EM 299 Adrenal Cortex

Fenestrated Capillaries

Scanning electron micrograph (SEM) of the zona reticularis, the innermost layer of the adrenal cortex. The cells are arranged in anastomosing cords with all cells closely associated with fenestrated capillaries.

• Adrenal Cells (yellow): Numerous cell surface extensions project into the intercellular and pericapillary spaces
• Fenestrated Capillaries (blue): Endothelial cells contain fenestrations, or pores, 80 to 100 nm in diameter (typically with thin diaphragms)
  • Relatively few fenestrations are seen in this specimen
• Macrophages (purple): Irregularly shaped cells covered by many processes

These adrenal cells primarily produce androgens (steroid sex hormones) that are converted into more active forms by the gonads.

Courtesy of Pietro Motta, Department of Anatomy, University of Rome, Rome, Italy; Masaki Muto and Tsuneo Fujita, Department of Anatomy, Niigata University, Niigata, Japan.