ATI Fluid and Electrolytes

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. Cerebrospinal fluid and the humors of the eye are not considered extracellular fluids. Extracellular fluids are fluids found outside the cells, such as interstitial fluid and lymph. Cerebrospinal fluid is found within the central nervous system, while the humors of the eye (aqueous humor and vitreous humor) are located within the eyeball, making them distinct from extracellular fluids.

Correct Answer: D

Rationale: A low pH indicates acidosis (normal pH is 7.35 to 7.45). The PaCO2 is also low, which causes alkalosis. The bicarbonate is low, which causes acidosis. The pH bicarbonate more closely corresponds with a decrease in pH, making the metabolic component the primary problem. Therefore, the correct interpretation of the arterial blood gas results is metabolic acidosis with a compensatory respiratory alkalosis. Choices A, B, and C are incorrect because they do not accurately reflect the primary acid-base disturbance and the compensatory response seen in the given results.

Correct Answer: B

Rationale: Chloride (Cl-) is the most abundant anion in blood plasma. It plays a crucial role in maintaining osmotic balance and acid-base homeostasis. Bicarbonate (Choice A) is important for buffering acids in the body but is not the most abundant negative ion in blood plasma. Hydroxide (Choice C) is not typically found in high concentrations in blood plasma. Phosphate (Choice D) is an important anion in the body but is not as abundant as chloride in blood plasma.

Correct Answer: D

Rationale: The correct answer is D, ADH and aldosterone. Both antidiuretic hormone (ADH) and aldosterone increase water retention by the kidneys, thereby increasing blood volume. ADH acts on the kidneys to increase water reabsorption, while aldosterone acts on the kidneys to promote sodium reabsorption, leading to water retention. Choice A, ADH, is partially correct as it alone increases water retention. Choice B, aldosterone, is also partially correct as it alone increases water retention. Choice C, ANH (atrial natriuretic hormone), actually decreases water retention by promoting sodium excretion and inhibiting aldosterone release.