Key Points. 1  Megaloblasts are large nucleated RBC precursors with noncondensed chromatin. 2  The most common causes of megaloblastic, macrocytic anemia are deficiency or defective utilization of vitamin B12 or folate. 3  Do CBC, RBC indices, reticulocyte count, and peripheral smear.
vein. 1. Any of the blood vessels that carry blood toward the heart. Veins are thin-walled and contain valves that prevent the backflow of blood. All veins except the pulmonary vein (which returns to the heart from the lungs) carry blood having low levels of oxygen. 2.
vein (vÄn) n. 1. a. Anatomy Any of the membranous tubes that form a branching system and carry blood to the heart from the cells, tissues, and organs of the body. b. A blood vessel of any kind; a vein or artery: felt the blood pounding in her veins.