Dura mater

The dura mater (from the Latin "hard mother") is the tough and inflexible outermost of the three layers of the meninges (the other two being the pia mater and the arachnoid). It protects the brain, spinal cord and forms various structures within the cranial cavity. Around the spinal cord it forms a loose fitting sleeve called the "Dural sheath" which extends past the spinal cord (which end at L2 = second lumber vertebra) to about the S2 (second sacreal vertebra).

A subdural hematoma occurs when there is an abnormal collection of blood between the dura and the arachnoid, usually as a result of torn blood vessels in a case of head injury.