Chapter 5 Skeletal System Skeletal system: bones, joints, cartilages, ligaments 2 divisions: Axial and…

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Classification 2 types of bone (osseous) tissue Compact dense, looks smooth Spongy needlelike pieces, lots of space Divided into 4 groups based on shape (1)Long bones Shaft with head at both ends Compact All limbs except wrist and ankles


Chapter 5 Skeletal System

Skeletal system: bones, joints, cartilages, ligaments

2 divisions: Axial and Appendicular

Bones 206Functions

Support/frameworkProtectionMovementStorage minerals (calcium and phosphorus), fats in internal cavitiesBlood cell formation hematopoiesis in marrow


2 types of bone (osseous) tissueCompact dense, looks smoothSpongy needlelike pieces, lots of spaceDivided into 4 groups based on shape(1)Long bonesShaft with head at

both ends

CompactAll limbs except wrist

and ankles

(2)Short bonesCube-shapedSpongyAnkles and wristsSesamoid form in tendons

ex. patella

(3)Flat bonesThin, flat, curvedCompact layered around spongySkull, ribs, sternum (4)Irregular bonesDont fit into other threeVertebrae, hip bones

Long Bone Structure

Diaphysis shaftCompact bonePeriosteum protective connective membranePerforating (Sharpeys) fibers

connect membrane and bone

Epiphyses endsThin compact layer around spongyCovered by articular cartilage decreases frictionIn adults: epiphyseal line bony


In kids: epiphyseal plate cartilage causes lengthwise growth

CavityYellow marrow (medullary cavity)In adultsFat depositsRed marrowIn kidsBlood cell formationIn adults this marrow

is in spongy, flat


Bone Markings

Where muscles, tendons, ligaments attach or where vessels and nerves pass2 types: projections (processes) and depressions (cavities)

Microscopic Anatomy

Osteocytes mature bone cellsFound in cavities called lacunaeLacunae form circles (lamellae) around a central canal (Haversian canal) which carries blood vessels and nervesOsteon (Haversian system) each complexCanaliculi canals that come off central canal and lead to lacunaePerforating (Volkmanns) canals run at right angles to shafts

Formation, growth, & remodeling

Ossification bone formation2 stepsHyaline cartilage model is covered with bone matrix by osteoblasts (bone forming cells)Cartilage is broken down and leaves the medullary cavityBy birth only cartilage regions left are:Articular cartilage covers ends stays for lifeEpiphyseal plates area of longitudinal growthNew cartilage is added on surface away from medullary cavityCartilage closest to cavity is broken down and replaced by bone

Appositional growth diameter increaseOsteoblasts in periosteum add bone to external diaphysisGrowth controlled by growth hormone and sec hormonesBones remodel (change) because of:Calcium levels in bloodDecrease in calcium PTH released activates osteoclasts which break down bone to release calciumIncrease in calcium hypercalcemia calcium deposits formPull of gravity and musclesCauses bones to become thicker and form projections for attachment


Closed (simple) fractures clean break under skinOpen (compound) fractures ends pierce skinReduction realignmentClosed placed/coaxed by handsOpen surgery

RepairHematoma formsBreak splinted by a fibrocartilage callusBony callus forms replaces cartilageBone remodelingTypesComminuted

many fragments

common in older


Compression crushedDepression pressed inward skull fracture Impacted ends forced into each other fallsSpiral twisting forces sportsGreenstick partial break kids

Other Disorders

Sprain tendon/ligament damageArthritisOsteoarthritis (OA) aka wear and tear arthritisRheumatoid arthritis (RA) autoimmune bodys immune system is attacking itselfGouty arthritis gout uric acid builds up and is deposited in jointsOsteoporosis bone



aka articulationsFunctionsHold bones togetherAllow movement2 ways to classify(1)Function amount of movementSynarthroses immovableAmphiarthroses slightly movableDiarthroses freely movable

(2)Structurally FibrousJoined by fibrous tissueSynarthroses Ex. skull suturesCartilaginousJoined by cartilageMost amphiarthrosesEx. pubic symphysis, intervertebral jointsA few synarthroses epiphyeal plates, btw ribs and sternum

SynovialSeparated by a joint cavity w/ synovial fluidFound in limbs4 featuresArticular cartilage over


Fibrous articular capsuleJoint cavity enclosed by capsuleContains synovial fluidReinforcing ligamentsMay have bursae (fluid filled sacs) or a tendon sheath (completely wraps tendons in high friction areas)

Synovial joint types based of shapePlane gliding flat surfaces wrist nonaxialHinge uniaxial elbow, knee, fingersPivot uniaxial radioulnar joint, atlas and axis

Condyloid biaxial side/side and back/forthBtw metacarpals and phalangesSaddle biaxial carpometacarpal of thumb twiddlingBall and socket multiaxial shoulder, hip


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