Vertebral column, spinal cord, spinal nerves and meninges Dr. Andrew Deane MS 5025Q [email protected] (317)274-7802 Parts of a Typical Vertebrae 7 4 3 2 1 5 7 6 2 5 4 1 superior view lateral view 1 – body 2 – pedicle 3 – lamina 4 – spinous process 5 – articulating process 6 – vertebral (spinal) canal 7 – transverse process 2 i. Support ii. Movement iii.Protection dorsal Spinous process Lamina Articular process *superior Transverse Pedicle process Vertebral Body ventral 4 vertebral curvatures: i. Cervical (C1-C7) (lordosis) i. Thoracic (T1-T12) (kyphosis) C1 – C7 ii. Lumbar (L1-L5) (lordosis) i. Sacral (pelvic) (S1-S5) (kyphosis) T1-T12 L1-L5 S1-S5 coccyx Abnormal Curvatures of the Vertebral Column Normal Kyphosis Lordosis Scoliosis 5 Scoliosis 6 Gray’s Anatomy for Students, 3rd ed. Fig. 2.25 superior intervertebral notch When viewed from the lateral aspect, there are two notches – one superior to the pedicle (the inferior superior intervertebral notch) intervertebral and the other inferior to it (the notch inferior intervertebral notch). When two vertebrae are stacked on top of one another, the two intervertebral notches come together to form foramina the intervertebral foramen. This is the site of exit of spinal nerves as they arise from the spinal cord and pass out into the periphery of the body. 7 Cervical i. Transverse foramina for vertebral arteries ii. Large triangular vertebral foramen iii. Short, bifid (uncinate) spinous process iv. Zygopophyseal articulation: anterior/posterior but at ~45 degree angle Thoracic i. Articular facets for ribs ii. Heart shaped body iii. Elongated, posteriorly deflected spinous process iv. Zygopophyseal articulation: anterior/posterior at ~90 degree angle Lumbar i. Large, bean shaped body ii. Shortened, squared and posteriorly projecting spinous processes iii. Zygopophyseal articulation: concave/convex Cervical – C1; ‘Atlas’ Cervical – C2; ‘Axis’ i.No body !!!! i.Dens (odontoid process) ii.Large superior articulating processes (concave) which articulate with the occipital condyles Foramen maGnum Dens Spinous D process Occipital condyle C1 Atlanto-occipital joint Atlanto-axial joint C2 Body Transverse liGament of atlas Frontal radiograph of atlanto-axial joint D C1 Posterior tubercle 11 Sacrum Sacral canal Median sacral crest Lateral sacral Ala crest Promontory Sacral hiatus Sacral cornua Transverse process 12 What is a joint (arthrosis)? • A site of union between two or more skeletal elements • Classes of joints are based on type of tissue interposed between the skeletal elements Classes of Joints Synovial joints Non-Synovial joints (diarthroses) (synarthroses) syn = “together” • Synovial fluid between skeletal elements • Free movement permitted • E.g., shoulder, elbow, hand, hip, knee, ankle Fibrous joints Cartilaginous joints • Dense fibrous c.t. • Cartilage between skeletal elements between skeletal elements • Slight movement permitted • Little or no movement permitted • If hyaline cartilage = synchondrosis; • E.g., sutures of skull e.g., epiphyseal growth plates • If fibrocartilage = symphysis; e.g., iv discs, pubic symphysis A Typical Synovial Joint Features of Synovial Joints • Articular (hyaline) cartilage • Fibrous joint capsule • Joint space with synovial fluid • Synovial membrane lining • Capsular ligaments • Sensory nerves and blood vessels to capsule, periosteum, and subchondral bone, but not cartilage Joints of the Vertebral Column • Intervertebral • Costovertebral Two types: • Symphysis • Synovial Posterior longitudinal ligament Vertebral Ligaments • Anterior longitudinal ligament • Posterior longitudinal ligament • Ligamentum flavum • Interspinous ligament • Supraspinous ligament Ligamenta flava Anterior longitudinal ligament Ligamentum nuchae Interspinous ligament Supraspinous ligament Vertebral canal Contents of the Vertebral Canal The vertebral canal contains: • Epidural/extradural fat • Internal vertebral venous plexus • MeninGes • Spinal cord 19 Spinal cord vasculature Posterior spinal aa. Anterior spinal a. The spinal cord receives its blood supply from a descending longitudinal source, • one anterior spinal artery (via vertebral a.) • two posterior spinal arteries (via posterior inferiror cerebellar aa.) They are supplemented by a series of segmental arteries at each vertebral level. Arterial Supply to Spinal Cord “Horizontal” feeder arteries enter vertebral canal via IVFs at each level and segmental spinal aa. that give rise to radicular branches that follow along nerve roots (“radix”/radicular) to the cord At various levels, the segmental spinal aa give rise to 8-10 segmental medullary aa. That “reinforce” longitudinal vessels Great radicular artery or artery of Adamkiewicz – largest of these: Arises between T9 and L2, usually on left side, in 85% of