Which of the following types of cells is primarily responsible for the destruction of old cells and invasive micro-organisms?
- A. Basophils
- B. Eosinophils
- C. B-cells
- D. Macrophages
Correct Answer: D
Rationale: Macrophages are a type of white blood cell that plays a crucial role in the immune system by engulfing and digesting cellular debris, foreign substances, microbes, cancer cells, and old or damaged cells. Basophils are primarily involved in allergic reactions and parasitic infections, eosinophils combat multicellular parasites and have a role in allergic reactions, and B-cells are responsible for producing antibodies. Therefore, the correct answer is macrophages as they are specialized in phagocytosis and removal of unwanted cells and microorganisms.
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Which of the following bones is a component of the appendicular skeleton?
- A. Xiphoid process
- B. Symphysis pubis
- C. Sacrum
- D. Sternum
Correct Answer: B
Rationale: The correct answer is B: Symphysis pubis. The symphysis pubis is a component of the appendicular skeleton, specifically part of the pelvic girdle. The xiphoid process (Choice A) is part of the axial skeleton, located at the lower end of the sternum. The sacrum (Choice C) is also part of the axial skeleton, forming the posterior part of the pelvis. The sternum (Choice D) is part of the axial skeleton, located in the center of the chest.
Which part of the brain regulates heart rate, respiratory rate, and blood pressure?
- A. Corpus Callosum
- B. Medulla Oblongata
- C. Pituitary Glands
- D. Pineal Glands
Correct Answer: B
Rationale: The correct answer is the Medulla Oblongata. This part of the brain is responsible for regulating essential autonomic functions such as heart rate, respiratory rate, and blood pressure. The Corpus Callosum is responsible for connecting the left and right hemispheres of the brain, not for regulating these vital functions. The Pituitary Glands and Pineal Glands are part of the endocrine system and are not directly involved in regulating heart rate, respiratory rate, and blood pressure.
Which of the following electrolytes plays an essential role in the clotting of blood?
- A. sodium
- B. magnesium
- C. calcium
- D. potassium
Correct Answer: C
Rationale: Calcium plays an essential role in the clotting of blood by being involved in several steps of the coagulation process. It is necessary for the conversion of prothrombin to thrombin, which is a crucial step in forming blood clots. Sodium, magnesium, and potassium do not directly participate in the clotting cascade and are not associated with the coagulation process. Therefore, the correct answer is calcium.
Which of the following cardiac valves prevents blood from returning to the left ventricle of the heart?
- A. pulmonic
- B. mitral
- C. tricuspid
- D. aortic
Correct Answer: D
Rationale: The correct answer is the aortic valve. The aortic valve is located between the left ventricle and the aorta, preventing the backflow of blood into the left ventricle once it has been pumped out during systole. Choice A, pulmonic, is incorrect as it is associated with the right side of the heart. Choice B, mitral, is incorrect as it is the valve between the left atrium and ventricle. Choice C, tricuspid, is incorrect as it is located between the right atrium and ventricle.
Which of the following ions is most abundant in extracellular fluid?
- A. Calcium
- B. Chloride
- C. Sodium
- D. Potassium
Correct Answer: C
Rationale: Sodium is the most abundant ion in extracellular fluid. It plays a crucial role in maintaining fluid balance, nerve function, and muscle contraction. Calcium (Choice A) is mainly found in bones and teeth, Chloride (Choice B) is the major anion in extracellular fluid but not the most abundant ion, and Potassium (Choice D) is found predominantly inside cells.