MCAT Biology Question 164: Answer and Explanation

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Question: 164

14. To facilitate the process of birth, an infant's head is somewhat flexible. This flexibility is given in part by the two fontanelles, which are soft spots of connective tissue in the infant's skull. With time, the fontanelles will close through a process known as:

  • A. endochondral ossification.
  • B. intramembranous ossification.
  • C. bone resorption.
  • D. longitudinal growth.

Correct Answer: B

Explanation:

Bones form in one of two ways: endochondral ossification and intramembranous ossification. Endochondral ossification is the replacement of a cartilaginous skeleton with bone and occurs mostly in long bones, eliminating choice (A). Intramembranous ossification is the formation of bone from undifferentiated connective tissue cells (mesenchyme) and occurs mostly in the skull, making choice (B) the correct answer. Bone resorption is the breakdown of bone, not its formation, eliminating choice (C). Longitudinal growth occurs in long bones and is responsible for increasing height over time, but does not play a role in fontanelle ossification, eliminating choice (D).

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