people. Reinforces blood supply to lower cord (lumbosacral enlargement). Clinical note: Occlusion >> Spinal cord infarction/spinalcord ischemia >> devastating paralysis of lower limb Venous Drainage of Spinal Cord • Single anterior and posterior spinal vv. • Pairs of veins near nerve root entrance/exit from spinal cord • Veins drain into internal vertebral venous plexus 22 Vertebral Venous Plexus • Freely anastomotic network of vv within spinal canal + surrounding the vertebral column • Base of skull to sacrum • Drains blood from VC + SC • Lack valves – bidirectional flow • Connect with other vv of body • May be involved in metastasis of CA 23 Laminectomy MeninGes: • D • A • P 24 Meninges There are 3 layers, or meninges, that surround the components of the central nervous system (brain and spinal cord): 1. dura mater (outermost) 2. arachnoid 3. pia mater (innermost) Epidural space: cross section view contains fat and extensive venous anastomosis Dura mater Spinal cord Dura mater (tough mother) is the external outer tough covering that extends to S2 levels of the vertebral canal. This blind end pouch is the dural sac. The dura mater also extends out along each spinal nerve to the distal end of the spinal ganglion where it becomes continuous with the epineurum of the spinal nerves. These extensions are termed dural sleeves. Meninges The arachnoid membrane (spider’s web) is an avascular membrane deep to the dura mater and follows the dura mater out into the dural sleeves and caudally into the dural sac. Epidural space Dura mater Spinal cord Arachnoid membrane • The subarachnoid space is filled with cerebrospinal fluid and contains superficial arteries and veins of the spinal cord. Meninges The pia mater (delicate mother) is the deepest meningeal layer. It is adherent to the surface of the spinal cord. Epidural space Dura mater Arachnoid membrane Spinal cord Pia mater Denticulate ligaments are lateral extensions of the pia mater (saw tooth membranes) which help to anchor the spinal cord to the dura mater Filum terminale is the caudal extension of the pia mater that passes through the middle of the cauda equina and then pierces the dura mater to attach to the coccyx. The spinal cord The spinal cord extends from the foramen Cervical magnum to approximately the level of the disc enlargement between vertebrae L1 and L2 in adults. The point of termination is called the conus medullaris. A thin filament of pia mater off the surface of the spinal cord - the filum terminale – descends and anchors the spinal cord to the coccyx The spinal cord exhibits two enlargements: lumbar - The cervical enlargement (C4-T1) enlargement - The lumbar enlargement (L2-S3). Conus These enlargements represent increased Medularis Filum terminale neuronal density in these areas as they (LII) supply the upper and lower limbs through the brachial and lumbosacral “plexuses” respectively The spinal cord The spinal cord exhibits 31 pairs of spinal nerves: 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal Cervical spinal nerves exit above their respective vertebrae BUT thoracic and lumbar spinal nerves exit below the vertebrae. - There are 7 cervical vertebrae but 8 cervical spinal nerves. End of spinal cord vertebral level LII The spinal cord terminates bluntly at vertebral Cauda equina level L2 as the conus medullaris. Below this point the remaining pairs of spinal nerves descend in an arrangement that looks like a horse's tail - the cauda equina. L2 30 Filum terminale internum Filum terminale externum S2 S1 The spinal cord ends at the conus medullaris at L2, but the dural sac ends at S2. 31 Conus medularis Filum terminale Lumbar Spinal Puncture Lumbar puncture is performed for retrieval of cerebrospinal fluid (CSF) from the lumbar spinal cistern. The patient is placed in the left decubitus position, flexed in the fetal posture. A needle puncture is made at the L3/4 or L4/5 interspace near the midline of the back, to avoid the spinal cord that ends at approximately L2. Because the dura and arachnoid mater are practically adherent to one another, the needle puncture traverses both meningeal layers simultaneously upon entering the subarachnoid space. Spinal cord The spinal cord has an outer region of White Matter which is composed mainly of myelinnated axons. The spinal cord has an inner region of Gray Matter which is composed of neuronal and glial cell bodies Spinal cord The gray matter is divided into: a Posterior (Dorsal) Horn which contains neurons that receive sensory information from dorsal spinal ganglia neurons. an Anterior (Ventral) Horn which contains somatic motor neurons that innervate skeletal muscles. It is a one neuron chan that is involved in innervating skeletal muscles. Dorsal horn Formation of a typical Spinal nerve Dorsal Root- somatic