anatomy of spine

ANATOMY OF SPINE

Dr Pankaj N SurangeMBBS, MD, FIPP

Interventional Pain and Spine specialist

A-P X-ray of a scoliotic spine in the coronal plane.

The CORONAL PLANE, also called the FRONTAL PLANE, is a vertical cut that divides the body into front and back sections. Physicians look at the coronal plane when they view an A-P (anterior-posterior) x-ray of the spine to evaluate scoliosis.

Anatomical Planes

Lateral X-ray of a kyphotic spine in the sagittal plane.

The SAGITTAL or MEDIAN PLANE is a vertical cut that divides the body into left and right sections. The sagittal view is seen by surgeons on a lateral x-ray of the spine.

Anatomical Planes

CT Scan of a thoracic vertebra in the axial plane.

The AXIAL or TRANSVERSE PLANE is a horizontal cut that divides the body into upper and lower sections. To best view the axial plane of the spine, surgeons will often obtain a CT scan with axial cuts.

Anatomical Planes

• Protection of – spinal cord and nerve roots– internal organs

Functions of the Spine

• Flexibility of motion in six degrees of freedom

Left and RightSide Bending

Flexion and Extension Left and Right Rotation


To achieve these functions, the spine must have:

• Resistance to axial loading forces, accomplished by:

– Kyphotic and lordotic sagittal plane curves

– Increased mass of each vertebra from C1 to the sacrum

• Elasticity accomplished by:– Alternating lordotic and kyphotic

curves– Multiple MOTION SEGMENTS


• The FUNCTIONAL UNIT of the spine• Composed of:

– Connecting ligaments

– Two adjacent vertebrae– The intervertebral disc

– Two facet joints and capsules

The Motion Segment

• Primary CurvesSagittal Plane Curves

• Secondary Curves

Cervical Lordosis 20°- 40°

Sacral Kyphosis

Lumbar Lordosis 30°- 50°

Thoracic Kyphosis 20°- 40°

Sagittal Plane Curves

• Cervical– Upper cervical: C1-C2– Lower cervical: C3-C7

• Sacrococcygeal: 9 fused vertebrae in the sacrum and coccyx.

• Thoracic: T1-T12

• Lumbar: L1- L5

Regions of the Spine

• Line of gravityAuricle of the ear

Odontoid

Body of C7

Anterior to thoracic spine

Posterior to L3

Mid femoral heads

Regions of the Spine

Basic Vertebral StructuresBasic Vertebral Structures

Cervical Thoracic Lumbar

There are two types of bone tissue:• Cortical bone: dense, outer shell of the

vertebra

Detail of Cortical Bone

Haversian System

Detail of Cancellous Bone

• Cancellous bone: inner, spongy bone

Types of Bone Tissue

Vertebral Body

Pedicle

LaminaSuperior Articular Process

SpinousProcess

Transverse Process

Vertebral Foramen

Vertebral Structures

Superior Articular Process

Inferior Articular Process

Zygapophyseal Joint

(Facet Joint)

Pars



• Pedicle notchesSlight Notch

Deep Notch

Intervertebral Foramen

• INTERVERTEBRAL FORAMEN through which the spinal nerve

roots leave the spinal cord

• Anterior ArchComprised of:– Vertebral body – Anterior 1/3 of the pedicles

• Posterior ArchComprised of:– Posterior 2/3 of the pedicles– Lamina– Processes

Vertebral Arches

The Atlas (C1)

Transverse Process

Transverse Foramen

Anterior Tubercle

Articular Facet for Dens

Lateral Mass

LaminaPosterior Tubercle

Superior Articular

Facet

Superior View

The Axis (C2)

Odontoid Process (Dens)

Body

Transverse Process

Inferior Articular

Facet

Superior Articular

Facet

Anterior View Posterior View

Lateral Mass

Spinous Process

Lower Cervical Vertebrae

• C3 to C7– May be referred to as

the subaxial region– Disc at every level– Vertebral structures

are similar

Lower Cervical Vertebrae C3 - C7

Transverse ProcessBody

Sulcus for Spinal Nerve

Lateral Mass

Lamina

Pedicle

Superior Articular Facet

Vertebral Foramen

Bifid Spinous Process

Transverse Foramen

Axial View

Sulcus for Spinal Nerve

UncinateProcess

Uncovertebral Joint(Joint of Luschka)

Lower Cervical Vertebrae C3 - C7

Anterior View

The vertebral bodies of the subaxial cervical spine have upward projections on the lateral margins called UNCINATE PROCESSES.

