The adrenal cortex is derived from which embryonic layer?

The adrenal cortex originates from the mesoderm, which is one of the three primary germ layers formed during embryonic development. The mesoderm is responsible for the development of various structures including muscles, bones, and connective tissues, as well as the cardiovascular system and certain glands.

Specifically, the adrenal cortex is part of the adrenal glands, which are located on top of each kidney. The development of the adrenal cortex begins early in embryogenesis and is crucial for the production of steroid hormones, such as cortisol and aldosterone, that are key regulators of metabolism and electrolyte balance in the body.

In contrast, the endoderm layer gives rise to internal structures, including the gastrointestinal tract and respiratory systems. The ectoderm primarily forms the skin and nervous system, while the neuroectoderm, a derivative of the ectoderm, specifically contributes to neural structures—including the brain and spinal cord but not the adrenal cortex. Therefore, the correct answer, identifying the adrenal cortex's mesodermal origin, reflects the developmental biology of this gland and its embryonic lineage.