 The thin ascending limb is found in the medulla of the kidney, and the thick ascending limb can be divided into a part that is in the renal medulla and a part that is in the renal cortex.The ascending limb is much thicker than the descending limb.At the junction of the thick ascending limb and the distal convoluted tubule are a subset of 15-25 cells known as the macula densa that are part of renal autoregulation through the mechanism of tubuloglomerular feedback.