Cross sectional anatomy chapter 4 spine

Laminae

(2)- continue posteriorly and medially to from a spinous process

Pedicles

(2)- project from the body to meet with 2 laminae § On the upper and lower surfaces of the pedicles is a concave surface termed the vertebral notch.

Transverse processes

(2)- project laterally from the aprrox. Junction of the pedicle and lamina

Articular processes

(4)- arise from the junctions of the pedicles and laminae to articulate with adjacent vertebrae and form the zygapophyseal joints (facets joint)(gives additional support and allow movement of vertebral column) § Superior (2) § Inferior (2)

Cervical Vertebrae (C1-C7)

(7)- most mobile section of the spine

Saphenous nerve

- longest nerve -descends along the medial aspect of the leg to the ankle, accompanied by the great saphenous vein. -innervates the anterior lower leg, some of the ankle, and part of the foot

Odontoid process- (C2-C3)

- projects into the anterior vertebral foramen and articulates with the anterior arch of the atlas to act as a pivot for rotational movement of the atlas.

Pars interarticularis

- small bony segment that joins the superior and inferior facet joints. ○ The weakest portion of the vertebrae, making it the most vulnerable to injury.

Kyphosis

- spinal disorder in which an excessive convex curvature or forward rounding of the thoracic spine occurs. ○ Overtime can cause an exaggerated hunchback, which can be separated into cervical, thoracic, lumbar, sacral, and coccygeal sections.

Spinal Meninges

Has 3 layers Dura Mater, Arachnoid Mater and Pia Mater.

abdominal muscles

The muscle groups that run the length of the spine can be divided into regions according to their location: capitis cervicis thoracis lumborum (Table 4.1). • Two additional muscles that are commonly visualized in the lumbar region of the spine are the quadratus lumborum and the psoas muscles, which are considered _______________.

The muscles of the back

can be separated into three groupings or layers: -superficial layer (splenius muscles) -intermediate layer (erector spinae group) -deep layer (transversospinal group)

Thoracic Vertebrae

• 12 vertebra that make up the thoracic section. -They have typical vertebrae configurations except for their 4 characteristics costal facets (Demi facets)

Sacrum and Coccyx

• 5 vertebrae that fuse to form the sacrum. ○ Their transverse processes combine to form the lateral masses (alae) which articulate with the pelvic bones at the sacroiliac joints

ligamentum nuchae

• Another important ligament of the cervical region ○ which serves as an attachment point for muscles in the posterior portion of the neck. This expansive ligament extends from the external occipital protuberance of the cranium to the spinous processes of the cervical vertebrae ○ continues inferiorly as the supraspinous ligament.

Lumbar vertebrae

- 5 vertebrae; Their massive bodies increase in size from superior to inferior ○ The entire weight of the upper body is transferred from L5 to the base of the sacrum across the L5-S1 intervertebral disk.

Sacral Plexus

- Arising from L4-L5 and S1-S4, the nerves of the sacral plexus innervate the buttocks, posterior thigh, and feet. ○ These nerves converge toward the inferior sacral foramina to unite into a large, flattened band. -Most of this nerve network continues into the thigh as the sciatic nerve ○lies against the posterolateral wall of the pelvis between the piriformis muscle and internal iliac vessels, just anterior to the sacroiliac joint

supraspinous ligament

- a narrow band of fibers that runs over and connects the tips of the spinous processes from the seventh cervical vertebra to the lower lumbar vertebrae.

Spondylosis

- a unilateral or bilateral fracture or defect of the pars interarticularis. ○ Most common at L5 and is a frequent cause of low back pain in adolescent athletes

Scoliosis

- abnormal lateral curvature of the spine ○ Can occur from congenital bony abnormalities of The spine presents at birth, growth abnormalities during adolescence, and degenerative spinal changes or injury that occurs during adulthood.

Spondylolisthesis

- an anterior slippage of one vertebrae over another. ○ When the pars interarticularis of C2 is fractured, it is usually the result of hyper extension of the head and is commonly called a hangman's fracture.

nucleus pulposus

- contains up to 85% water at birth, which gradually decreases as a person ages (in a herniated disk it pushes out of the annulus fibrosis and pushes against cord.

