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Home , Cervical enlargement, Interspinous ligament, Lumbar enlargement, Vertebral column

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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 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) () i. Thoracic (T1-T12) () C1 – C7 ii. (L1-L5) (lordosis) i. Sacral (pelvic) (S1-S5) (kyphosis) T1-T12

L1-L5

S1-S5

Abnormal Curvatures of the Vertebral Column

Normal Kyphosis Lordosis

5 Scoliosis

6 Gray’s 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 . 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 ii. Large triangular iii. Short, bifid (uncinate) spinous process iv. Zygopophyseal articulation: anterior/posterior but at ~45 degree angle

Thoracic i. Articular facets for ii. 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; ‘’ Cervical – C2; ‘’ i.No body !!!! i.Dens (odontoid process) ii.Large superior articulating processes (concave) which articulate with the Foramen magnum Dens

Spinous D process Occipital condyle

C1 Atlanto-occipital

Atlanto-axial joint C2 Body

Transverse of atlas Frontal radiograph of atlanto-axial joint

D

C1

Posterior tubercle 11

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 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., , , , , ,

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 e.g., epiphyseal growth plates • If fibrocartilage = ; e.g., iv discs, A Typical

Features of Synovial Joints

• Articular (hyaline) cartilage

• capsule

• Joint space with synovial fluid

• Synovial membrane lining

• Capsular

• Sensory nerves and blood vessels to capsule, periosteum, and subchondral , 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 • •

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 (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 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 Venous Drainage of Spinal Cord

• Single anterior and posterior spinal vv. • Pairs of near entrance/exit from spinal cord • Veins drain into internal vertebral venous plexus

22 Vertebral Venous Plexus • Freely anastomotic network of vv within + 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

Meninges: • D • A • P

24 Meninges There are 3 layers, or meninges, that surround the components of the central (brain and spinal cord): 1. (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 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 is the caudal extension of the pia mater that passes through the middle of the 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 .

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 (C4-T1) enlargement - The (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 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 's - 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 , to avoid the spinal cord that ends at approximately L2.

Because the dura and 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 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 sensory fibers from the periphery to the . These fibers originate from spinal ganglion neurons located external to the spinal cord.

rootlets

rootlets Dorsal root Spinal Ganglion (DRG)

Spinal Ganglion-collection of nerve cell bodies outside the central nervous system. Pseudonipolar neurons that have central processes ending in the dorsal horn; peripheral processes most time associated with a sensory receptor. There are no synapses in the spinal ganglia. It is located in the . Formation of a typical Spinal nerve

Ventral Root-motor fibers that innervate somatic muscles. These originate from anterior horn neurons.

rootlets

rootlets Formation of a typical Spinal nerve

Spinal Nerve is a relatively short structure that is formed by union of ventral root and dorsal root and is therefore a “mixed” (sensory & motor modalities) nerve . Its two branches include: • dorsal primary ramus - mixed motor and sensory fibers that innervates epaxial muscles and overlying skin • ventral primary ramus – mixed motor and sensory fibers innervates hypaxial muscles and overlying skin. Motor and Sensory Pathways Between Spinal Cord and Spinal Nerve

To brain

To thalamus Dorsal root Dorsal root ganglion (DRG) Dorsal horn Dorsal ramus *Association neurons

ventral ramus

Ventral horn *motor neuron

spinal nerve Dorsal root