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Fig.1) Schematic diagram of the nephron (yellow), relevant circulation (red/blue), and the four methods of altering the filtrate. The nephron is the functional unit of the kidney. [3] This means that each separate nephron is where the main work of the kidney is performed. A nephron is made of two parts:
Within the nephron of the kidney, the ascending limb of the loop of Henle is a segment of the heterogenous loop of Henle downstream of the descending limb, after the sharp bend of the loop. This part of the renal tubule is divided into a thin and thick ascending limb ; the thick portion is also known as the distal straight tubule , in contrast ...
Glomerular filtration rate (GFR) is the volume of fluid filtered from the renal (kidney) glomerular capillaries into the Bowman's capsule per unit time. [4] Central to the physiologic maintenance of GFR is the differential basal tone of the afferent (input) and efferent (output) arterioles (see diagram).
For example, the urine concentration in humans can be as concentrated as 1400 mOsm which is limited by the length of our loop of Henle, i.e., 2.2 mm. While a camel's loop of Henle, which is around 4.1 mm, can reach 2800 mOsm. Another example is the Australian mouse whose loop of Henle, 5.2 mm, can make the medulla as salty as 9000 mOsm. [8]
The nephron is composed of a renal corpuscle and a renal tubule. 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 ...
Each nephron begins in a renal corpuscle, which is composed of a glomerulus enclosed in a Bowman's capsule. Cells, proteins, and other large molecules are filtered out of the glomerulus by a process of ultrafiltration , leaving an ultrafiltrate that resembles plasma (except that the ultrafiltrate has negligible plasma proteins ) to enter Bowman ...
The nephron by itself is similar to pronephros as a whole organ. [18] The simplest nephrons are found in the pronephros, which is the final functional organ in primitive fish . [ 19 ] The nephrons of the mesonephros, the functional organ in most anamniotes called opisthonephros , [ 20 ] are slightly more complex than those of the pronephros. [ 19 ]
In contrast, the epithelium transitions to a simple squamous type in the thin segment, which is less metabolically active and has minimal surface specializations. The presence of aquaporin-1 channels in the thin segment facilitates high water permeability, crucial for water reabsorption as part of the kidney's countercurrent exchange mechanism .