The congenital defect where the vertebrae do not close, leaving the spinal cord unprotected, is known as what?

The condition characterized by incomplete closure of the vertebrae, which results in the spinal cord being unprotected, is known as spina bifida. This congenital defect occurs when the neural tube, which forms the spine and surrounding structures during early embryonic development, fails to close properly. As a result, various types of spina bifida can develop, with varying levels of severity and implications for neurological function, depending on how much of the spinal cord and nerves are affected.

In this context, it is essential to recognize that "myelomeningocele" is a specific type of spina bifida where the spinal cord and nerve roots protrude through the spinal column. While myelomeningocele is a serious manifestation of spina bifida, the broader term spina bifida encompasses all forms of this defect. The other conditions listed, such as arteriovenous malformation—which pertains to a vascular anomaly—and Menier's disease, which is related to ear issues, are not relevant to the defect involving the spinal column. Therefore, identifying spina bifida as the correct answer highlights the primary term for the condition in question.