Spinal Cord Anatomy- General Overview PDF

Spinal Cord Prof. Dr. Selda Önderoğlu Near East University Faculty of Medicine Department of Anatomy ◼ Begins at:Foramen magnum ◼ Ends at: L3 (newborn), L1 (adult) ◼ Longer in males than females, length: males about 45 cm ◼ Superiorly; continuous with medulla o...

Spinal Cord Prof. Dr. Selda Önderoğlu Near East University Faculty of Medicine Department of Anatomy ◼ Begins at:Foramen magnum ◼ Ends at: L3 (newborn), L1 (adult) ◼ Longer in males than females, length: males about 45 cm ◼ Superiorly; continuous with medulla oblongata  Medulla oblongata Spinal cord Enlargements of spinal cord (SC) ◼ Cervical enlargement – The region where Spinal nn. form the brachial plexus – Diameter, about 38 mm ◼ Lumbar enlargement – The region where Spinal nn. form the lumbosacral plexus – Diameter, about 35 mm – After lumbar enlargement it becomes thin and forms conus medullaris ( this is the lower end of Spinal cord) Conus medullaris& cauda equina ◼ Spinal cord narrows below after lumbosacral enlargement ◼ Conus medullaris;is the lower end of spinal cord ◼ Cauda equina (pony tail):Below conus medullaris Roots of spinal nn. Surrounding the filum terminale L1-L3 Cauda equina ◼ Spinal cord is shorter than vertebral column ◼ More caudal spinal n roots descend around the spinal cord & reach their corresponding intervertebral foramina ◼ Thus; they form sheaf of spinal nerve roots, distal to the apex of the cord, called as cauda equina Meninges of spinal cord ◼ The membranes surrounding the spinal cord :meninges 3 in number: from outside inside ◼ Dura mater (spinalis) ( has 2 layers) ◼ Arachnoid mater (spinalis) ◼ Pia mater (spinalis) Pia (because they are the Continuation of meninges of brain) ◼ Pia mater terminates (closes) at the inferior limit of spinal cord (L1) ◼ Dura mater and arachnoid mater terminates at S2 level. Filum terminale filum terminale: pia mater below L1 L1-S2: fil.term.internum S2-coccyx: fil.term.externum Note that:Pia mater terminates (closes) at the inferior limit of spinal cord (L1) Dura mater and arachnoid mater terminates at S2 level. Denticulate ligament ◼ Spinal cord is suspended within dural sac by denticulate ligaments on each side; It is the Extension of pia mater; 20 – 22 in number ◼ With arachnoid mater attaches to the inner surface of dural sac External features of spinal cord ◼ Anterior median fissure ◼ Posterior median sulcus ◼ Anterolateral sulcus ◼ Posterolateral sulcus(dorsolat.) A spinal cord segment ◼ Is the part of Spinal Cord from where a pair of Spinal Nerves arise;one from right &one from left side ◼ There are 31 segments of spinal cord ◼ 8 in cervical region ◼ 12 in thoracic region ◼ 5 in lumbar region ◼ 5 in sacral region ◼ 1 in coccygeal region ◼ So, 31 pairs of SPINAL NERVES Spinal n. ◼ Posterior root: enters spinal cord from posterolateral sulcus, brings sensory information from periphery ◼ Anterior root: leaves spinal cord from anterolateral sulcus, motor ◼ Fila radicularia (rootlets); the fibres forming the anterior and posterior roots Spinal nerve: Roots&rami ◼ Spinal cord is located in the vertebral canal ◼ Spinal nerves leave the vertebral canal by passing through the intervertebral foramen why there are 8 pairs of spin. Nn. At cervical level?? Because..... ◼ C1 spinal nerve (suboccipital n.) leaves vertebral canal bw.: atlas – occipital bone dermatome, axial line ◼ Dermatome: the Skin region innervated by one spinal n. ◼ Axial line: In some regions; the spinal nerves innervating the two neighbouring dermatome areas do not originate from the neighbouring segments. → Line between this type of two dermatome regions ◼ By the axial