MCAT Biology Question 32: Answer and Explanation
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Question: 32
2. Which of the following associations of a primary germ layer and an adult organ is correct?
- A. Endoderm—cardiac muscle
- B. Endoderm—lens of the eye
- C. Ectoderm—fingernails
- D. Mesoderm—lungs
Correct Answer: C
Explanation:
To answer this question, it could be useful to review quickly the embryonic layers. The ectoderm gives rise to the integument (the epidermis, hair, nails, and the epithelia of the nose, mouth, and anal canal), the lens of the eye, and the nervous system (including the adrenal medulla). The endoderm gives rise to the epithelial linings of the digestive and respiratory tracts and parts of the liver, pancreas, thyroid, and bladder. Finally, from the mesoderm arise the musculoskeletal system, the circulatory system, the excretory system, the gonads, and the adrenal cortex. Therefore, the only incorrect association can be found in choice (C) because the fingernails are derived from ectoderm.