Q.Dialysing unit (artificial kidney) contains a fluid which is almost same as plasma except that it has
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Kidney Disorders and Support Systems
Think of your kidneys as the body's master filtration plant. Every drop of your blood passes through them about 300 times a day. They sort out what to keep — water, salts, nutrients — and what to throw away: urea, creatinine, excess acids, and other metabolic waste. When this filtration system breaks down, waste builds up in the blood. That is the core problem behind every kidney disorder.
Uraemia — When the Filter Clogs
Uraemia literally means "urine in the blood." It is the condition that results when the kidneys fail to remove nitrogenous wastes (mainly urea) from the blood. Normally, urea is filtered out and excreted in urine. When filtration stops, urea accumulates.
Symptoms include nausea, vomiting, fatigue, confusion, and eventually coma. The skin may develop a characteristic "uremic frost" — white crystals of urea deposited on the skin as the body tries to sweat out what the kidneys cannot remove. Uraemia is not a disease itself; it is the consequence of kidney failure.
Uraemia is a medical emergency. Without intervention, it is fatal. The only treatments are dialysis or a kidney transplant.
Renal Failure — Acute vs Chronic
Renal failure means the kidneys have lost their ability to filter blood adequately. It comes in two forms:
Acute renal failure happens suddenly — from a severe infection, a drug overdose, a blocked urinary tract, or a sudden drop in blood flow to the kidneys. It is often reversible if the underlying cause is treated quickly.
Chronic renal failure develops slowly over months or years, usually from long-standing conditions like diabetes, high blood pressure, or glomerulonephritis (inflammation of the kidney's filtering units). Damage is progressive and irreversible. The patient moves through stages: from mild loss of function (stage 1) to end-stage renal disease (stage 5), where the kidneys are working at less than 15% of normal capacity.
Chronic renal failure is silent in early stages. By the time symptoms appear — swelling, fatigue, itching, loss of appetite — significant damage has already occurred.
Renal Calculi — Stones in the Plumbing
Renal calculi are kidney stones — hard deposits of minerals and salts that form inside the kidneys. Most are made of calcium oxalate, but uric acid, struvite, and cystine stones also occur.
Stones form when urine becomes too concentrated in certain substances, allowing crystals to clump together. Dehydration, a diet high in oxalate (spinach, nuts, chocolate), and certain metabolic disorders increase the risk.
A small stone may pass unnoticed. A larger one can lodge in the ureter, causing excruciating pain (renal colic) that radiates from the flank to the groin. Blood in the urine, nausea, and frequent painful urination are common.
Treatment depends on size: small stones pass with hydration and pain relief; larger ones may need lithotripsy (shock waves to break them up) or surgical removal.
Dialysis — The Artificial Kidney
When kidneys fail, dialysis takes over their job. There are two main types:
Haemodialysis — Blood is pumped out of the body through a tube, passed through a dialyser (a machine with a semipermeable membrane), cleaned, and returned. The dialyser acts like an artificial kidney: waste products diffuse from the blood into a dialysis fluid (dialysate) that has the correct concentration of electrolytes. This is done 3–4 times a week, each session lasting 3–5 hours.
Peritoneal dialysis — A catheter is placed into the abdominal cavity. Dialysis fluid is introduced, and the peritoneum (the membrane lining the abdomen) acts as the filter. Waste diffuses from blood vessels in the peritoneum into the fluid, which is then drained out. This can be done at home, often overnight.
Dialysis principle: Diffusion of waste down a concentration gradient across a semipermeable membrane. Blood has high waste concentration; dialysate has zero waste. Waste moves from blood → dialysate.
Dialysis is life-saving but not a cure. It replaces filtration but not the kidney's other functions — hormone production (erythropoietin for red blood cells, calcitriol for bone health) and precise electrolyte balance. Patients on dialysis often develop anaemia and bone disease.
Kidney Transplantation — The Permanent Fix
A kidney transplant is the surgical placement of a healthy kidney from a donor into a patient with end-stage renal disease. The donor can be a living person (usually a relative) or a deceased donor. …
The dialysing fluid used in an artificial kidney has essentially the same composition as blood plasma, except that it contains no nitrogenous wastes such as urea.
