Excretory System Archives

1. In dialysis for kidney failure patients, the dialysing fluid is iso-os

In dialysis for kidney failure patients, the dialysing fluid is iso-osmotic to

Blood

Urine

Water

Body fluid

This question was previously asked in

UPSC CISF-AC-EXE – 2018

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In dialysis for kidney failure patients, the dialysing fluid is iso-osmotic to Blood.

– Dialysis is a process that filters waste products and excess fluid from the blood when the kidneys are unable to perform these functions.
– The dialysing fluid, or dialysate, is a sterile solution that is separated from the patient’s blood by a semi-permeable membrane (the dialyser or peritoneum).
– The dialysate is carefully formulated to have an osmotic pressure similar to that of normal blood plasma (making it iso-osmotic to blood) to prevent damage to blood cells and large shifts in fluid balance.
– Waste products like urea and creatinine, which are in high concentration in the patient’s blood, diffuse across the membrane into the dialysate where their concentration is low.
– Excess electrolytes in the blood can also be removed, and necessary electrolytes added to the blood from the dialysate, facilitating balance.
– Water removal (ultrafiltration) is typically achieved by creating a pressure gradient or sometimes by adding glucose to the dialysate to increase its osmotic pressure slightly compared to blood, but the base solution is iso-osmotic.

While the dialysate composition aims to restore the body’s overall fluid and electrolyte balance (related to “Body fluid”), the direct interaction is with the blood flowing through the dialyser. Therefore, its osmotic property is most critically matched to blood plasma to ensure safe and effective filtration and solute exchange without causing harm to blood cells.

2. In humans, urea is mainly formed from the metabolism of which one of t

In humans, urea is mainly formed from the metabolism of which one of the following components of food ?

Fatty acids

Vitamins

Amino acids

Glucose

This question was previously asked in

UPSC CAPF – 2023

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Urea is the main nitrogenous waste product excreted by mammals. It is formed in the liver through the urea cycle, which processes excess amino groups from the breakdown of amino acids. Amino acids are the building blocks of proteins, and their metabolism yields nitrogen that must be eliminated from the body, primarily as urea.

Amino acids, derived from protein digestion, contain nitrogen. The liver converts this excess nitrogen into urea for excretion.

Fatty acids are primarily metabolized for energy storage and production. Vitamins are organic compounds required in small amounts for various metabolic processes. Glucose is the primary source of energy through cellular respiration. While the metabolism of fats, carbohydrates, and proteins are interconnected, urea formation specifically relates to the detoxification of nitrogen from amino acid breakdown.

3. Which part of nephron of the human kidney is responsible for filtratio

Which part of nephron of the human kidney is responsible for filtration of blood for excretion ?

Collecting duct

Renal vein

Ureter

Bowman's capsule

This question was previously asked in

UPSC NDA-2 – 2024

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Filtration of blood in the human kidney for the purpose of excretion occurs in the renal corpuscle, specifically within the structure known as Bowman’s capsule. Blood is filtered from the glomerulus (a network of capillaries) into the space within Bowman’s capsule.

The nephron is the functional unit of the kidney. It consists of the renal corpuscle (Glomerulus and Bowman’s capsule) and the renal tubule. The renal corpuscle is where the initial step of urine formation, glomerular filtration, takes place.

After filtration in Bowman’s capsule, the filtrate passes through the renal tubule (proximal convoluted tubule, loop of Henle, distal convoluted tubule), where essential substances are reabsorbed back into the blood, and waste products are further secreted into the tubule. The collecting duct collects urine from multiple nephrons before it travels to the renal pelvis and out via the ureter. The renal vein carries purified blood away from the kidney.

4. Urea is produced by metabolism of

Urea is produced by metabolism of

Proteins

Carbohydrates

Lipids

Both Proteins and Carbohydrates

This question was previously asked in

UPSC CDS-2 – 2022

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Urea is the main nitrogen-containing metabolic waste product in mammals. It is synthesized in the liver and excreted by the kidneys.

– Urea is produced from the breakdown of amino acids, which are the building blocks of proteins. When proteins are consumed in excess of the body’s needs or when tissues are broken down, the amino groups from amino acids are removed (deamination). These amino groups are converted into ammonia, which is toxic. The liver then converts ammonia into urea through the urea cycle.
– Carbohydrates and lipids are primarily metabolized for energy, producing carbon dioxide and water as waste products, not significant amounts of nitrogenous waste like urea.

Elevated levels of urea in the blood (azotemia or uremia) can indicate kidney dysfunction, as the kidneys are responsible for filtering urea out of the blood.

5. The foul smell of urine of a healthy man having healthy food, when spi

The foul smell of urine of a healthy man having healthy food, when spilled on floor, is mainly due to the bacterial decomposition of

urea into sulphur dioxide

sugar into carbon dioxide

lipids into methane

urea into ammonia

This question was previously asked in

UPSC CDS-2 – 2017

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When urine containing urea is exposed to air, bacteria (such as those commonly found in soil or on surfaces) break down the urea through a process called hydrolysis, producing ammonia. Ammonia is a volatile gas with a strong, pungent odor that causes the foul smell.

The enzymatic decomposition of urea by bacteria yields ammonia and carbon dioxide.

Fresh urine from a healthy individual is usually sterile and has little odor. The characteristic strong smell develops upon standing or spilling, due to the bacterial breakdown of urea. This is why ammonia is often used in cleaning products, although its smell is undesirable in other contexts.

6. Which one of the following is the correct sequence of organs that occu

Which one of the following is the correct sequence of organs that occur in the path of urine flow in human body?

Kidney, ureter, urinary bladder, urethra

Kidney, urinary bladder, ureter, urethra

Kidney, ureter, urethra, urinary bladder

Urinary bladder, kidney, urethra, ureter

This question was previously asked in

UPSC CDS-1 – 2020

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The urinary system in humans produces, stores, and eliminates urine. Urine is formed in the kidneys through filtration and reabsorption processes. From the kidneys, urine travels down two tubes called ureters to reach the urinary bladder, a muscular sac that stores urine. When the bladder is full, urine is expelled from the body through a tube called the urethra.

The correct sequence of organs in the path of urine flow is: Kidney $\rightarrow$ Ureter $\rightarrow$ Urinary Bladder $\rightarrow$ Urethra. Any other order would be incorrect based on the physiological process of urine formation, transport, storage, and elimination.

The kidneys are the primary organs of the urinary system, filtering blood to produce urine. The ureters are conduits. The urinary bladder is a temporary reservoir. The urethra is the final passage out of the body. This sequence ensures that urine is collected and stored before voluntary or involuntary expulsion.

7. Which one of the following statements is correct?

Which one of the following statements is correct?

Urea is produced in liver.

Urea is produced in blood.

Urea is produced from digestion of starch.

Urea is produced in lung and kidney.

This question was previously asked in

UPSC CDS-1 – 2019

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The correct answer is A. Urea is the principal nitrogenous waste product in humans and other mammals. It is synthesized in the liver through a metabolic pathway known as the urea cycle (or ornithine cycle). This process converts ammonia, a toxic byproduct of protein metabolism, into less toxic urea. Urea is then released into the bloodstream and transported to the kidneys for excretion in urine.

Urea is primarily synthesized in the liver through the urea cycle.

Amino acids from dietary protein are broken down in the liver, producing ammonia. The urea cycle combines ammonia with carbon dioxide to form urea. The kidneys filter urea from the blood, concentrating it in urine for elimination from the body. The lungs are involved in gas exchange (oxygen and carbon dioxide), and the digestion of starch yields glucose, not urea.