Disorders of the Excretory System
கழிவுநீக்க மண்டலக் கோளாறுகள்
Glycosuria plus ketonuria points to diabetes mellitus; uremia points to kidney failure. Read the urine and you read the disease.
The idea
Malfunctioning of the kidneys can lead to accumulation of urea in blood, a condition called uremia, which is highly harmful and may lead to kidney failure. In such patients urea can be removed by haemodialysis. Blood drawn from a convenient artery is pumped into a dialysing unit after adding an anticoagulant like heparin. The unit has a coiled cellophane tube surrounded by dialysing fluid with the same composition as plasma except the nitrogenous wastes; the porous cellophane membrane allows passage of molecules based on the concentration gradient, and since nitrogenous wastes are absent in the dialysing fluid they move out freely, clearing the blood. The cleared blood is pumped back to the body through a vein after adding anti-heparin. Kidney transplantation is the ultimate method for correcting acute renal failure; a functioning kidney is used, preferably from a close relative, to minimise the chance of rejection by the immune system. Renal calculi are stones or insoluble masses of crystallised salts (oxalates, etc.) formed within the kidney. Glomerulonephritis is inflammation of the glomeruli of the kidney. Presence of glucose (glycosuria) and ketone bodies (ketonuria) in urine are indicative of diabetes mellitus.
Why it matters
When the kidneys fail, wastes and excess ions build up in blood; dialysis and transplant replace the filtering job the kidneys can no longer do.
NEET lens
Match pairs: uremia — urea in blood; renal calculi — mass of crystallised salts (oxalates) in kidney; glomerulonephritis — inflammation of glomeruli; glycosuria — glucose in urine; gout — uric acid in joints (skeletal disorder, often paired here). Dialysis: heparin before, anti-heparin after; dialysing fluid = plasma minus nitrogenous wastes. Transplant from a close relative reduces rejection.
Clinical significance
Haemodialysis is a lifesaving procedure for thousands of kidney patients in India each week. Because the dialyser only removes substances that are absent from the dialysing fluid, it cannot make hormones like erythropoietin, so dialysis patients often need treatment for anaemia.
Introduction
When kidneys malfunction, wastes accumulate in blood. Dialysis, transplantation and urine tests are the main tools for managing kidney disorders.
Core concept
Uremia: accumulation of urea in blood → may lead to kidney failure. Haemodialysis: blood from an artery + heparin (anticoagulant) → dialysing unit (coiled cellophane tube in dialysing fluid = plasma composition minus nitrogenous wastes) → wastes diffuse out down the concentration gradient → anti-heparin added → back through a vein. Kidney transplant: ultimate method for acute renal failure; donor preferably a close relative to minimise rejection. Renal calculi: stone/insoluble mass of crystallised salts (oxalates etc.) in the kidney. Glomerulonephritis: inflammation of glomeruli. Urine analysis: glucose (glycosuria) + ketone bodies (ketonuria) indicate diabetes mellitus.
Go deeper
An artificial kidney removes nitrogenous wastes and excess ions such as K+ from blood; its failure or absence would cause their build-up — so 'nitrogenous waste build-up' and 'non-elimination of excess potassium' are what dialysis prevents, not what it causes.
From Class 10
Class 10 mentioned dialysis as an artificial kidney. NEET asks how it works and names the common kidney disorders.