Epidural space

Information about 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.
Latinspatium extradurale
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.

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Anatomy of torso (primarily): the spinal cord
Spinal nerveDorsal (Root, Ganglion, Ramus) • Ventral (Root, Ramus) • Sympathetic trunk • rami communicantes (Gray, White)
Gray matter/Rexed laminaePosterior horn (Column of Clarke, Substantia gelatinosa of Rolando, Nucleus proprius) • Lateral horn • Anterior horn • Central canal/Substantia gelatinosa centralis
White matter: somatic/ascending (blue)
White matter: motor/descending (red)
LayersEpidural space • Dura mater • Subdural space • Arachnoid mater • Subarachnoid space • Pia mater
Other structuresDenticulate ligaments • Conus medullaris • Cauda equina • Filum terminale • Cervical enlargement • Lumbar enlargement • Anterior median fissure
spinal chord is a thin, tubular bundle of nerves that is an extension of the central nervous system from the brain and is enclosed in and protected by the bony vertebral column.
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skull is a bony structure found in many animals which serves as the general framework for the head. The skull supports the structures of the face and protects the head against injury.

The skull can be subdivided into two parts: the cranium and the mandible.
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Latin}}} 
Official status
Official language of: Vatican City
Used for official purposes, but not spoken in everyday speech
Regulated by: Opus Fundatum Latinitas
Roman Catholic Church
Language codes
ISO 639-1: la
ISO 639-2: lat
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Elsevier, the world's largest publisher of medical and scientific literature, forms part of the Reed Elsevier group. Based in Amsterdam, the company has substantial operations in the UK, USA and elsewhere.
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loading dose to initiate the nerve block.

Typically, the effects of the epidural are noted below a specific level on the body (dermatome). This level (the "block height") is chosen by the anaesthetist. The level is usually 3-4 dermatomes higher than the point of insertion.
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vertebral column (backbone or spine) is a column of 34 vertebrae, the sacrum, intervertebral discs, and the coccyx situated in the dorsal aspect of the torso, separated by spinal discs. It houses the spinal cord in its spinal canal.
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The dura mater (from the Latin "hard mother"), or pachymeninx, is the tough and inflexible outermost of the three layers of the meninges surrounding the brain and spinal cord. (The other two meningeal layers are the pia mater and the arachnoid mater.
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The spinal canal (or vertebral canal or spinal cavity) is the space in vertebrae through which the spinal cord passes. It is a process of the dorsal human body cavity. This canal is enclosed within the intervertebral foramen of the vertebrae.
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The arachnoid mater is one of the three meninges, the membranes that cover the brain and spinal cord. It is interposed between the two other meninges, the more superficial dura mater and the deeper pia mater, and is separated from the pia mater by the subarachnoid space.
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For the anatomy term, see Subarachnoid space.


SubArachnoid Space is a San Francisco-based psychedelic rock band founded in 1996 by Mason Jones, the owner of the independent music label Charnel Music.
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spinal chord is a thin, tubular bundle of nerves that is an extension of the central nervous system from the brain and is enclosed in and protected by the bony vertebral column.
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The lymphatic system is a complex network of lymphoid organs, lymph nodes, lymph ducts, lymphatic tissues, lymph capillaries and lymph vessels that produce and transport lymph fluid from tissues to the circulatory system.
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Arteries are muscular blood vessels that carry blood away from the heart.[1] All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood.

The circulatory system is extremely important for sustaining life.
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In anatomy, in the occipital bone, the foramen magnum (Latin: 'great hole') is one of the several oval or circular apertures in the base of the skull (the foramina), through which the medulla oblongata (an extension of the spinal cord) enters and exits the skull vault.
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skull is a bony structure found in many animals which serves as the general framework for the head. The skull supports the structures of the face and protects the head against injury.

The skull can be subdivided into two parts: the cranium and the mandible.
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The sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones.
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The sacrococcygeal membrane is a tough fibrous membrane about 10mm long which extends from the inferior tip of the sacrum to the body of the coccyx in humans. It covers the inferior limit of the epidural space and is analogous to the ligamentum flavum found at other levels in the
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The periosteum is a thin layer of dense, irregular connective tissue membrane that covers the outer surface of a bone in all places except at joints. (The outer surface of bone at joints is covered with "articular cartilage", a type of hyaline cartilage.
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skull is a bony structure found in many animals which serves as the general framework for the head. The skull supports the structures of the face and protects the head against injury.

The skull can be subdivided into two parts: the cranium and the mandible.
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The middle meningeal artery (Latin arteria meningea media) is typically the first branch of the first part (retromandibular part) of the maxillary artery; one of the two terminal branches of the external carotid artery.
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The periosteum is a thin layer of dense, irregular connective tissue membrane that covers the outer surface of a bone in all places except at joints. (The outer surface of bone at joints is covered with "articular cartilage", a type of hyaline cartilage.
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Extradural haemorrhage
Classification & external resources

Nontraumatic epidural hematoma in a young woman. The grey area in the top left is organizing hematoma, causing midline shift and compression of the ventricle.
ICD-10 I 62.1 , S 06.4
ICD-9 432.
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The subdural space (or subdural cavity) is an artificial space created by the separation of the arachnoid mater from the dura mater as the result of trauma or pathologic process.
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whale can refer to all cetaceans, to just the larger ones, or only to members of particular families within the order Cetacea. The last definition is the one followed here. Whales are those cetaceans which are neither dolphins (i.e.
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The superior and inferior vena cava are collectively called the venae cavae. They are the veins that return de-oxygenated blood from the body into the heart. They both empty into the right atrium.
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eMedicine is an online clinical medical knowledge base that was founded in 1996 by Scott Plantz and Richard Lavely, two medical doctors. It was sold to WebMD in January 2006.
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Torso is an anatomical term for the central part of the many animal bodies (including that of the human) from which extend the neck and limbs. It is sometimes referred to as the trunk. The torso includes the thorax and abdomen.
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spinal chord is a thin, tubular bundle of nerves that is an extension of the central nervous system from the brain and is enclosed in and protected by the bony vertebral column.
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The term spinal nerve generally refers to the mixed spinal nerve, which is formed from the dorsal and ventral roots that come out of the spinal cord. The spinal nerve is the bit that passes out of the vertebrae through the intervertebral foramen.
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In anatomy and neurology, the dorsal root (or posterior root) is the afferent sensory root of a spinal nerve.

At the distal end of the dorsal root is the dorsal root ganglion, which contains the neuron cell bodies of the nerve fibres conveyed by the root.
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