1 The NERVOUS SYSTEM Spinal Cord and Spinal Nerves and meninges Dr. K V K

16-2 The Spinal Cord Provides a vital link between the brain and the rest of the body. Exhibits some functional independence from the brain. The spinal cord and its attached spinal nerves serve two important functions. pathway for sensory and motor impulses responsible for reflexes

16-3 Structure of the Spinal Cord A typical adult spinal cord ranges between 42 and 45 centimeters (cm) (16 to 18 inches) in length. Viewed in cross section, it is roughly cylindrical, but slightly flattened both posteriorly and anteriorly. Its external surface has two longitudinal depressions. the posterior (or dorsal) median sulcus, dips internally on the posterior surface the anterior (or ventral) median fissure, is observed on its anterior surface

16-4 Location and Distribution of White Matter The white matter of the spinal cord is external to the grey matter. White matter on each side of the cord is also partitioned into three regions. A posterior funiculus lies between the posterior grey horns on the posterior side of the cord and the posterior median sulcus. The white matter region on each lateral side of the spinal cord is the lateral funiculus. The anterior funiculus is composed of tracts of white matter that occupy the space on each anterior side of the cord between the anterior grey horns and the anterior median fissure. The anterior funiculi are interconnected by the white commissure.

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16-7 Regions of the Spinal Cord The cervical region is the superior-most region of the spinal cord. continuous with the medulla oblongata contains neurons whose axons form the cervical spinal nerves The thoracic region lies inferior to the cervical region. attached to this region are the thoracic spinal nerves The lumbar region is a shorter segment of the spinal cord that contains the neurons for the lumbar spinal nerves The sacral region lies inferior to the lumbar region and contains the neurons for the sacral spinal nerves The coccygeal region is the most inferior “tip” of the spinal cord. one pair of coccygeal spinal nerves arises from this region.

16-8 Spinal Nerves The spinal cord is associated with 31 pairs of spinal nerves that connect the CNS to muscles, receptors, and glands. Each side of the spinal cord contains 8 cervical nerves (called C1–C8), 12 thoracic nerves (T1–T12), 5 lumbar nerves (L1–L5), 5 sacral nerves (S1–S5), and 1 coccygeal nerve (Co).

16-9 Spinal Nerves 31 pairs of spinal nerves connect the central nervous system to muscles, glands, and receptors Each spinal nerve is formed from the union of thousands of motor and sensory axons. Motor axons originate from the spinal cord. Each anterior root and its corresponding posterior root unite within the intervertebral foramen to become a spinal nerve. Contain both motor axons and sensory axons. Each spinal nerve is associated with the vertebra of the same number.

Spinal nerves and vertebral levels 10

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16-12 Structure of the Spinal Cord The spinal cord is shorter than the vertebral canal that houses it. The tapering inferior end of the spinal cord is called the conus medullaris and it marks the official “end” of the spinal cord proper. Inferior to this point, nerve roots (groups of axons collectively called the cauda equina) project inferiorly from the spinal cord. Within the cauda equina is the filum terminale, a thin strand of pia mater that helps anchor the conus medullaris to the coccyx.

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16-14 Arrangement and Functions of the Spinal Meninges Are continuous with the cranial meninges. Structures that encircle the spinal cord, listed from outermost to innermost are: vertebra epidural space Dura mater subdural space arachnoid subarachnoid space pia mater

Them Meninges of the cord 16-15

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Ligament denticulatum Triangular shaped Or dental shaped Lateral extensions Of the Pia matter Attached to the Dura matter and Gives support to The spinal cord 16-18

Filum terminale(pia matter) Note the narrow cord Of pia matter just inferior to the conus Medullaris(end) of the Cord Cm:conus medullaris Ce:cauda equina 16-19

Lumbar cystern Is the sub- Arachnoid space Which is the Largest,extends From L1 to S2 Where the Dura Matter ends

Spinal cord in the Fetus Note in the fetus The cord extends The whole length of the Vertebral canal(into the – Sacral canal) 16-21

Cerebrospinal fluid circulation 16-22

Spinal canal 1.Intervertebral Disc 2.Body of vertebra 3.Dura matter 4.Epidural space (extradural space) 5.Spinal cord 6.Sus Arachnoid space

Structures in the sagittal plain See the MRI picture above A sagittal view of the human thoracic spinal cord, showing the (1) intervertebral discs, (2) vertebral bodies, (3) Dura, (4) epidural space, (5) spinal cord, and (6) subdural space. (refer the previous picture) 16-24

Anterior spinal artery Is the branch of the vertebral artery and Supply the spinal Cord only in the Upper region. The lower regions are Supplied by the Medullary segmental Arteries from below. 25

Arteries of spinal cord 26

16-27 Location and Distribution of Grey Matter In the spinal cord, Grey Matter is centrally located. Its shape resembles a letter H or a butterfly. The grey matter may be subdivided into the following components: anterior horns lateral horns posterior horns the grey commissure

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16-30 Nerve Plexuses A network of interweaving anterior rami of spinal nerves. Anterior rami of most spinal nerves form nerve plexuses on both the right and left sides of the body. Nerve plexuses then split into multiple “named” nerves that innervate various body structures. Principal plexuses are the cervical plexuses, brachial plexuses, lumbar plexuses, and sacral plexuses.

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32 Cross-sectional anatomy of the spinal cord

LUMBAR-PUNCTURE A lumbar puncture is done to:lumbar puncture Find a cause for symptoms possibly caused by an infection (such as meningitis), inflammation, cancer, or bleeding in the area around the brain or spinal cord (such as subarachnoid hemorrhage).meningitiscancersubarachnoid hemorrhage Measure the pressure of cerebrospinal fluid (CSF) in the space surrounding the spinal cord. If the pressure is high, it may be causing certain symptoms. A lumbar puncture may also be done to: Put anesthetics or medicines into the CSF. Medicines may be injected to treat leukemia and other types of cancer of the central nervous system.anestheticsleukemianervous system 33

34 Clinical Significance Lumbar puncture between L3/L4 or L4/L5 (L4 spinous process in line with highest points on iliac crests). Used to draw CSF, measure pressure, nerve block, or epidural anastheasia,administration of cancer drugs because of the large lumbar cistern(storehouse)

PROCEDURE OF LUMBAR PUCTURE The needle is Inserted between Spine any level Below the L1 but Above the sacrum In adults. 35

36 Lumbar puncture