These processes articulate with the level above to form the UNCOVERTEBRAL JOINT. These are also called JOINTS OF LUSCHKA.

Vertebra Prominens (C7)

SpinousProcess

Axial View

C7 is referred to as the VERTEBRA PROMINENS because it has a longer and larger spinous process than the other cervical vertebrae.

This spinous process is not usually bifid.

Thoracic Vertebrae• Body - progressive increase in mass

from T1 to T12

• Pedicles - small diameter

• Laminae - vertical, with “roof tile” arrangement

• Spinous processes - long, overlapping, projected downward

• Intervertebral foramen - larger, less incidence of nerve compression

Thoracic Vertebrae, T1-T12• Body - heart shaped when viewed

superiorly.

• Vertebral foramen - round

• Pedicles - small in diameter

• Spinous processes - long and projected downwards

• Articular processes

Superior ArticularProcess

Inferior ArticularProcess

Thoracic Vertebrae, T1-T12

• Body - L1 to L5 progressive increase in mass

• Pedicles - longer and wider than thoracic; oval shaped

• Spinous processes - horizontal, square shaped

• Transverse processes - smaller than in thoracic region

• Intervertebral foramen - large, but with increased incidence of nerve root compression

Lumbar Vertebrae, L1-L5

The SacrumSacral Horns

Sacral Ala

PediclesDorsalForamina

Sacral Hiatus

CoccyxPosterior View

Inverted triangle shape

CoccyxLateral View

Sacral Promontory

Sacral Tilt30°-60°

Sacral Canal

1

2

3

4

5

Sacral Hiatus

The Sacrum

• Intervertebral disc

• End plate

• Apophyseal ring

– Cartilaginous layer– Bony layer

Intervertebral Disc

• Fibrocartilaginous joint of the motion segment

• Make up ¼ the length of the spinal column

• Present at levels C2-C3 to L5-S1

• Allows compressive, tensile, and rotational motion

• Largest avascular structures in the body

Intervertebral Disc

Intervertebral Disc

• Annulus Fibrosus– Outer portion of the disc

Lamellae

– Great tensile strength

– Made up of lamellae

Annulus Fibrosus

• Layers of collagen fibers• Arranged obliquely 30° • Reversed contiguous

layers

Intervertebral Disc• Nucleus Pulposus Nucleus

Pulposus– Inner structure– Gelatinous– High water content– Resists axial forces

Occipitocervical JointOccipital Condyles

ForamenMagnum

articulate with C1 superior

facets

Atlantoaxial Joint

C1

C2

Dens

Zygapophyseal joints

JOINT between the atlas (C1) and the axis (C2); has a range of motion in the transverse plane for rotation.

The DENS of C2 acts as a pivot point for the rotation of C1.

The articulating surfaces of the two vertebrae form ZYGAPOPHYSEAL (FACET) JOINTS that allow flexion-extension, side bending, and rotational movements.

Also called ZYGAPOPHYSEAL JOINTS.

The facet joints are formed by the articular processes of adjacent vertebrae. The inferior articular process of a vertebra articulates with the superior articular process of the vertebra below.

These are synovial gliding joints

Facet joints are oriented in different planes depending on their anatomic location.

The Facet Joints

Uncovertebral JointsUncovertebral

JointThe bony elevations on the superior lateral margins of the cervical vertebrae are called UNCINATE PROCESSES.

The uncovertebral joints are not true joints

These joints articulate with the inferior, lateral aspect of the vertebra above to form the UNCOVERTEBRAL JOINTS, also known as the JOINTS OF LUSCHKA. These are fibrous joints

Uncinate Process

The T2-T9 thoracic vertebra have facets superiorly and inferiorly at the posterior aspect of the vertebral body that form the COSTOVERTEBRAL joints.

Costovertebral JointsCostovertebral

joints

Rib

Costotransverse joints

Axial View

In the thoracic spine, the RIBS articulate with the vertebrae at both the body and the transverse processes.

At all thoracic levels there is a facet where the rib articulates with the transverse process. These are called the COSTOTRANSVERSE joints.

