The brain's toughest wrapping is called tough mother, a name borrowed from Arabic
Dura mater is Latin for tough mother, a translation of an Arabic phrase meaning the thick mother of the brain. It is the outermost of three membranes around the brain and spinal cord, a leathery sheet that folds inward to partition the skull and splits open to form channels draining blood from the brain.
Inside the skull the dura has two layers. The outer one is really the lining of the skull bone itself; the inner one is the true dura. For most of their extent the two are fused into a single thick fibrous membrane, but where they part, they create the dural venous sinuses, channels that collect blood and cerebrospinal fluid and empty into the internal jugular vein. Tiny outgrowths of the arachnoid, the middle membrane, poke into these sinuses and act as one-way valves to let fluid drain. Around the spinal cord the dura has only one layer and forms the thecal sac. Most of it develops from neural crest cells.
At key boundaries the inner layer folds into the cranial cavity like internal walls. The falx cerebri drops into the groove between the two hemispheres, while the tentorium cerebelli forms a tent separating the cerebellum and brainstem from the back of the cerebrum. A smaller fold partly divides the cerebellum's halves, and the smallest, the sellar diaphragm, is a round sheet roofing over the pituitary gland with a hole for its stalk.
Its blood supply shifts by region. In the middle of the skull the main vessel is the middle meningeal artery, which enters through a small opening called the foramen spinosum. The dura is also richly supplied with nerves: above the tentorium by branches of the trigeminal nerve, below it by upper neck nerves and a branch of the vagus. Bleeding around it takes two forms: blood between dura and skull usually comes from an artery, while torn bridging veins after head trauma cause bleeding beneath the dura.
Several newer findings link it to the neck. In 2011 researchers described a connective-tissue bridge from a small muscle at the back of the head to the cervical dura, a connection proposed as one explanation for headaches arising from the neck. The dura can stretch abnormally in connective tissue disorders such as Marfan syndrome, and holes in it can cause spontaneous spinal fluid leaks. Because of concern about Creutzfeldt-Jakob disease, the American Red Cross treats receiving a dura mater transplant as a risk factor for blood donation.
Source: Dura mater
