Dura mater

The dura mater is the outer meninges that protect the central nervous system (brain and spinal cord).

In the column, it is a hollow cylinder formed by a fibrous and thick wall, solid and not very extensible. It extends to the 2nd or 3rd sacral vertebra. Both the pia mater and the arachnoid mater are called the leptomeninges.

The internal surface is smooth and polished and corresponds to the endosteal layer, while the external one is regularly rounded and responds to the bony and ligamentous walls of the vertebral canal, corresponding to the meningeal layer (dura mater itself that does not continue into the vertebral canal), from which it is separated by the epidural space. The latter, free in its posterior part, is in contact with the posterior longitudinal ligament anteriorly. Laterally, it continues around each spinal nerve, which it accompanies by becoming increasingly thinner outside the intervertebral foramen.

The upper end continues without sharp boundaries with the cranial dura. By its external surface, it adheres to the foramen magnum and the atlas. The lower end constitutes the dural cul-de-sac, which stops at the level of S2-S3. Contains the cauda equina and the filum terminale. The latter, in the lower part of the dural sac, perforates the dura mater, which is applied against it, sheathing it. It descends to the first coccygeal vertebra. The dura attaches to the anterior aspect of the sacral canal.

Specializations

Specializations are specific areas of the dura, such as the falx cerebri or falx cerebri, where the dura rises toward the surface and folds in the midline of the brain, giving rise to the area that separates the right hemisphere from the left. It goes into the interhemispheric fissure.

The specialization Falx cerebelli or falx cerebellum goes between the cerebellar hemispheres. The Tentorium cerebelli, also called the tentorium cerebellum, is an area of the dura mater that is located perpendicular to the falx cerebri, which runs between the occipital lobe and the cerebellum.

These areas of specialization or expansions are nothing more than extensions located between different parts of the brain which they separate. The sagittally arranged expansions are the falx cerebellum and the falx cerebri; the horizontally arranged expansions are the tentorium cerebellum, the tentorium olfactory bulb, Meckel's cavum (covering the trigeminal nerve ganglion), and the diaphragm sella turcica.

Another area of specialization is the areas where venous blood collects back to the heart, which are the venous sinuses.

Venous sinuses

The cranial and spinal dura mater have characteristic differences. The cranial dura mater presents a vascularized layer in contact with the internal bony surface of the skull. This meninge presents venous sinuses, which are covered by endothelium, these sinuses are formed by dura mater unfolding, they carry venous blood. The venous sinuses can be divided into odd and even.

Paired venous sinuses:

• Transverse breast, which transversally surrounds the tentorium cerebelli
• Seno sigmoideo
• Seno cavernoso
• Higher and lower petrous breasts
• Esphenoparietal breasts

Unnumbered venous sinuses:

• Upper sagital breast, located on the upper edge of the cerebri falx
• Lower sagital breast, located on the lower edge of the cerebri falx
• Occipital
• Straight ahead
• Parietal breast etc.