The Back

Subarachnoid Space

Between arachnoid and pia mater. Ends around SII Contains CSF Extends farther than the spinal cord, for this reason, lumbar punctures can be performed below LII without endangering cord

Supraspinous Ligament

Connects and passes along the tips of the vertebral spinous processes from CVII to the sacrum. Near the head, turns into Ligamentum Nuchae

Suboccipital Muscles

Deep muscles in upper cervical region. Help extend and rotate head Connect atlas (CI) to the axis (CII) and connect both vertebrae to the base of the skull Contraction extends head at atlanto-axial joint Innervated by posterior ramus of first cervical nerve Vascular supply from branches of the vertebral and occipital arteries Rectus Capitis Posterior Major Rectus Capitis Posterior Minor Obliquus Capitis Inferior Obliquus Capitis Superior

Suboccipital Triangle

Formed by suboccipital muscles Contain: - Rectus Capitis Posterior Major - forms medial border of triange - Obliquus Capitis Superior - forms lateral border - Obliquus Capitis Inferior: forms inferior border

Ligamenta Flava

Ligament. Pass between laminae of adjacent vertebrae. Form part of the posterior surface of the vertebral canal. Each ligamenta flavum runs between the posterior surface of the lamina on the vertebra below to the anterior surface of the lamina above Resist separation of the laminae in flexion, assist in extension back to the anatomical position

Rhomboid Major

Superficial Muscle Originates from the spinous process of the upper thoracic vertebrae and attaches to the scapula below the Rhomboid minor Innervated by Dorsal Scapular Nerve (C4, 5) Retracts (adducts) and elevates scapula

Levator Scapulae

Superficial Muscle Slender, descends from transverse processes of the upper cervical vertebrae to the upper portion of the scapulae Innervated by branches of anterior rami of nerves C3 and C4 and dorsal scapular nerves Elevates scapula

Rhomboid Minor

Superficial Muscle Superior to Rhomboid Major Small, cylindrical muscle that arises from ligamentum nuchae of neck Attaches to the medial scapular border opposite the root of the spine of the scapula Retracts (adducts) and elevates scapula, alongside Rhomboid Major

Latissimus Dorsi

Superficial Muscle Group Large, flat triangular muscle that begins in lower portion of back and tapers to a narrow tendon where it attaches to humerus anteriorly Innervated by thoracodorsal nerve (C6 - C8) Extends, adducts and medially rotates humerus

Pia Mater

Thin inner membrane of the meninges, firmly adheres to spinal cord surface

Arachnoid Mater

Thin membrane underneath dural mater. Separated from pia mater via subarachnoid space Ends at SII

Posterior and Anterior Rootlets

Will form a single pair of spinal nerves Laterally, they join on each side to form a spinal nerve Each spinal nerve divides as it emerges from a intervertebral foramen into two branches: posterior rami and anterior rami

Grey and White Matter in Spinal Cord

Within small central canal in spine Grey: rich in nerve cell bodies, form columns along cord, form H's White: surrounds the grey, rich in nerve cell processes. Form large bundles that ascend/descend cord to other levels or carry info to/from brain

Together, the two Rhomboid muscles...

retract or pull the scapula toward the vertebral column With other muscles, they help rotate the lateral aspect of the scapula downward

Symphyses between vertebral bodies (Intervertebral Discs)

- Formed by layer of hyaline cartilage on each vertebral body and an intervertebral disc which lies between the layers -Intervertebral disc consists of an outer anulus fibrosus (outer ring of collagen surrounding fibrocartilage in a lamellar configuration, limits rotation between vertebrae) which surrounds a central nucleus pulposus (fills center of disc, absorbs compression forces, is gelatinous)

Joints between vertebral arches (Zygapophysial Joints)

-Synovial joints between superior and inferior articular processes - In cervical regions, slope inferiorly from anterior to posterior, facilitates flexion and extension - In thoracic regions, oriented vertically and limit flexion and extension, facilitate rotation - In lumbar regions, curved and adjacent joint surfaces, adjacent processes interlock, limit ROM, allows flexion and extension

Intermediate Muscle Group

1. Consist of muscles attached to the ribs, tend to serve a respiratory function 2. Deep to the Superficial Muscles. Extrinsic muscles (originate from locations other than the back) 3. Innervated by anterior rami of spinal nerves 4. Include: - Serratus Posterior Superior - Serratus Posterior Inferior

