Tentorium

Tentorium

The term tentorium has several anatomical meanings, but it is most commonly used to describe a feature of the vertebrate brain as well as an internal head skeleton in arthropods.

Vertebrate anatomy: tentorium cerebelli

In humans and other mammals, the tentorium cerebelli is a horizontal fold of dura mater that forms a tent-like roof over the cerebellum and separates it from the inferior aspects of the cerebral hemispheres. It is a bilayer dural reflection that is continuous with the falx cerebri. The tentorium attaches to the skull at several points, including the posterior clinoid processes and the petrous part of the temporal bone, and it spans laterally toward the occipital bone. The free edge of the tentorium gives rise to the tentorial notch (incisure), which accommodates the brainstem as it passes from the brainstem into the spinal cord. Several venous sinuses run along or near the margins of the tentorium, including portions of the transverse and superior petrosal sinuses. Clinically, the tentorium is relevant in tentorial or transtentorial herniation, a condition in which increased intracranial pressure drives brain tissue through the tentorial notch, potentially compressing the midbrain and cranial nerves.

Arthropod anatomy: internal head skeleton

In insects and other arthropods, the tentorium refers to an internal, sclerotized framework within the head capsule. This structure provides mechanical support for the brain and serves as an attachment site for several head muscles. The exact shape and components of the tentorium vary among groups but its general function is to strengthen the head and aid in feeding and sensory movements.

Overall, tentorium denotes either a brainfold that partitions cranial spaces in vertebrates or an internal head skeleton in arthropods.