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The proximal tubule is the segment of the nephron in kidneys which begins from the renal pole of the Bowman's capsule to the beginning of loop of Henle.At this location, the glomerular parietal epithelial cells (PECs) lining bowman’s capsule abruptly transition to proximal tubule epithelial cells (PTECs).
The collecting duct system of the kidney consists of a series of tubules and ducts that physically connect nephrons to a minor calyx or directly to the renal pelvis.The collecting duct participates in electrolyte and fluid balance through reabsorption and excretion, processes regulated by the hormones aldosterone and vasopressin (antidiuretic hormone).
Tubular secretion occurs at Proximal Convoluted Tubule (PCT) and Distal Convoluted Tubule (D.C.T); for example, at proximal convoluted tubule, potassium is secreted by means of sodium-potassium pump, hydrogen ion is secreted by means of active transport and co-transport, i.e. anti-porter, and ammonia diffuses into renal tubule.
The transport of glucose across the proximal tubule cell membrane involves a complex process of secondary active transport (also known as co-transport). [3] This process begins with the Na + /K + ATPase on the basolateral membrane. This enzyme uses ATP to pump 3 sodium ions out of the cell into the blood while bringing 2 potassium ions into the ...
The distal convoluted tubule has a different structure and function to that of the proximal convoluted tubule. Cells lining the tubule have numerous mitochondria to produce enough energy for active transport to take place. Much of the ion transport taking place in the distal convoluted tubule is regulated by the endocrine system.
OAT1, OAT3, and OATP4C1 transport small organic anions from the plasma into the S2 cells. MDR1, MRP2, MRP4 and URAT1 then transports these organic anions from the cytoplasm of the S2 cells into the lumen of the proximal convoluted tubules. These organic anions are then excreted in the urine. [5]
In one study for paracellular transport across the tight junction in kidney proximal tubule, a dual pathway model was proposed, consisting of large slit breaks formed by infrequent discontinuities in the tight junction complex and numerous small circular pores. [20]
The renal corpuscle is a blood-filtering part of the nephron and is located in the cortex. The renal tubule extends from the renal corpuscle to the medulla into the loop of Henle and then returns back to the cortex. Finally, the renal tubule flows with its distal end into its collecting duct, which is common to several nephrons.