Axial skeleton

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  • The Axial SkeletonBy- Dr. Armaan Singh

  • I highly recommend Professor Wissmans sitesFor bones: out all his links:

    Also check out:

    Site for xrays & other diagnostic procedures:

  • is an example of Prof Wissmans bone site; this doesnt show the roll-over answers

  • THE SKELETAL SYSTEMThe Axial SkeletonThe skeleton consists ofBones (206)CartilagesJoints also called articulations, are the junctions between skeletal elementsLigaments connect bonesDivided into axial and appendicular

  • Axial skeleton - forms long axis of bodySkullVertebral columnThoracic cage

    Appendicular skeleton appendages and what they attach toUpper limbs (arms)Pectoral girdle (shoulder)Lower limbs (legs)Pelvic girdle

  • Axial skeletonSkullVertebral columnThoracic cageAxial skeleton is shown in green

  • The SkullCranial bones (or cranium)Enclose the cranial cavity, which supports and protects the brainAttachment sites for some head and neck musclesFacial bones (anterior aspect of skull)Form framework of faceForm cavities for sense organs of sight, taste and smellProvides openings for passage of air and foodHold the teethAnchor the muscles of the face

  • CraniumVault calvaria = skullcapForms superior, lateral and posterior aspects of skull, and forehead

    Base or floor: inferior partProminent bony ridges divide cranial base into 3 fossae (steps) anterior, middle and posterior

    Anterior cranial fossaMiddle cranial fossaPosterior cranial fossa (looking down on the floor of the skull)

  • Cranial bonesFrontal boneParietal bones (paired)Occipital boneTemporal bones (paired)Sphenoid boneEthmoid bone

  • Cranial bonesparietalparietalfrontaltemporalparietal


  • Temporal bonesthis is the right temporal bone looking at it from the right side

  • Sphenoid Ethmoid Small cranial bones

  • SuturesImmovable, interlocking joints of flat bones of skullIrregular, saw-toothed appearanceLargest 4 skull sutures: where bones articulate with parietal bonesCoronalSagittalSquamousLambdoid (FIND THEM)

  • Find: coronal, squamous and lamboid sutures

  • Find: sagittal and lambdoid sutures

  • Cranial cavity houses brainSmaller cavitiesHousing middle and inner earNasal cavityOrbitsSinusesOpenings (foramina, canals, fissures) for:Spinal cordBlood vesselsTwelve cranial nerves: I-XII

  • Remember, the skull is composed of:Cranial bones (or cranium)[these were just reviewed]


    Facial bones (anterior aspect of skull)Form framework of faceForm cavities for sense organs of sight, taste and smellProvides openings for passage of air and foodHold the teethAnchor the muscles of the face

  • Facial bonesMandibleVomerMaxillae (paired)Zygomatics (paired)Nasal (paired)Lacrimal (paired)Palatines (paired)Inferior nasal conchae (paired)

  • MandibleVomerMaxillae (paired)Zygomatics (paired)Nasal (paired)Lacrimal (paired)Palatines (paired)Inferior nasal conchae (paired)Facial bones:

  • Mandible (lower jaw)Maxilla (there are 2 which fuse, forming the upper jaw)

  • Nasal cavity

    Of bone and cartilageRoof is ethmoids cribriform plateFloor formed by palatine processes of the 2 maxillae and horizontal plates of palatine bonesThese nasal-floor structures form roof of the mouth, called the hard palatenasal boneethmoidvomerinf nasal concha(part of slide 18)maxilla___________

  • Nasal cavityTo left, bones forming the left lateral wall of the nasal cavity (nasal septum removed)To right, nasal cavity with nasal septum in place, showing how the ethmoid bone, septal cartilage, and vomer make up the septum

  • OrbitCone-shaped bony cavities holding the eyes, muscles that move the eyes, some fat and tear-producing glands; you dont need to know all these bones that form it, just realize how complex it is and recognize the optic canal (optic nerve passes out through it)(right orbit shown)

  • Paranasal sinusesAir-filled sacs in the bonesParanasal because they cluster around and connect to the nasal cavity

  • Hyoid boneOnly bone which does not articulate with any other boneMoveable base for the tonguePoints of attachment for neck muscles that raise and lower the larynx during swallowing

  • Remember that the Axial skeleton includes:

    SkullVertebral columnThoracic cageAxial skeleton is shown in green

  • The Vertebral ColumnFetus and infant: 33 separate bones, or vertebrae

    Adult: 24 vertebraeInferior 9 have fused formingThe sacrum (5) andThe coccyx (4)

  • VertebraeCervical 7Thoracic - 12Lumbar - 5Sacrum (5 fused)Coccyx (4 fused)

  • Spinal curvaturesCervical and lumbar are concave posteriorly* (lordosis)Thoracic and sacral are convex posteriorly* (kyphosis)Abnormal (see lab book p120): Too much of either Scoliosis (more than 10 degrees of lateral curvature)

    *when viewed from the side

  • Abnormal curvatures

  • Non-bony partsIntervertebral discs anulus fibrosis and nucleus pulposus)Anterior longitudinal ligamentPosterior longitudinal ligamentLigamentum flavum

  • Anterior longitudinal ligament: wide, strong and attaches to vertebrae as well as discs (prevents hyperextension)Posterior longitudinal ligament: narrow and relatively weak, attaching only to discsNote intervertebral foramen vs vertebral foramen on next slides *

  • Structure of a typical vertebra

  • Cervical vertebrae (C1-C7)C1 (atlas)C2 (axis)

  • SmallestLightestMost flexibleTriangular vertebral foramenTransverse processes have foramina (transverse foramen)Spinous process bifid (forked) except for C7Cervical Vertebrae

  • Heart shaped bodyAdditional small costal facets (costal=ribs)Round or oval vertebral foramenForm posterior part of rib cageThoracic Vertebrae T1-T12

  • Massive blocklike bodiesShort, thick hatchet-shaped spinous processesLimited mobilityLumbar Vertebrae L1-L5

  • The SacrumShapes posterior wall of pelvis

    Composite bone of 5 fused vertebrae

    Sacral foramina allow passage of vessels & nervesCoccyx(the tailbone)

  • Remember that the Axial skeleton includes:

    SkullVertebral columnThoracic cageAxial skeleton is shown in green

  • The Thoracic Cage

  • Sternum RibsManubrium


    Xiphoid process

    True ribs 1-7

    False ribs 8-12

    Floating ribs 11,12

  • Vertebral and Sternal Articulations

  • Typical rib

  • Disorders of the axial skeletonScoliosis (over 10% curvature)



    Vertebral compression fractures

    Spinal stenosis

  • FontanelsUnossified remnants of membranesPresent at birthAnterior fontanel largestCalled soft spotsOssify by 1 - 2 yearsContinue to ossify into adulthood; the sutures can become fused in old age

  • Some abnormalities (early fusion) of sutures: craniosynostosisMetopic Synostosis and trigonocephaly

    A: Preop B: 2 years after frontal orbital advancementSagittal synostosis and scaphocephalyThe most common suture to fuse is the middle or sagittal suture. Often the back or front of the skull will be worse but the overall shape is a long skull with a shortened distance from ear to ear.

    From -

    Pre-opCAT scanDiagram of surgery2 years post-op