Intervertebral foramina

- formed by where the superior and inferior notches of adjacent vertebrae meet. ○ Allow for the transmission of spinal nerves and blood vessels.

• thecal sac

- is formed by the spinal meninges -continuous with the cranial meninges ○ Anterior thecal sac- adheres top the posterior longitudinal ligament and is separated from the vertebral column by an epidural space that contains fat and vessels

Sciatic nerve

- largest nerve in the body. -exits the pelvis through the greater sciatic foramen and continues to descend vertically along the posterior thigh. -In its course, it divides into the tibial and peroneal nerves, which innervate the posterior aspect of the lower extremity.

Ring like arches

- located posteriorly that attaches to the sides of body, creating a space called the vertebral foramen.

Vertebral end plate

- the compact bone on the superior and inferior surfaces of the body.

Ligaments

- there are several _________ and membranes of the spine that serve to connect the cervical vertebrae and the cranium to provide mobility and protection for the head and neck. -Apical Alar Transverse (Cruciform)

Vertebral arch

- this is formed by: ○ Pedicles (2)- project from the body to meet with 2 laminae § On the upper and lower surfaces of the pedicles is a concave surface termed the vertebral notch. ○ Laminae (2)- continue posteriorly and medially to from a spinous process ○ The spinous process (1) ○ Transverse processes (2)- project laterally from the aprrox. Junction of the pedicle and lamina ○ Articular processes (4)- arise from the junctions of the pedicles and laminae to articulate with adjacent vertebrae and form the zygapophyseal joints (facets joint)(gives additional support and allow movement of vertebral column) § Superior (2) § Inferior (2)

Spinal veins

- valveless external venous plexuses -communicate freely with the vertebral veins and intracranial venous sinuses -The veins that drain the spinal cord follow the same segmental organization as their arterial counterparts. -The central gray matter of the cord is drained by the anterior and posterior central veins located in the anterior median fissure and posterior sulcus, respectively. -The outer white matter is drained by small radial veins that encircle the spinal cord within the pia mater. -The venous blood collected by these tiny veins drains into the anterior and posterior median (spinal) veins created by the longitudinal venous channels within the pia mater on the anterior and posterior surfaces of the spinal cord. -The anterior and posterior median veins drain into the anterior and posterior radicular veins that parallel the ventral and dorsal nerve roots. They eventually empty into the intervertebral veins that accompany the spinal nerves through the intervertebral foramina.

intercostal arteries

-Arising from the posterior aspect of the descending aorta are segmental arteries that supply the vertebral column and spinal cord. -They are termed the _____________ in the thoracic region and lumbar arteries in the lumbar region. -These vessels extend toward the intervertebral foramen, where they divide into spinal branches. _After giving off an anterior and posterior branch to the walls of the vertebral column, the spinal branches divide into anterior and posterior radicular arteries that pass along the ventral and dorsal roots into the spinal cord

Lordotic curves

-The cervical and lumbar sections convex forward, creating... -(LLC)

kyphotic curves

-Thoracic and sacral sections convex backward, creating... -(STK)

anterior longitudinal ligament

-a broad fibrous band that extends downward from C1 along the entire anterior surface of the vertebral bodies to the sacrum. • This ligament connects the anterior aspects of the vertebral bodies and intervertebral disks to maintain the stability of the joints and to help prevent hyperextension of the vertebral column. • It is thicker in the thoracic region than in the cervical and lumbar regions, providing additional support to the thoracic spine.

dorsal root ganglion

-an oval enlargement of the dorsal root that contains the nerve cell bodies of the sensory neurons, is located in the intervertebral foramen

The gray matter

-composed of nerve cells and runs the entire length of the cord. -It is centrally located and surrounds the central canal, which contains cerebrospinal fluid and is continuous with the ventricles of the brain -has the appearance of a butterfly. The two posterior projections are the dorsal horns, and the two anterior projections are the ventral horns

