Epidural space
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| Epidural space | |
|---|---|
 | |
| The medulla spinalis and its membranes. | |
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| Diagrammatic representation of a section across the top of the skull, showing the membranes of the brain, etc. | |
| Latin | spatium extradurale |
| Gray's | subject #193 875 |
| Dorlands/Elsevier | s_16/12746475 |
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- For a discussion about the anesthetic procedure, see Epidural.
Overview
In the spine, the epidural space is the space outside the tough membrane called the dura mater (sometimes called the "dura"), and within the spinal canal, which is formed by the surrounding vertebrae. Adherent to the inside of the dura is a much thinner and more fragile membrane, the arachnoid mater. Enclosed within the arachnoid is the subarachnoid space, which contains the cerebrospinal fluid, and the spinal cord.
In humans
In the spine, the epidural space contains lymphatics, spinal nerve roots, loose fatty tissue, small arteries, and a network of large, thin-walled blood vessels called the epidural venous plexus.
The upper limit of the epidural space is the foramen magnum, which is the point where the spine meets the base of the skull. The lower limit is at the tip of the sacrum, at the sacrococcygeal membrane.
In the head, the dura is continuous with the periosteum, the tough fibrous lining of the inside of the skull. This means that, in the head, the epidural space is known as a potential space, which means that normally it does not exist. In rare circumstances, a torn artery (e.g. the middle meningeal artery) may cause bleeding which is sufficient to separate both the dura and periosteum from the bone; this is an epidural hematoma.
The space between the dura and the arachnoid (in both head and spine), the subdural space, is also a potential space. Bleeding may also occur here.
In other mammals
In other mammals, the relationship between the spinal canal and its contents is similar to that in humans, although many species possess a tail into which the epidural space is prolonged.
A unique property of the epidural venous plexus is that the veins are prevented from collapsing due to external pressure because the bony spinal canal prevents that pressure being transmitted. This means that for many diving mammals, e.g. whales, when diving a large fraction of venous return to the heart takes place via the epidural space, as veins such as the vena cava may be substantially compressed by the pressure at depth.
External links
sv:Epiduralrum
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Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
