The Fine Structure of Normal Rabbit Inferior Vena Cava

Summary Normal rabbit inferior vena cava has been examined with the electron microscope. Endothelium forms a continuous coating without pores or basement membrane. Occasional small vessels are present in the intima. Beneath the endothelium is a connective tissue space containing fibrils and amorphous ground substance. There is an internal elastic layer which is fenestrated and branching and rough on both endothelial and medial surfaces. With specific staining the vesicular structure of elastin is seen. The smooth muscle cells of the media are distinct entities; there is no conclusive evidence of their regular attachment either to the elastic lamina or to each other. The smooth muscle cells do not have a prominent basement membrane and are surrounded by an intercellular connective tissue space containing collagen fibrils and occasional small patches of elastin. The adventitia contains collagen fibres, blood vessels and nerve fibres.