to increase the surface area for reabsorbtion
Proximal tubule
At the proximal convoluted tubule, reabsorption of water, glucose, amino acids, and ions (such as sodium, potassium, and chloride) from the filtrate back into the bloodstream occurs. Waste products and toxins are also secreted into the tubule for excretion in the urine.
The largest volume of water reabsorption in the kidneys occurs in the proximal convoluted tubule. This is the first segment of the renal tubule where approximately 65-70% of the filtered water is reabsorbed back into the bloodstream.
The distal tubule
Previous answer on this page was "distal convoluted tubule". But answerer did not give any justification or references. Commonly-held opinion is that the DCT is the site of tubular drug secretion (e.g. penicillins), however, I've not seen any science to back this up. On the other hand, some recent studies point to drug transport in the proximal convoluted tubule via the OAT (organic anion transporter) family. See for example, Takeda et al. JPET 302:666-671. (http://dx.doi.org/10.1124/jpet.102.034330 has full text) --Dr.Dom
to increase the surface area for reabsorbtion
the three main portions of the renal tubule are the proximal convoluted tubule, the loop of henle, and the distal convoluted tubule. the proximal convoluted tubule is the first portion. The proximal (convulated) tubule.
The distal convoluted tubule or the collecting tube.
Proximal convoluted tubule, Loop of henle and Distal convoluted tubule.
Proximal tubule
Proximal convoluted tubules have brush borders or microvilli on the inner edge of the tubule. Distal convoluted tubules do not have this structure.
The proximal convoluted tubule drains into the loop of Henle.
The parts of a nephron in order are the renal corpuscle (glomerulus and Bowman's capsule), proximal convoluted tubule, loop of Henle (descending and ascending limbs), distal convoluted tubule, and collecting duct.
The proximal convoluted tubule is closest to the glomerular capsule. The distal convoluted tubule is farther away.
The proximal convoluted tubule
In the proximal convoluted tubule
Tubular secretion occurs in the distal convoluted tubes. The secretion also happens in the collecting ducts and also in the proximal convoluted tubule.