201. Calcitriol formed by the kidneys is most directly associated with:
ⓐ. regulation of calcium balance in the body
ⓑ. breakdown of urea into ammonia
ⓒ. control of bladder emptying
ⓓ. filtration of proteins through the glomerulus
Correct Answer: regulation of calcium balance in the body
Explanation: Calcitriol is the active form of vitamin D and is formed with the help of the kidneys. It is important in maintaining calcium balance in the body by promoting calcium absorption and supporting proper mineral homeostasis. This function connects the kidneys to bone health and mineral metabolism. It shows again that the kidneys are not only excretory organs but also organs with important endocrine roles. Without proper calcitriol formation, calcium regulation may be disturbed. This makes calcitriol a significant functional product of the kidneys.
202. Which statement best summarizes why the kidneys are considered homeostatic organs?
ⓐ. They only remove urine from the bladder at regular intervals
ⓑ. They mainly serve as storage sacs for metabolic wastes
ⓒ. They help maintain stable internal conditions by regulating water, ions, pH, and certain hormones
ⓓ. They function only when nitrogenous wastes are present in excess
Correct Answer: They help maintain stable internal conditions by regulating water, ions, pH, and certain hormones
Explanation: The kidneys are called homeostatic organs because they help keep the internal environment of the body stable. They regulate water content, electrolyte concentration, and acid-base balance, all of which are essential for normal cellular activity. In addition, they produce or activate important substances such as erythropoietin, renin, and calcitriol. This means their role extends far beyond simple waste removal. They continuously adjust the composition of body fluids to keep body conditions within normal limits. That broad regulatory function is why the kidneys are so central to homeostasis.
203. A patient is losing large amounts of water through sweating on a hot day. Which kidney function is most directly responsible for helping restore internal balance in this situation?
ⓐ. Erythropoietin production
ⓑ. Osmoregulation
ⓒ. Calcitriol formation
ⓓ. Urochrome secretion
Correct Answer: Osmoregulation
Explanation: When a person loses a lot of water, the body must adjust the balance between water and dissolved substances in body fluids. The kidney function most directly related to this is osmoregulation. Through changes in urine volume and concentration, the kidneys help conserve water and maintain the proper osmotic condition of the blood and tissue fluids. This is different from erythropoietin production, which affects red blood cell formation, or calcitriol formation, which is linked with calcium balance. That makes osmoregulation the most relevant kidney function here.
204. Assertion: The kidneys contribute to homeostasis even when no obvious urinary problem is present. Reason: They continuously regulate water, ions, pH, and certain hormone-related functions in the body.
ⓐ. Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
ⓑ. Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion
ⓒ. Assertion is true, but Reason is false
ⓓ. Assertion is false, but Reason is true
Correct Answer: Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
Explanation: The kidneys work continuously, not only when a person is visibly urinating or when waste levels are extremely high. Their role in homeostasis includes constant adjustment of water balance, electrolyte levels, and acid-base status. They also produce or activate important regulatory substances such as erythropoietin, renin, and calcitriol. Because of this, their contribution is ongoing and essential even during ordinary daily conditions. The reason directly explains why the assertion is true.
205. Which comparison best distinguishes erythropoietin from calcitriol as kidney-related substances?
ⓐ. Erythropoietin mainly supports red blood cell formation, whereas calcitriol mainly supports calcium balance
ⓑ. Erythropoietin mainly promotes water reabsorption, whereas calcitriol mainly lowers urine output
ⓒ. Erythropoietin mainly controls bladder emptying, whereas calcitriol mainly regulates glomerular filtration
ⓓ. Erythropoietin mainly regulates sodium loss, whereas calcitriol mainly removes urea
Correct Answer: Erythropoietin mainly supports red blood cell formation, whereas calcitriol mainly supports calcium balance
Explanation: Erythropoietin and calcitriol are both important kidney-related substances, but their physiological roles are different. Erythropoietin acts mainly in relation to blood by stimulating red blood cell production in the bone marrow. Calcitriol, in contrast, is associated with calcium balance and mineral homeostasis in the body. Neither is mainly concerned with bladder emptying or direct urea removal.
