Low magnification image of a section through the connective tissue of the
lip, showing a small artery (upper right) and its accompanying vein
(lower left), surrounded by connective tissue. Note the relationship between
the diameter of the lumen and the thickness of the wall of the two vessels.
The wall of the artery is relatively thick compared to the diameter of the
lumen, whereas the wall of the vein is relatively thin compared to the diameter
of the lumen.
