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Role of kidney in homeostasis, Excretion of foreign chemicals, drugs,…
Role of kidney in homeostasis
Acid base balance
Kidneys have crucial role in maintaining acid base balance: Reabsorb bicarbonate from urine and excrete hydrogen ions in the urine.
Exchange between K+ and H+ ions happens in DT. Around 20-30% re-absorption of HCO3- occurs.
About 70-80% of HCO3 reabsorption occurs in PCT
Buffer system
Bicarbonate buffer system CO2=H2Om <-> H2CO3 <->H++HCO3-
Ammonia buffer system NH3 + H+ =NH4+
Phosphate buffer system HPO4- + H+=H2PO4
Alkalosis: excretion of bicarbonate
increase in kidney, and it leads to loss of bicarbonate from the extracellular fluid alkalization of urine.
Acidosis :kidney eliminates more amount of hydrogen ions and HCO3- reabsorbs into the blood.
Control of fluid and electrolyte balances
KIdneys have vital role to controlling volume and
composition of body fluids.
Kidneys help to maintain concentration of
electrolyte by controlling its
concentration in the body.
By active and passive transport
kidney balance potassium, phosphorus,sodium, calcium, and magnesium.
DT: Reabsorption of Sodium and magnesium and secretion of potassium and magnesium also occurs.
Loop of Henle: Reabsorption of 65% magnesium,25% sodium, 25% calcium and 27% of K+ happens.
PCT: 65% potassium reabsorbed by co- transport with sodium+, 65% sodium reabsorbed, and 25% magnesium actively re-absorbed.
Secretion of hormone
Erythropoietin stimulates the production of RBC in bone marrow.
Calcitrol, which is produced in kidney has a role in maintain calcium and phosphorus homeostasis
Renin helps to synthesis angiotensin 2. It has many functions in the body.
Controle of arterial blood pressure
Sodium excretion directly regulates by Renal Artery Perfusion Pressure
Kidney has an important role in the regulation of arterial blood pressure.
RAAS
Angiotensin 1 and ACE in lungs together becomes Angiotensin 2
The efferent arteriole become constricted with the effect of Angiotensin 2 and causes decreased blood flow and increased hydrostatic pressure, so glomerular filtration increases.
Step 2: Aldosterone is synthesized with the effect of angiotensin 2 in adrenal gland
Aldosterone works in principle cells and alpha interrelated cells in the collecting duct.
Renin converts angiotensinogen into Angiotensin 1
Reabsorption of sodium and water occur with aldosterone. Then sodium and water comes into cells and potassium moves out into the collecting duct. Fluid volume and blood pressure are increased
Step 1: Renin is release after sensing low BP buy juxtaglomerular apparatus
Waste products from metabolism are eliminated through the kidneys.
Uric acid
Urea (from amino acids)
Metabolites of hormone
Creatinine (from muscle)
Bilirubin (Hemoglobin breakdown
Excretion of foreign chemicals, drugs, metabolic waste
and hormone metabolites
Reaction of kidney in alkalosis and acidosis
MIND MAP