Ultrastructural characteristics of blood vessels in the infant and adult human cerebral cortex

Blood vessels in frontal and temporal cerebral cortex of adults and two infants aged 5 months and 5 years were studied by electron microscopy. The cells outside the endothelium were classified on their ultrastructural characteristics. Fibroblasts had prominent rough endoplasmic reticulum and few mitochondria in the cytoplasm. They were different from pericytes, which contained a prominent Golgi apparatus but only a few, isolated profiles of rough endoplasmic reticulum. Smooth muscle cells were distinguished from fibroblasts and pericytes by the presence of filaments and caveolae. Perivascular cells were characterised by the presence of lysosomes and granules of different sizes and electron densities, and were present at all ages studied. Plasma cells had abundant rough endoplasmic reticulum in the cytoplasm, and were present only in the 5-month-old infant cortex. Cortical vessel diameter increased with age.