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.
Wiktionary (0.00 / 0 votes) Rate this definition: vein (Noun). A blood vessel that transports blood from the capillaries back to the heart. vein (Noun). (used in plural veins) The entrails of a shrimp. vein (Noun). In leaves, a thickened portion of the leaf containing the vascular bundle. vein (Noun).
The correct way to define a vein is to say that a vein is a blood vessel that carries blood back to the heart. This is a simple but vital concept as whilst the pulmonary veins carry blood back to the heart, the blood they carry is oxygenated blood brought back to the heart from the lungs following gas exchange (carbon dioxide exchanged for oxygen).