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The formation of urine begins within the functional unit of the kidney, the nephrons. Urine then flows through the nephrons, through a system of converging tubules called collecting ducts. These collecting ducts then join together to form the minor calyces, followed by the major calyces that ultimately join the renal pelvis. From here, urine ...
The formation of urine takes place in microscopic structures called nephrons, about one million of which are found in a normal human kidney. Blood enters the kidney though the renal artery and flows through the kidney's vasculature into the glomerulus, a tangled knot of capillaries surrounded by Bowman's capsule.
Blood flows into these capillaries through the afferent arterioles and leaves through the efferent arterioles. The high hydrostatic pressure forces small molecules in the tubular fluid such as water , glucose , amino acids , sodium chloride and urea through the filter, from the blood in the glomerular capsule across the basement membrane of the ...
This filtrate then flows along the length of the nephron, which is a tubular structure lined by a single layer of specialized cells and surrounded by capillaries. 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.
The loop of Henle is the most prominent feature of the mammalian kidney. These loops provide the most efficient way to reabsorb water and create concentrated urine, allowing mammals to save water in their bodies. [138] After passing through the loop of Henle, the fluid becomes hypertonic relative to the blood plasma. [139]
A urine test is any medical test performed on a urine specimen. The analysis of urine is a valuable diagnostic tool because its composition reflects the functioning of many body systems, particularly the kidneys and urinary system , and specimens are easy to obtain. [ 1 ]
The gaps between these endothelial cells are called fenestrae. The walls have a unique structure: there are pores between the cells that allow water and soluble substances to exit and after passing through the glomerular basement membrane and between digitating podocyte foot processes, enter the capsule as ultrafiltrate.
Schematic of semipermeable membrane during hemodialysis, where blood is red, dialysing fluid is blue, and the membrane is yellow. Kidney dialysis (from Greek διάλυσις, dialysis, 'dissolution'; from διά, dia, 'through', and λύσις, lysis, 'loosening or splitting') is the process of removing excess water, solutes, and toxins from the blood in people whose kidneys can no longer ...