Adrenal gland. Light micrograph of a section through the adrenal gland. This image shows the junction of the adrenal cortex (the gland's outer part, upper, darker) and the adrenal medulla (lower). The region of the adrenal cortex seen is the zona reticularis, which is made of clumps of secretory cells (dark purple). It produces small amounts of steroid hormone precursors. The adrenal medulla consists of closely-packed clumps of cells that secrete the hormones noradrenaline and adrenaline; these are released in response to stress, and act to increase heart rate and promote the release of glucose into the bloodstream. Magnification: x160 at 35mm size.