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).
A vein is an elastic blood vessel that transports blood from various regions of the body to the heart. Veins can be categorized into four main types: pulmonary, systemic, superficial, and deep veins.Pulmonary veins carry oxygenated blood from the lungs to the left atrium of the heart.Systemic veins return deoxygenated blood from the rest of the body to the right atrium of the heart. Superficial veins are located close to the surface of the skin and are not located near a corresponding artery.Deep veins are located deep within muscle tissue and are typically located near a corresponding artery with the same name (for example coronary arteries and veins). vein can range in size from 1 millimeter to 1-1.5 centimeters in diameter. The smallest veins in the body are called venules. They receive blood from the arteries via the arterioles and capillaries.