Endocrine gland
The adrenal glands are located above the kidneys in humans and in front of the kidneys in other animals. The adrenal glands produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. It controls the behaviour during crisis and emotional situations. It stimulates the heart and its conducting tissues and metabolic processes.
Development of the endocrine system
The fetal adrenal cortex can be identified within four weeks of gestation. The adrenal cortex originates from the thickening of the intermediate mesoderm.
At five to six weeks of gestation, the mesonephros differentiates into a tissue known as the gonadal ridge. The gonadal ridge produces the steroidogenic cells for both the gonads and the adrenal cortex. The adrenal medulla is derived from ectodermal cells. Cells that will become adrenal tissue move retroperitoneally to the upper portion of the mesonephros. At seven weeks of gestation, the adrenal cells are joined by sympathetic cells that originate from the neural crest to form the adrenal medulla. At the end of the eighth week, the adrenal glands have been encapsulated and have formed a distinct organ above the developing kidneys. At birth, the adrenal glands weight approximately eight to nine grams (twice that of the adult adrenal glands) and are 0.5% of the total body weight. At 25 weeks, the adult adrenal cortex zone develops and is responsible for the primary synthesis of steroids during the early postnatal weeks.