5% the the oxygen transported in the blood is dissolved in plasma or the cytosol the red blood cell while the remaining 98.5% is bound to hemoglobin. The oxygen bound to hemoglobin is in equilibrium v the oxygen dissolved in plasma i m sorry is concerned PO2. The oxygen is transported bound to the heme portions the the hemoglobin molecule. The binding the oxygen to hemoglobin relies upon the PO2 in the surrounding fluid. The higher the PO2 the greater the binding.
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due to the fact that there are 4 binding sites on the hemoglobin molecule the number of oxygen molecules on a hemoglobin molecule varieties from none come four. When four oxygen molecules room bound to the molecule, that is stated to it is in 100% saturated. At 100% saturation 1 gram that hemoglobin carries 1.34 ml of oxygen. The math:
Hemoglobin in blood 12-17gm/dL or an typical of 150 gm/L
Oxygen transferring capacity 1.34 ml/gram x 154 grams/liter ~ 200 ml/L
Cardiac calculation 5 liter/minute Blood offers 5 liter/minute x 200 ml O2 /L = 1000 ml O2/min.
Tissues require 250 ml O2 /min. Therefore, under resting conditions venous blood is tho 75% saturated. Anemia is a diminish in O2 carrying capacity of the blood. Through anemia, tissues may not be gave with the oxygen lock need and also fatigue occurs much more readily.
Hemoglobin Oxygen Disassociation Curve The curve that reflects percent saturation that hemoglobin as a role of PO2 is s-shaped (sigmoidal). The s-shaped nature that the curve have the right to be explained in the following way:
At low partial pressures the affinity of hemoglobin because that O2 is low. An rise in PO2 results in just a small increase in percent saturation.
together the PO2 increases the hemoglobin molecule acquires at least one molecule of O2. The binding that one molecule that O2 to hemoglobin reasons a conformational adjust in the hemoglobin the increases the affinity that the remaining subunits for oxygen. This is dubbed positive cooperativity. The optimistic cooperativity causes the steep part of the curve as the PO2 goes native 15 mm Hg to 60 mm Hg.
native 60 mm Hg come 80 mm Hg the slope of the curve decreases due to the fact that as the O2 binding to hemoglobin under binding sites become available. Above a PO2 the 80 mm Hg the steep of the curve becomes almost flat.
in ~ the PO2 that the systemic arteries of 100 mm Hg the hemoglobin is 98% saturated. In ~ the PO2 the the systemic veins the hemoglobin is 75% saturated. At rest the organization takes only about 25% the the O2 transported in the blood.
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The hemoglobin oxygen disassociation curve can change either come the left or come the right. Once the curve move to the right, the affinity the oxygen for hemoglobin decreases and oxygen deserve to be more easily unloaded. When the curve move to the left, the affinity the oxygen because that hemoglobin increases and oxygen have the right to be an ext easily loaded.

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factors Affecting Affinity the Hemoglobin because that O2 components that impact the affinity that hemoglobin for oxygen include:
1. Temperature A greater temperature cause a decrease in affinity. In much more active tissue with a higher temperature O2 unloads an ext easily.
2. PH Hydrogen ion increases (pH decreases) in much more active tissue. This decreases the affinity the hemoglobin by the Bohr effect which can be express in this equation