Vascular pattern of the guinea pig tympanic membrane.

The vascular organization of the guinea pig tympanic membrane was studied by light microscopy in India-ink-, colored-gelatin-, or horseradish peroxidase (HRP)-injected specimens. The ultrastructural localization of the vessels was examined by transmission electron microscopy in HRP-injected material. We found that the tympanic membrane is supplied by two arterial sources, the superior and inferior tympanic arteries, both of which arise from the posterior auricular artery. The superior tympanic artery gives off arterioles which, in the tympanic membrane, run centrifugally from the attachment of the manubrium, while the inferior tympanic artery emits arterioles which run centripetally from the tympanic annulus. Both sets of arterioles divide into capillaries and form a monolayered polygonal meshwork. The capillaries drain into venules which run between arterioles in the membrane and empty into either the superior tympanic vein located at the manubrium or the inferior tympanic vein at the annulus.