The T1 and T10-T12 vertebral bodies have only one costal facet.

Rib

Lateral View

Costovertebral joints

Costotransverse joint

Rib

Costovertebral Joints

Sacroiliac Joint

Sacroiliac Ligaments

SacrumIlium

The superior lateral surface on either side of the sacrum articulates with the inner aspects of the pelvis. This area forms the capsular, synovial SACROILIAC JOINT.

In some cases the sacroiliac joint is a hidden source of back pain.

Upper Cervical LigamentsOccipitoatlantal Ligament Complex

Anterior occipitoatlantal ligament

Posterior occipitoatlantal ligament

Lateral occipitoatlantal ligament

Anterior View

Upper Cervical LigamentsOccipitoaxial Ligament Complex

Alar ligaments (2)Apical ligament

Posterior cutaway view

Occipitoaxial ligament

Posterior view

Lower Cervical, Thoracic, and Lumbar Ligaments

•Extending from the axis (C2) anteriorly to the sacrum.

•Is broader at the level of each vertebral body than at the level of the discs where the fibers adhere to the annulus fibrosus.

•Attaches to each vertebral body superiorly and inferiorly at the levels of the end plates.

Anterior Longitudinal Ligament (ALL)

Intertransverseligaments

Costal ligaments


The INTERTRANSVERSE LIGAMENTS extend from the inferior surface of the entire length of the transverse process to the superior surface of the adjacent transverse process.

The COSTAL LIGAMENTS connect the heads of the ribs to the vertebrae.

Posterior longitudinal ligament


POSTERIOR LONGITUDINAL LIGAMENT (PLL)

• Is weaker than the ALL.

• It runs from the axis (C2) caudally to the sacrum.

•The PLL is narrow at the levels of the vertebrae, but the fibers extend laterally at the disc levels. These fibers may help to contain herniated disc material.

•Like the ALL, the PLL is attached to the vertebra at the superior and inferior margins, and to the annular fibers of the intervertebral disc.

Interspinous ligament

Ligamentum nuchae


The INTERSPINOUS LIGAMENT connects each adjacent spinous process.

In the cervical spine the interspinous ligament becomes part of the LIGAMENTUM NUCHAE, that extends cranially to insert into the occiput.

The SUPRASPINOUS LIGAMENT is a very strong band connecting the tips of contiguous spinous processes. It extends from C7 to the sacrum.

Supraspinous ligament

Ligamentum nuchae


Above C7 these fibers are part of the LIGAMENTUM NUCHAE.

Ligamentum flavum


LIGAMENTUM FLAVUM

Also called the YELLOW LIGAMENT

Consists of elastic fibers oriented vertically that extend from the anterior inferior surface of the lamina above to the superior posterior surface of the lamina below.

The ligamentum flavum tends to thicken as it progresses down the spine, beginning at the axis (C2) and extending to the sacrum.

The ILIOLUMBAR LIGAMENTS extend from the transverse processes of L4 and L5 to the iliac crest.

Iliolumbar ligaments

Anterior View Posterior View

Lumbosacral Ligaments

Lumbosacral Ligaments

Anterior View

Lumbosacral ligaments

The LUMBOSACRAL LIGAMENT is a thick, fibrous band that extends from the anterior, inferior aspect of the transverse process of L5 to the lateral surface of the sacrum.

Sacroiliac LigamentsShort sacroiliac ligaments

Posterior View

Long sacroiliac ligaments

The SACROILIAC LIGAMENTS are as follows:

• short sacroiliac ligaments: composed of horizontal fibers extending from the sacrum to the posterior part of the iliac bone

• long sacroiliac ligaments: composed of fibers extending vertically from the sacrum to the posterior superior iliac spine

Posterior Spinal Muscle Groups

Iliocostalis

The superficial posterior muscles are collectively called the ERECTOR SPINAE, comprising three groups:

Longissimus

Spinalis

ErectorSpinae


semispinalis capitis

semispinalis cervicis

semispinalis thoracis

The middle, or intermediate, muscle group of the spine is called the SEMISPINALIS GROUP:


Multifidus

Intertransversarii attachments between spinous processes

Rotatores (longus and brevis)

Rotatores cervices

Rotatores thoracis

Rotatores lumborum

Levatores costae (longus and brevis)

The deep muscle layer consists of the following groups:

Arteries of the Cranial and Cervical Region

Foramen lacerum

Vertebral artery

Carotid artery

Two VERTEBRAL ARTERIES, one located on each side the cervical vertebrae. These arteries are branches of the right and left subclavian vs. that exit from aorta.

