Role of kidney in
homeostasis
Regulation of
blood pressure
When juxtaglomerular apparatus
senses low pressure, it release
renin
Renin acts via Renin-
angiotensin system
Renin causes vasoconstriction of efferent
arteriole, leads an increased GFR and
peripheral vasoconstriction result an increase
in arterial blood pressure
Presence of dehydration, sodium deficiency
or hemorrhage in our body causes a decrease
in blood volume and blood pressure
This will stimulate kidney
to produce Renin which produce
angiotensin 1. It is converted to
angiotensin || via angiotensin-
converting enzyme
Angiotensin || stimulates the adrenal cortex
for the production of aldosterone which helps
to reabsorb more sodium and water into
blood and excretion of more potassium
in to the urine.
Results in increased blood volume
and blood pressure
Regulation of body fluid volume
and osmolality
ADH- It is secreted from posterior pituitary pituitary gland
and found in the collecting duct of kidney tubule
ADH acts on the water channel, when a rise in
plasma osmolality, causes a reabsorption of
water in to the blood, leads dilution of plasma and
a fall in plasma osmolality
A decreased plasma osmolality causes a reduction in
the secretion of ADH by negative feedback
Aldosterone- It is secreted by the adrenal cortex,
its secretion controlled by Peptide, angiotensin ||,
and it acts on the distal tubule
Increased secretion of Aldosterone causes an
increase in reabsorption of sodium and water
Atrial Natriuretic Peptide- Released from
cardiac atrial cells due to fluid overload
When ANP inhibits the secretion of
aldosterone, which causes a reduction in the release
of renin and ADH, results an excretion of sodium
and water, leads a decrease in fluid volume
Regulation of electrolyte
balance
Potassium- Aldosterone is involved in
the regulation of potassium
An increased extracellular potassium
stimulates adrenal cortex to produce
aldosterone which acts on the distal tubule
to secrete potassium in to the urine
When the aldosterone level falls,
less potassium secreted in to the urine
Calcium- It is important for nerve and
muscle conduction
Reabsorption of calcium depends on the
production of parathyroid hormone
Phosphate- It is important to maintain the
plasma pH in buffer system
When plasma phosphate level is low, the filtered
phosphate is reabsorbed in the proximal tubule
and if it is high, it is excreted in urine
Magnesium- important intracellular cation,
for the production and storage of energy
Increased secretion of parathyroid hormone
causes an increase in magnesium reabsorption
in tubules
Excretion of metabolic
waste products, foreign
chemicals, drugs, and
hormone metabolites
Kidneys are responsible for
eliminating waste products from body
Excess ions, sodium, potassium,
calcium, magnesium, chloride,
bicarbonate, phosphate, and ammonium
Metabolic wastes such as urea,
creatinine, uric acid, and nitrogenous waste
Drug metabolites excreted through
the kidneys, these are detoxified from the liver
Erythropoietin production
It is produced from the kidney's
erythropoietin cells to maintain
normal blood cell count and prevent
anemia
If hypoxia occurs, it will stimulate in the
production of erythropoietin and it will stop
when hypoxia corrected.