The white matter

-comprises the external borders of the cord and is more abundant. -myelinated axons

dorsal horns

-contain neurons and sensory fibers that enter the cord from the body periphery via the dorsal roots at the posterolateral sulcus. These are called the afferent (sensory) nerve roots

ventral horns

-contain the nerve cell bodies of the efferent (motor) neurons. -The efferent (motor) nerve roots exit the spinal cord via the ventral root to be distributed throughout the body

The filum terminale

-descends through the subarachnoid space to the inferior border of the thecal sac, where it is reinforced by the dura mater. -After leaving the thecal sac, it eventually exits the sacral canal through the sacral hiatus and attaches to the coccyx, providing an anchor between the spinal cord and the coccyx

interspinous ligaments

-extends between adjacent spinous processes throughout the spinal column

The anterior median fissure

-extends into the spinal cord at an average depth of 3 mm. The posterior median sulcus is shallower but together with this, separates the spinal cord into symmetric right and left halves.

posterior longitudinal ligament

-narrower and slightly weaker than the anterior longitudinal ligament. -It lies inside the vertebral canal and runs along the posterior aspect of the vertebral bodies. -Unlike the anterior longitudinal ligament, it is attached only at the intervertebral disk and adjacent margins. -It is separated from the middle of each vertebra by epidural fat, which provides passage of the basivertebral veins. -This ligament runs the entire length of the vertebral column beginning at C2. -This ligament helps prevent posterior protrusion of the nucleus pulposus and hyperflexion of the vertebral column.

Spinal Cord

-protected by CSF(cerebrospinal fluid) -CSF contained in the thecal sac -functions as a large nerve cable that connects the brain with the body. -It begins as a continuation of the medulla oblongata at the inferior margin of the brainstem and extends to approximately the first lumbar vertebra. -tapers into a cone-shaped segment called the conus medullaris -retains the anterior and posterior fissures of the medulla oblongata, which extend along the length of the spinal cord. -comprised of white (myelinated axons) and Grey Matter.

The lateral masses

-provide the lateral boundaries of the sacral canal, which is a Continuation of the vertebral canal. □ Triangular shaped sacral terminates at the sacral hiatus and communicates with the 1st 4 pairs of sacral foramina for the passage of the S1-S4 nerve roots. ○ Located within the lateral masses are the sacral foramina that allow for the passage of spinal nerves.

The denticulate ligaments

-run between the ventral and dorsal nerve roots within the spinal column -attaches to the dura, preventing lateral movement of the spinal cord within the thecal sac.

stability of the vertebral column

Several ligaments enclose the vertebral column to help protect the spinal cord and maintain the ____________ . Two of the larger ligaments are the anterior and posterior longitudinal ligaments

dorsal and ventral rami

Shortly after emerging from the intervertebral foramen, each nerve divides into _________________, which contain both motor and sensory fibers

dorsal rami

The __________ of all spinal nerves extend posteriorly to innervate the skin and muscles of the posterior trunk.

tectorial membrane

The ___________ is a broad ligament that extends from the clivus of the occipital bone to the posterior body of the axis, covering the dens, transverse, apical, and alar ligaments. - forms the anterior boundary of the vertebral canal and is continuous with the posterior lon- gitudinal ligament

anterior radicular (arteries)

The _______________ arteries contribute blood to the anterior spinal artery

basivertebral veins

The anterior sections of the internal and external plexuses communicate via a network of veins called the _________________, which drain the vertebral bodies. The large _________________ emerge from the posterior surfaces of the vertebral bodies.

posterior median sulcus.

There is a shallow depression on each side of the ____________ called the posterolateral sulcus. These depressions mark the location where the ventral nerve rootlets enter the spinal cord

annulus fibrosis

a firm outer portion termed the __________- the fibers surround and help contain the nucleus pulposus □ They attach to the anterior and posterior longitudinal ligaments, which help increase the stability of the spine.

ventral rami

the ______________ of T2-T12 pass anteriorly as the intercostal nerves to supply the skin and muscles of the anterior and lateral trunk. ○ The ______________ of all other spinal nerves form complex networks of nerves called plexuses. -These plexuses serve the motor and sensory needs of the muscles and skin of the extremities. -The four major nerve plexuses are the cervical, brachial, lumbar, and sacral

posterior radicular (arteries)

the _______________ arteries contribute blood to the posterior spinal arteries.

