Calcification of the internal elastic lamina
of coronary arteries.
The MCA is a muscular artery and muscular arteries generally have the same basic composition as elastic arteries but the elastic tissue is reduced to a well-defined, fenestrated elastic sheet, the internal elastic lamina
, in the tunica intima, and a diffuse external elastic lamina in the tunica adventitia.
The perimeter and area of the lumen, the length of the internal elastic lamina and the area it enclosed, the length of the outer limit of the media and the area it enclosed were measured on each arterial section (Figure 1).
The total length of the internal elastic lamina is not altered by collapse of the artery after removal from the circulation.
Histopathologically, Fibromuscular Dysplasia (FMD) is heterogeneous with various degrees of collagen hyperplasia, internal elastic lamina
rupture and disorganization of the tunica media.
In all the slides, thickness of tunica intima was measured from luminal border upto internal elastic lamina; tunica media was measured between internal elastic lamina and external elastic lamina whereas thickness of tunica adventitia was measured from external elastic lamina up to its outermost boundary which could be easily identified.
The intima, as a function of age, consisted of splitting of the internal elastic lamina into two membranes between which smooth muscle fibers were seen, constituting the 'musculoelastic layer'.
Microscopy of the vessel wall showed medial disruption, fragmentation of the internal elastic lamina
, and transmural fibrosis (Figure 3, Movat pentachrome stain; I indicates intima; M, media; T, thrombus; and arrows, fragmented internal elastic lamina
Thickness of intima was measured at 400x magnification from endothelial cell surface to internal elastic lamina
, with the help of ocular micrometer which was calibrated against stage micrometer.
At 400X magnification, thickness of intima (in um) from endothelial margin to the internal elastic lamina
was measured at three areas of maximum intimal lesion11.