Tubular Function

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TUBULAR FUNCTION
They perform intelligent functions of the kidney.
Tubular reabsorption:
-Proximal tubule: 65%-Loop of Henle: 15%, distal tubule: 10%
This dal a total of 90%, reaching 10% to the collecting tubules where most of resorbable 9 / 10 passing urine less than 1 / 10.
Peritubular capillary exchange
-
Friendly forces in the peritubular capillary absorption:
* Interstitial hydrostatic pressure: 6 mmHg.
* Colloid osmotic pressure in peritubular capillaries: 32 mmHg.
- Forces opposed to the reabsorption:
* Capillary hydrostatic pressure: 13 mmHg
* Interstitial colloid osmotic pressure: 15 mmHg.
So the forces of resorption for a total of 38 mmHg. and those who oppose it gives us 28 mmHg. and the final result for the reabsorption is 10mmHg.
Tubular transport mechanism
Proximal tubules: Na + K + ATPase, which maintains low intracellular sodium concentration, intracellular potential of 70mV.
-Coupled secondary active transport of Na and K pump
Sodium-Contratrasporte-anion, the anions are glucose, amino acids and carbonate.
"In the final portion of the proximal tubule in the carbonate, glucose and amino acids are completely resorbable.
"In the initial portion bicarnonato reabsorvibles the sodium and the thin portion of sodium chloride.
ASA DE HENLE
-Descending: Water
"Ascending: Cl, Na, K, Mg, Ca
Distal and collecting tubules
-First portion:
is resorbable by a Na Na and Cl cotransporter of the apical membrane.
* This portion is impermeable to water as the thick portion of Henle's loop.
"The last portion of the TD: Na reabsorption occurs in primary cells or light, is produced by simple diffusion.
Tubular secretion
The main substances secreted by the distal tubules are:
Hydrogen: TP contratrasporte secretion in the TD and collector is secreted by primary active secretion resides in intercalated cells brown.
Potassium is secreted by principal cells or light, whose other function is the reabsorption of sodium, both processes occur by simple diffusion THROUGH THE apical membrane chemical gradient created by Na ions, K ATPase, whose activity is stimulated by aldosterone.
SHARES in tubules specific substance
-Sodium reabsorption
* Sodium-solute Cotrasporte
* Sodium-hydrogen countertransport
* Transport of sodium chloride driven.
* Diffusion of sodium ion channels induced by aldosterone
DEPENDENT ACTIVE TRANSPORT OF SODIUM TRANSPORT
Water, chloride, carbonate, and urea.
- Reabsorption and secretion of K: the K ion is absorbed in the first two thirds of the proximal tubule and secreted in the last third of the proximal tubule and the descending portion of the loop of Henle.
"In the distal tubules leading secret cells and intercalated cells resorbable or brown.
-Secretion of potassium in the distal nephron:
Hydrogen-secretion:
in the proximal tubules, in distal and collecting tubules.
-Reabsorption of water:in proximal tubules is isosomotica reabsorption in the distal tubules and collecting water reabsorption depends on the activity of antidiuretic hormone.



Hormonal control of tubular reabsorption
-Aldosterone
induces the formation of sodium ion channel in the apical membrane of distal and collecting tubular epithelium.
-Angiotensin II increased secretion of aldosterone action on the efferent arteriole vascoconstricotora increases glomerular capillary pressure that brings two consequences:
* A decrease of the hydrostatic pressure in the peritubular capillary.
* Increased colloid osmotic pressure in peritubular capillary
* Stimulates the activity of the Na pump and K in the TP.
-Antidiuretic Hormone:It controls the water permeability in the DT and collecting ducts.
-Atrial natriuretic peptide: released by the cardiac atria, inhibits the release of aldosterone in the adrenal cortex and thus have indirect effect on Na and water reabsorption.
TUBULAR TRANSPORT
Tubular-load
plasma concentration x = filtracion/100 rate
Threshold plasmatic is the plasma concentration with which the load exceeds the transport maximum tubular and is lost in the urine.
Plamates The glucose threshold of 180 mg/100 ml. plasma, the maximum transport of glucose is 320 mg / min
Plasma Clearance
It is a work of the kidney to remove certain substances in plasma deleted from body fluids.
-Plasma clearance of a substance:is the quantity of plasma making it clear or clean of a substance, per minute, by action of the kidney:
C = Excretion Urinary / plasma concentration.
"The clarification might be caused by glomerular filtration, tubular secretion or both mechanisms.
-Determination of GFR by plasma clearance:
-Clearance for the amino-hippuric acid.
Osmolar-Clarification
Cosm = Osm X Urine / plasma osmolarity
Water-free Aclarameinto
Countercurrent mechanism
It is a mechanism to produce a hypertonic medulla and factors are:
Secondary-active transport of sodium
Horseshoe-shape of the loop of Henle
-Impermeable thick ascending portion of Henle's loop
"The action of the vasa recta
-Recycling of urea between medullary collecting tubules and branches of the loop of Henle ascendetes.
The first three mechanisms are: countercurrent multiplier.
The action of the vasa recta is called: contraconrriente exchanger.
REGULATION OF osmolarity
1-Mechanism osmoreceptors - ADH
found in the preoptic area of the hypothalamus, the area called AV3V.
2-Be: We are in the areas anterolateral preoptic area of the hypothalamus. An increase of extracellular Na 2 mEq of thirst or produces an increase of 4 mOsm / L.
* Changes trigger of the Thirst
-
Increasing the extracellular osmolarity
-A decrease in extracellular volume and blood pressure
Decrease of the extra-and intracellular K.
-Angiotensin II and III
-Dryness of the pharyngeal mucosa
3-Reflections Hormonal:Gauer reflex - Henry inhibits secretion of ADH
REGULATION OF SODIUM EXCRETION
-Sodium intake of 150 mEq a day -
"The filtration is 2600 mEq sodium per day and 150 mEq Elmina
Sodium-dependent excretion of aldoesterona, is a steroid hormone produced by the glomerular layer of the cortex supprarenal.
-The amount of aldosternoa is regulated by the renin-angiotensin system.
Actions of Aldosterone increases active Na transport in the TD and collectors, increase the secretion of K, aldosterone regulates the amount of body Na.

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