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MENINGES

The meninges of the cranial cavity serve many functions, including to protect and anchor the central nervous system and to provide a route for blood to travel to the brain. It also encloses the cerebrospinal fluid, a nurturing fluid that also cushions the brain against impact. The folds of the dura mater also form venous channels through which deoxygenated blood flows before reaching the jugular and ophthalmic veins to leave the cranium. As the nerves of the central nervous system exit to the periphery, the dura mater will merge with the nerves to separate the individual fibers, becoming the endoneurial connective tissue of the peripheral nerve.

  1. Identify the periosteal and meningeal layers of the dura mater, which separate at various locations to form dural sinuses (Figure 5.1).

Figure 5.1

The brain and spinal cord encased in dura mater.

  1. Identify the superior sagittal sinus at the top of the falx cerebri, the dura mater extending along the length of the hemispheres of the cerebrum (Figure 5.2).

  1. Note any arachnoid granulations on the superior sagittal sinus.

  2. Identify the inferior sagittal sinus at the bottom of the falx cerebri.

  3. Trace the inferior sagittal sinus posteriorly where it becomes the straight sinus between the falx cerebri and tentorium cerebelli, a “tent” of dura mater over the cerebellum.

  4. Identify the transverse sinus running horizontally within the posterior dura.

  5. Identify the confluens of the sinuses where the transverse, superior sagittal, and straight sinuses meet.

  6. Identify the middle meningeal artery as it courses through the dura mater.

  7. Identify the impression of the sigmoid sinus on the interior surface of the cranium.

  8. Cut through the tentorium cerebelli to remove the dura from the brain. Retain the dura mater.

  9. Identify the arachnoid mater membrane as it has collapsed on the surface of the brain (Figure 5.3).

Figure 5.3

The brain and spinal cord with dura mater removed to reveal arachnoid and pia mater.

  1. The pia mater is intricately associated with the surface of the brain parenchyma and contains blood vessels.

  2. Between the arachnoid mater and the pia mater in situ is the location of the cerebrospinal fluid.

THE GROSS BRAIN AND SPINAL CORD

The structure of the brain, its gyri, and sulci (or “hills” and “valleys”) are tightly controlled developmentally and produce remarkably similar patterns across individuals. For this reason, each gyrus and region of the surface of the brain has specific and well-defined functions. This knowledge is critical for diagnosing and understanding neurological and behavioral deficits that can be caused by ...

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