Deep Group of Back Muscles

1. Intrinsic - develop originally in the back 2. Innervated by posterior rami of spinal nerves 3. Related to movement of spine and head 4. Include: - Splenius Capitis - Splenius Cervicis - Erector Spinae - Transversospinales - Interspinales - Intertransversarii Vascular supply through branches of various arteries

Two Sources of Arterial Supply to the Spinal Cord

1. Longitudinally oriented vessels that arise superior to cervical portion of cord and descend on the cord surface 2. Feeder arteries that enter the canal through intervetebral foramina at each level (segmental spinal arteries)

Superficial Muscle Group

1. Related to and involved in movement of upper body. 2. Extrinsic muscles (originate from locations other than the back). 3. Innervated by anterior rami of spinal nerves 4. Include: - Trapezius - Latissimus Dorsi - Rhomboid Major - Rhomboid Minor - Levator Scapulae

Thoracic, Lumbar and Sacral Spinal Regions

1. Supports thorax, points of attachment for ribs 2. Supports abdomen 3. Transmits weight to lower limbs through pelvic bones. Framework for posterior aspect of pelvis

Vertebral Body, Arch and Canal

1. Weight-bearing component, linked to adjacent vertebral bodies by intervertebral discs and ligaments. Increases in size going down 2. Forms lateral and posterior part of vertebral foramen 3. Formed by all the vertebral foramina together. Contains and protects spinal cord. Continuous with cranial cavity of the head through the foramen magnum

Thoracic Vertebrae

12, characterized by articulation with ribs Two partial facets on each side of vertebral body for articulation with head of its own rib and head of rib below Each transverse process also has a facet for articulation with tubercle of own rib Body is heart shaped, circular vertebral foramen

Vertebral arch of each vertebra consists of Pedicles and Laminae...

2 Pedicles, bony pillars that attach the vertebral arch to the vertebral body 2 Laminae are flat sheets of bone that extend from each pedicle to meet in the middle and form the roof of the vertebral arch

Lumbar Vertebrae

5, large size Lack facets for rib articulation, transverse processes are thin and long Vertebral body is cylindrical, triangular vertebral foramen

Cervical Vertebrae

7 between thorax and skull Small size, presence of a foramen in each transverse process Vertebral body is short in height and square shaped. Has a concave superior surface and convex inferior surface Transverse processes are trough shaped, perforated by round foramen transversarium Spinous process is short and bifid (split) Vertebral foramen is triangular

31 pairs of spinal nerves

8 Cervical (1-8) 12 thoracic (1-12) 5 lumbar (1-5) 5 sacral (1-5) 1 coccygeal (Co)

Spinal Segment

Area of the cord that gives rise to anterior and posterior rootlets which will form a single pair of spinal nerves

Anterior Rami

Bigger Innervate most other skeletal muscles, including limbs and trunk and most of the skin, except for the head Form all major somatic plexuses (cervical, brachial, lumber, and sacral) Also associated with major visceral components of the PNS

Anterior and Posterior longitudinal ligaments

Both on the anterior and posterior surfaces of the vertebral bodies and extend along most of the vertebral column Anterior: attached to base of skull, extends inferiorly to attach to anterior surface of sacrum. Attached to vertebral bodies and intervertebral discs along way Posterior: on the posterior surfaces of vertebral bodies, lines the anterior surface of the vertebral canal. Upper part that connects CII to the intracranial aspect of the base of the skull = tectorial membrane

Atlas

C1, articulates with head. Lacks a vertebral body (vertebral body fuses onto CII to become the dens during development) No intervertebral disc between CI and CII Ring-shaped, composed of two lateral masses interconnected by an anterior and posterior arch Lateral masses articulate above with an occipital condyle of the skull and below with the super articular process (bean shaped and concave) of CII

Axis

CII. Characterized by large, tooth-like dens that extend up from vertebral body. Dens held in position by transverse ligament of the atlas behind it. Dens acts as a pivot that allows the atlas and head to rotate on axis, side to side

Transversospinales Muscles

Deep to erector spinae, run obliquely upward and medially from transverse to spinous processes Bilaterally: extend spine Unilaterally: pull spinous processes toward transverse processes on that side, cause trunk to turn/rotate in opposite direction Semispinalis Muscles: most superficial, begin in lower thoracic region and end by skull. Multifidus: deep to semispinalis, span length of vertebral column, most developed in lumbar region Rotatores: deepest of all, present throughout length of spine, best developed in thoracic region, fibers pass up and medially from transverse to spinous processes, passing two vertebrae (long) or attach to adjacent vertebrae (short)

