Anatomy 2.1 Deep Back - Dr. Calilao

1st Semester

ANATOMY 2.1 DEEP BACK

SY 2013-2014

DR. CALILAO JULY 23, 2013 OUTLINE I. Back II. Vertebra A. Typical Vertebra Vertebra B. Cervical Vertebra C. Thoracic Vertebra D. Lumbar Vertebra Vertebra E. Sacrum F. Coccyx III. Joints and Ligaments IV. Muscles A. Extrinsic B. Intrinsic C. Suboccipital Suboccipital and Deep Neck V. Nerve Supply VI. Blood Supply A. Arterial Supply B. Venous Drainage C. Lymphatic Drainage

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OBJECTIVES Demonstrate knowledge and understanding of the anatomy of the deep back by: Describing the general structure of the o vertebral column. Identifying the distinguishing o characteristics characteristics of a representa r epresentative tive vertebra from the cervical, thoracic, lumbar and sacral regions. Identifying the deep back musculature, o including the muscles in the suboccipital region as to their general attachments, innervation, actions, blood supply and lymphatic drainage.

References: References : Specific books, journals, etc. P lease cite properly. Legend: Italicized – quoted from the lecturer; bold – emphasis, or from references

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II. VERTEBRAE Encompasses the neck and back to which the head, neck, and limbs are a ttached (from the cranium to coccyx) 33 vertebrae (24 movable) arranged in five regions: 7 cervical o 12 thoracic o 5 lumbar o 5 sacral-fuse to form the sacrum o 4 coccygeal-fuse to form the coccyx o Size of vertebral vertebral bodies progressively increases in size as it descends towards sacrum, sacrum, from the sacrum, it decreases progressively From the column, weight is transmitted transmitted to the p elvic girdle, which transmits it to the lower limbs Maximal size is at L5

FUNCTIONS    

Protects spinal cord and spinal nerves Supports the weight of the body superior to the level of the pelvis Provides a partly rigid and flexible axis for the body Plays an important role in posture and locomotion

I. BACK Skin and subcutaneous subcutaneous tissue Muscles Superficial layer : upper limbs o o Deeper layers / “true back muscles” : posture Vertebral column Vertebrae, IV discs, associated ligaments o Ribs in thoracic region Spinal cord and meninges Membranes that cover the spinal cord) o Nerves and vessels

CURVATURES

Transcribers: Group 2: M alimban, Manalili, Manarang, Mandac, Maniulit, Manuel, M aramba, Margate, Martin, Martinez

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Primary curvature – at birth (concave anteriorly, convex posteriorly) Thoracic o Sacral o Secondary curvature (convex anteriorly, concave  posteriorly) Cervical curvature o 1st  of secondary to appear  Forms when the baby learns to  hold its head up Lumbar curvature o 2nd of secondary to appear  Forms when toddler begins to  walk *Four curvatures are well established in adults

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7 processes 3 for muscle attachment (spinous and transverse o processes) 4 participate in synovial joints(superior and o inferior articular processes/facets) PEDICLES - Pedicle comes from the Latin term pediculus meaning little foot. This is the diminutive form of the Latin pes or foot. It is applied to processes that resemble a foot or act as a foot or stem. These are thick stems of bones that project posteriorly from the body of the vertebra. They form the medial wall of the transverse foramen and the lateral wall of the vertebral foramen. Their superior surfaces are covered by the superior articular facets. LAMINA - The term lamina is Latin for plate, leaf, or thin scale. It describes thin plate-like structures, typically bone. These are thickened plates of bone between the transverse and spinous processes. They are vertically flattened and provide attachment for many muscles and ligaments. Etymology

 A. Typical Vertebra 

Vertebral body

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Vertebral arch

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Regional Characteristics of Vertebrae

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B. Cervical Vertebra     

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Body: small and wide Vertebral foramen: large and triangular Nearly horizontal articulation of ar ticular facets Relative thickness of IV discs Small amount of surrounding body mass *Greatest range and variety of movement: flexion, extension, lateral flexion, and limited rotation C3-C6 Typical Cervical Vertebrae Body: Superolateral projection (uncus) Foramen: Page 2 of 16

