Presentation on theme: "GROSS ANATOMY OF THE SPINAL CORD"— Presentation transcript:
1GROSS ANATOMY OF THE SPINAL CORD Dr. Andrea D. Székely
2LOCATION AND MAJOR FEATURES The spinal cord lies in the vertebral canal and continues in the medulla oblongata.(least modified and most caudal portion of the neural tube)SHAPE: elongated, tubular, conicalROSTRAL END: medulla oblongata/foramen magnumCAUDAL END: conus terminalis/lumbothoracic transitionANCHORED: filum terminale (pia mater) to sacral canal/coccyxRELATIVE POSITION:fetal - corresponding to the vertebral level,newborn - conus terminalis at L3,adult - L1/L2The spinal cord is divided into cervical, thoracic, lumbar, sacral and coccygeal regions.The grey matter is enlarged at the origins of the brachial and lumbosacral plexus (intumescentia cervicalis et lumbalis, C5-T1 and L2-L3).
4EMBRYOLOGYThe spinal cord develops from the NEURAL PLATE from above the notocord. With the folding of the NEURAL TUBE the central canal is formed (lining: ependyme). Neuroepithelial cells will give rise to neurons and glia. (Head mesenchyme) the DRG and the sympathetic neurones derive from the neural crest. The proneurones form a mantle zone (grey matter) with the axons growing towards the surface and so is the marginal zone formed (turns later into white matter).The notochord secrets a factor known as Sonic hedgehog or SHH. As a result, the floor plate then also begins to secrete SHH, and this will induce the basal plate to develop motoneurons. Meanwhile, the overlying ectoderm secretes bone morphogenetic protein (BMP). This induces the roof plate to begin to secrete BMP, which will induce the alar plate to develop sensory neurons.The alar plate and the basal plate are separated by the sulcus limitans.Additionally, the floor plate also secretes netrins. The netrins act as chemoattractants to decussation of pain and temperature sensory neurons in the alar plate across the anterior white commissure, where they then ascend towards the thalamus.The marginal zone develops into a massive passage of axans divided into 3 funiculi by the grey matter, posterior, lateral and anterior.
6EXTERNAL FEATURES, SPINAL NERVES Anterior median fissurePosterior median sulcus (or septum)Posterior intermediate septum (only C1-C8, upper T)Lateral anterior area (ventral roots of spinal nerves)Lateral posterior sulcus (dorsal roots of spinal nerves)The spinal regions are further subdivided into externalsegments giving rise to pairs of nerves (C1-C8, T1-T12,L1-L5, S1-S5, Co1). The idea of segmentation is basedon the pattern of nerve fibres conjoining in one spinal nerve.31 pairs of spinal nerves arise/ pass through theintervertebral foramina. The lower lumbar and sacralnerves form the cauda equina.Nerves are composed by a dorsal (sensory) and aventral (motor) root, except for C1 where the dorsal root may be absent in some people.The dorsal root is intersected by the accumulation ofpseudounipolar sensory nerve cells (dorsal root ganglion, DRG).
7THE SPINAL SEGMENT External segments Origins of nerve pairs (C1-C8, T1-T12, L1-L5, S1-S5, Co1).Basic rule :One spinal nerve is formed by all the axons emerging from one single spinal segment1 NERVE – 1 SEGMENTEach segment is a „functional unit”, representing one body regionlimited independence – controlled by the brain stem and cortex) via descendingtractsIntersegmental coordination- ascending fibres to higher centres- propriospinal fibres within the cord
8MEMBRANES OF THE SPINAL CORD DURA MATEREnvelops the cord, descends to S2 vertebra, betweenL2 and S2 the sac contains only the cauda equina.Each nerve passes through the intervertebral foramen retaining its dural cover, it continues as perineurium.Endorachis - connective tissue „outer layer” of thespinal dura mater - epidural space (content: fat,internal vertebral venous plexus)ARACHNOID MATERLines the dural cavity, rather large subarachnoideal,but insignificant subdural space.LUMBAR PUNCTION - below L2PIA MATERAdheres to the spinal cord and roots, its lateral aspect gives rise to the denticulate ligament (21 on each side) reaching the arachnoid mater. It lies between the dorsal and ventral nerve roots.
9THE CLINICAL ANATOMY OF SPINAL ANESTHESIALAYERS TO PENETRATESkinSupraspinal ligamentInterspinal ligamentLig. flavumEndorachisEpidural spaceDura mater spinalisArachnoid materSubarachnoid space
10VASCULAR SUPPLY OF THE SPINAL CORD ARTERIES2 anterior spinal arteries (later fuse) supply the grey matter, and parts of the lateral and anterior funiculus.2 posterior spinal arteries supply the dorsal horns and the dorsal funiculus.Arcuate anastomoses exist between the sidesLongitudinal vascular system: contain the spinal branches (from the vertebral, intercostal, lumbar, lateral sacral vessels and supply the vertebrae, meninges, the nerve roots and the medulla, joining the anterior and posterior spinal branches.Radicular system: vessels following the nerve roots supply the spinal segments.Radicular branches arise segmentally from the ascending cervical, deep cervical, intercostal, lumbar and sacral arteries.Anterior radicular branches: 6-10, left predominance. Largest branch: artery of Adamkiewicz - apparent at the lumbar enlargement.Posterior radicular branches: 10-23, no explicit left predominance.Vulnerable segments: T1-T3 posteriorly, T3 and L1 anteriorly
11VASCULAR SUPPLY OF THE SPINAL CORD VEINS (NO VALVES)The pattern of vessels is similar to that of the arteries.Anterior longitudinal venous trunk1 anteromedian vein: takes up the sulcal veins2 anterolateral veins: take up the ant-lat vesselsPosterior longitudinal venous trunk1 posteromedian vein: drains the posterior funiculus2 posterolateral veins: drain the dorsal horns+ a strip of the lateral funiculus.The vessels drain into 5-10 posterior radicular veinsVENOUS VASOCORONA - coronal anastomotic veins connecting the longitudinal vesselsThe blood is drained into the internal vertebral venous plexus (epidural venous plexus), where the plexus is connected to thoracic, abdominal and intercostal veins, then to the external vertebral venous plexus to reach the azygos and hemiazygos veins.N.B. connections to the prostatic plexus represent a route by which malignous tumors may metastasize!!
12DERMATOMESdermatome a piece of skin innervated by the same spinal nerveC 8, Th 12, L 5 und S 5At the edes there are always overlapping supply fields
13CLINICAL RELEVANCES DISCUS HERNIA WHAT MAY DAMAGE THE SPINAL CORD? - Pressure (e.g. tumor or discus hernia),- Rupture (horizontal damage separating the segmentscausing paralysis),- Inflammations (Myelitis, multiplex sclerosis),- Failing blood supply- Degenerative proceduresDISCUS HERNIA
14CROSS SECTIONS OF THE SPINAL CORD CERVICAL LEVEL
15CROSS SECTIONS OF THE SPINAL CORD THORACIC LEVEL