Hematopoietic stem cell in bone marrow committed to produce erythrocyte- the red blood cells. Once mature these cells continuously egress out into general circulation to perform their normal function in the body. Bone marrow generally separated from peripheral blood via sinusoid membrane that has small pores in its endothelial layer. RBCs egress out through specific sites (pores) from endothelial layer. During maturation process RBCs lose its nucleus and became discoid shape. That imparts the greater deformability into them so they could easily squeeze out through marrow aperture. The egress of RBCs further accelerated as a result of humoral factors (releasing factors) i.e. stress, cytokines, chemokines, erythropoietin and proteolytic enzymes like GTPases.
Fatima Zafar*, Razia Iqbal, Muhammad Faheem Malik, Muhammad Irfan, Mubashar Hussain