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Large and triangular (to accommodate the enlargement of spinal cord) Enlargement due to brachial  plexus which innervates the upper limb Presence of transverse foramen Vertebral artery passes through the o transverse foramen of cervical vertebrae except for C7 Transverse foramen of C7 is either small or o absent Artery goes up, except at C1 where its o course is horizontal Spinous process: Bifid o Uncus (aka uncinate process): Elevated superolateral projections of the o body Carotid Tubercle Same as a nterior tubercle of C6 o Area where you can compress the common o carotid artery during cases of trauma to control bleeding o

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C7 

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Spinous process Long and not bifid o Aka vertebra prominens Can be seen when neck is f lexed in 70% of o population) Vertebral artery does not pass here Transmit only accessory veins o

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C2 Vertebra/AXIS Strongest 2 large superior articular facets Dens (odontoid process) Tooth-like in feature o Large bifid spinous process 2 large superior facets Articulation of C1 and C2 Permits rotation, turn head side to side o Dens as pivot o o Joint involved in saying “NO”(Atlanto-axial) Held in socket formed: Anteriorly: posterior portion of the anterior o arch of C1 Posteriorly: Transverse ligament of a tlas o

C. Thoracic Vertebra   

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C1 Vertebra/ATLAS No body, no spinous process Ring-shaped with paired lateral ma sses Widest of the cervical vertebrae Has lateral ma sses o Transverse process project from lateral o masses Superior articular facet a rticulate with occipital condyles Similar with the Titan god Atlas who o carried the world on his shoulders as punishment (world = skull) Groove for vertebral artery Area where the course of artery is o horizontal Artery needs to enter foramen magnum to o enter cerebral circulation

General Characteristic: COSTAL FACETS - articulate with the r ibs 1. Superior costal facet - a rticulates with the head  of the rib 2. Inferior costal facet - articulates with the head  of the rib 3. Transverse costal facet - articulates with the tubercle of the rib

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Figure X. Anterior view of the superior portion of the ribs highlighting T1

Figure X. Left: thoracic vertebrae, Right: rib  A. TYPICAL THORACIC VERTEBRA (T5 - T8)

2. T9 - T12 - features similar to lumbar vertebra - tubercles similar to the accessory and mamillary process of lumbar vertebra T12 - transition from thoracic to lumbar is most evident  subjected to high tensional stress  most commonly fractured vertebrae Superior Half: thoracic in character; with costal facets a nd articular process that permits rotator movement Inferior Half: lumbar in character; devoid of costal facets; with articular process that permits flexion and extension 

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Superior view

Lateral view of T12

D. Lumbar Vertebra

Lateral view      

Body : Heart - shaped Vertebral Foramen: Circular, smaller  Articular Facets: Vertically-oriented Spinous Process: Long, slope posterioinferiorly, overlapping  Attachment to the Ribs: Costal attachment  Movements Permitted: rotation ( greatest degree is allowed in the thoracic o region) limited flexion, extension and lateral flexion o

B. ATYPICAL THORACIC VERTEBRA 1. T1 - T4 - characteristics similar to cervical vertebra T1 Spinous Process: Long (can be as long as the vertebra prominens) Superior Edge: has complete costal facet for articulation with the 1st  rib Inferior Edge: has demifacet (half facet) for articulation with the 2nd rib 

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L1 - L5: - biggest unfused vertebra of the vertebral column - strong and ca pacitated for weight-bearing and protection of spinal cord - highly flexible for movement (flexion, extension, rotation) L5 - largest of all movable vertebra - carries the weight of the whole upper body Characteristics of the Parts: Body: large, kidney-shaped Vertebral Foramen: triangularly-shaped; larger than thoracic v. but smaller that cervical v. Transverse Processes: long and slender  Accessory Process on posterior surface of base of o each process  Articular Processes: well-defined Superior Facets: concave, directed posteromedially o Inferior Facets: convex, directed anterolaterally o Mamillary Process: posterior to superior articular o process Spinous Processes: thick, broad, hatchet-shaped, short, sturdy  

