Disorders of the Excretory System

When kidneys fail to filter blood properly, nitrogenous wastes (mainly urea) start building up in the blood. This is dangerous because urea and other wastes become toxic at high levels and disturb water balance, salt balance, and pH.

Kidney problem = Waste stays in blood + body homeostasis gets disturbed.

Uremia: When the Blood gets Dirty

When kidneys malfunction, they stop filtering urea. This leads to the accumulation of Urea in the blood.

  • Name: Uremia.
  • Danger: Highly harmful and can lead to Kidney Failure.
  • Fix: The urea must be removed artificially using Hemodialysis.

Hemodialysis (The Artificial Kidney)

This is a machine that cleans the blood when the kidneys can't. It works on the principle of concentration gradient.

The Process (Step-by-Step):

  1. Drain (Artery): Blood is taken out from a convenient Artery.
  2. Prevent Clotting: An anticoagulant called Heparin is added (so blood doesn't clot inside the machine pipes).
  3. The Filter Unit: The blood passes through a coiled cellophane tube submerged in a tank of dialysing fluid.
    • The Magic Trick: This fluid has the exact same composition as plasma EXCEPT it has NO nitrogenous waste.
  4. Diffusion: Since the blood has high waste and the fluid has zero waste, the waste moves OUT into the fluid freely through the porous cellophane membrane.
  5. Return (Vein): The clean blood is pumped back into the body through a Vein.
    • Important: Before returning, Anti-heparin is added to restore normal clotting ability.

Renal Failure (Kidney Failure)

  • Condition: The kidneys stop working partially or completely.
  • The Ultimate Cure: While dialysis helps, the permanent correction is Kidney Transplantation.
  • The Donor: Ideally, a close relative is chosen. This is to ensure the body's immune system doesn't attack the new kidney (Rejection).

Renal Calculi (Kidney Stones)

  • What are they? Hard, stone-like masses formed inside the kidney.
  • Made of: Crystallized salts, primarily Oxalates (like Calcium Oxalate).

Glomerulonephritis

  • The Name Says it All:
    • Glomerulo = Glomerulus.
    • Nephr = Kidney.
    • itis = Inflammation.
  • Condition: Inflammation of the glomeruli of the kidney.

Disorders of the Excretory System

  • Dialysis Path: Artery →\rightarrow Machine →\rightarrow Vein. (Out via A, In via V).
  • The Heparin Switch: Heparin goes IN (to stop clots), Anti-heparin goes OUT (to allow clots).
  • The Fluid Secret: Dialysing fluid = Plasma minus Waste.
  • Stones: Think "Oxalates".
  • -itis: Always means Inflammation (e.g., Tonsillitis, Appendicitis, Glomerulonephritis).

💡 Questions and Answers

Q1. What exactly is Uremia?

Answer: Uremia is a dangerous condition where Urea accumulates in the blood because the kidneys are failing to filter it out.

Q2. Why do we add Heparin during dialysis?

Answer: Blood naturally clots when it leaves the body. We add Heparin (an anticoagulant) to prevent the blood from clotting and clogging up the dialysis machine.

Q3. What are kidney stones made of?

Answer: They are hard crystals made mostly of Oxalates (insoluble salts).

Q4. What happens in Glomerulonephritis?

Answer: It is the inflammation (swelling/irritation) of the glomeruli in the kidney, which affects filtration.

Q5. Why is a close relative the best donor for a kidney transplant?

Answer: To prevent Rejection. The patient's immune system is less likely to attack and destroy a kidney from a close relative because the tissues match better.