Intimal thickening of human femoral arteries with special regard to elastin, Part 1. Diffuse intimal thickening due to growth and age.

In infants, human femoral arteries display seam-like internal elastic lamina (IEL) covered with endothelium on the luminal side and with smooth muscle cells (SMC) on the medial side. At birth the growth of IEL is finished, correlated with a loss of microfibrils (MF) at the periphery. With the onset of the postnatal vessel growth the joints of IEL seem to be mechanically widened until they have the appearance of gaps with progressing age. After the age of 40 years there are often rod-like crystallites in the IEL, probably composed of cholesterol esters. A small first consecutive lamina (CL) can be seen already in childhood; it enlarges until the 3rd decade of life and is interpreted as a substitute to the "fragmented" IEL. After the 5th decade of life the first CL is arranged within the intima at a certain distance from the IEL and consisting of loosely arranged elastic fibrils. In very old arteries (beyond the 8th decade of life) gaps are rarely seen in the first CL. In individuals over the age of 30 years, the space between IEL and the first CL is occupied by smooth muscle cells (SMC) which are tightly packed. Additional CLs above the first CL can be found in elderly individuals, there CL obviously contribute to the intimal thickening. The ultrastructure of the elastic elements of the vessel wall and their possible function are discussed.