Chapter 7:

The Axial Skeleton*

Human SkeletonHuman Skeleton = 206 BonesAxial Skeleton:-longitudinal axis-80 bonesAppendicular Skeleton:-limbs-126 bones*

The Axial SkeletonFigure 71a*

Axial Skeleton*

Appendicular Skeleton*

Axial Skeleton FunctionSupport and protect organs in dorsal and ventral body cavitiesProvide surface area for muscle attachment:Adjust position of head, neck, & trunkPerform respiratory movementsStabilize appendicular skeleton*

Bones of the Axial SkeletonThe skull: 22 bones8 cranial bones:form the braincase or cranium 14 facial bones:protect and support entrances to digestive and respiratory tracts Skull bones interconnect at immovable joints called suturesDense fibrous CT*

Skull: 22 Bones*

Cranial BonesEnclose the cranial cavityWhich contains the brain: and its fluids, blood vessels, nerves, and membranes*

The Facial Bones Superficial facial bones:for muscle attachment Maxillary, Lacrimal, Nasal, Zygomatic, and MandibleDeep facial bones:separate the oral and nasal cavitiesform the nasal septum Palatine bones, Inferior nasal conchae, and Vomer

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The Maxillary BonesThe largest facial bonesFigure 710a*

Functions of the Maxillary Bones Support upper teethForm inferior orbital rimForm lateral margins of external naresForm upper jaw and hard palateContain maxillary sinuses (largest sinuses)*

The Palatine BonesFigure 710b,c*

Functions of the Palatine BonesForm the posterior portion of the hard palateContribute to the floors of the orbits*

The structures and functions of the nasal complex.*

The Small Bones of the Face Figure 711*

Functions of the Nasal Bones Nasal BonesSupport the bridge of the nose Connect to cartilages of the distal part of the nose (external nares)VomerForms the inferior portion of the bony nasal septumInferior Nasal ConchaeTo create air turbulence in the nasal cavityTo increase the epithelial surface areaTo warm and humidify inhaled air

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The Mandible Forms the lower jawFigure 712a,b*

The Hyoid BoneFunction:Supports the larynxAttaches muscles of the larynx, pharynx, and tongue

Figure 712c*

Marks of the Hyoid BoneGreater horns (greater cornua):support larynxattach muscles of the tongueLesser horns (lesser cornua):attach stylohyoid ligaments support hyoid and larynx*

SkullFour major sutures:Lambdoid: - separates occipital bone from parietal bonesCorona: - separates frontal bone from parietal bonesSagittal: - separates parietal bonesSquamous: - (2) separates temporal bone from parietal bone*

SuturesThe immovable joints of the skull Figure 73a, b*

SuturesFigure 73c*

SuturesFigure 73d, e*

The Orbital ComplexPortions of 7 cranial and facial bones Figure 713*

The Orbital ComplexForms the eye sockets (orbits):frontal bone (roof)maxillary bone (floor)maxillary, lacrimal and ethmoid bones (orbital rim and medial wall)sphenoid and palatine bones*

The Nasal ComplexBones of the nasal cavities and paranasal sinuses Figure 714*

The Nasal Complex: SinusesSinuses: air filled chambers inside flat bonesFunction:Reduce weight of boneHouse mucus membranes that moisten and clean incoming airFound in:Sphenoid, ethmoid, frontal, palatine, and maxillary bones*

The differences between the skulls of infants, children, and adults.*

Skull DevelopmentIntramembranous ossification from many centers of ossificationDuring development:brain grows more rapidly than cranial bonesGrowing skull bones are held together by bands of fibrous CT to provide flexibilityExpansion of brain, compression for birthLarge intersections of CT between the bones = fontalels (soft spots)Persist until age 5Around age 5:Brain stops growing in size, solid sutures form between cranial bones*

The Infant SkullFusion is not complete at birth: 2 frontal bones4 occipital bonesseveral sphenoid and temporal elements Fontanels Are areas of fibrous connective tissue (soft spots) Cover unfused sutures in the infant skull Allow the skull to flex during birth*

The 4 FontanelsAnterior fontanel:frontal, sagittal, and coronal suturesOccipital fontanel:lambdoid and sagittal suturesSphenoidal fontanels:squamous and coronal suturesMastoid fontanel:squamous and lambdoid sutures*

Infant Skull*

Skull Development AbnormalitiesCraniostenosis:Premature closure of frontanels,Without surgery, the brain is crushedMicrocephaly:- Brain fails to enlarge- Cranium remains small*

CraniostenosisMicrocephaly*

In which bone is the foramen magnum located?sphenoidoccipital boneethmoidparietal bone*

Toms suffers a blow to the skull that fractures the right superior lateral surface of his cranium. Which bone is fractured?frontal boneright temporal boneright parietal boneethmoid*

Which bone contains the depression called the sella turcica? What is located in this depression?sphenoid bone; pituitary glandethmoid; olfactory epitheliumtemporal bone; inner earlacrimal bone; tear apparatus*

The vertebral regions, the curvatures of the vertebral column, and their functions.*

The Vertebral Column: 26 BonesThe spine or vertebral column:protects the spinal cordsupports the head and body7 cervical vertebrae (C1-C7)12 Thoracic vertebrae (T1-T12)5 Lumbar vertebrae (L1-L5)1 Sacrum (5 fused)1 Coccyx (3-5 fused)*

