The tubules of the nephron can be divided into the following segments- proximal convoluted tubule, proximal straight tubule, loop of Henle, macula densa, distal convoluted tubule, connecting segment, cortical collecting tubule, and medullary collecting tubule. The segmental subdivision of the nephron is based upon different permeability and transport characteristics that translate into important differences in function. Fluid filtered at the glomerulus is basically an ultrafiltrate of plasma. The hormones that influence renal function generally work by activating specific cellular proteins via phosphorylation or by inducing the synthesis of new proteins. A hormone can initiate these events by affecting turnover of adenyl cyclase, guanyl cyclase, and phophatidyl inositol or with steroid hormones, RNA transcription.