![]() During stress, the adrenal medulla and zona fasciculata of the cortex can interact directly. Cortisol secretion from the zona fasciculata is controlled by circadian secretion of ACTH, the stress-induced stimulation of the HPA, and the negative feedback regulation of the HPA by cortisol. The adrenal cortex respond to the hypothalamic-pituitary axis (HPA) via corticotropic releasing factor (CRF) from the hypothalamus which causes the pituitary to secrete adrenocorticotropic hormone (ACTH) which acts on the zona fasciculata cells to produce cortisol. ![]() During stress cholesterol is converted to cortisol and the zona fasciculata decreases in size. Zona fasciculata cells, unlike the cells in the zona glomerulosa, possess the enzymes 17α-hydroxylase and 11β-hydroxylase, which promote the conversion of progesterone to cortisol. ![]() This layer has large, lipid-rich, polyhedral cells that store large amounts of cholesterol which is a precursor of cortisol. The middle layer of the adrenal cortex is the zona fasciculata which makes up about 80% of the mature adrenal cortex.
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