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The muscle tension in the afferent arteriole is modified based on the difference between the sensed concentration and a target concentration. [5] Vasodilation of the afferent arteriole, which results in increased glomerular filtration pressure and tubular fluid flow, occurs when MD cells detect a chloride concentration that is below a target value.
Tubular secretion occurs simultaneously during re-absorption of filtrate. Substances, generally produced by body or the by-products of cell metabolism that can become toxic in high concentration, and some drugs (if taken). These all are secreted into the lumen of renal tubule. Tubular secretion can be either active or passive or co-transport.
The processes of blood plasma filtration, tubular reabsorption and tubular secretion occur in the kidneys, and urine formation is a result of these processes. [8] The kidneys produce renin [32] and erythropoietin [33] hormones, and are involved in the conversion of vitamin D to its active form. [34]
The glomerulus (pl.: glomeruli) is a network of small blood vessels (capillaries) known as a tuft, located at the beginning of a nephron in the kidney. Each of the two kidneys contains about one million nephrons. The tuft is structurally supported by the mesangium (the space between the blood vessels), composed of intraglomerular mesangial cells.
The four mechanisms used to create and process the filtrate (the result of which is to convert blood to urine) are filtration, reabsorption, secretion and excretion. Filtration or ultrafiltration occurs in the glomerulus and is largely passive: it is dependent on the intracapillary blood pressure. About one-fifth of the plasma is filtered as ...
The proximal tubule is the segment of the nephron in kidneys which begins from the renal pole of the Bowman's capsule to the beginning of loop of Henle.At this location, the glomerular parietal epithelial cells (PECs) lining bowman’s capsule abruptly transition to proximal tubule epithelial cells (PTECs).
PAH is not reabsorbed and is secreted, so excretion = filtration + secretion. As with glucose, the transfer is at the proximal tubule, but in the opposite direction: from the peritubular capillaries to the lumen. At low levels, all the PAH is transferred, but at high levels, the transport maximum is reached, and the PAH takes longer to clear.
This blood leaves the glomerulus via the efferent arteriole, which supplies the peritubular capillaries. The higher osmolarity of the blood in the peritubular capillaries creates an osmotic pressure which causes the uptake of water. Other ions can be taken up by the peritubular capillaries via solvent drag. Water is also driven into the ...