Epidural space Epidural space The medulla spinalis and its membranes . 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 For a discussion about the anesthetic procedure , see Epidural . 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 Dictionary at eMedicine Epidural+space `` Anatomy of the Epidural Space '' at washington.edu Spinal cord epidural space , dura mater , subdural space , arachnoid mater , subarachnoid space , pia mater , denticulate ligaments , conus medullaris , cauda equina , filum terminale , cervical enlargement , lumbar enlargement , anterior median fissure , dorsal root , dorsal root ganglion , dorsal ramus , ventral root , ventral ramus , sympathetic trunk , gray ramus communicans , white ramus communicans grey matter : central canal , substantia gelatinosa of Rolando , reticular formation , substantia gelatinosa centralis , interneuron , anterior horn , lateral horn , posterior horn ( column of Clarke , dorsal spinocerebellar tract ) white matter : anterior funiculus : descending ( anterior corticospinal tract , vestibulospinal fasciculus , tectospinal tract ) , ascending ( anterior spinothalamic tract , anterior proper fasciculus ) lateral funiculus : descending ( lateral corticospinal tract , rubrospinal tract , olivospinal tract ) , ascending dorsal spinocerebellar tract , ventral spinocerebellar tract , spinothalamic tract , lateral spinothalamic tract , anterior spinothalamic tract , spinotectal tract , posterolateral tract , lateral proper fasciculus , medial longitudinal fasciculus posterior funiculus : fasciculus gracilis , fasciculus cuneatus , posterior proper fasciculus Epidural space spatium extradurale 193 875 Gray767.png The medulla spinalis and its membranes . Gray769.png Diagrammatic representation of a section across the top of the skull , showing the membranes of the brain , etc. s_16 12746475 Epidural+space 