Q1. Which organ in the human excretory system is responsible for filtering waste products from the blood?
a) Liver
b) Lungs
c) Kidneys
d) Pancreas
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Correct Answer: c) Kidneys
Explanation: The kidneys play a vital role in the excretory system by filtering metabolic waste products, excess ions, and toxins from the bloodstream. They regulate blood volume, pressure, and pH by producing urine, which is then transported to the bladder for excretion through the urethra.
Q2. What is the primary nitrogenous waste product excreted by humans?
a) Urea
b) Ammonia
c) Uric acid
d) Creatinine
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Correct Answer: a) Urea
Explanation: Urea is the primary nitrogenous waste product excreted by humans. It is formed in the liver as a result of protein metabolism and is transported to the kidneys for excretion in urine. Urea accounts for the majority of nitrogenous waste eliminated from the body.
Q3. Which part of the nephron is responsible for reabsorbing water and essential solutes back into the bloodstream?
a) Glomerulus
b) Bowman’s capsule
c) Proximal convoluted tubule
d) Distal convoluted tubule
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Correct Answer: c) Proximal convoluted tubule
Explanation: The proximal convoluted tubule (PCT) is the segment of the nephron responsible for reabsorbing water, glucose, amino acids, and ions back into the bloodstream from the glomerular filtrate. It plays a crucial role in maintaining the body’s water balance and regulating blood composition.
Q4. Which hormone regulates the concentration of sodium ions and water in the urine by acting on the distal convoluted tubule and collecting ducts?
a) Aldosterone
b) Antidiuretic hormone (ADH)
c) Renin
d) Atrial natriuretic peptide (ANP)
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Correct Answer: a) Aldosterone
Explanation: Aldosterone is a hormone produced by the adrenal glands that regulates sodium and potassium ion balance in the body. It acts on the distal convoluted tubule and collecting ducts of the nephron to increase sodium reabsorption and potassium secretion, thus regulating blood pressure and blood volume.
Q5. Which structure connects the kidneys to the bladder and transports urine from the kidneys to the bladder?
a) Ureter
b) Urethra
c) Renal artery
d) Renal vein
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Correct Answer: a) Ureter
Explanation: The ureters are muscular tubes that connect each kidney to the bladder. They transport urine from the renal pelvis of the kidney to the urinary bladder for storage and eventual excretion. Peristaltic contractions of the ureter walls help propel urine toward the bladder.
Q6. Which segment of the nephron is responsible for the formation of concentrated urine by reabsorbing water under the influence of antidiuretic hormone (ADH)?
a) Glomerulus
b) Loop of Henle
c) Bowman’s capsule
d) Distal convoluted tubule
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Correct Answer: b) Loop of Henle
Explanation: The Loop of Henle is the segment of the nephron responsible for establishing and maintaining the osmotic gradient in the renal medulla, which is essential for the formation of concentrated urine. Water reabsorption occurs in the descending limb, while ion reabsorption occurs in the ascending limb, under the influence of ADH.
Q7. Which gland produces the hormone erythropoietin, which stimulates the production of red blood cells in response to low oxygen levels?
a) Thyroid gland
b) Pituitary gland
c) Adrenal gland
d) Kidney
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Correct Answer: d) Kidney
Explanation: The kidneys produce erythropoietin, a hormone that stimulates the bone marrow to produce red blood cells (erythropoiesis) in response to low oxygen levels in the blood. Erythropoietin secretion increases when oxygen delivery to the kidneys is reduced, such as in cases of hypoxia or anemia.
Q8. Which of the following is a function of the urinary bladder?
a) Filtration of waste products
b) Reabsorption of water and ions
c) Storage and temporary retention of urine
d) Production of urine
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Correct Answer: c) Storage and temporary retention of urine
Explanation: The urinary bladder is a hollow muscular organ that stores urine temporarily before it is excreted from the body through the urethra. When the bladder fills to a certain capacity, stretch receptors signal the urge to urinate, prompting the bladder to contract and expel urine.
Q9. What is the functional unit of the kidney responsible for the filtration of blood and formation of urine?
a) Glomerulus
b) Nephron
c) Loop of Henle
d) Bowman’s capsule
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Correct Answer: b) Nephron
Explanation: The nephron is the functional unit of the kidney responsible for filtering blood, reabsorbing essential substances, and secreting waste products to form urine. Each kidney contains millions of nephrons, each comprising a renal corpuscle (glomerulus and Bowman’s capsule) and renal tubules.
Q10. Which of the following substances is primarily responsible for maintaining the acid-base balance in the body through renal excretion?
a) Urea
b) Ammonia
c) Bicarbonate ions
d) Creatinine
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Correct Answer: c) Bicarbonate ions
Explanation: Bicarbonate ions (HCO3-) play a crucial role in maintaining the acid-base balance (pH) of the body. The kidneys regulate blood pH by reabsorbing filtered bicarbonate ions and secreting hydrogen ions into urine, thereby controlling the bicarbonate buffer system and acid-base equilibrium.