What is the most important regulator of the amount of sodium in the body?

Correct Answer: A

Rationale: The correct answer is A: Kidneys. The kidneys play a crucial role in regulating the amount of sodium in the body. They achieve this by filtering blood and controlling the excretion or reabsorption of sodium. The small intestine is primarily responsible for nutrient absorption, not sodium regulation. The large intestine is mainly involved in water absorption and waste elimination, not sodium balance. The skin helps regulate body temperature through sweating and does not directly regulate sodium levels.

Correct Answer: C

Rationale: The correct answer is C. Overhydration can occur when intravenous fluids are administered too quickly, overwhelming the body's ability to excrete the excess fluid. Choices A, B, and D are incorrect. Choice A is incorrect because overhydration is less common than dehydration. Choice B is incorrect because while overhydration can strain the kidneys, it is not due to the burden being too heavy. Choice D is incorrect because dehydration is more common than overhydration.

Correct Answer: A

Rationale: The correct answer is A, blood pressure. Blood pressure is the primary force that pushes fluid out of the capillaries into the surrounding tissues. This pressure difference is essential for the exchange of nutrients, gases, and waste products between the blood and tissues. Choices B, C, and D are incorrect as they do not represent the primary force responsible for pushing fluid in blood capillaries.

Correct Answer: C

Rationale: The correct answer is C: Sodium. Sodium (Na+) is the most abundant cation in the extracellular fluid, including blood plasma. It plays a crucial role in maintaining fluid balance, nerve function, and is essential for various physiological processes. Choice A, Potassium, is also an important ion in the body but is predominantly found intracellularly. Choice B, Calcium, is an essential mineral in the body but is not the most abundant positive ion in blood plasma. Choice D is incorrect as sodium is the primary positive ion in blood plasma, with a much higher concentration compared to potassium.

Correct Answer: A

Rationale: The correct answer is A: 80%. Newborns can have a body water content as high as 80% due to their higher total body water compared to adults. Choice B (70%) is incorrect because newborns typically have a higher body water percentage. Choice C (60%) is also incorrect as it underestimates the body water content in newborns. Choice D (90%) is incorrect as it overestimates the body water percentage in newborns.

Correct Answer: B

Rationale: The correct answer is 'Intracellular fluid.' Intracellular fluid refers to the fluid contained within the cells, constituting a significant portion of the body's total water content. Choices A, C, and D are incorrect. Plasma is the liquid component of blood outside the cells, interstitial fluid is the fluid surrounding cells in tissues, and the combination of plasma and intracellular fluid is not the specific term for the fluid inside the cell.

Correct Answer: A

Rationale: The correct answer is A: Kidneys. The kidneys play a crucial role in regulating the amount of sodium in the body. They achieve this by filtering blood and controlling the excretion or reabsorption of sodium. The small intestine is primarily responsible for nutrient absorption, not sodium regulation. The large intestine is mainly involved in water absorption and waste elimination, not sodium balance. The skin helps regulate body temperature through sweating and does not directly regulate sodium levels.

Correct Answer: D

Rationale: The correct answer is D. All the listed organs (lungs, skin, and intestines) contribute to fluid loss from the body. Lungs contribute to fluid loss through respiration, skin through sweating, and intestines through excretion. Therefore, none of the organs listed in the options retain fluids within the body. Choices A, B, and C are incorrect because all of these organs play a role in fluid output from the body.

Correct Answer: B

Rationale: The correct answer is B, Interstitial fluid. Interstitial fluid is the fluid that surrounds and occupies the spaces between cells, providing them with nutrients and removing waste. Choices A, C, and D are incorrect because intracellular fluid refers to fluid inside cells, plasma refers to the liquid component of blood, and electrolyte refers to substances that dissociate into ions in solution, affecting fluid balance but not specifically found in spaces between cells.