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Between hip bones Forms roof of the posterosuperior wall of the posterior half of the pelvic cavity S1-S5: vertebral bodies progressively decrease because it is not for weight bearing Pelvic girdle bony ring formed by the hip bones and sacrum o where lower limbs are attached o

FUNCTION Provides strength and stability to the pelvis and transmits weight of body to the pelvic girdle Supports vertebral column 

Superior view of L2

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PARTS 

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Base of Sacrum Superior surface of S1 o  Apex of Sacrum Tapering inferior end o Has an oval facet for articulation with the coccyx o Sacral Promontory Anterior projecting edge of the body of S1 o Important obstetric landmark o

Lateral view of lumbar vertebra 

Sacral Foramina For exit of posterior and anterior rami of the o spinal nerves

Posterior view of L3-L4

E. Sacrum

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DESCRIPTION Wedge-shaped Composed of sacral vertebrae (S1-S5) From birth, sacral vertebrae are connected by o hyaline cartilage and separated by IV discs Fusion starts after age 20 o Most of IV discs remain unossified until or o beyond middle life  

 Anterior sacral foramina: 4 pairs, larger Posterior sacral foramina: 4 pairs, smaller

 Auricular surface Superolateral surface o Looks like an auricle (external ear) o Articulates with ilium to form sacroiliac joint o Covered with hyaline cartilage o

Dorsal Surface (rough, convex) 

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Facets of the superior articular processes Articulate with inferior articular facets of L5 and o for the lumbosacral angle 5 Prominent Longitudinal Ridges Median sacral crest: o Page 5 of 16

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Fused rudimentary spinous processes of superior 3-4 sacral vertebra Intermediate sacral crest: Fused rudimentary articular processes Lateral sacral crest Tips of transverse processes of the f used sacral vertebrae

Only coccygeal vertebrae that has transverse processes which are connected to the sacrum Rudimentary articular process form coccygeal cornua which articulate with sacral cornua COCCYGEAL VERTEBRAE 2-4 Fuse during middle life and resemble beak of bird 

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II. JOINTS AND LIGAMENTS LIGAMENTS

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Sacral Hiatus Absence of the laminae and spinous processes of o S5 (sometimes S4) Leads to sacral canal o Sacral Cornua Inferior articular processes of S5 vertebra o Project inferiorly on each side of sacral hiatus o Important landmark in locating sacral hiatus o Sacral Canal Continuation of vertebral canal in the sacrum o Cauda Equina: o Found in the sacral canal  Roots emerging below the level of L1  vertebra Descend past termination of the spinal  cord 

 A. PRIMARY/MAIN LIGAMENTS: 1. Anterior Longitudinal Ligament (ALL)* a. Anterior Atlanto-axial Ligament b. Anterior Atlanto-occipital Ligament 2. Posterior Longitudinal Ligament (PLL) B. ACCESSORY LIGAMENTS 1. Ligamentum Flavum/ Ligamentum Flava (Plural) 2. Interspinous Ligaments 3. Supraspinous Ligaments 4. Intertransverse Ligaments 5. Ligamentum Nuchae  A. PRIMARY/MAIN LIGAMENTS The ALL and PLL are continuous bands that run from the top to the bottom of the spinal column along the vertebral bodies. They prevent excessive movement of the vertebral bones.

