Physiology of Human Regulation and Reproduction



Physiology of Human Regulation and Reproduction

Task 3 (M2)

Proximal Convoluted Tubule

The proximal tubules are part of the nephron, a system that filters the blood that passes through the kidneys . Born of the urinary pole of the glomerulus and is continuous with the thin descending limb of Henle. It measures approximately 15 mm long and 55 nanometers in diameter. Its walls are composed of a single layer of cuboidal cells (cuboidal epithelium). These cells have luminal side microvilli widely developed called "brush border", which provides a very large surface area for the main function of the proximal tubule: reabsorption. This is to absorb some of the nutrients filtered blood back and let the ultrafiltrate remains in the loop of Henle.

The proximal convoluted tubule is the portion of the renal tubule of thenephron of the kidney that leads from the Bowman's capsule to the loop of Henle . It consists of a layer of epithelial cells covered by microvilli, which are extensions of cell membranes and give it a brush. The main function of the proximal tubule is the reabsorption of chlorine ions, amino acids, potassium and other substances of glomerular ultrafiltration (Brodie, 2005).

The Loop Of Henle

Its function is to provide a means osmotic suitable for the nephron can concentrate the urine, through a mechanism countercurrent multiplier using ion pumps in the bone to absorb the ions in the urine. The water present in the filtrate flows through channels aquaporin (AQP), leaving the tube in favor of passively concentration gradient created by the ion pumps. In the kidney , the loop of Henle is a forked tube (similar to the letter "U") located in the nephrons . That portion of the nephron that leads from the proximal convoluted tubule to the distal convoluted tubule . Named after its discoverer, FGJ Henle . The handle has a fork in the renal medulla , so that the first part (the falling) lower crust to the core, and the second (the ramus) goes up to the cortex.

The rising portion of the loop of Henle is continuous with the distal convoluted tubule , where reabsorption occurs again and secretion of ions , to further concentrate the urine. The primary filtrate from the glomerulus passes to the proximal convoluted tubule , which connects with the descending limb of Henle's loop (with a wide zone cortical and medullary close), which has low permeability to ions and urea , but is highly permeable to water , since it has aquaporin channel type 1 (AQP1), constitutive expression in both the apical side as in the basolateral. This area absorbed 20% of the filtered water (Bronstein, 2011).

As water is drawn from the light of the handle downward, filtering inside the tube is increasingly concentrated in sodium chloride, so that it is absorbed to a greater extent in the ascending loop, thus increasing the osmolarity of gap: there is therefore a countercurrent multiplier effect. Since downward flow of the handle and the handle are rising in opposite directions, a stratification occurs osmotic: at the beginning ...