A small pool of stem cells replenishes the human body with about 200 billion new blood cells daily. But the elaborate circuitry that determines if a cell will develop into a T cell, red blood cell, or one of the nine or more other blood cell types remains largely unknown. A research team led by scientists from the Broad Institute and Brigham and Women’s Hospital has taken a systematic approach to help decipher this circuitry, compiling a comprehensive catalog of the factors that determine a blood cell’s fate. Their work appears in the January 21 issue of Cell.
The impedance of extremeeties such as fingers, arms and legs changes with the blood flow in and out, so this provides another method for plethysmography.
The arterial pulse wave has a very low amplitude and is superimposed on the venous blood volume changes. Pulse wave measurements are possible in many locations including the head (this measurement is called rheoencephalography). Pulse waves can also be measured in the fingers and toes with photoplethysmography.