206. A student says, “The kidneys only remove nitrogenous wastes and have nothing to do with the circulatory system.” Which correction is most accurate?
ⓐ. The statement is correct because blood pressure is controlled only by the heart
ⓑ. The statement is incorrect because the kidneys influence circulation through renin and also support blood physiology through erythropoietin
ⓒ. The statement is incorrect because the kidneys directly pump blood like accessory hearts
ⓓ. The statement is correct because kidney hormones act only inside nephrons and never affect the blood
Correct Answer: The statement is incorrect because the kidneys influence circulation through renin and also support blood physiology through erythropoietin
Explanation: The kidneys are not limited to eliminating nitrogenous wastes. They also influence the circulatory system by releasing renin, which helps regulate blood pressure through the renin-angiotensin mechanism. In addition, they produce erythropoietin, which promotes red blood cell formation and therefore affects the oxygen-carrying capacity of blood. These are important systemic roles that go far beyond excretion alone. The kidneys do not pump blood like hearts, but they do regulate major aspects of internal circulation and blood composition. So the student’s statement is incomplete and incorrect.
207. Which of the following is not a homeostatic function of the kidneys?
ⓐ. Maintaining acid-base balance of the blood
ⓑ. Helping regulate electrolyte composition of body fluids
ⓒ. Storing urine for a period before elimination
ⓓ. Contributing to osmoregulation
Correct Answer: Storing urine for a period before elimination
Explanation: Storing urine is mainly the function of the urinary bladder, not a homeostatic function of the kidneys themselves. In contrast, regulating acid-base balance, electrolyte levels, and water balance are all true homeostatic roles of the kidneys. These functions help maintain stable internal conditions required for normal cell activity. It helps separate kidney physiology from the roles of other urinary organs.
208. If kidney production of calcitriol became severely impaired, which body regulation would be most directly affected?
ⓐ. Calcium balance and related mineral homeostasis
ⓑ. Voluntary control of the external urethral sphincter
ⓒ. Filtration pressure in Bowman’s capsule alone
ⓓ. Yellow colour of urine due to urochrome
Correct Answer: Calcium balance and related mineral homeostasis
Explanation: Calcitriol is the active form of vitamin D associated with kidney function, and it plays an important role in calcium balance. If its formation is impaired, the body becomes less effective at maintaining proper mineral regulation, especially involving calcium. This is different from neural control of micturition or the pigment responsible for urine colour. It is also not limited to filtration pressure at the glomerulus. The key consequence is disturbance of mineral homeostasis rather than a direct problem of urine transport.
209. Which of the following is correctly called an accessory excretory organ in humans?
ⓐ. Lungs
ⓑ. Urinary bladder
ⓒ. Ureter
ⓓ. Urethra
Correct Answer: Lungs
Explanation: Accessory excretory organs are organs other than the kidneys that also help remove certain metabolic wastes from the body. The lungs are included in this group because they eliminate carbon dioxide and water vapour produced during cellular respiration. In contrast, the urinary bladder, ureter, and urethra are parts of the urinary system concerned mainly with storage or transport of urine rather than being accessory excretory organs. The idea of “accessory” means that these organs assist in excretion but are not the principal urine-forming organs. So the lungs are a correct example of an accessory excretory organ.
210. The excretory role of the lungs is mainly the removal of:
ⓐ. urea and uric acid
ⓑ. bile pigments and cholesterol
ⓒ. carbon dioxide and water vapour
ⓓ. sodium chloride and lactic acid
Correct Answer: carbon dioxide and water vapour
Explanation: The lungs remove carbon dioxide produced during respiration and also eliminate some water in the form of water vapour during exhalation. Because both of these are metabolic waste products, the lungs perform an excretory role in addition to their respiratory function. They do not mainly remove urea or uric acid, which are more closely associated with the kidneys. They also do not eliminate bile pigments, which are linked with the liver. The lungs are therefore accessory excretory organs because of their role in removing gaseous wastes.
