Spinal Cord Anatomy PDF

Suez Canal University Faculty Of Medicine Presented By Dr. Bassma M. Dessouki Lecturer of Anatomy & Embryology Depart.  Beginning: At foramen magnum as a continuation of medulla oblongata.  Termination:  In adults: Opposite L1 - L2.  In newborn: at the level of...

Suez Canal University Faculty Of Medicine Presented By Dr. Bassma M. Dessouki Lecturer of Anatomy & Embryology Depart.  Beginning: At foramen magnum as a continuation of medulla oblongata.  Termination:  In adults: Opposite L1 - L2.  In newborn: at the level of L3 vertebra.  Its lower end tapers into a cone forming the conus medullaris.  Spinal segment is the portion of spinal cord which gives origin to a pair of spinal nerves. The spinal cord consists of 31 spinal segments;  8 Cervical.  12 thoracic.  5 lumbar.  5 scaral.  1 Coccygeal. The size of segment depends upon the amount of tissue supplied by each segment. 1. Anterior median fissure: A deep midline groove along the entire length the anterior aspect of spinal. 2. Posterior median sulcus: A shallow sulcus on the posterior aspect of the spinal cord. 3. 2 Anterolateral sulci & 2 Posterolateral sulci: at the attachment of the spinal nerve roots. 4. Posterior median septum extends from posterior median sulcus into the substance of the cord to a variable extent.  Cervical enlargement: In the region of C5–T1 spinal segments. The nerves arising from these segments form brachial plexus. Lumbar enlargement: In the region of L2–S3 spinal segments. The nerves arising from these segments form the lumbar & sacral plexus.  Central mass of grey matter: H-shaped and is divided into symmetrical right and left masses, which are connected across the midline by a transverse grey commissure.  The central canal : passes through the center of the grey commissure.  Horns: Each lateral mass of grey matter is divided into: 1. Posterior horn (sensory). 2. Anterior horn (motor). 3. Lateral horn (autonomic) only in the thoracic segments and upper two lumbar (T1-L2) segments. In each half of the spinal cord, the white matter is divided into three parts called columns:  Posterior column, between the posterior median septum and the posterior horn.  Lateral column, between the anterior and posterior horns.  Anterior column, between the anterior median fissure and the anterior horn. The anterior white columns are joined together by the white commissure.  31 pair of spinal nerves: emerge from corresponding segments; so we have: 8 Cervical. 12 thoracic. 5 lumbar. 5 scaral. 1 Coccygeal. The spinal nerve emerge by 2 roots as follows:  The anterior root (motor root) emerges along the anterolateral sulcus.  The posterior root (sensory root) attached to the posterolateral sulcus.  The anterior and posterior roots of the spinal nerve unite within their appropriate intervertebral foramina to form the nerve trunk. Direction and exit of spinal nerve roots Since the spinal cord is shorter than the vertebral canal, the course of spinal nerve roots in the vertebral canal to reach the appropriate intervertebral foramen varies. Also as the number of nerves is not corresponding to vertebral number; being 8 cervical nerves and there are only 7 cervical vertebrae; the exit of the nerves in relation to the corresponding vertebrae varies also.  Outer tough dense layer continues with the cranial dura mater Extension: down to lower border of S2 vertebra. Attachment: firmly attached to Foramen magnum Tectorial membrane & posterior longitudinal ligament on body of axis vertebra.  Subdural space: It is the space between the spinal dura and arachnoid mater containing a thin film of serous fluid. Epidural space: It is the space between the spinal dura and vertebrae containing internal vertebral venous plexus It is a thin transparent vascular membrane Extension: lower border of S2 vertebra. Subarachnoid space:  The space between arachnoid mater and pia mater.  It is filled with cerebrospinal fluid (CSF)  lumbar cistern: widened Subarachnoid space below conus medullaris It contains cauda equina and filum terminale in a pool of CSF Lumbar puncture: a needle Is introduced in lumbar cistern in between L3 and L4 or L4 and L5 vertebra to withdraw CSF or injection of anesthetic agent or dye. It is a vascular membrane that closely invests the spinal cord. Processes of pia mater: 1. Filum terminale: Thin thread-like prolongation of pia mater beyond the conus medullaris. It pierces the dura, passes through the sacral canal and hiatus. Attachment: to the dorsum of the first coccyx piece. 2. Denticulata ligament: 21 teeth-like lateral projections from spinal pia. Between the dorsal and ventral nerve roots. Pass through subarachnoid space and arachnoid mater.  Attachment: to the inner surface of the dura. 1. Anterior spinal artery Origin: from vertebral arteries; each vertebral artery gives one small spinal branch that unite together to form single anterior spinal artery. course: It runs caudally in the anterior median fissure of the spinal cord. supply provided: supplies the anterior two-third of the cord. 2. Posterior spinal arteries Origin: vertebral or posterior inferior cerebellar artery. Course: Each artery runs down in the posterolateral sulcus. Supply provided : posterior one-third of the cord. 3. Spinal branches of segmental arteries: Origin: 1. In Neck: deep cervical, ascending cervical, 2. In Thorax: posterior intercostal, 3. In Abdomen: lumbar. 4. In Pelvis: lateral sacral arteries. Course: They reach the spinal cord as the anterior and posterior radicular arteries along the corresponding roots of the spinal nerves, respectively. Supply provided: They mainly nourish the nerve roots. Give medullary feeder to reinforce the spinal arteries NB. Arteria Radicularis Magna: is a large radicular artery originate from lower posterior intercostal or upper lumbar arteries. it is the main source of supply to the lower part of spinal cord. Its occlusion leads to lumbosacral cord ischemia The veins draining the cord form six longitudinal venous channels around the cord: 1. Two median longitudinal, one in the anterior median fissure and the other in the posterior median sulcus. 2. Two anterolateral, one on either side, posterior to the anterior nerve roots. 3. Two posterolateral, one on either side, posterior to the posterior nerve roots. Communication: Superiorly: with the cranial dural venous sinus. In vertebral canal: with the internal vertebral venous plexus. Drainge: by radicular veins into segmental veins.