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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).
The collecting duct system begins in the renal cortex and extends deep into the medulla. As the urine travels down the collecting duct system, it passes by the medullary interstitium which has a high sodium concentration as a result of the loop of Henle's countercurrent multiplier system. [1]: 67
The medullary rays of the cortex contain the proximal straight tubules, the cortical part of the thick ascending limb of the loops of Henle, and the cortical part of the collecting ducts. [72] The cortex is divided into lobules, each of which is a medullary ray in conjunction with connected to it nephrons, and interlobular arteries that pass ...
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 ...
To achieve such balance between water and ions, the loop of Henle coordinates its function with the collecting duct to regulate the amount of water to reabsorb or to excrete. While the loop of Henle makes the medulla of the kidney salty, the collecting duct regulates the permeability of water that could be reabsorbed to such salty environment.
It contains the renal corpuscles and the renal tubules except for parts of the loop of Henle which descend into the renal medulla. It also contains blood vessels and cortical collecting ducts. The renal cortex is the part of the kidney where ultrafiltration occurs. [2] Erythropoietin is produced in the renal cortex. [3]
Urea is usually excreted as a waste product from the kidneys. However, when plasma blood volume is low and ADH is released the aquaporins that are opened are also permeable to urea. This allows urea to leave the collecting duct into the medulla, creating a hyperosmotic solution that "attracts" water.
A cortical lobule (or renal lobule) is a part of a renal lobe. It consists of the nephrons grouped around a single medullary ray , and draining into a single collecting duct . Its near identical parallel is the rectal lobe [ citation needed ] , which is present in the majority of mammals.