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Human blood with red blood cells, T cells (orange) and platelets (green)

Copyright Dennis Kunkel Microscopy, Inc.

Human blood with red blood cells, T cells and platelets 

This microscopic look at human blood reveals that nearly half of our blood is composed of red blood cells. These lozenge-shaped cells have the all-important role of delivering oxygen to our tissues. T cells (orange) are an essential part of the immune system. Platelets (green), the smallest blood cells, clump together into clots to stanch bleeding after an injury.

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This page last reviewed on August 30, 2017