line; n. fibres innervating the two neighbouring dermatomes do not pass to each other Internal structure of spinal cord:gray&white matter ◼ Gray matter: contains Neurons, neuroglia and blood vessels Butterfly shaped ◼ White matter: contains Nerve fibres ,neuroglia, blood vessels – Anterior funiculus – Posterior funiculus – Lateral funiculus  Gray matter has: ◼ Anterior horn ◼ Posterior horn ◼ Lateral horn (bw.T1 – L3 (L2) ◼ In the examination of spinal cord 3-dimensionally; anterior column, posterior column, lateral column (columna intermedia) ◼ Central canal (contains Cerebrospinal Fluid) ant.&post to central canal: ◼ Anterior gray commissure ◼ Posterior gray commissure  Central canal ◼ Within the gray matter,all along the spinal cord and caudal half of medulla oblongata ◼ Opens above: into 4th ventricle ◼ In the conus medullaris, it expands as a fusiform terminal ventricle ◼ Contains cerebrospinal fluid (CSF) internal structure of spinal cord at different segments Laminae of the gray matter ◼ 10 laminae ◼ Depending upon to dimension, shape, cellular characteristics, density of neurons Laminae I – IV (post. horn): are related to sensory pathways (afferent pathways) Lamina IX (ant. Horn): contains:Alpha motor neurons,Gamma motor neurons ◼ ,Interneurons Related to motor pathways (efferent pathways)  White matter ◼ Formed by axons located in: ◼ Posterior funiculus ◼ Lateral funiculus ◼ Anterior funiculus ◼ Posterior funiculus; in cervical and upper thoracic segments, has dorsal-intermediate sulcus; divided into fasciculus gracilis (medial) and fasciculus cuneatus (lateral) ◼ Anterior white commissure ◼ Posterior white commissure SPINAL REFLEX Fibers coming from receptors in the muscles, joints and skin reach to the post horn neurons They do not reach the cortical areas Fibers directly arise from alfa motor neurons (lamina IX) and form involuntary movements Eg. You touch to fire than pull your hand immediately Aa. of spinal cord ◼ Located In the subarachnoidal space ◼ Vertebral aa. ◼ Radicular aa. Vertebral a. ◼ Is a Branch of subclavian a. ◼ Passes through foramina of all cervical transverse processes, except 7th ◼ Enters cranium through foramen magnum ◼ Give: -- Posterior spinal a. (2 in number) --Anterior spinal a. (1 in number) – 2 anterior spinal aa. Unite ,form single anterior spinal a. in the ant median fissure Courses the anterior spinal artery Radicular aa These are the Spinal branches of Neighboring aa during the course of spinal cord namely: -Ascending cervical a. -Deep cervical a. -Intercostal aa. -Lumbar aa. -Lateral sacral aa. Spinal branches Course along spinal nn. Pass through intervertebral foramina Divide into: anterior and posterior radicular aa. Anastamose with ant+post spinal aa and form arterial vasocorona Artery of Adamkiewicz ◼ In the lumbar region, on the left side, one of the anterior radicular branches has a greater caliber than the others ◼ A. radicularis magna ◼ On the left side of spinal cord, supplies blood to lower thoracic and upper lumbar regions (main artery) Vv. of spinal cord ◼ Anterior spinal v. ◼ Posterior spinal v. ◼ Venous vasocorona ◼ These vv. unite and drain into ant and post radicular vv. ◼ Ant, post radicular vv. → ant and post internal vertebral venous plexuses (epidural venous plexus)  Connections of epidural venous plexus ◼ Thoracal vv. ◼ Abdominal vv. ◼ Intercostal vv. ◼ Ant external vertebral venous plexus ◼ Post external vertebral venous plexus ◼ Prostatic venous plexus ◼ Pelvic venous plexus ◼ at the level of foramen magnum, ant and post internal vertebral venous plexuses give branches, which connect with vertebral v., sigmoid sinus, occipital sinus