Week 6 Flashcards
Define gas exchange
diffusion of O2 and CO2 in lungs and in peripheral tissue. O2 will diffuse from alveoli into blood, CO2 will diffuse from blood into alveoli to be released into environment on exhalation.
Dalton’s law of partial pressures
- partial pressure of a gas in a mixture of gases is the pressure that gas would exert if it occupied the total volume of the mixture.
- Thus partial pressure is the total pressure multiplied by the fractional concentration of dry gas
Ficks Law of diffusion
-(V̇ x )=(D)(A)(ΔP)/ ΔX
Henry’s law
used to convert the partial pressure of gas in the liquid phase to the concentration of gas in the liquid phase
Transport of oxygen from the atmosphere to the tissues
Oxygen is breathed in through mouth/nose, travels down trachea where it is humidified, travels into the alveoli of the lungs, into the capillaries, into the pulmonary vein, to the left atrium, to the left ventricle, to the aorta, down arteries, into tissue capillaries, diffuses across capillaries into tissue.
normal values of oxygen in dry air, humidified air, alveoli, mixed venous blood, and systemic arterial blood
- Dry inspired air: 160
- Humidified tracheal air: 150
- Alveolar air: 100
- Mixed venous blood: 40
- Systemic arterial blood: 100
ways that oxygen can be carried in a solution
• Dissolved O2 -only 2% of total O2 in blood
-only form that produces partial pressure
• Bound to Hemoglobin -98% of total O2 in blood
-Hemoglobin has four subunits 2a and 2B each containing heme, and each subunit can carry one O2
variants of hemoglobin
- Methemoglobin: When the iron component of the heme moieties is in the ferric, or Fe 3+ ,state and does not bind O 2 . Caused by oxidation of Fe 2+ to Fe 3+by nitrites and sulfonamides as well as a congenitally when there is a deficiency of methemoglobin reductase
- Fetal hemoglobin (hemoglobin F, HbF): two β chains are replaced by γ chains . Allows for higher affinity for O 2 facilitating O 2movement from the mother to the fetus. HbF is the normal variant present in the fetus and is gradually replaced by hemoglobin A within the first year of life.
- Hemoglobin S.: abnormal variant of hemoglobin that causes sickle cell disease. α subunits are normal and the β subunits are abnormal. Forms sickle-shaped rods in the red blood cells, distorting the shape of the red blood cells which can result in occlusion of small blood vessels. The O 2 affinity of hemoglobin S is less than the O 2 affinity of hemoglobin A.
how combination of oxygen with hemoglobin influences the shape of the oxyhemoglobin dissociation curve
the curve increases in steepness because of increase in affinity for oxygen as each subunit of hemoglobin binds to oxygen (positive cooperation)
O 2 -binding capacity
maximum amount of O 2 that can be bound to hemoglobin per volume of blood,
Hemoglobin saturation
all 4 subunits are carrying an oxygen molecule
O 2 content
actual amount of O 2 per volume of blood
Mechanism for Oxygen loading and unloading
When the tissue needs the oxygen the hemoglobin will be triggered to be less tightly bound to the oxygen than when the tissue does not need the oxygen
Right shift
- decreased affinity of hemoglobin for O2 causing unloading of O2 in the tissues
- causes thalacemia: decreased saturation
Causes of right shift
○ Increases in P co 2: occurs with increase of metabolic activity in tissues increasing CO2 production
○ Decreases in pH: occurs with increase of metabolic activity in tissues producing H+ and decreasing pH. This then causes a decreased affinity of hemoglobin for O 2 ,
○ Increases in temperature: heat is produced by the working muscle causing more O 2 to be released to the tissue.
○ Increases in 2,3-diphosphoglycerate (2,3-DPG) concentration. 2,3-DPG is a byproduct of glycolysis in red blood cells that increases in hypoxic conditions. 2,3-DPG binds to the β chains of deoxyhemoglobin and reduces their affinity for O 2 causing delivery of O 2 to the tissues.
Causes of Left shift
increased affinity of hemoglobin for O 2 causing unloading of O 2 in the tissues to be more difficult
