The tectorial membrane is a relatively thin superior extension of the posterior longitudinal ligament. It extends between the posterior aspect of the vertebral body of the axis (C2) and the clivus of the occipital bone, stretching posterior to the dens (without attaching to it!). As you can see in the 3D model, some fibers of the membrane are also present on the posterior aspect of the body of the C3 vertebra.

In the superior direction, the tectorial membrane can sometimes extend up to the spheno-occipital synchondrosis. Laterally, it reaches the entrance of the hypoglossal canal. Anterior to the tectorial membrane lies the cruciate ligament of the atlas. Both structures (the cruciate ligament and the tectorial membrane) are separated by a thin layer of loose areolar tissue, preventing direct connection.

The tectorial membrane consists of two types of fibers - superficial and deep. These fibers expand as they approach the occipital bone.

The deep fibers have a strong central (median) band that extends from the body of the axis to the clivus. Both lateral bands of the deep fibers stretch toward the atlanto-occipital joints, blending with the joint capsules and inserting into the occipital bone.
The superficial fibers cover the deep fibers and merge with the cranial dura mater at the basilar part of the occipital bone.

Functionally, the tectorial membrane provides stability to the upper cervical spine and skull during flexion and extension of the neck. It helps limit excessive movements by restricting head and neck flexion and extension. Additionally, it also plays a crucial role in preventing excessive posterior displacement of the dens of the axis (C2).

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Tectorial membrane