The adrenal gland consists of two distinct endocrine organs - outer cortex derived from mesoderm, and inner medulla derived from neuroectoderm. The cortex makes up 90% of the gland and is grossly yellow due to lipid content. Both compartments are enclosed in a common connective tissue capsule. The adrenal cortex is divided into three zones which are regulated by the ACTH. They are (from capsule inwards) : zona glomerulosa, zona fasciculata, and zona reticularis. They are clearly seen in this low power image. The adrenal cortex synthesizes several corticosteroid hormones.