VIEWS: 51 PAGES: 37 POSTED ON: 8/8/2012
Beginning: At the foramen magnum as a continuation of the Medulla Oblongata of the brain. Shape: Cylindrical. Length: About (45) cm. Occupies: Upper 2/3 of the vertebral (spinal) canal of the vertebral column. (1) Up till the 3rd month of Fetal Life: The spinal cord occupies the Entire Length of the vertebral canal. (2) At birth : It terminates at the level of L3. (3) Children : It ends at the Upper Border of the 3rd Lumbar vertebra. (4) Adults : It terminates at the Intervertebral disc (1st- 2nd ) Lumbar vertebrae. Cervical: (C3- T1) Segments. For the Brachial Plexus. Lumbar: (L1- S3) Segments. For the Lumbar and Sacral Plexuses. Conus Medullaris: A conical termination Caudal to the Lumbar Enlargement. FilumTerminale: A filament of connective tissue arises from the tip of the conus. It is attached to the 1st Coccygeal Vertebra. Anterior: Deep Anterior (Ventral) Median Fissure. Posterior: Shallow Posterior Median Sulcus. The Spinal Cord receives Information from and Controls the Movement of the Trunk and Limbs. It has (31) paired Spinal Nerves. Two linear series (6-8) of Nerve Fascicles are attached to the Dorsolateral and Ventrolateral aspects of the cord. The Fascicles coalesce to form Dorsal and Ventral Nerve Roots. The Roots pass to their corresponding Inter vertebral Foramena. Near which they join to form the Spinal Nerve Proper. Carry: Primary Afferent Neurons from the peripheral sensory receptors to the spinal cord and brain stem. Their cell bodies are in the Dorsal Root Ganglia. Carry : 1.Efferent neurons (Lower Motor Neurons) Their cell bodies are located in the Spinal Gray matter. 2.Preganglionic Autonomic neurons. Spinal Nerves are Mixed. Contain: Both Afferent and Efferent fibers. Each spinal nerve is divided into Dorsal and Ventral Rami. Dorsal Ramus : Thin. Supplies muscles and skin of the back. Ventral Ramus : Larger. Supplies muscles and skin of the Front of the body and limbs. Connected to the Sympathetic Chain by the The spinal cord is Segmented. In the Living The approximate level of the segments is identified by the Posterior Spinous Process of the vertebrae. Cervical Segments: One spine Higher than their corresponding vertebrae. C7 Segment is adjacent to C6 Vertebra. Thoracic segments : Two spines Higher . Lumbar segments : Three- Four spines Higher. Cervical Region : Cervical segments lie adjacent to their corresponding Vertebral Bodies. 1-7 C : Above the Upper Seven Cervical Vertebrae. C8 : Below 7th Cervical Vertebra. T1 and the rest of the nerves: Below their Corresponding Vertebrae. The Lumbar and Sacral nerves take an Oblique Course to reach the intervertebral foramina. The resulting leash of nerve roots forms the Cauda Equina. Pia Mater The inner most layer. A delicate ,vascular membrane. It is Closely applied to the surface of the spinal cord. It extends inferiorly as the Filum Terminale. A flat membrane formed from Pia Mater. Extension: Along a midway line between the dorsal and ventral nerve roots. Laterally to adhere to the Arachnoid and Dura. The spinal cord is suspended in the middle of the dural sheath. Arachnoid: A a fibrous membrane. It Loosely covers the spinal cord. Dura: A dense, strong fibrous membrane. It is continuous superiorly with the Meningeal layer of the Cranial Dura. They extend along Each Nerve Root and become continuous with its Epineurium. Inferiorly They extend to the 2nd sacral vertebra. Epidural Separates Dural Sheath from the Vertebral Canal. Contains the Internal Vertebral Venous Plexus. Subdural A thin space. Separates Dura from Arachnoid. Subarachnoid Contains Cerebro Spinal Fluid. Terminates At the level of S2 Held in position by : Laterally : Denticulate Ligament. Inferiorly : Filum Terminale. The spinal cord is Cushioned against Trauma by: Cerebrospinal Fluid. Site : Subarachnoid Space (L2-L3 or L3 –L4). Not Allowed in Children. Indications: 1. Diagnostic purposes. 2. Radiological study (Myelography). Injection of Anaesthetics into the Epidural Space It is for Surgical Procedures as in Labour. 1. Anterior spinal artery. 2. Posterior spinal Arteries. 3. Radicular Arteries. A single Y shaped artery. Arises from :Vertebral artery at the level of the medulla. Supplies the cord at the Cervical Level. It is most vulnerable in the anterior part of the cord particularly in the Thoracic Segment. Its Occlusion causes Acute Thoracic Syndrome with Paraplegia and Incontinence. Two arteries. Arise from . Vertebral Or Posterior Inferior Cerebellar arteries. Spinal Arteries (Anterior &Posterior) are Insufficient alone to supply the cord Below the Cervical Level. Origin from following arteries : 1. Ascending cervical 2. Intercostal. 3. Lumbar. They share in the arterial supply of the cord Below the Cervical Level. They Anastomose freely with the Spinal Arteries. Artery of Adamkiewicz. It may arise from: Intercostal or Lumbar arteries. It supplies Lower half of the spinal cord (T8 –L3). These are Vulnerable Segments. Occlusion of the artery may cause Muscle weakness and Paralysis. Six Longitudinal Interconnecting Venous Channels. (1) Anterior and Posterior Spinal veins in the midline. (2) Anterolateral and Posterolateral paired veins situated near the lines of attachment of the Ventral and Dorsal roots. (3) Anterior and Posterior Radicular Veins. (4) Internal vertebral venous plexus in the Epidural Space. (5) External Vertebral Venous Plexus. (6) Ascending Lumbar, Azygos and Hemiazygos Veins. The spinal nerve roots can be injured by Compression of Prolapsed Intervertebral Discs It is manifested by: 1. Paraesthesia (tingling sensations). 2. Weakness and wasting of the muscles. 3. Numbness of the skin corresponding to the dermatomal distribution. 4. Loss of Tendon Reflexes. (A) Cervical Pain in the neck radiating to the arm and hand. (B) Lumbar 1. Back pain. 2. Sciatica ( radiation of pain into the legs) . A large Lumbosacral prolapsed disc can cause paralysis of the bladder and incontinence.
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