CROSS SECTIONAL ANATOMY OF SPINE

By Vivek jr 115/5/12

C7 – Prom. Spinous Process

T3- Level with Medial Scapular Spine

T7 – Inferior angle of scapula

L2 – Lowest Rib

L4 – Iliac Crest

Flexibility and Mobility

Flexion (forward bending) Extension (backward bending) Side bending (left and right) Rotation (left and right) Combination of above

MUSCLES ASSOCIATED WITH

Cervical vs Thoracic vs Lumbar

Cervical vertebrae

Smallest

Foramen in each transverse process

ATLAS

C1 –Atlas

Forms the joint connecting the skull and spine

Has no body

AXIS (Second cervical vertebra)

(C2) of the spine is named the axis.

It forms the pivot upon which the Atlas- rotates

strong odontoid process which rises perpendicularly from the upper surface of the body.

Thoracic Vertebra

Intermediate in size Increase in size as one

proceeds down the spineThey are distinguished by

the presence of facets on the sides of the bodies

Facets on the transverse processes of all, except the eleventh and twelfth,

Lumbar Vertebra

The lumbar vertebrae are the largest segments of the movable part of the vertebral column

Absence of a foramen in the transverse process,

Absence of facets on the sides of the body.

The cervical curve, convex forward, C1/2 – C7

The thoracic curve, is concave

T2 – T12

The lumbar T12 – L4, It is convex anteriorly.

The pelvic curve L4/5 - Coccyx

The spinal cord• Gross anatomy

– 3 layers of meninges– Epidural space (fat & vessels)– CSF – subarachnoid space– Terminates at L1/2 vertebral level

(conus medullaris)• Dura extends to S2 vertebral

level– Connects via filum terminale &

denticulate ligaments (pia)– 31 pairs of spinal nerves (mixed)

• cauda equina– Cervical & lumbar enlargements

Spinal Cord Anatomy

• Conus medullaris – terminal portion of the spinal cord• Filum terminale – fibrous extension of the pia mater; anchors

the spinal cord to the coccyx• Denticulate ligaments – delicate shelves of pia mater; attach

the spinal cord to the vertebrae• Spinal nerves – 31 pairs attach to the cord by paired roots

– Cervical nerves are named for inferior vertebra – All other nerves are named for superior vertebra

• Cervical and lumbar enlargements – sites where nerves serving the upper and lower limbs emerge

• Cauda equina – collection of nerve roots at the inferior end of the vertebral canal

The 3 Meningeal Layers• Dura mater:

– outer layer of spinal cord– subdural space:

• between arachnoid mater and dura mater

• Arachnoid mater:– middle meningeal layer– subarachnoid space:

• between arachnoid mater and pia mater

• filled with cerebrospinal fluid (CSF)

• Pia mater:– inner meningeal layer

The Meninges

Structures of the Spinal Cord

• Paired denticulate ligaments:– extend from pia mater to

dura mater– stabilize side-to-side

movement

• Blood vessels:– along surface of spinal pia

mater– within subarachnoid space

Cross-sectional anatomy of the spinal cord

Intervertebral Disk

Each disc forms a cartilaginous joint to allow slight movement of the vertebrae, and acts as a ligament to hold the vertebrae together.

The annulus fibrosus consists of several layers of fibrocartilage. The strong annular fibers distribute pressure evenly across the disc.

The nucleus pulposus contains loose fibers- like JELLY. The nucleus of the disc acts as a shock absorber, absorbing the impact of the body's daily activities and keeping the two vertebrae separated.

Spinal Nerves

Figure 13.6

• The cervical enlargement corresponds with the attachments of the large nerves which supply the upper limbs.

• It extends from about the C-3 to T-2, its maximum circumference (about 38 mm.) being on a level with the attachment of the sixth pair of cervical nerves.

• The reason behind the enlargement of the cervical region is because of the increased neural input and output to the upper limbs.

• The lumbar enlargement (or lumbosacral enlargement) gives attachment to the nerves which supply the lower limbs.

• It commences about the level of T11, and reaches its maximum circumference, of about 33 mm., at L1 (lumbar vertebra), below which it tapers rapidly into the conus medull

Nerve Plexuses• All ventral rami except T2-T12 form interlacing nerve

networks called plexuses• Plexuses are found in the cervical, brachial, lumbar, and

sacral regions• Each resulting branch of a plexus contains fibers from

several spinal nerves• Fibers travel to the periphery via several different routes• Each muscle receives a nerve supply from more than

one spinal nerve• Damage to one spinal segment cannot completely

paralyze a muscle

The 4 Major Plexuses of Ventral Rami

1. Cervical plexus2. Brachial plexus3. Lumbar plexus4. Sacral plexus

Cervical Plexus

Figure 13.8

C1-C4 (c5-PHRENIC N.)

Brachial Plexus

Figure 13.9aC5-C8+T1 – FORM THE BRACHIAL PLEXUS

Lumbar Plexus

Figure 13.10

Arises from (T12) L1-L4 and innervates the thigh, abdominal wall, and psoas muscle

Sacral Plexus

Figure 13.11

-Arises from L4-S4 and serves the buttock, lower limb, pelvic structures, and the perineum.

Figure 13.7b

SPINAL NERVE INNERVATION: BACK, ANTEROLATERAL THORAX, AND ABDOMINAL WALL

Spinalis muscleLongismus thoracis

Iliocostalis thoracis

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