Explain the process of haemodialysis

Haemodialysis is the artificial process by which urea is removed from the body of the patient.

i. Blood drained from an artery is
pumped into a dialysing unit after the addition of anticoagulant like heparin.

ii. The unit contains a coiled cellophane tube surrounded by a dialysing fluid having the same composition as that of plasma except the nitrogenous wastes. 

iii. The porous cellophane membrance of the tube allows the passage of molecules based on concentration gradient. As nitrogenous wastes are absent in the dialysing fluid, these substances
freely move out, thereby clearing the blood.

iv. The cleared blood is pumped back to the body through a vein after adding anti-heparin to
it. This method is a boon for thousands of uremic patients all over the world.

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Write a note on artificial kidney.

Artificial kidney or Haemodialysis : It is the artificial removal of the nitrogenous wastes from the body. It is used in those patients whose kidney tubules do not function properly so that the metabolic wastes start accumulating in the blood and they need to be eliminated frequently. It can be explained in following points.

1. In the process, the blood of the patient is pumped from one of the main arteries and cooled to 0°C.

2. It is then mixed with an anticoagulant heparin and passed through cellophane tube.

3. This cellophane tube is a semipermeable membrane which allows only small molecules like urea, uric acid, creatinine and mineral ions to pass out but the macromolecules like proteins are not able to pass through it.

Write a note on artificial kidney.

Fig. Diagram of Artificial Kidney

4. This cellophane tube is suspended in a salt solution which is isotonic with the blood plasma. Now, as the blood flows through this tube metabolic wastes are filtered out of the blood in the salt solution.

5. The purified blood is mixed with antiheparin to restore its normal coaguability and is then pumped into the body through a vein.

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What is kidney/renal failure ?


Kidney failure is the partial or total inability of kidneys to carry on excretory functions.

Symptoms :

(a) Kidney failure leads to uremia i.e. an excess of urea and other nitrogenous wastes in the blood.

(b) Salt-water imbalance.

Causes : Many factors can cause kidney failure. Among these prominent are

1. tubular injury

2. infection

3. bacterial toxins

4. glomerulonephritis.

5. fluid and electrolyte depletion

6. internal precipitation of calcium and urates

7. haemorrhage.

 

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 Describe juxta glomerular feed back circuit to control kidney function.

Juxta glomerular Apparatus (JGA) has a complex regulatory role and it controls multihormonal Renin-Angiotensinogen System (RAAS). It responds to decrease in blood pressure in afferent arteriole of glomerulus. Afferent arteriole's cells release an enzyme called renin into blood stream.

Renin converts angiotensinogen present in plasma into angiotensin II peptide. Functions of Angiotensin II :

1. Angiotensin II is a hormone which increases B.P. by causing arterioles to contract.

2. Angiotensin II also increases blood volume in following two ways.

(a) It signals the PCT to absorb more H20 and more NaCl.

(b) It also stimulates adrenal cortex to release aldosterone which induces the DCT to absorb Naand water.

Therefore, B.P. and blood volume is increased and it completes the feed back circle.

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 ANF opposes RAAS, Explain.

ANF is released by walls of atria or auricles. ANF (Atrial Natiuretic Factor) is secreted in response to increase of B.P. or blood volume.

ANF checks the secretion of renin-angitensin mechanism, and thus inhibits reabsorption of NaCl by collecting duct and also stops release of aldosterone. ANF is a vasodilator whereas the Angiotensin II is a vasocontrictor. 

 

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