 Distal straight tubule, which is also referred to as the thick ascending limb of the loop of Henle, is the continuation of the thin ascending limb. The distal straight tubule ascends through the medulla and enters the cortex in the medullary ray to reach the vicinity of its renal corpuscle of origin. The distal straight tubule then leaves the medullary ray and makes contact with the vascular pole of its parent renal corpuscle. At this point, the epithelial cells of the tubule adjacent to the afferent arteriole of the glomerulus are modified to form the macula densa. The distal tubule then leaves the region of the corpuscle and becomes the distal convoluted tubule.
 Distal convoluted tubule is less tortuous than the proximal convoluted tubule; thus, in a section showing the cortical labyrinth, there are fewer distal tubule profiles than proximal tubule profiles. At its termination, the distal convoluted tubule empties into a collecting duct that lies in the medullary ray via either an arched collecting tubule or a shorter tubule simply called the connecting tubule.
The loop of Henle forms the entire U-shaped portion of a nephron.
The proximal straight tubule, the thin descending limb with its hairpin turn, the thin ascending limb, and the distal straight tubule are collectively called the loop of Henle. In some nephrons, the thin descending and ascending segments are extremely short; therefore, the hairpin turn may be made by the distal straight tubule.
Types of Nephrons
Several types of nephrons are identified, based on the location of their renal corpuscles in the cortex (see Fig. 20.3):  Subcapsular nephrons or cortical nephrons have their renal corpuscles located in the outer part of the cortex. They have short loops of Henle, extending only into the outer medulla. They are typical of the nephrons described previously, wherein the hairpin turn occurs in the distal straight tubule.
 Juxtamedullary nephrons make up about one eighth of the total nephron count. Their renal corpuscles occur in proximity to the base of a medullary pyramid. They have long loops of Henle and long ascending thin segments that extend well into the inner region of the pyramid. These structural features are essential to the urine-concentrating mechanism, which is described in a further section.
 Intermediate nephrons or midcortical nephrons have their renal corpuscles in the midregion of the cortex. Their loops of Henle are of intermediate length.
The collecting tubules begin in the cortical labyrinth, as either connecting tubules or arched collecting tubules, and proceed to the medullary ray, where they join the collecting ducts. The collecting ducts within the cortex are referred to as cortical collecting ducts. When cortical collecting ducts reach the medulla, they are referred to as medullary collecting ducts. These ducts travel to the apex of the pyramid, where they merge into larger collecting ducts (up to 200 m), the papillary ducts (ducts of Bellini) that open into the minor calyx (see Fig. 20.4). The area on the papilla that contains the openings of these collecting ducts is called the area cribrosa.