Blood blood clotting in a transparent container. When blood is drawn in a glass container and left undisturbed for about an hour, four different layers can be seen. A dark clot forms at the bottom (the "black bile"). Above the clot is a layer of red blood cells (the "blood"). Above this is a whitish layer of white blood cells (the "phlegm"). The top layer is clear yellow serum (the "yellow bile"). The ABO blood group system was discovered in the year 1900 by Karl Landsteiner. Jan Janský is credited with the first classification of blood into the four types (A,
Angiocrine growth factors Angiocrine growth factors Angiocrine growth factors are molecules found in blood vessels' endothelial cells that can stimulate organ-specific repair activities in damaged or diseased organs. Endothelial cells possess tissue-specific genes that code for unique growth factors, adhesion molecules and factors regulating metabolism. The discovery emerged after the entirety of active genes in endothelial cells was decoded, resulting in an atlas of organ-specific blood vessel cells. The atlas documented hundreds of already-known genes that had never been associated with these cells. Organs dictate the structure and function of their own blood vessels, including the repair molecules they secrete. Each organ produces