Excretory Products and Their Elimination - Disorders (Uraemia, Renal failure, Renal calculi, Nephritis, Dialysis)
Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Uraemia: A clinical condition characterized by the accumulation of excess urea () and other nitrogenous waste products in the blood due to the failure of the kidneys to excrete them. It is highly toxic and can lead to kidney failure.
Renal Failure (Kidney Failure): A condition where the kidneys stop functioning effectively, leading to an inability to maintain homeostasis of body fluids. The ultimate treatment for acute renal failure is a kidney transplantation from a matching donor.
Hemodialysis: A process used to remove urea and other wastes from the blood of uraemic patients. Blood is drained from a convenient artery, pumped into a dialysing unit after adding an anticoagulant like heparin.
Mechanism of Dialysis: The dialysing unit contains a coiled cellophane tube surrounded by dialysing fluid. The fluid has the same composition as plasma except for nitrogenous wastes. Wastes move from the blood into the fluid based on the concentration gradient across the porous cellophane membrane.
Renal Calculi: Also known as kidney stones, these are insoluble masses of crystallized salts (e.g., calcium oxalates, ) formed within the kidney, which can cause severe pain and blockage.
Glomerulonephritis (Nephritis): Inflammation of the glomeruli of the kidney, often caused by an immune response or infection, leading to the presence of protein or blood cells in the urine ( or ).
📐Formulae
, where is Glomerular Hydrostatic Pressure.
💡Examples
Problem 1:
Explain why the dialysing fluid used in hemodialysis must lack nitrogenous wastes like urea.
Solution:
The dialysing fluid is kept free of nitrogenous wastes to create a steep concentration gradient.
Explanation:
According to the principles of simple diffusion, molecules move from an area of higher concentration to lower concentration. Since the patient's blood has high levels of urea () and the dialysing fluid has zero urea, these toxic substances diffuse out of the blood through the semi-permeable cellophane membrane into the fluid.
Problem 2:
What are the necessary steps taken before and after the blood passes through the artificial kidney during hemodialysis?
Solution:
Addition of heparin before and anti-heparin after the process.
Explanation:
Before entering the dialyser, blood is cooled and mixed with an anti-coagulant like heparin to prevent clotting inside the machine. After the urea is removed, the blood is warmed to body temperature and mixed with anti-heparin to restore its normal clotting ability before being pumped back into the patient's vein.