Brachial

• C8 (T1)- __________ plexus- large, complex network of nerves arising from the five ventral rami of C5-C8 and T1. ○ -located posterior to the subclavian artery as it courses toward the axillary region of the shoulder. -The roots of the __________ plexus emerge between the anterior and middle scalene muscles to form three trunks: superior, middle, and inferior. The trunks continue laterally and inferiorly to form three cords just posterior to the clavicle. The cords extend through the axilla to form five terminal branches: the musculocutaneous, axillary, median, radial, and ulnar nerves. These nerves provide innervation for the muscles of the upper extremity and shoulder, with the exception of the trapezius and levator scapula muscles

Lordotic and Kyphotic Curves

• Curvatures associated with vertebral column provide spinal flexibility and distribute compressive forces over the spine.

suboccipital

• The _________ region of the spine is reinforced with Atlantooccipital and tectorial membranes.

cervical (plexus)

• The ___________ plexus- arises from the upper four ventral rami of C1-C4 to innervate the neck, the lower part of the face and ear, the side of the scalp, and the upper thoracic area. ○ The major motor branch of this plexus is the phrenic nerve, which is formed by the branches of C3, C4, and the upper division of C5. -This nerve descends vertically down the neck and passes into the superior thoracic aperture, where it continues inferiorly to the diaphragm

veins of the vertebral column

• The _______________ form an extensive network of internal and external venous plexuses, named according to their corresponding location in the vertebral column. ○ The internal venous plexuses lie within the vertebral canal in the epidural space and are divided into anterior and posterior internal plexuses ○ The valveless external venous plexuses communicate freely with the vertebral veins and intracranial venous sinuses and are located at the outer surfaces of the vertebral column. They can be divided into the anterior and posterior external plexuses. ○ The anterior external venous plexuses run directly in front of the vertebral bodies, ○ the posterior external venous plexuses run along the posterior aspect of the vertebral arches. ○ The anterior sections of the internal and external plexuses communicate via a network of veins called the basivertebral veins, which drain the vertebral bodies. The large basivertebral veins emerge from the posterior surfaces of the vertebral bodies. ○ The internal and external venous plexuses, along with the radicular veins, drain into the intervertebral veins, ending in the vertebral, intercostal, lumbar, and sacral veins.

two regions

• The spinal cord is enlarged in ___________ by the cell bodies of nerves that extend to the extremities. The cervical enlargement extends from the vertebral bodies of approximately C3-C7, and the lumbosacral enlargement occurs within the lower thoracic region.

Spinal Arteries

• The spinal cord is supplied by the anterior spinal artery, paired posterior spinal arteries, and a series of spinal branches. -The anterior spinal artery is formed, just caudal to the basilar artery, by the union of two small branches of the vertebral arteries. -It runs the entire length of the spinal cord in the anterior median fissure and supplies the anterior two-thirds of the spinal cord. -The posterior spinal arteries arise as small branches of either the vertebral or the posterior inferior cerebellar arteries. They descend along the dorsal surface of the spinal cord and supply the posterior one-third of the spinal cord. There exist frequent anastomoses joining the two posterior spinal arteries with each other and with the anterior spinal artery.

Vertebral canal

• The succession of the vertebral formaina forms the vertebral canal. - contains and protects the spinal cord.

Body and vertebral arch (posterior arch)

• Vertebra vary in size and shape from section to section but a typical vertebra consists of 2 main parts:

Lumbar

• ___________ plexus- consists of six nerves arising from the ventral rami of T12 and L1-L4. -situated on the posterior abdominal wall, between the psoas major muscle and the transverse processes of the lumbar vertebrae. -In general, it serves the lower abdominopelvic region and anterior and medial muscles of the thigh

Vertebral column

• structure that supports The weight of the body, helps maintain posture, and protects the delicate spinal cord and nerves.

