Moderate

The brain is a very delicate structure with little room to move around. Surrounding the brain and the spinal cord are three protective layers in addition to the skull and the vertebral column. Directly surrounding the brain and spinal cord is the pia mater. Following the pia mater is the arachnoid mater. Between the pia mater and the arachnoid mater is the subarachnoid space where the cerebrospinal fluid circulates. Finally, the protective layer is the dura mater is loosely attached to the arachnoid mater but is strongly associated with the skull bone.Depending on the type of injury, a certain type of vein and/or artery are more susceptible to injury. For example, the meningeal artery and vein run through the foramen spinosum and travel between the two layers making up the dura mater. As the artery and the vein are traveling in between the dura mater, there is a vulnerable region at the temple. A strike to the temple region could rupture these vessels and result in a epidural hematoma. Traveling from the cerebral cortex to the venous dural sinus (located at certain regions between the two layers of the dura mater) is the cerebral vein. When an injury results in the dura mater shifting away from the arachnoid mater, the cerebral vein could rupture and lead to a subdural hematoma. When a physician performs a lumbar puncture, he/she is extracting cerebrospinal fluid. Through which of the follow structure(s) must the needle pass?I. Dura materII. Arachnoid materIII. Pia mater

Correct answer: B. I and II

  • A. I
  • B. I and II
  • C. III and I
  • D. III

Explanation

As described in the passage, the innermost layer is the pia mater, then the arachnoid space, arachnoid mater and finally the dura mater. The dura mater is the outermost layer prior to the skull/vertebral column. Therefore, during a lumbar puncture, the needle will have to pass through the dura mater first then through the arachnoid mater to get to the subarachnoid space.

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