211. Which accessory excretory organ helps remove bile pigments from the body?
ⓐ. Skin
ⓑ. Lungs
ⓒ. Kidney
ⓓ. Liver
Correct Answer: Liver
Explanation: The liver plays an accessory excretory role by helping eliminate substances such as bile pigments and excess cholesterol through bile. Bile pigments arise from the breakdown of haemoglobin and are removed from the body through the digestive tract. This makes the liver important not only in digestion and metabolism but also in excretion. The skin mainly removes sweat, while the lungs remove carbon dioxide and water vapour. The kidney is the principal excretory organ, not an accessory one in this context. So the liver is the organ most directly associated with the excretion of bile pigments.
212. Sweat released by the skin commonly contains:
ⓐ. only carbon dioxide and oxygen
ⓑ. water, salts, and small amounts of urea
ⓒ. bile pigments and large plasma proteins
ⓓ. glucose and amino acids in high concentration
Correct Answer: water, salts, and small amounts of urea
Explanation: The skin acts as an accessory excretory organ because sweat glands remove water, mineral salts, and small amounts of nitrogenous wastes such as urea. Sweat may also contain traces of substances like lactic acid. This excretory role is not the main function of the skin, but it still contributes to waste removal and helps in maintaining internal balance. The skin does not normally excrete bile pigments or large plasma proteins. It also does not eliminate high concentrations of glucose and amino acids in healthy conditions. So sweat is best described as containing mainly water, salts, and small amounts of urea.
213. Why is the liver considered an accessory excretory organ even though it is not part of the urinary system?
ⓐ. It helps remove certain waste substances such as bile pigments and also converts ammonia into urea
ⓑ. It stores urine before the kidneys begin filtration
ⓒ. It directly carries urine to the urinary bladder through ducts
ⓓ. It performs micturition when the bladder is full
Correct Answer: It helps remove certain waste substances such as bile pigments and also converts ammonia into urea
Explanation: The liver contributes to excretion in more than one way. It removes bile pigments and certain other waste materials through bile, and it also converts highly toxic ammonia into urea, which can then be eliminated by the kidneys. These actions make the liver an important supporting organ in waste management even though it does not produce urine directly. This is why it is called an accessory excretory organ rather than a principal urinary organ. The liver is therefore linked with both detoxification and excretory support. Its role shows that excretion in the body is not limited to the urinary system alone.
214. Which statement best distinguishes the excretory role of the skin from that of the lungs?
ⓐ. The skin removes bile pigments, while the lungs remove cholesterol
ⓑ. The skin forms urine, while the lungs store it
ⓒ. The skin converts ammonia into urea, while the lungs excrete uric acid
ⓓ. The skin removes sweat containing water and salts, while the lungs remove carbon dioxide and water vapour
Correct Answer: The skin removes sweat containing water and salts, while the lungs remove carbon dioxide and water vapour
Explanation: Both the skin and lungs act as accessory excretory organs, but they eliminate different waste products. The skin mainly removes water, salts, and traces of nitrogenous waste through sweat. The lungs remove carbon dioxide and water vapour during exhalation. Neither of these organs forms urine, and neither takes over the liver’s role in bile-related excretion. So the best comparison is the difference between sweat excretion and gaseous waste removal.
215. Which of the following is not mainly an excretory function of the liver?
ⓐ. Elimination of bile pigments through bile
ⓑ. Conversion of ammonia into urea
ⓒ. Removal of some cholesterol through bile
ⓓ. Removal of carbon dioxide during expiration
Correct Answer: Removal of carbon dioxide during expiration
Explanation: Removal of carbon dioxide during expiration is the function of the lungs, not the liver. The liver’s accessory excretory roles include eliminating bile pigments, helping remove cholesterol through bile, and converting toxic ammonia into urea. These functions connect the liver closely with waste management and detoxification. However, the liver does not take part in gaseous exchange with the external environment. That role belongs to the respiratory system, especially the lungs.