Intervertebral disks

•- shock absorbing cartilage that separates the vertebral bodies. ○ Consist of a central mass of soft, semigelatinous material called the

ligamenta flava

•strong ligaments (consisting of yellow elastic tissue) present on either side of the spinous processes. -They join the laminae of adjacent vertebral arches, helping to preserve the normal curvature of the spine

Unite

□ Just outside the intervertebral foramina, the ventral and dorsal roots __________ to form the 31 pairs of spinal nerves. -Of these nerve pairs, 8 correspond to the cervical region, -12 belong to the thoracic section -5 correspond to the lumbar region -5 correspond to the sacrum, and -1 belongs to the coccyx -Each spinal nerve provides a specific cutaneous distribution that can be demonstrated on a dermatome map

great anterior radicular artery (artery of Adamkiewicz)

□ The largest of the radicular arteries -arises in the lower thoracic and upper lumbar region, typically between T12 and L3. -This vessel makes a major contribution to the anterior spinal artery and provides the main blood supply to the inferior two-thirds of the spinal cord.

uncinate processes

○ Also unique to the C3-C7 vertebrae are the ___________ -These hook shaped projections are located bilaterally on the superior end plates of the vertebral bodies where the lateral edges curve upward. - they help to prevent later was movement of the cervical vertebrae.

cauda equina

○ At the termination of the spinal cord, nerves continue inferiorly in bundles. -This grouping of nerves has the appearance of a horse's tail and is termed the ____________, which exits through the lumbosacral foramina.

coccyx

○ Located inferior to the 5th sacral segment is the ________, which consists of 3-5 small fused bony segments. -The ________ represents the most inferior portion of the vertebral column.

5th sacral segment

○ The spinous process of the _____________ is absent, leaving an opening termed the sacral hiatus. -Located at the sides of the sacral hiatus are the inferior articular processes of the _____________, which project downward as the sacral Cornu.

Apical ligament

○ a midline structure that connects the apex of the Odontoid process to the inferior margin of the clivus.

Transverse ligaments

○ extends across the vertebral foramen of C1 to form a sling over the posterior surface of the Odontoid process. -It has a small band of longitudinal fibers that ascend to attach to the posterioinferior aspect of the clivus and inferiorly to attach to the body of the axis. -Holds the Odontoid process of C2 against the anterior arch of C1 -Sometimes called the Cruciform ligament because of its cross like appearance when viewed in the coronal plane.

Subarachnoid space

○ filled with CSF and blood vessels that supplies the spinal cord -The potential space between the pia mater and the arachnoid mater.

The 1st sacral segment

○ has a prominent ridge located on the anterior surface of the body termed the sacral promontory. -Used to separate the abdominal cavity from the pelvic cavity.

femoral nerve

○ the largest branch of the lumbar plexus descending beneath the inguinal ligament. -At the level of the lesser trochanter, the femoral nerve divides into several branches, the largest being the saphenous nerve

The conus medullaris

○ the most inferior portion of the spinal cord and is located at approximately the level of T12-L1.

Arachnoid mater

○ thin transparent membrane -attached to the inner surface of dura mater -Connected to the pia mater by numerous delicate strands, creating the spider like appearance associated with the arachnoid mater.

Dura mater

○ tough outer layer that extends to S2 -creates thecal sac -Each spinal nerve is surrounded by dura mater that extends through the intervertebral foramen called dural nerve root sleeve -epidural space- separates from vertebral column; contains fat and vessels

Costal facets (Demi-facets)

○- 2 located on the body and 2 located on the transverse processes, that articulate with the ribs -The head of the ribs articulate with the vertebral bodies at the costovertebral joints -The tubercle of the ribs articulates with the costotransverse joints. ○ The spinous processes of the thoracic vertebrae are typically long and slender, projecting inferiorly over the vertebral arches.

Alar ligament

○- 2 strong bands that extend obliquely from the sides of the Odontoid process and upward to the lateral margins of the occipital condyles to limit rotation and flexion of the head.

