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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).
Increasing permeability of the inner medullary portion of the collecting duct to urea by regulating the cell surface expression of urea transporters, [17] which facilitates its reabsorption into the medullary interstitium as it travels down the concentration gradient created by removing water from the connecting tubule, cortical collecting duct ...
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
At this location, in the wall of the last portion of distal straight tubule, there is a modified region of tubular epithelium called the macula densa.(Fig. 5 in Kumaran and Hanukoglu 2020) [5] Cells in the macula densa respond to changes in the sodium chloride levels in the distal tubule of the nephron via the tubuloglomerular feedback (TGF) loop.
The medullary collecting duct is the main site of ANP regulation of sodium excretion. [25] ANP effects sodium channels at both the apical and basolateral sides. [ 25 ] ANP inhibits ENaC on the apical side and the sodium potassium ATPase pump on the basolateral side in a cGMP PKG dependent manner resulting in less sodium re-absorption and more ...
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.
In the adult, it forms a continuous smooth outer zone with a number of projections (cortical columns) that extend down between the pyramids. 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.
Cardiac physiology or heart function is the study of healthy, unimpaired function of the heart: involving blood flow; myocardium structure; the electrical conduction system of the heart; the cardiac cycle and cardiac output and how these interact and depend on one another.