Segmental Back Muscles

Deep, innervated by posterior rami of spinal nerves Levatores Costarum: arise from transverse processes of CVII and TI/TXI. Oblique lateral and down direction, insert into rib. Contraction elevates ribs Interspinales: pass between adjacent spinous processes and the intertransversarii (pass between adjacent processes). Postural muscles, stabilize adjoining vertebrae during spine motion to allow for more effective action of large muscle groups

Segmental Spinal Arteries

Enter vertebral canal through intervertebral foramina After entry, give rise to anterior and posterior radicular arteries at each level. Arteries follow and supply the anterior and posterior roots. Also give off segmental medullary arteries which pass directly and reinforce the longitudinally oriented vessels

Transverse Process

Extends posterolaterally from junction of pedicle and lamina on each side Site for articulation with ribs in thoracic region

Intervertebral Foramina

Formed on each side between vertebrae and intervertebral discs Allows things like nerves and blood vessels to pass in and out of vertebral canal Formed by the inferior vertebral notch on the pedicle of the vertebra above and the superior vertebral notch on the pedicle of the vertebra below Bordered posteriorly by zygapophysial joint between articular processes of the 2 vertebrae and anteriorly by the intervetebral disc and adjacent vertebral bodies Place where spinal cord goes and passes inferiorly through column

Serratus Posterior Inferior

Intermediate muscle group Deep to the latissimus dorsi near the base of the spine Attached to the vertebral column and associated structures medially, ascend to attach to the ribs Innervated by the anterior rami of lower thoracic nerves (T9 - T12) Depresses ribs 9 - 11 and may prevent lower ribs from elevating when the diaphragm contracts

Serratus Posterior Superior

Intermediate muscle group Deep to the rhomboid muscles at the top of the body Attached to the vertebral column and associated structures medially, descend to attach to the ribs Innervated by Anterior Rami of upper thoracic nerves (T2 - 5) Elevate ribs 3 - 5

Erector Spinae Muscles

Largest group of intrinsic back muscles. Primary extensors of the spine and head. Acting bilaterally: straighten spine and pull head back. Acting unilaterally: bend spine laterally and turn head to one side Iliocostalis: outer column of muscles, associated with costal elements Longissimus: middle column of muscles, largest of erector spinae subdivision, extend from common tendon or origin to base of skull Spinalis: most medial column, smallest of the subdivisions, interconnects the spinous processes of adjacent vertebrae. Generally absent in the cervical region

Intrinsic Muscles

Maintain posture and move the spine (flexion/anterior bending, extension, lateral flexion and rotation) Deep muscles, innervated by posterior rami of spinal nerves Support and move vertebral column, participate in moving the head. One group moves ribs relative to spine Suboccipital, splenius, erector spinae (longissimus, iliocostalis, spinalis)

Extrinsic Muscles

Move the upper limbs and ribs Generally innervated by anterior rami of spinal nerves Superficial group related to upper limbs, intermediate layer related to thoracic wall Trapezius Levator Scapulae Rhomboid major and minor Latissimus Dorsi Serratus posterior superior and inferior (intermediates)

Semispinalis Capitis

Muscle in Transversospinales Group Attaches to the skull Bilaterally: pulls head posteriorly Unilaterally: pulls head back and turns it, causing chin to move up and to the side (similar to erector spinae)

Iliac Crest

Nonvertebral skeletal landmark Palpable along entire length. Position of posterior superior iliac spine is visible as the sacral dimple just lateral to the midline Horizontal line between highest points of crests can be drawn - crosses through spinous process of LIV

Spinal Dura Mater

Outermost meningeal membrane Separated from the vertebral column bones by the extradural space

External Occipital Protuberance

Palpable in the midline at the back of the head, superior to the airline Nonvertebral skeletal landmark

Superior and Inferior Vertebral Notches

Participate in forming intervertebral foramina Exist between the vertebral body and the origin of the articular processes - each pedicle is notched on its inferior and superior surfaces

Interspinous Ligaments

Pass between adjacent vertebral spinous processes Attach from base to the apex of each spinous process Blend with the supraspinous ligament posteriorly and the ligamenta flava anteriorly