216. Which statement best summarizes why lungs, liver, and skin are called accessory excretory organs?
ⓐ. They replace the kidneys completely in urine formation
ⓑ. They store metabolic wastes until the bladder is empty
ⓒ. They also help remove certain wastes from the body, although the kidneys remain the chief excretory organs
ⓓ. They are microscopic parts of the nephron working outside the kidney
Correct Answer: They also help remove certain wastes from the body, although the kidneys remain the chief excretory organs
Explanation: Lungs, liver, and skin are called accessory excretory organs because they assist in removing waste materials from the body, but they do not replace the kidneys as the main excretory organs. The kidneys remain the chief organs for removal of nitrogenous wastes and for urine formation. The accessory organs contribute in more specialized or limited ways, such as removal of carbon dioxide by the lungs, bile pigments by the liver, and sweat components by the skin. The organs are therefore “accessory” because they assist, not because they perform the main urinary role.
217. A student says, “The skin is only a protective and temperature-regulating organ, so it has no role in excretion.” Which correction is best?
ⓐ. The statement is correct because only kidneys and lungs remove wastes
ⓑ. The statement is incorrect because sweat glands also remove water, salts, and small amounts of urea
ⓒ. The statement is correct because sweat contains only oils and no dissolved wastes
ⓓ. The statement is incorrect because the skin converts ammonia into urea like the liver
Correct Answer: The statement is incorrect because sweat glands also remove water, salts, and small amounts of urea
Explanation: The skin is not the chief excretory organ, but it still contributes to excretion through the activity of sweat glands. Sweat contains water, salts, and small quantities of nitrogenous waste such as urea. This means the skin helps remove certain waste materials from the body while also participating in temperature regulation. The student’s statement is therefore incomplete because it ignores this accessory excretory role. The skin does not replace the kidneys, but it does assist in waste removal. That supporting role is why it is called an accessory excretory organ.
218. Assertion: The lungs are accessory excretory organs even though they are primarily respiratory organs. Reason: They remove carbon dioxide and water vapour, both of which are metabolic waste products.
ⓐ. Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
ⓑ. Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion
ⓒ. Assertion is true, but Reason is false
ⓓ. Assertion is false, but Reason is true
Correct Answer: Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
Explanation: The lungs are mainly known for gas exchange in respiration, but they also remove substances that must be eliminated from the body. Carbon dioxide is produced during cellular respiration, and excess carbon dioxide must be excreted to maintain normal internal balance. Water vapour is also lost during exhalation. Because these substances are metabolic wastes, their removal is an excretory function. The reason directly explains why the lungs are classified as accessory excretory organs.
219. Which of the following is not an accessory excretory organ in humans?
ⓐ. Skin
ⓑ. Liver
ⓒ. Lungs
ⓓ. Urinary bladder
Correct Answer: Urinary bladder
Explanation: Accessory excretory organs are those that help remove certain wastes from the body besides the kidneys. The skin, liver, and lungs all fit this description because they eliminate sweat components, bile-related wastes, and gaseous wastes respectively. The urinary bladder, however, does not remove wastes by itself. It mainly stores urine after the kidneys have formed it and before it is expelled from the body. So it belongs to the urinary system but not to the accessory excretory organs. Storage is not the same as excretion.
220. A blockage prevents bile from reaching the intestine normally. Which accessory excretory function would be most directly affected?
ⓐ. Removal of carbon dioxide by the lungs
ⓑ. Elimination of bile pigments by the liver
ⓒ. Loss of water and salts through sweat glands
ⓓ. Reabsorption of water in the collecting duct
Correct Answer: Elimination of bile pigments by the liver
Explanation: The liver helps in excretion by passing bile pigments and certain other substances into bile, which normally reaches the intestine. If bile flow is blocked, this excretory pathway is directly disturbed. The lungs and skin would still continue their own accessory excretory functions, but liver-related elimination of bile pigments would be affected. The collecting duct belongs to kidney function and is unrelated to bile transport. It shows that the liver’s excretory role depends on the normal movement of bile.
