where is most sodium reabsorbed in the kidney
Renal sodium reabsorption Most of the reabsorption (65%) occurs in the proximal tubule. In the latter part it is favoured by an electrochemical driving force, but initially it needs the cotransporter SGLT and the Na-H antiporter. Sodium passes along an electrochemical gradient (passive transport) from the lumen into the tubular cell, together with water and chloride which also diffuse passively. Water is reabsorbed to the same degree, resulting in the concentration in the end of the proximal tubule being the same as in the beginning. In other words, the reabsorption in the proximal tubule is isosmotic.
Vein Veins are less muscular than arteries and are often closer to the skin. There are valves in most veins to prevent backflow.
Syndrome of inappropriate antidiuretic hormone secretion Urinalysis reveals a highly concentrated urine with a high fractional excretion of sodium (high sodium urine content compared to the serum sodium).[11] A suspected diagnosis is based on a serum sodium under 138. A confirmed diagnosis has seven elements: 1) a decreased effective serum osmolality - <275 mOsm/kg of water; 2) urinary sodium concentration high - over 40 mEq/L with adequate dietary salt intake; 3) no recent diuretic usage; 4) no signs of ECF volume depletion or excess; 5) no signs of decreased arterial blood volume - cirrhosis, nehprosis, or congestive heart failure; 6) normal adrenal and thyroid function; and 7) no evidence of hyperglycemia (diabetes mellitus), hypertriglyceridemia, or hyperproteinia (myeloma).
Urinary system The first step in urine formation is the filtration of blood in the kidneys. In a healthy human the kidney receives between 12 and 30% of cardiac output, but it averages about 20% or about 1.25 L/min.