Distal convoluted tubule
The distal convoluted tubule (DCT) is a portion of kidney nephron between the loop of Henle and the collecting duct system. It is partly responsible for the regulation of potassium, sodium, calcium, and pH.
Physiology
The DCT regulates pH by absorbing bicarbonate and secreting protons (H+) into the filtrate. Sodium and potassium levels are controlled by secreting K+ and absorbing Na+.
Sodium absorption by the distal tubule is mediated by the hormone aldosterone. Increased levels of aldosterone cause increased sodium absorption, and vice versa.
The DCT also participates in calcium regulation by absorbing Ca2+ in response to parathyroid hormone.
Histology
Histologically, cells of the DCT can be differentiated from cells of the proximal convoluted tubule since:
