CNS 1.pdf

Study anatomy C.N.S. (1) Dr. wagih el-husseiny DR. WAGIH EL-HUSSEINY C.N.S. 1 1 DR. WAGIH EL-HUSSEINY C.N.S. 1 The spinal cord ...

Study anatomy C.N.S. (1) Dr. wagih el-husseiny DR. WAGIH EL-HUSSEINY C.N.S. 1 1 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 3 DR. WAGIH EL-HUSSEINY C.N.S. 1 4 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  DR. WAGIH EL-HUSSEINY C.N.S. 1 TRANSVERSE SECTION OF THE SPINAL CORD  In transverse section, the spinal cord is formed from an inner H-shaped gray matter surrounded peripherally by white matter.  The central canal lies in the center of the gray matter.  This canal communicates above with the central canal of the medulla oblongata and below it ends blindly where it dilates and forms the terminal ventricle.  The external surface of the spinal cord has 2 fissures: 1. Anterior median fissure: deep longitudinal groove in the anterior median plane. 2. Posterior median sulcus: shallow groove in the posterior median plane. 9  DR. WAGIH EL-HUSSEINY C.N.S. 1  These fissures divide the spinal cord incompletely into right and left halves which are connected by: 1. Posterior gray commissure: behind the central canal. 2. Anterior gray commissure: infront of the central canal. 3. Anterior white commissure: lies in the floor of the anterior median fissure.  : is formed from: 2 anterior horns containing motor cells. 2 posterior horns containing sensory cells. 2 lateral horns are present in 2 sites only : 1. All thoracic and upper 2 lumbar segments where they contain sympathetic nerve cells. 2. Middle 3 sacral segments where they contain parasympathetic cells.  Each spinal nerve attached to the spinal cord by: 1. Anterior root attached to the antero-lateral sulcus. 2. Posterior root attached to the potero-lateral sulcus. 10 DR. WAGIH EL-HUSSEINY C.N.S. 1 11  DR. WAGIH EL-HUSSEINY C.N.S. 1 Spinal nerves  31 pairs.  Arranged as 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal.  Each pair attached to the spinal cord by 2 roots: 1. Ventral root: motor and formed from the axons of the nerve cells in the anterior and lateral horns. 2. Dorsal horn: sensory and it has an oval ganglion called dorsal root ganglion (pseudo- unipolar). ✓ The central processes of this ganglion enter the spinal cord through the posterior root and divide into medial and lateral divisions. ✓ The medial division forms the gracile and cuneate tracts in the posterior white column. ✓ The lateral division synapse around the cells of the posterior horn.  The dorsal and the ventral roots join together at the inter-vertebral foramen to form the spinal nerve which is very short and divides into 2 rami: 1. Posterior ramus (mixed): supply muscles and skin of the back. 2. Anterior ramus (mixed): much larger than the posterior ramus and supply muscles and skin of the front of the trunk and limbs. 12 DR. WAGIH EL-HUSSEINY C.N.S. 1  Exit of the spinal nerves: ✓ Upper 7 cervical nerves: each nerve emerges above its corresponding cervical vertebra. ✓ The 8th cervical nerve: emerges below the 7th cervical vertebra. ✓ From T1 to L5 nerves: each one exit below the corresponding vertebra. ✓ From S1 to S4 nerves: each one exit from the vertebral canal through the anterior and posterior sacral foramina as ventral and dorsal rami. ✓ The 5th sacral and the coccygeal nerves: leave the vertebral canal through the sacral hiatus surrounding the filum terminale 13 DR. WAGIH EL-HUSSEINY C.N.S. 1  Obliquity of the spinal nerves: ✓ As the spinal cord is shorter than the vertebral canal and the segments not coincide with the corresponding vertebrae. ✓ The upper spinal nerves are short and horizontal. ✓ The lower spinal nerves become longer and more oblique. ✓ The lowermost are nearly vertical and surround the filum terminale to form the cauda equine. ✓ It likes the tail of the hoarse. ✓ It’s the filum terminale and its surroundings of the ventral and dorsal nerve roots of the lower spinal nerves (below L1) in their way to their corresponding inter- vertebral foramina to exit from the vertebral canal. 14 DR. WAGIH EL-HUSSEINY C.N.S. 1 15 DR. WAGIH EL-HUSSEINY C.N.S. 1 16 DR. WAGIH EL-HUSSEINY C.N.S. 1 17 DR. WAGIH EL-HUSSEINY C.N.S. 1  BLOOD SUPPLY OF THE SPINAL CORD A. Arterial: 1. Anterior spinal artery: ✓ It’s abranch from the 4th part of vertebral artery inside the cranial cavity. ✓ The arteries of both sides unite to form 1 anterior spinal artery which descends through foramen magnum and passes infront of the anterior median sulcus. ✓ It supplies the anterior 2/3 of the cross sectional area of the spinal cord. 2. Posterior spinal artery: ✓ It’s a branch from the 4th part of vertebral artery inside the cranial cavity. ✓ It descends through the foramen magnum. ✓ Each artery divides into 2 branches which pass 1 infront and 1 behind the dorsal nerve roots. ✓ They supply the posterior 1/3 of the spinal cord. 18 DR. WAGIH EL-HUSSEINY C.N.S. 1 3. Redicular arteries: ✓ They enter the vertebral canal through the intervertebral foramina. ✓ They arise from the following arteries: In the cervical region: from the 2nd part of the vertebral artery and the descending cervical artery (branch from inferior thyroid artery). In the thoracic region: from posterior inter-costal and sub-costal arteries. In the lumbar region: from the lumbar arteries (give upper 4 pairs) and the median sacral artery (gives the 5th pair). In the sacral region: arise from the lateral sacral arteries. 4. Arteriolaris rediculosa magna: ✓ It’s one of redicular arteries. ✓ It’s enlarged to supply the lumbar enlargement of the spinal cord. ✓ It also called large redicular artery or Adamkiewcz artery. ✓ It may arise from any of the posterior inter-costal or lumbar arteries. 19 DR. WAGIH EL-HUSSEINY C.N.S. 1 20 DR. WAGIH EL-HUSSEINY C.N.S. 1 B. Venous drainage of the spinal cord: ✓ The veins of the spinal cord form 6 longitudinal channels situated as follows: 1. One infront of anterior median fissure. 2. On behind dorsal median sulcus. 3. One behind each nerve root. ✓ These venous channels are drained by anterior and posterior redicular veins into the internal vertebral venous plexus. ✓ The internal vertebral venous plexus: It's situated in the epidural (extradural) space which lies between the dura and the vertebral canal. It communicates above with the basilar vertebral venous plexus and communicates laterally with the external vertebral venous plexus. It's drained by intervertebral veins which drain into: 1. Vertebral veins. 2. Posterior intercostal and subcostal veins. 3. Lumbar and lateral sacral veins. 21