Atlantooccipital membrane

○- consists of an anterior and posterior portion which serve to connect the arches of the atlas with the occipital bone. -anterior -passes from the anterior arch of the atlas and connects to the base of the occipital bone at its anterior margin. This ligament is the superior extension of the anterior longitudinal ligament. -posterior -extends from the posterior arch of C1 to the occipital bone, closing the posterior portion of the vertebral canal between the cranium and C1.

Body (anterior element)

○- cylindrical; anteriorly located and functions to support body weight.

C2- Axis

○- has a large Odontoid process (Dens) that project upward from the superior surface of the vertebral body

C7- (vertebra prominence)

○- has a long spinous process that is typically not bifid -This spinous process is easily palpable posteriorly at the base of the neck.

C3-C6

○- have a unique configuration with their bifid spinous processes

Subdural space

○- potential space that runs between the arachnoid and dura mater.

Cornua

○- superior projections off the 1st coccygeal segment -Have ligamentous attachments to the sacral Cornu that provide additional stability to the articulation between the sacrum and coccyx.

C1- Atlas

○- supports the head i. Its large superior articular process articulate with the occipital condyles of the cranium to form the atlantooccipital joint. ii. Ring like structure that has no body and no spinous process. iii. Consist of anterior arch, posterior arch and 2 lateral masses 1) The lateral masses provide the only weight bearing articulation between the cranium and vertebral column

deep layer (transversospinal group)

○consist of several short muscles that are located in the groove between the transverse and spinous processes of the vertebrae. -They can be separated into the □ Semispinalis muscles- arise from the thoracic and cervical transverse processes and insert on the occipital bone and spinous processes in the thoracic and cervical regions. -These muscles form the largest muscle mass in the posterior portion of the neck. □ Multifidus muscles- consist of many fibrous bundles that extend the full length of the spine and are the most prominent in the lumbar region. □ Rotatores- The deepest of the transversospinal muscles. -which connect the lamina of one vertebra to the transverse process of the vertebra below. -They are best developed in the thoracic region and have a primary function to flex and rotate the vertebral column

intermediate layer (erector spinae group)

○consists of massive muscles that form a prominent bulge on each side of the vertebral column. -The erector spinae muscle group is the chief extensor of the vertebral column and is arranged in three vertical columns, the □ iliocostalis layer (lateral column)- run superiorly to attach to the angles of the lower ribs and transverse processes of C7-C4. □ longissimus layer (intermediate column)- run superiorly to insert into the tips of the transverse processes of the thoracic and cervical regions, medial to the angles of the lower ribs, and the mastoid process □ the spinalis layer (medial column)- extends from the spinous processes of the upper lumbar and lower thoracic regions to the spinous processes of the superior thoracic spine, cervical spine, and occipital bone. -The spinalis muscles are most prominent in the thoracic region and may be absent or blend with the semispinalis muscles in the cervical region -This muscle group arises from a common broad tendon from the posterior part of the iliac crest, sacrum, and inferior lumbar spinous

Pia mater

○highly vascular layer that closely adheres to the spinal cord. -spider like appearance associated with the Arachnoid mater -At the distal end of the spinal cord, approximately L1, this con- tinues as a long, slender strand called the filum terminale. -lateral extensions of the ___________ leave the spinal cord to form pairs of denticulate ligaments, which attach to the dura, preventing lateral movement of the spinal cord within the thecal sac.

L5

○largest of the lumbar vertebrae and is characterized by its massive transverse processes.

superficial layer (splenius muscles)

○located on the lateral and posterior aspect of the cervical and upper thoracic spine. -These bandage-like muscles originate on the spinous processes of C7-T6 and the inferior half of the ligamentum nuchae -They are divided into a cranial portion, the splenius capitis, which inserts on the mastoid process of the temporal bone and on the lateral aspect of the occipital bone, and a cervical portion, the splenius cervicis, which inserts on the transverse processes of C1-C3. -Together they act to extend the head and neck.