- Because the dialysing tube is made of porous cellophane, substances move across it along their concentration gradient. …
The dialysing fluid used in haemodialysis matches plasma in almost every respect except that it deliberately contains no nitrogenous wastes, so urea diffuses out of the blood into it.
Haemodialysis works by passing a patient's blood through a coiled porous cellophane tube immersed in a dialysing fluid inside an artificial kidney unit.
- This dialysing fluid is prepared to have the same composition as normal blood plasma in terms of its other components, but it deliberately carries no nitrogenous wastes such as urea. …
Method: Reasoning Out Artificial-Organ / Dialysis Questions from First Principles
This method applies to any question about how a life-support device (dialysis machine, ventilator, etc.) is designed to mimic or exploit the body's own physiology — you can derive the answer even without memorising the device's exact specification.
Steps
Step 1: Identify the natural function being replaced
Ask what job the organ normally does, and which part of that job the device is standing in for. Here, the kidney's job of removing nitrogenous waste (urea) from blood is being replaced by the dialysis machine.
Step 2: Identify the physical principle the device relies on
Most artificial-organ devices lean on a simple physical process rather than active biological transport. Dialysis relies on diffusion — movement of a substance across a porous membrane from where it is more concentrated to where it is less concentrated.
Step 3: Work out what concentration difference is required …
- TG EAPCET 2022Set ap-2022-07-30-FN1 markMCQQ.Assertion (A): Renal calculi are hard crystalline structures formed in urinary tract. Reason (R): They are formed when the concentration of oxalates is high in urine. The correct option among the following is (A) is true, (R) is true and (R) is the correct explanation for (A) (B) (A) is true, (R) is true but (R) is not the correct explanation for (A) (C) (A) is true but (R) is false (D) (A) is false but (R) is true
›Reveal solutionSolution
Renal calculi (kidney stones) are indeed hard crystalline structures found in the urinary tract, and their formation is primarily driven by high concentrations of substances like oxalates in the urine. Both statements are true, and the reason correctly explains the assertion.
The Science Behind Kidney Stones: When Urine Gets Too Crowded
Imagine trying to dissolve too much sugar in a glass of water; eventually, it won't dissolve anymore and will start to settle at the bottom as crystals. This simple analogy helps us understand the formation of kidney stones, medically known as renal calculi. Our urine is a complex solution containing various dissolved salts, minerals, and waste products. Under normal conditions, these substances remain dissolved. However, when the balance is disrupted—perhaps due to high concentrations of certain substances, changes in urine pH, or insufficient fluid intake—these dissolved components can precipitate out, crystallize, and aggregate to form solid masses. These "stones" can vary greatly in size and composition, and their presence in the urinary tract can cause significant pain, blockages, and other complications.
Let's break down the given assertion and reason:
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Analyzing Assertion (A): "Renal calculi are hard crystalline structures formed in urinary tract."
- Reasoning: This statement accurately describes renal calculi. "Renal" refers to the kidneys, and "calculi" means stones. These are indeed solid, hard masses that develop from crystals separating from the urine. They typically form in the kidneys but can travel anywhere along the urinary tract, which includes the kidneys, ureters (tubes connecting kidneys to bladder), bladder, and urethra (tube carrying urine out of the body). Their crystalline nature is fundamental to their formation and their characteristic hardness.
- Therefore, Assertion (A) is true.
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Analyzing Reason (R): "They are formed when the concentration of oxalates is high in urine."
- Reasoning: This statement points to a major cause of kidney stone formation. The most common type of kidney stone, accounting for about 70-80% of all cases, is composed of calcium oxalate. Oxalate is a natural substance found in many foods (like spinach, rhubarb, nuts, chocolate, tea) and is also produced by the liver. When the concentration of oxalate in the urine becomes excessively high (a condition known as hyperoxaluria), it can combine with calcium to form insoluble calcium oxalate crystals.
- [!TIP] The formation of stones is often a multi-factor process. It's not just high oxalate; often, high calcium levels (hypercalciuria), low urine volume (dehydration), certain dietary habits, genetic predispositions, and even specific medical conditions can contribute. However, high oxalate concentration is a primary and direct risk factor for the most common type of stone. …
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