“Horse tail”

F. Coccyx

Small triangular bone Fusion of the 4 rudimentary coccygeal vertebrae Remnant of skeleton of the embryonic tale-like caudal eminence, which is present in human embryos from the end of 4th wk until the beginning of the 8 th wk May flex anteriorly when sitting indicating that is receiving some weight FUNCTION Provides attachment for the gluteus maximus, coccygeal muscles and anococcygeal ligament(the median fibrous band of the pubococcygeus muscles ) COCCYGEAL VERTEBRA 1 Usually not fused with the other coccygeal vertebrae and would sometimes fuse with sacral bone Largest and broadest   

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Found posterior to the vertebral bodies Narrower and weaker band extending from C2 to sacrum Attaches mostly to the IV discs and to a lesser extent to the posterior surface of the vertebral bodies Well provided with nociceptive (pain) nerve endings **If you have bone spurs, it is perceived as back pain **  Annulus fibrosus that are absent posteriorly in some cervical regions may be painful sometimes FUNCTION: Weakly resists hyperflexion of the vertebral column Prevents herniation of the nucleus pulposus 

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 ANTERIOR LONGITUDINAL LIGAMENT

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B. ACCESSORY LIGAMENTS OF INTERVERTEBRAL JOINTS 1.LIGAMENTUM FLAVUM/ LIGAMENTUM FLAVA (Plural)

DESCRIPTION: Compact, strong and broad fibrous band which covers the anterior and lateral surfaces of the vertebral bodies and IV discs Extends as a band that goes up from the anterior surface/pelvic surface of the sacrum up to the level of the anterior tubercle of C1 and anterior surface of the foramen magnum FUNCTION: Prevents hyperextension of the vertebral column Only ligament that limits extension (All other IV ligaments limit flexion) BECOMES: (So named according to structures that they span) 1. Anterior atlanto-occipital ligament- above C1 but below the skull 2. Anterior atlanto-axial ligament -above C2 but below C1, the  ALL 2. POSTERIOR LONGITUDINAL LIGAMENT 

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DESCRIPTION: Flavus meaning yellow Bands of elastic tissue that connects successive lamina from one another Thickest in lumbar region FUNCTIONS:  

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DESCRIPTION:

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Resist separation of vertebral lamina by limiting abrupt flexion of vertebral column Help preserve normal curvatures of vertebral column  Assist with straightening of column after flexing BECOMES: 1. Posterior Atlanto-Occipital Membrane - – above C1 2.Posterior Atlanto-Axial Membrane – between C2 & C1 

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5. LIGAMENTUM NUCHAE (Nuchal Ligament) DESCRIPTION: Thick and strong made up of fibroelastic tissue band Extends from the occipital protuberance and the posterior surface of the foramen magnum Descends to attach to spinous processes of the cervical vertebra FUNCTION:  Attachment of muscles  

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2. INTERSPINOUS LIGAMENTS - run between the spines but the fibers extend from the base to the apex 3. SUPRASPINOUS LIGAMENTS - connects only the tips of the spinous processes from C7 to sacrum

JOINTS OF THE VERTEBRAL COLUMN JOINTS OF VERTEBRAL BODIES : Symphyses (secondary cartilaginous /slightly movable joints) designed for weight-bearing; articulating surfaces are connected by the IV discs JOINTS OF VERTEBRAL ARCHES : Zygapophysial Joints (plane synovial joints, surrounded by thin joint capsule) - permit gliding movements bet. articular processes;

4. INTERTRANSVERSE LIGAMENTS Connects the transverse processes

Type of movement permitted in the vertebra: determined by shape and disposition of articular surfaces Range of movement: determined by the size of the IV discs relative to the body of the vertebrae that it connects **Cervical and lumbar: weight bearing function is carried out by the IV discs however, in the cervical and lumbar regions, the articular surfaces are the zygapophysial joints that also have some form of weight-bearing function. So the articulations at the zygapophysial  joints in the cervical and lumbar region help the IV discs in the weight-bearing function *Movements of Vertebral Column (Moore) The following movements of the vertebral column are possible  flexion, extension, lateral flexion and rotation. The range of movement of the

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vertebral column varies according to the region and the individual. The normal range of movement possible in healthy young adults is typically reduced by 50% or more as they age. The mobility of the column results primarily  from t he compressibility and elasticity of the IV discs. The range of movement of the vertebral column is limited by the: Thickness, elasticity, and compressibility of the IV discs. Shape and orientation of the zygapophysial joints. Tension of the joint capsules of the above joints. Resistance of the back muscles and ligaments (such as the ligamenta flava and the posterior longitudinal ligament).  Attachment to the thoracic (rib) cage. Bulk of the surrounding tissues.    

