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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).
Though the collecting duct is normally impermeable to water, it becomes permeable in the presence of antidiuretic hormone (ADH). ADH affects the function of aquaporins, resulting in the reabsorption of water molecules as it passes through the collecting duct. Aquaporins are membrane proteins that selectively conduct water molecules while ...
By means of a countercurrent multiplier system, which uses electrolyte pumps, the loop of Henle creates an area of high urea concentration deep in the medulla, near the papillary duct in the collecting duct system. Water present in the filtrate in the papillary duct flows through aquaporin channels out of the duct, moving passively down its ...
The major functions of these lining cells are the reabsorption of water and small molecules from the filtrate into the blood, and the secretion of wastes from the blood into the urine. Proper function of the kidney requires that it receives and adequately filters blood.
The collecting ducts from each cluster of nephrons usually drain into an archinephric duct, which is homologous with the vas deferens of amniotes. However, the situation is not always so simple; in cartilaginous fish and some amphibians, there is also a shorter duct, similar to the amniote ureter, which drains the posterior (metanephric) parts ...
The epithelium of the Thick segment is low simple cuboidal epithelium. The epithelium of the Thin segment is simple squamous. [4]They can be distinguished from the vasa recta by the absence of blood, and they can be distinguished from the thick ascending limb by the thickness of the epithelium.
The medulla is divided into outer and inner regions. The outer region consists of short loops of Henle and collecting ducts, and the inner region consists of long loops of Henle and collecting ducts. [28] After passing through the loop of Henle, the fluid becomes hypertonic relative to the blood plasma. [78] The renal portal system is absent in ...
The medullary ascending limb is largely impermeable to water. Sodium (Na + ), potassium (K + ) and chloride (Cl − ) ions are reabsorbed by active transport . The predominant mechanism of active transport in this segment is through the Na + /K + /Cl − co-transporter NKCC2 as well as the sodium/hydrogen exchanger NHE3 . [ 3 ]