juxta-glomerular complexa group of cells lining the efferent glomerular vessels of the kidney, that detect changes in blood volume. The cells secrete the enzyme RENIN when blood volume decreases, with subsequent release of ALDOSTERONE from the adrenal cortex, resulting in increased sodium retention. When the blood osmotic concentration increases, release of ADH occurs, and both these factors reverse the decrease in blood volume, an example of a FEEDBACK MECHANISM.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005