Spinal Cord Anatomy PDF

DR. WAGIH EL-HUSSEINY C.N.S. 1 The spinal cord  Gross features: ✓ It lies in the upper 2/3 of the vertebral canal. ✓ Its average of length is 45 cm & length of vertebral canal is 60 cm...

DR. WAGIH EL-HUSSEINY C.N.S. 1 The spinal cord  Gross features: ✓ It lies in the upper 2/3 of the vertebral canal. ✓ Its average of length is 45 cm & length of vertebral canal is 60 cm. ✓ It begins at the lower border of foramen magnum and continuous above with the medulla oblongata. ✓ It ends at the lower border of L1 and continues below with the filum terminale. ✓ Its lower end is expanded to form the conus medullaris. ✓ It is cylindrical and has 2 enlargements: Cervical enlargement: at C4 to T1 segments corresponding to the origin of brachial plexus. Lumbar enlargement: at L1 to S3 segments corresponding to lumbar and sacral plexuses.  Relations of the spinal cord to the vertebral column: ✓ At the 3rd month of fetal life it occupies the whole length of the vertebral canal. ✓ At birth it ends at level of L3. ✓ In adults, it ends at the level of L1.  Segments of the spinal cord: ✓ It has 31 segments arranged as 8 cevical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal. ✓ Each segment gives a pair of spinal nerves. 2 DR. WAGIH EL-HUSSEINY C.N.S. 1  Meninges of the spinal cord:  The spinal cord surrounded by 3 meninges which continuous at foramen magnum with their corresponding of the brain. ✓ From inside outwards these are pia matter, arachenoid matter and dura matter. 1. Pia matter: ✓ It’s the inner vascular layer. ✓ It surrounds the spinal cord and follows its fissures. ✓ It ends with the spinal cord at level of L1 vertebra. ✓ Its lower end forms the filum terminale. ✓ The denticulate ligament emerges from its right and left borders. 5 DR. WAGIH EL-HUSSEINY C.N.S. 1 o It’s a fibrous strand extending from the lower border of the pia matter. o It descends through the vertebral canal surrounded by roots of lower spinal nerves to form cauda equine. o It pierces the arachenoid and dura matters at level of S2 emerging from sacral hiatus to be attached to back of coccyx. o It helps in fixation of spinal cord. o It’s a toothed longitudinal ligament one on each side of the spinal cord. o It extends along whole length of the spinal cord. o It has 21 pointed processes which emerge from pia matter midway between the anterior and posterior nerve roots. o These processes pierce the arachenoid matter and become attached to the dura matter. o It helps in fixation of the spinal cord. 2. Arachenoid matter: ✓ It’s the middle layer of the 3 meninges. ✓ It’s thin, transparent and impermeable membrane. ✓ It ends at level of S2. 6 DR. WAGIH EL-HUSSEINY C.N.S. 1 3. Dura matter: ✓ It’s the outer layer. ✓ It’s tough, dense and strong. ✓ It ends as aeachenoid matter at level of S2.  Spaces between the meninges: 1. Sub-arachenoid space: It lies between the arachenoid and pia matters. It contains C.S.F. 2. Sub-dural space: It lies between the dura and arachenoid matters. It contains small amount of serous fluid to lubricate the movement of dura which is a tough membrane. 3. Extra-dural space: It lies between the dura matter and the wall of the vertebral canal. It contains the internal vertebral venous plexus. 7 DR. WAGIH EL-HUSSEINY C.N.S. 1  Lumbar puncture: ✓ The sub-arachenoid space from L2 to S2 called lumbar cistern. ✓ It contains only the filum terminale and roots of lower spinal nerves. ✓ Hollow needles can be introduces safely into this space at L3-L4 or L4-L5 inter-vertebral discs. ✓ This is called lumbar puncture and it is done for the following purposes: 1. Spinal anesthesia as in injection of anesthetic in sub-arachenoid space. 2. To obtain a sample of C.S.F. for diagnosis of meningitis. 3. To inject radio-opaque dye in radiological examination of spinal cord (myelography).  Factors which fix the spinal cord: 1. Attachment of the filum terminale to the back of coccyx. 2. Attachment of the dentate ligament to the dura matter. 3. Attachment of the dura matter to the foramen magnum. 8