They ascend through the transverse foramen of C6 through C1,entering the skull through the foramen magnum where they join together to form the BASILAR ARTERY.

Anterior to the cervical vertebrae are the CAROTID ARTERIES, which ascend through the FORAMEN LACERUM and join with the vertebral arteries to form the CIRCLE OF WILLIS.

Arteries of the Cranial and Cervical Region

Vertebral arteries

Basilar artery

Circle of Willis

Internal carotid arteries

Arteries of the Thoracic and Lumbosacral RegionsVertebral artery Aortic arch

Ascending aorta

Descending aorta

Thoracic segmental arteries

Abdominal aorta

Bifurcation of the aorta Lumbar

segmental arteriesExternal iliac

artery (left & right) Internal

iliac artery (left & right)Femoral artery

(left & right)

Segmental Arteries At each vertebral level from T4 to the sacrum, a pair

of SEGMENTAL ARTERIES branches posteriorly from the aorta to supply blood to the vertebral body, posterior elements, spinal cord, and costal structures.

Aorta

Segmental arteries

Intercostal artery

Spinal branch

Anterior spinal artery

Posterior branch

Anastomoses

The most important venous structures in the cervical spine are the internal and external JUGULAR VEINS. The internal jugular veins follow a path similar to the carotid arteries. They should always be considered during any anterior cervical spine procedure.

Veins of the Cervical and Thoracic Region

External jugular

Anterior jugular

Internal jugular

Veins of the Thoracic and Lumbar RegionInternal jugular

Superior vena cavaAzygos

veinThoracic segmental veins

Hemiazygos vein

Lumbar segmental veins

Inferior vena cava

Common iliac veins

Batson’s PlexusThe AZYGOS SYSTEM is a large

network of veins draining blood from the intestines and other abdominal organs back to the heart. The segmental veins drain into the azygos vein located on the right side of the abdomen, or into the hemiazygos vein located on the left side.

The azygos system also communicates with a valveless venous network known as BATSON’S PLEXUS. When the vena cava is partially or totally occluded, Batson’s plexus provides an alternate route for blood return to the heart.

The vessels of Batson’s plexus may be referred to as epidural veins

Batson’s plexus

Spinal Nerve StructuresSpinal Cord• Contained in epidural space• Network of sensory and motor

nerves• Firm, cord-like structure

Foramen magnum

• Extends from foramen magnum to L1

• Terminates at the conus medularis

• The cauda equina begins below L1

• Filum terminale extends from conus medularis to the coccyx

Conus medularis

Cauda equina

Meninges

Dura mater

Subdural space

Arachnoid layer

Subarachnoid space: filled with CSF

Pia mater

Within the spinal canal, the spinal cord is surrounded by the EPIDURAL SPACE, filled with fatty tissue, veins, and arteries. The fatty tissue acts as a shock absorber.

The spinal cord is covered by MENINGES which has three layers.

Spinal Nerve Topography

31 pairs of spinal nerves• 8 cervical• 12 thoracic• 5 lumbar• 6 sacrococcygeal

Spinal NervesSpinal cord

Epidural space

Dura mater and Arachnoid layers

Subarachnoid space

Dorsal root

Ventral root

Dorsal root ganglion

Peripheral nerve

Autonomic Nervous SystemIndependent of voluntary control.

Controls glandular and cardiac function and smooth muscle such as that found in the digestive tract.

There are two components: sympathetic parasympathetic

The control centers of both systems are located outside the spinal cord in structures called GANGLIA.

Autonomic Nervous SystemThe SYMPATHETIC NERVOUS

SYSTEM consists of a series of ganglia extending from the skull to the coccyx, lying on each side of the vertebral bodies. These aligned ganglia look like a chain at each side of the spine and are often referred to as the sympathetic nerve chain.

Injury to the sympathetic nerve chain in the lumbar spine may result in genitourinary problems for the patient.

Each sympathetic ganglion has fibers that join to the adjacent spinal nerve.

The PARASYMPATHETIC NERVOUS SYSTEM has ganglia located close to the organs they control.

Thank You!Thank You!

anatomy of spine

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