Skeletal System Axial Skeleton. The Axial Skeleton Eighty bones segregated into three regions – Skull – Vertebral column – Bony thorax

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<ul><li><p>Skeletal SystemAxial Skeleton</p></li><li><p>The Axial SkeletonEighty bones segregated into three regionsSkullVertebral columnBony thorax</p></li><li><p>Bones of the Axial SkeletonFigure 7.1</p></li><li><p>The SkullThe skull=the cranium and facial bones Cranium protects the brain and is the site of attachment for head and neck musclesEight cranial bones two parietal, two temporal, frontal, occipital, sphenoid, and ethmoid</p><p>Facial bonesSupply the framework of the face, the sense organs, and the teethProvide openings for the passage of air and foodAnchor the facial muscles of expression</p></li><li><p>Frontal Bone &amp; Major MarkingsFigure 7.2a</p></li><li><p>Parietal Bones and Major Associated SuturesFour sutures mark the articulations of the parietal bones Coronal suture between parietal and frontal bonesSagittal suture where right and left parietal bones meet Lambdoid suture between parietal and occipital bonesSquamosal or squamous suture between parietal and temporal bones </p></li><li><p>Major SuturesFigure 7.3a</p></li><li><p>Occipital Bone &amp; Major MarkingsFigure 7.2b</p></li><li><p>Temporal BonesFigure 7.5</p></li><li><p>Temporal Bone &amp; Major MarkingsFigure 7.3a(a)External acoustic meatusMastoid processStyloid processZygomatic processTemporal bone</p></li><li><p>Sphenoid BoneButterfly-shaped bone that spans the width of the middle cranial fossa (depression)</p><p>Forms the central wedge that articulates with all other cranial bones</p></li><li><p>Sphenoid BoneFigure 7.6a</p></li><li><p>Ethmoid BoneMost deep of the skull bones; lies between the sphenoid and nasal bones</p><p>Forms most of the bony area between the nasal cavity and the orbits</p></li><li><p>Ethmoid BoneFigure 7.7</p></li><li><p>Facial BonesFourteen bones of which only the mandible and vomer are unpaired</p><p>The paired bones are the maxillae, zygomatics, nasals, lacrimals, palatines, and inferior conchae</p></li><li><p>Mandible and Its MarkingsFigure 7.8a</p></li><li><p>Maxillary BonesMedially fused bones that make up the upper jaw and the central portion of the facial skeleton</p></li><li><p>Zygomatic BonesIrregularly shaped bones (cheekbones) that form the prominences of the cheeks and the inferolateral margins of the orbits</p></li><li><p>Anterior Aspects of the SkullFigure 7.2a(a)Parietal boneNasal boneSphenoid bone(greater wing)Temporal boneEthmoid boneLacrimal boneZygomatic boneMaxillaMandibleMentalforamenFrontal boneGlabellaMiddle nasal conchaPerpendicular plateInferior nasal conchaVomer boneEthmoidbone</p></li><li><p>Hyoid BoneNot actually part of the skulllies just inferior to the mandible in the anterior neckOnly bone of the body that does not articulate directly with another bone</p><p>Attachment point for neck muscles that raise and lower the larynx during swallowing and speech</p></li><li><p>THORACIC CAGE</p></li><li><p>Bony Thorax (Thoracic Cage)The thoracic cage is composed of the thoracic vertebrae dorsally, the ribs laterally, and the sternum and costal cartilages anteriorly</p></li><li><p>Bony Thorax (Thoracic Cage)FunctionsForms a protective cage around the heart, lungs, and great blood vessels</p><p>Supports the shoulder girdles and upper limbs</p><p>Provides attachment for many neck, back, chest, and shoulder muscles</p><p>Uses intercostal muscles to lift and depress the thorax during breathing </p></li><li><p>Bony Thorax (Thoracic Cage)Figure 7.19a</p></li><li><p>Sternum (Breastbone)A dagger-shaped, flat bone that lies in the anterior midline of the thorax</p><p>Anatomical landmarks includethe jugular (suprasternal) notch, the manubrium, the sternal angle, the xiphoid process and the xiphisternal joint</p></li><li><p>RibsThere are twelve pair of ribs forming the flaring sides of the thoracic cage</p><p>All ribs attach posteriorly to the thoracic vertebrae</p><p>The superior 7 pair (true, or vertebrosternal ribs) attach directly to the sternum via costal cartilages</p></li><li><p>Ribs (continued)Ribs 8-12 (false, or vertebrocondral ribs) attach indirectly to the sternum via costal cartilage </p><p>Ribs 11-12 (floating, or vertebral ribs) have no anterior attachment</p></li><li><p>Structure of a Typical True RibBowed, flat bone consisting of a head, neck, tubercle, and shaftFigure 7.20a</p></li><li><p>Structure of a Typical True RibFigure 7.20b</p></li><li><p>Vertebral Column</p></li><li><p>Vertebral ColumnFormed from 26 irregular bones (vertebrae) connected in such a way that a flexible curved structure resultsCervical vertebrae 7 bones of the neckThoracic vertebrae 12 bones of the torsoLumbar vertebrae 5 bones of the lower backSacrum 5 fused bones inferior to the lumbar vertebrae that articulates with the hip bonesCoccyx-4 fused bones that make up the tailbone</p></li><li><p>Vertebral CurvatureSpine has an sinusoid (or s) shape due to curvatureConcave (posteriorly)=cervical and lumbarConvex (posteriorly)=thoracic and sacralAllows it to act like a spring when walking uprightProvides flexibility and resiliency</p><p>At birth, spine curved out like 4 legged animals</p></li><li><p>Vertebral ColumnFigure 7.13</p></li><li><p>Intervertebral DiscsAct as shock absorper</p><p>Cushion-like pad composed of two partsNucleus pulposus:inner gelatinous center gives the disc its elasticity and compressibility</p><p>Annulus fibrosus:surrounds the nucleus pulposus with a collar composed of collagen and fibrocartilage</p></li><li><p>Intervertebral DiscsAs one gets older, discs become thinner &amp; more rigidCauses slight decrease in heightMore herniated discs occurReturn to baby curvature of spine (hump)</p><p>Herniated Disc (slipped disc):Nucleus pulposus bulges out past annulus fibrosusPainful if presses on spinal cord or nerve</p></li><li><p>Regional Characteristics of VertebraeTable 7.2.1</p></li><li><p>General Structure of VertebraeFigure 7.15</p></li><li><p>Regional Characteristics of VertebraeTable 7.2.2</p></li><li><p>Cervicalneck</p><p>Atlas &amp; Axis (1st 2 vertebra)Modified to rotateNo intervertebral disc between them </p><p>Atlas carries skull (like Atlas of Greek mythology carries the world)Articulating surfaces allow head to move up and down (yes)</p><p>Altas rotates around dens of axisRotates head side to side (no)</p></li><li><p>Thoracic VertebraeFigure 7.17b</p></li><li><p>Thoracic and Lumbar VertebraThoracic:Attach to ribsLarger spines for muscle attachmentsLumbar:lower backThicker and well connected for support &amp; stability</p></li><li><p>Lumbar VertebraeFigure 7.17c</p></li><li><p>Sacrum and CoccyxSacrum:Bones fuse as developMakes up posterior of pelvisCoccyx:tailboneBones fuse as develop</p></li><li><p>Sacrum and Coccyx: Anterior ViewFigure 7.18a</p></li></ul>