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SECTION 1: BACK

Directions: Each of the numbered items or incomplete statements is followed by lettered options. Select the letter that most likely represents the best option for each question.

1. A 48-year-old man goes to his physician because of pain and paresthesia along the lateral aspect of the leg and the dorsum of the foot. The patient's symptoms suggest impingement of the L5 spinal nerve resulting from a herniated intervertebral disc. The L5 spinal nerve most likely exits between which of the following vertebrae?

A. L3–L4 vertebrae

B. L4–L5 vertebrae

C. L5–S1 vertebrae

D. S1–S2 vertebrae

1—C: Spinal nerves in the thoracic and lumbar vertebral region exit the vertebral canal below their associated vertebra. Therefore, the L5 spinal nerve exits below L5, between L5 and S1.

2. The muscles of the posterior aspect of the thigh, or hamstring musculature, are responsible for flexing the knee joint. Beginning with the motor neuron cell bodies in the gray matter of the spinal cord, identify the most likely pathway that axons would travel from the spinal cord to the hamstring muscles?

A. Ventral horn, ventral root, ventral ramus

B. Ventral horn, ventral root, dorsal ramus

C. Lateral horn, ventral root, ventral ramus

D. Lateral horn, dorsal root, dorsal ramus

E. Dorsal horn, dorsal root, ventral ramus

F. Dorsal horn, dorsal root, dorsal ramus

2—A: The ventral horn of the spinal cord gray matter houses motor neuron cell bodies and conveys motor neurons out through the ventral root into the segmental spinal nerve. All muscles of the limbs and body wall are innervated by ventral rami. Although the muscles are present along the posterior aspect of the thigh, muscles are still innervated by the ventral rami. Dorsal rami innervate the skin of the back and the deep back muscles, such as the erector spinae.

3. A 27-year-old man is brought to the emergency department after being involved in an automobile accident. Radiographic imaging studies indicate that he has sustained a fracture of the L1 vertebral arch and has a partially dislocated bone fragment impinging upon the underlying spinal cord. Which spinal cord level is most likely compressed by this bone fragment?

A. C1

B. L2

C. S3

D. T4

3—C: In an adult, the caudal end of the ...

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