Structure of the aortic wall in the guinea pig and rat

ABSTRACT

The segmental microscopic architecture of the aortic wall of guinea pigs and albino rats was studied at the thoracicascending (T2-3), thoracic descending (T6-7) and abdominal infrarenal (L5-6) levels. Variables such as layer thickness,the number of elastic lamellae in the medial layer, and the diameter of the aortic segments were analyzedhistomorphometrically. The aortic wall of both species showed the usual elastic pattern, although variable amounts ofelastic lamellae, collagen fibers and smooth muscle cells were observed in the segmental analyses. A marked reductionin the number of elastic lamellae in the medial layer and in vascular diameter was observed in the abdominal aorticsegment of both species. Intimal folds, a gradual decrease in elastic lamellae from the ascending to the aorta abdominalaorta and a meshwork of adventitial collagen fibers and elastic lamellae were observed. These data indicate that thereare small but significant segmental variations in the aortic wall of these two species.