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.
Artery: A vessel that carries blood high in oxygen content away from the heart to the farthest reaches of the body. Since blood in arteries is usually full of oxygen, the hemoglobin in the red blood cells is oxygenated.The resultant form of hemoglobin (oxyhemoglobin) is what makes arterial blood look bright red.y contrast, a vein is a blood vessel that carries blood low in oxygen content from the body back to the heart. The deoxygenated form of hemoglobin (deoxyhemoglobin) in venous blood makes it appear dark. Veins are part of the afferent wing of the circulatory system which returns blood to the heart.