Chapter 5 The Skeletal System. Introduction The adult skeleton is composed of 206 bones The adult skeleton is composed of 206 bones The skeletal system.
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Chapter 5The Skeletal System
IntroductionThe adult skeleton is composed of 206 bonesThe skeletal system is subdivided into 2 divisions:Axial skeletonAppendicular skeletonThe skeletal system includes joints, cartilages, & ligaments
Bones: An OverviewFunctions of the bonesSupportbones form the internal framework that supports & anchors all soft organsProtectionbones protect body organsMovementskeletal muscles, attached to bones by tendons, use the bones as levers to move the body & its parts
Bones: An OverviewFunctions of the bonesStoragefat is stored in the internal cavities of bones, and bone serves as a storehouse for minerals such as calciumBlood cell formationthis process is also called hematopoiesis & occurs within the marrow of certain bones
Classification of BonesThere are 2 basic types of bonesCompact bonedense & looks smoothSpongy bonecomposed of small needlelike pieces of bone & lots of open spaceBones are classified into 4 groups according to shapeLong boneslonger than they are wide; mostly compact bone; includes all the bones of the limbs
Classification of BonesBones are classified into 4 groups according to shapeShort bonescube-shaped; mostly spongy bone; includes all the bones of the wrist & ankle & also the patellaFlat bonesthin, flat, & curved; 2 thin layers of compact bone with a layer of spongy bone in between; includes the bones of the skull, ribs, & sternumIrregular bonesbones that do not fit any of the above categories; includes the bones of the hip & vertebrae
Classification of Bones
Structure of a Long BoneDiaphysisShaft of the boneMakes up most of the bones length & is composed of compact bonePeriosteumFibrous connective tissue membraneCovers & protects the diaphysis
Structure of a Long BoneEpiphysesEnds of the long boneproximal & distalConsists of a thin layer of compact bone that encloses an area filled with spongy boneArticular cartilageCovers the external surface of the epiphysesIt provides a smooth, slippery surface that decreases friction at joint surfaces
Structure of a Long BoneMedullary cavityThe cavity of the shaft that is primarily a storage area for adipose tissueAlso known as the yellow marrow cavity
Structure of a Long Bone
Bone Formation, Growth, & RemodelingThe skeleton is formed from two of the strongest & most supportive tissues in the bodycartilage & boneIn embryos, the skeleton is primarily made of hyaline cartilage, but in the young child most of the cartilage has been replaced by bone.
Bone Formation, Growth, & RemodelingOssificationprocess of bone formation & involves 2 phases:The hyaline cartilage is completely covered with bone matrix by bone-forming cells called osteoblasts.The hyaline cartilage is digested away, opening a medullary cavity within the newly formed bone.
Bone Formation, Growth, & Remodeling
Bone Formation, Growth, & RemodelingBones are always changing & are remodeled in response to changes in 2 factors:Calcium levels in the bloodIf blood calcium levels are too low, osteoclasts (bone-destroying cells) break down bone matrix & release calcium into the blood.If blood calcium levels are too high, calcium is deposited in bone matrix as hard calcium salts.The pull of gravity & muscles on the skeleton
Bone Formation, Growth, & RemodelingBone remodeling is essential if bones are to retain normal proportions & strength during long-bone growth as the body increases in size & weight
Bone FracturesBones are susceptible to fractures, or breaks, all through life.During youth, most fractures result from exceptional trauma that twists or smashes the bones. In old age, bones thin & weaken, & fractures occur more often.
Bone Fractures2 common types of fractures: (p 123)Simple (closed) fractures = a fracture in which the bones breaks cleanly but does not penetrate the skinCompound (open) fractures = when the broken bone ends penetrate through the skinFractures are treated by reductionrealignment of the broken bone ends
Axial SkeletonForms the longitudinal axis of the bodyDivided into 3 partsSkullformed by 2 sets of bonesCraniumencloses & protects the brain tissue; made up of several smaller bones (pp 126-127)Frontal boneforms the foreheadParietal bonesforms the superior & lateral wallsTemporal bonesinferior to the parietal bonesOccipital boneforms the back of the craniumSphenoid bonebutterfly-shaped & forms part of the floor of the cranial cavityEthmoid bonelies anterior to the sphenoid & forms the roof of the nasal cavity
Axial SkeletonFacial boneshold the eyes in position & allow the facial muscles to show our feelings (p 129)Maxillaeupper jawPalatine bonesform the posterior part of the hard palateZygomatic bonescheekbonesLacrimal bonesmedial walls of the eyes & has a groove that serves as a passageway for tearsNasal bonesforms the bridge of the noseVomer bonesingle bone in the median line of the nasal cavity (nasal septum)Inferior conchaecurved bones projecting from the lateral walls of the nasal cavityMandiblelower jaw; the largest & strongest bone of the face!!!