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CRANIOVERTEBRAL JOINTS : 1. ATLANTO-OCCIPITAL JOINTS •synovial joint of the condyloid type Joint between the atlas and the skull/occipital condyles Articulation is between the superior articular surface found at the lateral process of the atlas (shoulders of atlas) and the occipital condyles of the skull ( globe) Flexion and extension but to a little degree of lateral flexion and rotation YES joint Ligaments that reinforce: Anterior atlanto-occipital membrane from anterior longitudinal ligament between atlas and occiput  

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FUNCTION: Prevent excessive movement of atlanto-occipital joints MOVEMENTS PERMITTED: FLEXION AND EXTENSION, LATERAL FLEXION, ROTATION

2. ATLANTO-AXIAL JOINTS •synovial joint with no IV disc 3 articulations: o 2 Lateral-gliding type of synovial joint, two articulations between the inferior articular surface of the atlas and the superior articular surface of the axis o 1 Median-pivot type of synovial joint, between the odontoid process (dens) of the axis and the ring formed by the anterior arch and the transverse ligament of the atlas NO joint MOVEMENT PERMITTED: ROTATION LIGAMENTS THAT REINFORCE: 1.Cruciate Ligament  – cross-shaped; Superior and Inferior longitudinal ligament plus the transverse ligament 2. Alar Ligament – strong ligament that stabilize the atlanto-axial joint 3. Tectorial Membrane – membrane from posterior longitudinal ligament 

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a. IV. MUSCLES (see appendix)

SUPERFICIAL Splenius Origin: nuchal ligament & spinous process of C7 – T3 or T4 Function: cover and hold deep neck ms. in position Two parts: Splenius capitis – insertion: temporal bone and occipital bone Splenius cervicis – i: tubercles of transverse processes C1-C3 or C4 

Extrinsic -  All are innervated by ventral rami except trapezius which is innervated by cranial nerve 11/spinal accessory nerve – please refer to the appendix for details) a. Superficial (limb) i. Trapezius ii. Latissimus dorsi iii. Levator scapulae iv. Rhomboidius minor and major b. Intermediate (respiration) i. Serratus posterior superior – inspiration (elevates rib) ii. Serratus posterior inferior – for expiration(anterior rami)

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Intrinsic - Innervated by anterior rami For posture & control of vertebral column movement Extend from pelvis to cranium Deep f ascia attached: Medially – nuchal ligament , spinous process of vertebra, supraspinous ligament , & median crest  of sacrum Laterally – cervical & lumbar transverse processes, angles of the ribs

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INTERMEDIATE LAYER Erector Spinae (from lateral to medial: I love  shopping/sports  ) Chief extensors of vertebral column Posterior rami of spinal n. Iliocostalis (cervicalis, thoracis, lumborum) Longissimus (capitis, cervicis, thoracis) Spinalis (capitis, cervicis, thoracis)     

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DEEP Transversospinales Origin: transverse processes Posterior Rami of the spinal n. Semispinalis (capitis, cervicis, thoracis)  

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Extends  head, thoracic, and cervical regions of vertebral column; rotates contralaterally Multifidus – thickest at  lumbar o Stabilize vertebrae during local movement  Rotatores (brevis, longus) – deepest o Proprioception

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Receive communicating branches from the nearby gray rami communicantes Most of the meningeal branches run back through the foramina into the vertebral canal hence the name recurrent 

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First branches to arise from all 31 pairs of spinal nerves

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MINOR DEEP MUSCLES Posterior Rami of spinal n. (also anterior rami for intertransversarii) Interspinales – bet. spinous processes Extension & rotation o Intertransversarii – bet. transverse processes Lateral flexion & stabilization o Levators Costarum – to ribs Elevate ribs, assist in resp. & lateral flexion o 

