Smallest cardiac veins contribute to normal physiologic shunting of blood. As a consequence of the input of these vessels, blood in the left heart is less oxygenated than the blood found at the pulmonary capillary beds, albeit to a very small degree. The "openings of smallest cardiac veins" are located in the endocardium. Here the smallest cardiac veins return blood into the heart chambers from the capillary bed in the muscular cardiac wall, enabling a form of collateral circulation unique to the heart. Not every endocardial opening connects to the thebesian veins as some connect to the vessels of Wearn, which are arteries.
Anterior spinal veins Anterior spinal veins Anterior spinal veins (also known as anterior coronal veins and anterior median spinal veins) are veins that receive blood from the anterior spinal cord. There are two major components to venous draining: the intrinsic vessels which drain first, and the pial veins which drain second. Within the intrinsic vessels are a group of veins known as central veins. These are organized into individual comb-like repetitive structures that eventually fuse together once in the ventral median spinal fissure. After their fusion the group of central veins drains its combined contents into an anterior spinal vein. These veins can