Regions and Curves of the Vertebral Column26 bones: 24 vertebrae, the sacrum, and coccyxVertebral column is not straight4 curves bring the weight of the body in line with the central axisFigure 716*

The VertebraeFigure 720a*

Comparing Vertebrae*

Characteristics of the Sacrum and Coccyx The sacrum:is curved, more in males than in femalesprotects reproductive, urinary, and digestive organsThe coccyx:attaches ligaments and a constricting muscle of the anus

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4 Curvatures of the Vertebral ColumnCervical curveThoracic curveLumbar curveSacral curve*

Primary CurvesThoracic and sacral curves:are called primary curves (present during fetal development)or accommodation curves (accommodate internal organs)*

Secondary CurvesLumbar and cervical curves:are called secondary curves (appear after birth in first year of life)or compensation curves (shift body weight for upright posture)Necessary for bipedalismCervical: holds head upLumbar: standing*

Abnormalities in CurvatureKyphosis: - exaggerated thoracic curvatureLordosis: - exaggerated lumber curvatureScoliosis: - abnormal lateral curvature*

Construction of ColumnVertebral body: stackingtransfers weight along the spineIntervertebral disc:Spacing between bodies (not C1 and C2)Annulus Fibrosus: Outside FibrocartilageNucleus pulposus: InsideGel (cushion)Absorbs ShockLoss of water from discs = shrinking height*

Construction of ColumnElastic ligaments: link bodies for alignmentIntervertebral foramen: holes formed by spacing from discs, allow spinal nerves to exit columnVertebral arch:Bone attached to vertebral body, with body it forms vertebral foramenVertebral Foramen:Hole for spinal cordVertebral Canal:Bony canal for spinal cordFormed by stacking of vertebral foramen*

Structure of a VertebraFigure 717a,b*

The Vertebral CanalFigure 717d,e*

Spina bifidaVertebral arch fails to develop correctly at 3 weeks (fetus) and the spinal cord is unprotected or even exposed4/1000 births show some degreeDue to lack of folic acid*

Why does the vertebral column of an adult have fewer vertebrae than that of a newborn?Vertebrae are absorbed as adult stature is reached.Newborns require more support in the cervical region.The sacrum and coccyx fuse post-puberty.Vertebrae are formed that later become ribs.*

What is the importance of the secondary curves of the spine?balances weight of headbalances weight on lower limbsallows walkingprovides greater flexibility*

When you run your finger along a persons spine, what part of the vertebrae are you feeling just beneath the skin?superior articular processespediclestransverse processesspinous processes*

Joe suffered a hairline fracture at the base of the dens. Which bone is fractured, and where is it located?second cervical vertebra; posterior neckfirst cervical vertebra; posterior neckoccipital bone; posterior base of skullsacrum; posterior pelvis*

Examining a human vertebra, you notice that, in addition to the large foramen for the spinal cord, two smaller foramina are on either side of the bone in the region of the transverse processes. From which region of the vertebral column is this vertebra?thoraciclumbarsacralcervical*

Why are the bodies of the lumbar vertebrae so large?They develop first and therefore have longer to grow.To provide more flexibility.To distribute weight over a larger area.To provide greater protection to the lumbar spinal nerves.*

The significance of articulations between ribs, thoracic vertebrae, and sternum.*

The Thoracic CageThe skeleton of the chest:supports the thoracic cavityConsists of:24 Ribs 1 sternum (breastbone)*

The SternumThe sternum:a flat bonein the midline of the thoracic wall*

The Rib CageFormed of ribs and sternumFigure 722a*

Articulations of Ribs and VertebraeFigure 722b*

Functions of the Thoracic CageProtects organs of the thoracic cavity:heart, lungs, and thymusAttaches muscles:for respirationof the vertebral columnof the pectoral girdleof the upper limbs*

The RibsFigure 723*

Functions of RibsRibs:are flexibleare mobilecan absorb shockRib movements (breathing):affect width and depth of thoracic cagechanging its volume

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RibsRibs (costae):are 12 pairs of long, curved, flat bonesextending from the thoracic vertebraeRibs are divided into 3 types:1. 7 pairs of true ribs: Separate cartilage to attach to sternum2. 3 pairs of false ribs:Common shared cartilage to attach to sternum3. 2 pairs of floating ribs: - no cartilage, no attachment to sternum*

KEY CONCEPTThe axial skeleton:protects the brain, spinal cord, and visceral organs of the chestVertebrae:conduct body weight to the lower limbsLower vertebrae are larger and stronger:because they bear more weight*

How could you distinguish between true ribs and false ribs?True ribs attach directly to the sternum by their own costal cartilage.True ribs are entirely bony.False ribs are not part of the thoracic cage.True ribs are attached only to the sternum.*

Improper administration of cardiopulmonary resuscitation (CPR) can result in a fracture of which bone(s)?cervical vertebra and ribsthoracic vertebra and ribssternum and thoracic vertebrasternum and ribs*

What are the main differences between vertebrosternal and vertebrochondral ribs?Vertebrosternal ribs attach to the sternum.Vertebrochondral ribs attach to costal cartilage.Vertebrosternal ribs increase in curvature and length from 1 - 7.All of the above are true.*