Transport of O2 and CO2 in the blood

Transport of O2
For the most part, O2 is transported in the blood via binding to the heme moiety of hemoglobin. Hemoglobin is tetramer, whose four chains participate in cooperative binding to O2 depending on its partial pressure. Their affinity for O2 increases for greater pO2 values. Hemoglobin is fully saturated if pO2 = 100%; at pO2 = 50%, about half of the chains are bound to O2.

This is visualized by the dissociation curve.

Increased PCO2 decreases the pH, decreases the affinity of heme to O2, and shifts the curve right – Bohr effect. This helps release oxygen in regions where it is deficient.

you do need to talk about types - adult and fetal, and the different derivatives (methemoglobin etc)

''have to know that o2 is to some extent physically dissolved because that is impotant contributor to partial pressure registered by peripheral receptors, same for CO2. Also talk about hamburger effect - venous rbcs are bigger than arterial because ?!?!?!?!?!?''

You have chloride pulling in water, which is why venous RBCs are bigger

''Dissociation curve: talk about all 3 parts. The middle part is deeper - needed to work in body normally. Can read left to right or backwards.''

Transport of CO2
CO2 is produced in the tissues, diffuses in the blood. Inside erythrocytes, it reacts with water to form HCO3- and is released back into the plasma – this is the primary way how CO2 is transported.

Defects
Hypoxia: decreased delivery or use of O2 by tissue, when pO2 < 21 kPa

Multiple types:


 * Hypoxic: decreased decreased pO2 → decreased heme saturation. Due to higher altitude (lower pO2 in atmospheric), hypoventilation (can be mechanical - broken ribs), pathophysiological causes in regulatory centers, neuromuscular diseases, defects of diffusion, V/Q ratio, right-to-left shunts
 * Anaemic: reduced transport capacity (ex: hemoglobin problems or RBC problems).
 * Ischemic: due to circulatory problems (ex: artery obstruction, heart failure)
 * Histotoxic: due to cellular inability to take up or use O2 (ex: cyanide poisoning).

Hypercapnia: abnormal retention of CO2 leads to increased partial pressure (5.3-6.65 kPa). Can be due to decreased respiration or extension of dead space.


 * mild (5.3-6.65 kPa): causes stimulation of the respiratory center (therapeutic use: pneumoxid = mixture of oxygen + 2-5% CO2 )
 * around 10 kPa: CO2 narcosis. Respiratory depression; preceded by dyspnea, headache, and confusion
 * acute (over 12 kPa): significant respiratory depression, leads to coma and death