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SUBOCCIPITAL AND DEEP NECK Suboccipital Muscles – innervated by the posterior ramus of C1 (suboccipital nerve) 1. Rectus capitis posterior major Origin: Spinous process of vertebra C2 Insertion: Lateral part of the inferior nuchal line of occipital bone Action: Extension of head and atlanto-occipital joints 2. Rectus capitis posterior minor Does not form part of the sub-occipital triangle Origin: Posterior tubercle of posterior arch of vertebra C1 Insertion: Medial part of inferior nuchal line of occipital bone Action: Extension of head of atlanto-occipital joints 3. Obliquus capitis inferior Origin: Posterior tubercle of posterior arch of vertebra C2 Insertion: Transverse process of vertebra C1 4. Obliquus capitis superior Origin: Transverse process of vertebra C1 Insertion: Occipital bone between superior and inferior nuchal lines Action: Extension and lateral flexion of head of atlanto-occipital joint

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Only branches to arise from the mixed spinal nerve, arising immediately after it is formed and before its division into anterior and posterior rami, or from the anterior ramus immediately after its f ormation 2-4 of these arise on each side at all vertebral levels

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Initially convey localized pain sensation from the back produced: Acute herniation of an IV disc o Sprain o Contusion o Fracture o Tumors of the vertebral column o Transverse, ascending and descending branches: Periosteum (covering the surface of the o posterior vertebral bodies, pedicles and laminae Ligamentum flava o Anuli fibrosi of the posterior and posterolateral o aspect of the IV disc Posterior longitudinal ligament o Spinal dura mater o Blood vessels within the vertebral canal o Nerve supply to the periosteum, anuli fibrosi and ligaments supply pain receptors Nerve supply to the anuli fibrosi and ligament supply receptors for proprioception (sense of one’s position) Sympathetic fibers to the blood vessels stimulate vasoconstriction

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VI. BLOOD SUPPLY

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 A. Arterial Supply

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V. NERVE SUPPLY

Recurrent Meningeal Branches of the Spinal Nerve Supplies the fibroskeletal structure of the vertebral column and the meninges 

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Major Cervical Arteries (Neck Area) Vertebral Ascending Cervical Major Segmental Arteries (Trunk Ar ea) Posterior Intercostal (Thoracic Region) Subcostal and Lumbar (Abdomen) Iliolumbar, Lateral and Medial sacral (pelvis) Periosteal and equatorial branches (major cervical and segmental arteries) arise from the above arteries as they cross the external (anterolateral) surfaces of vertebrae These 2 branches plus their SPINAL BRANCHES supply the vertebrae.  Anterior vertebral canal branch Nutrient arteries - Supply most of the RED MARROW of the central vertebral body Posterior vertebral canal branch Spinal branches (from parent arteries) Give rise to radicular or segment medullary arteries – distributed to the posterior and anterior roots of spinal nerves and their coverings and to spinal cord.  ARTERIAL SUPPLY OF THE BACK CERVICAL REGION Occipital a. – from the external carotid Vertebral a. – from subclavian Deep cervical a. – from the branch of costocervical trunk THORACIC REGION – posterior intercostal artery LUMBAR REGION – subcostal and lumbar artery SACRAL REGION – iliolumbar and lateral sacral artery

B. Venous Drainage

vertebral venous plexuses. There is also anterolateral drainage from the external aspects of the vertebrae into segmental veins. Vertebral Column Plexuses (Internal and External) Extends along vertebral column from skull to coccyx Communicate through the foramen magnum (IV foramina) with occipital and basilar venous sinuses (within cranial cavity) Both densest anteriorly and posteriorly and relatively sparse laterally Walls are thin and channels are valveless Form Spinal veins a) Internal Vertebral Venous Plexus (Epidural venous plexus) lie within the vertebral canal but outside dura mater of spinal cord embedded in areolar tissue b) External Vertebral Venous Plexus Lie external to vertebral column and surround it Basivertebral Veins Form within the vertebral bodies Drain into external and especially the anterior internal vertebral venous plexus  

