Question

How kidney functions are regulated? Add a note on kidney transplantation?

Answer 1

Hypothalamus, juxtaglomerular apparatus (JGA) and heart plays a very important role in the functioning of the kidney and these help in the regulation of Na ion and water level in the body. Kidneys remove waste products and excess water and help in the regulation of blood pressure.

Complete answer:
The functioning of kidneys is monitored and regulated by hormonal feedback mechanisms involving hypothalamus, juxtaglomerular apparatus and heart.
Regulation involving Hypothalamus:
Osmoreceptors: These receptors present in the body and are activated by changes in blood volume, body fluid volume and ionic concentration.
When there is excessive loss of fluid from the body, Osmoreceptors activates and stimulates the hypothalamus(posterior pituitary gland) to release Antidiuretic hormone (ADH) or vasopressin from neurohypophysis.ADH stimulates reabsorption of water from the latter parts of the tubules (DCT,CD) and prevents from diuresis(excessive urination).
Increase in body fluids volume deactivates the osmoreceptors and suppresses the ADH release.
Diabetes Insipidus: The deficiency of ADH hormone leads to diabetes insipidus, causes huge amounts of urine and intense thirst.
Regulation involving Juxtaglomerular Apparatus:
In kidneys, the JGA acts as a Multi Hormonal renin angiotensin aldosterone system (RAAS).
When the glomerular blood flow decreases JG cells activates and releases renin. Renin converts angiotensin in blood to angiotensin 1 and further to angiotensin 2. Angiotensin 2 increases glomerular blood flow by contraction of arteries.
Angiotensin 2 also increases blood volume by two different methods:
By signaling the PCT to reabsorb more NaCl and water.
By stimulating the adrenal gland to release aldosterone. Aldosterone increases the reabsorption of Na ion and water from later parts of the tubule.
The walls of the atria of the heart releases Atrial Natriuretic Factor (ANF) causes vasodilation (dilation of blood vessels) and thereby decreases in blood pressure.

Note: Kidney Transplantation: The acute renal failures (kidney failure) can be corrected by this technique. A functioning kidney of a donor (close relative) is used in the transplantation to minimise its chances of rejection by the immune system of the host. Special drugs can help suppress the immune system of the recipient, so it does not reject a transplanted kidney. Some kidney failures are renal calculi and glomerulonephritis.