On average, how much of the body is composed of water?

Correct Answer: D

Rationale: The correct answer is D: 60 percent. Water makes up about 60% of the human body, serving essential functions like regulating temperature, transporting nutrients, and removing waste. This percentage varies slightly based on factors like age and gender but generally remains around 60%. Choice A (10%) is too low; the body needs more water to function properly. Choice B (20%) is also too low, as it underestimates the significant role of water in the body. Choice C (40%) is closer but still underestimates the actual percentage of water in the body. Ultimately, D (60%) is the most accurate representation of the average water content in the human body.

Correct Answer: A

Rationale: The correct answer is A: peritoneal fluid. The peritoneal fluid is found in the peritoneal cavity, which surrounds the intestines. It provides lubrication and protection for the intestines during movement and digestion. The other choices, B: pericardial fluid, C: intrapleural fluid, and D: synovial fluid, are associated with different body cavities and functions unrelated to the intestines. Pericardial fluid is found in the pericardial cavity surrounding the heart, intrapleural fluid is found in the pleural cavity surrounding the lungs, and synovial fluid is found in joints for lubrication and cushioning.

Correct Answer: C

Rationale: The primary anion of the intracellular fluid (ICF) is the phosphate ion (C). Phosphate ions play a crucial role in various cellular processes such as energy production (ATP), DNA/RNA synthesis, and buffering intracellular pH. Bicarbonate ion (A) is mainly found in the extracellular fluid, while chloride ion (B) is the major anion in the extracellular fluid. Anionic proteins (D) are not typically considered the primary anion of the ICF. Therefore, the correct choice is C as it best reflects the major anion present in the intracellular fluid.

Correct Answer: B

Rationale: The correct answer is B: urinary output by the kidneys. The kidneys play a crucial role in regulating blood pressure by adjusting the volume of blood in circulation through the control of water and electrolyte balance. Increased urinary output decreases blood volume, leading to a decrease in blood pressure, while decreased urinary output increases blood volume and blood pressure. This long-term regulation mechanism helps maintain blood pressure within a normal range over time. A: the baroreceptor reflex is a short-term regulator that responds to acute changes in blood pressure. C: shifting of fluid between interstitial fluid and plasma may affect blood volume temporarily but is not the primary long-term regulator of blood pressure. D: the thirst mechanism regulates fluid intake to maintain hydration but does not directly regulate blood pressure.

Correct Answer: A

Rationale: The correct answer is A because osmolarity is determined by the total concentration of solutes, both penetrating and non-penetrating, in a solution. In this case, even though the ionic composition may be different between the intracellular fluid (ICF) and extracellular fluid (ECF), the osmolarity remains the same because the overall concentrations of nonpenetrating solutes are equal in both compartments. Choices B and C are incorrect because the permeability of the plasma membrane and protein concentrations do not directly affect osmolarity. Choice D is incorrect because osmolarity refers to the concentration of solutes in a solution, and in this context, it is stated that the osmolarity of both compartments is the same despite the ionic composition differences.