SEM of RBC'c, partially frozen-hydrated from capillary smear, echinocyte showing projections. Echinocyte, in human biology and medicine, refers to a form of red blood cell that has an abnormal cell membrane characterized by many small, evenly spaced thorny projections. A more common term for these cells is burr cells. Red blood cells (RBCs), also called erythrocytes, are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen (O2) to the body tissues - via blood flow through the circulatory system. RBCs take up oxygen in the lungs or gills and release it into tissues while squeezing through the body's capillaries. Magnification @ 15,000s, 8x10 print.