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Intervertebral Veins Receive veins from the spinal cord a nd vertebral venous plexus Drain internal plexus Joined by tributaries from e xternal vertebral plexus a nd drain into the vertebral veins of the neck and segmental (intercostal, lumbar, sacral) veins of trunk 

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C. Lymphatic Drainage

Lymph Vessels Deep

Drain into Deep cervical Posterior mediastinal Lateral aortic Sacral nodes

From the Skin of Neck

Cervical nodes

From the Trunk Above Illiac crests Below Illiac crests

Axillary nodes Superficial inguinal nodes

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(A) The dense plexus of thin-walled vessels within the vertebral canal, the internal vertebral venous plexus, consists of valveless anastomoses between anterior and posterior longitudinal venous sinuses. (B) The venous drainage parallels the arterial supply and e nters the external and internal

It does not matter how slow you go so long as you do not stop. -Confucius

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 APPENDIX Characteristics Transverse Processes

Vertebra Body Cervical (typical)

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(Atypical) C1 (Atlas)

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C2 (Axis)

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Thoracic

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Small and wider from side to side than anteroposteriorly Superior surface concave with uncus of body (uncinate process) Inferior surface convex

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Vertebral Foramen Large and triangular

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Foramina transversarii and anterior and posterior tubercles; vertebral arteries and accompanying venous and sympathetic plexuses pass through foramina transversarii of all cervical vertebrae except C7 w/c transmits only small accessory vertebral veins

Articular Processes 

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Superior facets directed superioposteriorly Inferior facets directed inferioanteriorly Obliquely placed facets are mostly nearly horizontal in this region

Spinous Processes   

Short (C3-C5) Bifid (C3-C6) Process of C6 is long and C7 (vertebra prominens) longer

Ring-like; somewhat kidney-shaped when viewed superiorly or inferiorly No spinous process or body; consists of two lateral masses connected by anterior and posterior arches Concave superior articular facets create atlanto-occipital joints with the occipital condyles; flat inferior facets meet with the C2 vertebra to create lateral atlanto-axial joints Strongest cervical vertebra Distinguishing feature is the dens, which projects superiorly from its body and provides a pivot around which the atlas turns and carries the cranium Articulates anteriorly with the anterior arch of the atlas and posteriorly with the transverse ligament of the atlas Heart shaped Circular and Long, strong & extend Superior facets directed Long smaller than posterolaterally posteriorly and slightly One or two costal Slope those of laterally Length diminishes from T1 facets for posteroinferiorly cervical and Inferior facets directed articulation with to T12 (T1-10 have facets for Tips extend to level lumbar head of the rib articulation with tubercle of anteriorly and slightly of vertebral body rib) medially below Plane of facets lies on arc centered about vertebral body Massive Triangular Long and slender; accessory Superior facets directed Short and sturdy process on posterior surface posteromedially (or Kidney shaped Larger than in Thick, broad and of base of each process medially) superiorly thoracic and hatchet shaped Inferior facets directed smaller than in cervical anterolaterally (or laterally) Mammillary process on posterior surface of each superior articular process Wedge-shaped bone; composed of five fused sacral vertebrae Base is formed by the superior surface of S1 and the apex is the portion which tapers and articulates with the coccyx Small triangular bone; formed by fusion of 4 rudimentary coccygeal vertebrae Co1 usually not fused with the rest; largest and broadest; only Co v. with transverse process; Rudi mentary articular process for m coccygeal cornua which articulate with sacral cornua Co 2-4 fuse during midlife and resemble beak of bird 

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Lumbar

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Sacrum

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Coccyx

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Page 12 of 16

ANA 2.1

Page 13 of 16

ANA 2.1

Superficial Muscles

Extrinsic

Intermediate Muscles

Extrinsic

Superficial Intrinsic Muscles

Intermediate Intrinsic Muscles

Page 14 of 16

ANA 2.1

Deep Intrinsic Muscles

Page 15 of 16

ANA 2.1

Suboccipital Muscles and Suboccipital Triangle

Page 16 of 16