Posterior and Anterior Roots of Spinal Nerves

Posterior Root: contains sensory neuron processes bring info to the CNS. Cell bodies of sensory neurons clustered in spinal ganglion at distal end of posterior root Anterior Root: contain motor nerve fibers, carry signals away from CNS Both divide into rootlets which ultimate make up the posterior and anterior rami

Primary and Secondary Curvatures of Spine

Primary: curves in thoracic and sacral/coccygeal regions. Concave anteriorly Secondary: curves in the cervical and lumbar regions. Concave posteriorly

Superior and Inferior Articular Processes

Project from where pedicles and lamina meet Articulates with inferior and superior articular processes of adjacent vertebrae

Spinous Process

Projects posteriorly and inferiorly from the junction of two laminae, site for muscle and ligament attachment

Thoracolumbar Fascia

Sheet of connective tissue that covers the deep muscles of the back and trunk - important in overall region integrity and organization At top, passes in front of the serratus posterior superior and is continuous with deep fascia of neck In thoracic region, covers deep muscles and separates them from the superficial and intermediate muscles Attaches medially to the spinous processes of the thoracic vertebrae and laterally to the ribs

Scapula

Shoulder blade Spine, medial border and inferior angle of the scapula are visible and palpable Nonvertebral skeletal landmark

Longitudial Vessels consist of

Single anterior spinal artery: originates within cranial cavity as the union of two vessels that arise from the vertebral arteries. Result in one anterior spinal artery passing inferiorly along spinal cord Two posterior spinal arteries: originate in cranial cavity, right and left posterior arteries descent along spinal cord

Sacrum

Single bone representing five fused sacral vertebrae Triangular, apex pointed inferiorly, curved so it has a concave anterior surface and convex posterior surface Two large L-shaped facets for articulation with pelvic bones Posterior surface has four pairs of posterior sacral foramina and four pairs of anterior sacral foramina on anterior surface - passage of posterior and anterior rami

Coccyx

Small triangular bone at base. Articulates with inferior end of sacrum, 3/4 fused coccygeal vertebrae Small, no vertebral arches or canal

Posterior Rami

Smaller Innervate only intrinsic back muscles and associated narrow strip of skin on back

Splenius Capitis

Spinotransversales Muscle Innervated by posterior rami of cervical nerves Origin: lower half of ligamentum nuchae, spinous processes of CVII to TIV Insertion: Mastoid process, skull below lateral one third of superior nuchal line

Splenius Cervicis

Spinotransversales Muscle Innervated by posterior rami of lower cervical nerves Origin: spinous processes of TIII to TVI Insertion: Transverse processes of CI to CIII

Spinotransversales Muscles

Splenius Capitis and Splenius Cervicis Run from the spinous processes and ligamentum nuchae up and laterally Draw the head back and extend the neck together Individually, rotate head to one side

Trapezius

Superficial muscle group Origination: under head, external occipital protuberance Insertion: Lateral 1/3 of clavicle, acromion, spine of scapula Innervated by accessory nerve Functions to assist scapula rotation during abduction of humerus above horizontal - Upper fibers elevate - Middle fibers adduct - Lower fibers depress scapula

Appendicular Group

Superficial muscles that attach the superior part of the appendicular skeleton (clavicle, scapula, humerus) to the axial skeleton (skull, ribs, vertebral column)

Cervical Spinal Region

Supports and moves head Transmits spinal cord and vertebral arteries between head and neck Brain and cranial meninges are continuous with the spinal cord meninges at the foramen magnum

Two major joint types between vertebrae

Symphyses (cartilaginous) between vertebral bodies - intervertebral discs Synovial joints between articular processes Typical vertebra has 4 synovial joints (2 above and 2 below) and 2 sympheses (one above and one below)

Cauda Equina

Terminal cluster of roots Posterior and anterior roots of lumbar, sacral and coccygeal nerves pass inferiorly below the end of the spinal cord to reach their exit points from the vertebral canal

When performing a spinal tap, needle travels through

The adjacent vertebral spinous processes Through the supraspinous and interspinous ligaments Enters the extradural space Continues through the dura and arachnoid mater Reaches CSF in subarachnoid space

Ligamentum Nuchae

Triangular sheet-like structure in the median sagittal plane Base attached to the skull, apex attached to the tip of the spinous process of CVII, deep side attached to the posterior tubercle of CI and spinous processes of other cervical vertebrae Supports the head, resists flexion and helps return the head to the anatomical position