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Gas exchange occurs in the lungs, whereby CO 2 is released from the blood, and oxygen is absorbed. The pulmonary vein returns the now oxygen-rich blood to the left atrium. [10] A separate circuit from the systemic circulation, the bronchial circulation supplies blood to the tissue of the larger airways of the lung.
The human body requires and regulates a very precise and specific balance of oxygen in the blood. Normal arterial blood oxygen saturation levels in humans are 96–100 percent. [1] If the level is below 90 percent, it is considered low and called hypoxemia. [2] Arterial blood oxygen levels below 80 percent may compromise organ function, such as ...
A variant called leghemoglobin serves to scavenge oxygen away from anaerobic systems such as the nitrogen-fixing nodules of leguminous plants, preventing oxygen poisoning. The medical condition hemoglobinemia , a form of anemia , is caused by intravascular hemolysis , in which hemoglobin leaks from red blood cells into the blood plasma .
Arterial blood carries oxygen from inhaled air to all of the cells of the body, and venous blood carries carbon dioxide, a waste product of metabolism by cells, to the lungs to be exhaled. However, one exception includes pulmonary arteries, which contain the most deoxygenated blood in the body, while the pulmonary veins contain oxygenated blood.
The lungs have a unique blood supply, receiving deoxygenated blood sent from the heart to receive oxygen (the pulmonary circulation) and a separate supply of oxygenated blood (the bronchial circulation). The tissue of the lungs can be affected by several respiratory diseases including pneumonia and lung cancer.
Cerebral blood flow (CBF) is the blood supply to the brain in a given period of time. [8] In an adult, CBF is typically 750 millilitres per minute or 15.8 ± 5.7% of the cardiac output. [9] This equates to an average perfusion of 50 to 54 millilitres of blood per 100 grams of brain tissue per minute. [10] [11] [12]
Perfusion occurs during heart contraction when the oxygenated blood is pumped into the arteries. The arteries deliver the blood to the capillary bed of the tissues, where the oxygen is removed by diffusion. [7] Oxygen in the alveoli is diffused down the concentration gradient and transported into the blood through the pulmonary capillaries.
In medicine, oxygen saturation refers to oxygenation, or when oxygen molecules (O 2) enter the tissues of the body. In this case blood is oxygenated in the lungs, where oxygen molecules travel from the air into the blood. Oxygen saturation ((O 2) sats) measures the percentage of hemoglobin binding sites in the bloodstream occupied by oxygen ...