This includes nerves corresponding to lumbar low back vertebrae, as well as the sacrum the bony, triangular structure at the base of the spine. Both cranial and spinal meninges are broken down into three layers, with the inner two collectively referred to as the leptomeninges:.
In places, the meningeal layers are separated by gaps, and there also are spaces between the surrounding bone, as well as the enveloped brain and spinal cord.
These important anatomical features are:. The cranial meninges primarily receive blood from by the middle meningeal artery MMA , which is a branch of the internal carotid artery , which progresses up the neck.
On each side, the MMA enters the skull through an opening in its side called the foramen spinosum and continues through the epidural space. At the same opening—and running alongside the MMA—is the meningeal branch of the mandibular nerve.
Its two branches transmit signaling between the outermost meningeal layer and the brain, with its anterior branch communicating with the meningeal branch of the maxillary nerve.
Blood supply for the spinal meninges comes from a single anterior artery, as well as two paired posterior spinal arteries. Branches of the vertebral arteries, they arise at the base of the neck and take an upward course. As with all parts of the body, the meninges can be significantly impacted by genetic mutations.
These coding errors lead to neural tube defects, in which the meninges never fully forms. These potentially very severe diseases of the meninges include:. The primary task of the meninges is to provide protection and support for the brain and spine. This involves:. When the health of the meninges is affected, the consequences can be severe. This part of the body can be affected by bleeds and blood circulation problems, infections, and cancer, among other medical conditions.
Skull or spinal fracture can also significantly damage these membranes and warrants medical attention. Two closely related types of blood circulation issues that affect the meninges are hemorrhage and , hematoma. A hemorrhage occurs when there is bleeding in the brain or spine. Hematoma is a complication of a hemorrhage, where blood pools outside of blood vessels.
These potentially serious bleeding problems may arise due to trauma, bone fracture, or other health conditions. These intracranial bleeding problems are dangerous because they raise intracranial pressure ICP , or blood pressure within the skull, which can damage the brain. These issues are categorized based on the meningeal space being affected.
Infection of the meninges, known as meningitis, leads to inflammation of these membranes, causing a range of significant and dangerous health effects.
When cancer cells spread to the meninges, tumors, called meningiomas, form. The majority of these are actually benign; however, depending on their location and the activity of the cancer cells, these can be dangerous and fatal, or malignant.
Many factors determine the specific approach to clinical testing and diagnosis of meningeal health conditions. Doctors may need to figure out the root causes of any infection or inflammation, assess the extent of congenital malformation, or take on hematoma and bleeding.
Luckily, there are many tests and examinations they can use, including:. These layers are tasked with the essential job of protecting and nourishing the brain and spine. No doubt the burden due to congenital conditions, infections, injuries, or other disorders of these crucial membranes can be heavy.
These form an incomplete posterior median septum in the posterior midline of the spinal cord 1. The blood supply to the spinal arachnoid mater mirrors the other layers of the spinal meninges and comes from the one anterior and two posterior spinal arteries running the length of the spinal cord.
Supply to these comes from the basilar portion of the circle of willis and is reinforced by the segmental arteries at each level which themselves originate from a variety of sources see spinal cord blood supply 4. The largest of these segmental arteries and the dominant supplying artery to the thoracolumbar spinal cord is the artery of Adamkiewicz which has a variable origin 5.
The venous drainage principally follows the arterial supply. The anterior and posterior spinal veins drain into the segmental veins 4. The spinal arachnoid mater is innervated by sensory fibers of the meningeal branches of each spinal nerve.
These fibers branch off from each spinal nerve near the bifurcation of the ventral and dorsal rami 4. Please Note: You can also scroll through stacks with your mouse wheel or the keyboard arrow keys.
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