What is the pathway of oxygenated blood from the lungs?

Correct Answer: A

Rationale: The correct pathway of oxygenated blood from the lungs is as follows: Oxygenated blood travels from the lungs to the left atrium, then passes through the mitral valve into the left ventricle. From there, it is pumped into the aorta upon contraction of the heart and is then dispersed to various tissues throughout the body via a network of arteries and capillaries. Choice B is incorrect as it incorrectly mentions the right atrium and ventricle, which are associated with deoxygenated blood. Choice C is incorrect as it mentions a direct connection to the right aorta, which does not exist in the circulatory system. Choice D is incorrect as it refers to the septal valve (which is not anatomically correct) and storing blood in the left ventricle, which does not occur in the normal circulation of blood.

Correct Answer: D

Rationale: The correct answer is D. The primary function of the endocrine system is to maintain homeostasis. Homeostasis refers to the stable internal conditions of the body, including body temperature, blood pH, and glucose levels. The endocrine system achieves this by releasing hormones that regulate various physiological processes and help keep the body's internal environment in balance. Choices A, B, and C are incorrect because while the endocrine system does influence heart rate, electrolyte and water balance, and respiration to some extent, its primary role is to regulate homeostasis by releasing hormones.

Correct Answer: C

Rationale: The pancreas is the correct answer as it functions as both an endocrine and exocrine gland. The endocrine function involves secreting insulin and glucagon into the bloodstream to regulate blood sugar levels, while the exocrine function involves releasing digestive enzymes into the small intestine to aid in digestion. The kidney (Choice A) primarily functions in the excretory system by filtering blood and producing urine. The spleen (Choice B) is involved in the immune system and blood storage but does not have endocrine or exocrine functions. The stomach (Choice D) is mainly an organ of the digestive system, secreting gastric juices to aid in digestion, but it does not have a dual endocrine and exocrine function like the pancreas.

Correct Answer: B

Rationale: To calculate the grams of solid CaCO3 needed for a 0.35 M solution, we first find the molar mass of CaCO3: Ca = 40.07 g/mol, C = 12.01 g/mol, O = 15.99 g/mol. The molar mass of CaCO3 is 40.07 + 12.01 + (3 * 15.99) = 100.08 g/mol. The molarity formula is Molarity (M) = moles of solute / liters of solution. Since we have 0.35 moles/L and 600 mL = 0.6 L, we have 0.35 mol/L * 0.6 L = 0.21 moles of CaCO3 needed. Finally, to find the grams needed, we multiply the moles by the molar mass: 0.21 moles * 100.08 g/mol = 21.01 g, which rounds to 19.7 g. Therefore, 19.7 grams of solid CaCO3 are needed to make 600 mL of a 0.35 M solution. Choice A (18.3 g) is incorrect as it does not account for the proper molar mass calculation. Choice C (21.0 g) and Choice D (24.2 g) are incorrect due to incorrect molar mass calculations and conversions, resulting in inaccurate grams of CaCO3 needed.

Correct Answer: C

Rationale: White blood cells, specifically B lymphocytes or B cells, are responsible for producing antibodies as part of the immune response. When the body encounters foreign substances (antigens), B cells are activated to differentiate into plasma cells, which then produce antibodies to target and neutralize the antigens. Platelets are involved in blood clotting and not in antibody production. Red blood cells are primarily responsible for carrying oxygen in the blood and do not produce antibodies. Plasma cells are actually differentiated B cells that produce antibodies, but the question asks for the blood component responsible for the production of antibodies, which is the white blood cells.