Subarachnoid Space: Structure And Function | Kenhub

Anatomical structure

The subarachnoid space is characterized by a lattice-like, spider web appearance due to the presence of a filamentous network of trabeculae and varies greatly in depth depending on location, resulting in formation of subarachnoid cisterns. The two main elements contained in the subarachnoid space amongst the trabeculae are the cerebrospinal fluid and neurovasculature.

Cerebrospinal fluid

The subarachnoid space is filled with CSF which is produced by the choroid plexus within the ventricles of the brain. CSF flows through the ventricles of the brain and is received into the subarachnoid space from the fourth ventricle via the posterior cerebellomedullary cistern.

Arachnoid trabeculae

Arachnoid trabeculae Trabeculae arachnoideae Synonyms: none

Extending through the depth of the subarachnoid space are delicate connective tissue trabeculae. Formed by extensions of the deep layers of the arachnoid mater, the collagen-reinforced trabeculae cross the subarachnoid space to reach the pia mater and essentially function to stitch the pia mater and arachnoid mater together. Trabeculae vary in their shape and size and range from single or branched strands to tree shaped structures. Ultimately, they work together to form a trabecular network which takes on the appearance of honeycomb. The lattice arrangement of the trabeculae allows for the unobstructed passage and flow of CSF within the subarachnoid space and functions to loosely connect the arachnoid and pia mater as well as stabilize and suspend the brain and the spinal cord in one place. As a result, the trabeculae of the subarachnoid space contribute to the intracranial and intraspinal biomechanics.

Neurovascular structures

Also located within the subarachnoid space are the large cerebral arteries and veins, as well as the intracranial and intravertebral components of the cranial and spinal nerves, which traverse the trabeculae. Neurovascular structures of the subarachnoid space have been found to lie in close proximity to the arachnoid trabeculae for protective purposes. The arachnoid trabeculae provide a supporting framework to blood vessels of the subarachnoid space and therefore offer a degree of protection to these vital structures.

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