Kidney Function

Kidney transplantation or renal transplantation is a kidney transplant in a patient with end-stage renal disease. Depending on the source of the organ recipient, kidney transplantation is typically classified as deceased donor (formerly known as cadaveric) or living donor transplant. Kidney transplants from living donors are more thoroughly as transplant genetically related (living-relative) or unrelated transplant (living-unrelated), depending on whether or not there is a biological relationship between donor and recipient.

The kidney’s ability to perform many functions depends on three fundamental functions of filtration, reabsorption and secretion.

Filtration

The blood is filtered by nephrons, the functional units of the kidney. Each nephron begins in a renal corpuscle encapsulated in the capsule of Bowman. The cells, proteins and other large molecules are filtered out of the clusters by a process of ultrafiltration kidney, leaving one that looks like the ultrafiltered plasma (except that the plasma protein is ultrafiltered insignifcantes to enter the area of Bowman). Seepage is conducted by the Forces of Starling.

The ultrafiltered is passed through, in turn, by the proximal tubule, the loop of Henle, the distal convoluted tubule and collecting a series of ducts to form urine.

Reabsorption

Tubular reabsorption is the process by which solutes and water are removed from the tubular fluid and transported in the blood. Is called resorption (not absorption) because these substances have already been absorbed once (particularly in the intestines).

The reabsorption is a two-step process that begins with the active or passive extraction of substances from the tubular fluid into the renal interstitium (the connective tissue that surrounds the nefronas), then transport of these substances from the bloodstream into the interstitium. These transport processes are driven by Starling forces, diffusion and transportation assets.

Renal plasma threshold

The threshold is the minimum renal plasma concentration in the blood plasma of a substance that results in the excretion of the substance in urine.

For example, the threshold for renal plasma glucose is 170 to 180 mg per 100 ml. The Glycosuria (sugar in the urine) is when the plasma reaches and exceeds the threshold of the renal plasma glucose. When the plasma glucose concentration is very high, filtered glucose can saturate their transport carriers and reach up to this molecule. Any amount that will go up transport through the renal tubules and is excreted in urine.

Reabsorption indirect

In some cases, the reabsorption is indirect. For example, bicarbonate (HCO3-) is not a carrier, thus eliminating its involves a series of reactions in the lumen of the tubule and tubular epithelium. It begins with the secretion of active hidrogenión (H +) within the fluid through a tube exchanger Na / H:

* In the lumen
o The H + combines with HCO3-to form carbonic acid (H2CO3)
The carbonic anhydrase or luminal H2CO3 enzymatically converted to CO2 and H2O
or CO2 freely diffuses into the cell.
* In the epithelial cell
The AC or cytoplasmatic converts CO2 and H2O (which is    abundant in the cell) in H2CO3
H2CO3 or are easily disoccia H + and HCO3 -
or HCO3-is provided outside the basolateral membrane of the cells.

Hormones

Some key regulatory hormones reabsorption:

* Aldosterone, which stimulates the active reabsorption of sodium.
* Antidiuretic hormone, which stimulates the passive absorption of water.

Both hormones exert their effects mainly in the renal collecting duct.

The body is very sensitive to pH value. Outside the pH range that is compatible with life, proteins are denatured and digested, enzymes lose their ability to function, and the body is unable to sustain itself. The kidneys maintain the acid-base balance in the regulation of pH of the blood plasma. Gains and losses of acid and base must be balanced. Acids are divided into “volatile acids” [13] and “fixed acids” [14]

The main point of control for maintaining the balance is renal excretion. The kidney is directed towards the retention of sodium excretion or through the action of aldosterone, antidiuretic hormone (ADH or arginine-vasopressin), atrial natriurétrico peptide (ANP) and other hormones. The ranges abnormal fractional excretion of sodium can lead to acute tubular necrosis or glomerular dysfunction.