Axial SkeletonFetal skeletonthe skull of a fetus or newborn infant is different from an adult skull. When a baby is born, its skeleton is unfinished. The skull also has regions that yet to be converted to bone which are called fontanels. These are also known as the soft spots.
Axial SkeletonVertebral Column (p 131)Extends from the skull to the pelvisFormed from 26 irregular bonesRunning through the central cavity of the vertebral column is the spinal cordThe vertebrae are separated by pads of cartilage-intervertebral discs-cushion the vertebraeThe spinal cord curves & forms an S-shaped structureAbnormal spinal curvatures (p 132)ScoliosisKyphosislordosis
Axial Skeleton3 main types of vertebraeCervical vertebraeIdentified as C1 to C7Form the neck region to the spineThoracic vertebraeIdentified as T1 to T12Larger than cervical vertebraeLumbar vertebraeIdentified as L1 to L5Where most of the stress on the vertebral column occursSacrumformed by the fusion of 5 vertebraeCoccyxformed by the fusion of 3-5 tiny vertebrae; also known as the human tailbone
Axial SkeletonBony thoraxaka the thoracic cage (p 135)SternumAka the breastboneA flat bone & the result of the fusion of 3 bones:ManubriumBodyXiphoid processRibs12 pairsMales DO NOT have 1 rib less than females!!!3 types of ribs:True ribsthe 1st 7 pairs that are attached directly to the sternumFalse ribsthe next 5 pairs that are attached to the sternumFloating ribsthe last 2 pairs of false ribs that lack sternal attachment
Appendicular SkeletonComposed of 126 bones of the limbs & pectoral & pelvic girdlesBones of the shoulder girdle (p 139)Clavicleaka the collarboneScapulaaka the shoulder bladesBones of the upper limbs (pp 140-141)Armformed by a single bone=humerusForearm2 bones:Radiuson the thumb sideUlnaon the pinky side
Appendicular SkeletonHand3 sets of bonesCarpals8 bones that make up the wristMetacarpalsthe palm of the handPhalangesbones of the fingersBones of the pelvic girdle (p 142)Formed by 2 coxal bones called hip bonesEach hip bone is formed by the fusion of 3 bones:IliumIschiumpubis
Appendicular SkeletonDifferences between the male & female pelvis:Female pelvis is shallowerFemale bones are lighter & thinnerFemale sacrum is shorter & less curvedBones of the lower limbs (pp 144-145)Thighformed by a single bone=femurLeg2 bonesTibiashinbone=larger & more medialFibulalies next to the tibia
Appendicular SkeletonFoot3 sets of bonesTarsals7 bones that make up the posterior footMetatarsalsthe sole of the footPhalangesthe bones of the toes
JointsAlso called articulations2 main functionsHold bones together securelyGive the skeleton mobilityClassified in 2 waysFunctionallyStructurally
JointsFunctional classification--focuses on the amount of movement allowed by the jointImmovable jointSlightly movable jointsFreely movable jointsStructural classificationfocuses on the type of tissueFibrous jointsbones are united by fibrous tissueCartilaginous jointsbones are united by cartilageSynovial jointsjoint cavity contains synovial fluid
JointsTypes of synovial joints based on shapePlane jointshort slipping or gliding; ie joints of the wristHinge jointmovement in one direction; ie elbow, ankle, & the joints between the bones of the fingersPivot jointrotating movement; ie between the radius & ulnaCondyloid jointbones move from side to side or back & forth; ie your knuckles
JointsSaddle jointsame movement as condyloid; ie twiddling your thumbsBall-and-socket jointhead of one bone fits into a round socket; ie shoulder & hip joint
JointsInflammatory disorders of jointsArthritisInflammation of the jointMost widespread disease in the U.S.Symptoms=pain, stiffness, & swelling of the jointOsteoarthritisMost common type of arthritisChronic degenerative condition that affects the aged
JointsRheumatoid arthritisChronic inflammatory disorderAffects more women than menThe bodys immune system attempts to destroy tissuesGoutUric acid accumulates in the blood & may be deposited as needle-shaped crystals in the soft tissues of jointsUsually affects the great toe