Patents on Collecting duct system. List of terms related to Collecting duct system. Editor-In-Chief: C. Michael Gibson, M. The collecting duct system of the kidney consists of a series of tubules and ducts that connect the nephrons to the ureter. It participates in electrolyte and fluid balance through reabsorption and excretion, processes regulated by the hormones aldosterone and antidiuretic hormone. Anatomically, there are several components of the collecting duct system, including the connecting tubules, cortical collecting ducts, and medullary collecting ducts.
The collecting duct system is the last component of the kidney to influence the body's electrolyte and fluid balance. The wide variation in water reabsorption levels for the collecting duct system reflects its dependence on hormonal activation. The collecting ducts, particularly the outer medullary and cortical collecting ducts, are largely impermeable to water without the presence of antidiuretic hormone ADH, or vasopressin.
The collecting duct system participates in the regulation of other electrolytes, including chloride , potassium , hydrogen ions , and bicarbonate. The connecting tubule derives from the metanephric blastema , but the rest of the system derives from the ureteric bud. Because of this, some sources group the connecting tubule as part of the nephron , rather than grouping it with the collecting duct system.
Each component of the collecting duct system contains two cell types, intercalated cells and a segment-specific cell type:. The principal cell mediates the collecting duct's influence on sodium and potassium balance via sodium channels and potassium channels located on the cell's apical membrane. Aldosterone determines if the sodium channels transport ions. For their contribution to acid-base homeostasis, the intercalated cells play important roles in the kidney's response to acidosis and alkalosis.
Transverse section of pyramidal substance of kidney of pig, the bloodvessels of which are injected. Template:WikiDoc Sources. Cookies help us deliver our services. By using our services, you agree to our use of cookies. Aldosterone regulates the expression of sodium channels by the principal cells. Increased levels of the hormone aldosterone result in increased expression of sodium channels.
Therefore, an elevated level of aldosterone would result in increased absorption of sodium and secretion of potassium by the principal cells of the collecting duct system. The principal cells also express aquaporin channels, which allow water to pass through the principal cells. Therefore, both aldosterone and vasopressin regulate water and electrolyte homeostasis by the principal cells. The intercalated cells can be classified into alpha and beta. They are responsible for acid-base homeostasis.
Therefore, to emphasize, the principal cells are responsible for water and electrolyte homeostasis, whereas the intercalated cells are involved in acid-base homeostasis.
The pumps are responsible for the secretion of hydrogen ions. They are involved when apatient develops a state of acidosis. Clearly, these cells are responsible for acid-base homeostasis in the case of alkalosis. Balance in the function of both types of intercalated cells results in a state of physiologic acid-base homeostasis. An important note about water absorption in the collecting duct system must be emphasized. The osmotic gradient created by the countercurrent multiplier system in the Loop of Henle provides the force responsible for water reabsorption through the collecting ducts.
The rate of osmotic movement is determined largely by the permeability of collecting ducts to water, and it is directly proportional to the number of aquaporins in the collecting duct epithelial cells.
Therefore, this gives ADH its main role in collecting ducts, which is to facilitate transportation of aquaporin 2 from storage vesicles in the cytoplasm to the plasma membrane, achieved when ADH binds to its membrane receptors on collecting ducts to stimulate the fusion of aquaporin 2 with the membrane.
This leads to increased permeability of the collecting ducts and a resulting increase in the number of aquaporin 2 channels in the epithelial cells. Our medical articles are the result of the hard work of our editorial board and our professional authors. Strict editorial standards and an effective quality management system help us to ensure the validity and high relevance of all content. Read more about the editorial team, authors, and our work processes.
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