Skeletal System. The Skeletal SystemThe Skeletal System: Overview Components of the skeletal system  Bones (~ 206 in an adult)  Joints  Cartilages.

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  • Skeletal System

  • The Skeletal System: OverviewComponents of the skeletal systemBones (~ 206 in an adult)JointsCartilagesLigamentsTwo divisionsAxial skeletonAppendicular skeleton

  • Primary Functions of the Skeletal System1. Structural support framework for the attachment of soft tissues and organs2. Protection of soft organs Ribs protect the heart and lungsSkull protects the brainVertebrae shield the spinal cordPelvis protects digestive & reproductive organs

  • Primary Functions of the Skeletal System3. Storage calcium salts (Mineral reserve) & lipids (energy reserve in the yellow marrow)

    Yellow bone marrow

  • Primary Functions of the Skeletal System4. Red Blood cell formation red marrow

  • Primary Functions of the Skeletal System5. Leverage for body movements delicate to powerful motions

  • Bone CompositionTwo types of bone tissue:Compact bone: Homogeneous, relatively solid & protective outer layerSpongy bone: Open network of small needle-like pieces of bone

    Figure 5.2b

  • Bones CompositionMass of a bone attributed to three components2/3 calcium deposits1/3 collagen fibersOsteocytes & other cells ~ 2%

  • Classification of Bones on the Basis of ShapeFigure 5.1

  • Classification of Bones1. Long bonesHave a shaft with heads at both endsContain mostly compact boneExamples: Femur, humerus, metacarpals

  • Classification of Bones2. Short bonesGenerally cube-shapeContain mostly spongy boneExamples: Carpals, tarsals

  • Classification of Bones3. Flat bonesThin & often curvedThin layers of compact bone around a layer of spongy boneExamples: Skull, ribs, sternum

  • Classification of Bones4. Irregular bonesOdd shapesDo not fit into other categoriesExample: Vertebrae and pelvis

  • Gross Anatomy of A Long Bone

  • Gross Anatomy of a Long BoneDiaphysisShaftComposed of compact boneFigure 5.2a

  • Gross Anatomy of a Long BoneEpiphysis Ends of the boneComposed mostly of spongy boneCovered by articular cartilageArticulates with another bone at a jointFigure 5.2a

  • Structures of a Long BonePeriosteumOutside covering of the diaphysis isolates bone from surrounding tissuesFibrous connective tissue membrane provides passage for blood vessels & nervesFigure 5.2c

  • Structures of a Long BoneSharpeys fibers - Secure periosteum to underlying bone

  • Structures of a Long BoneArticular cartilageCovers the external surface of the epiphysesHyaline cartilageDecreases friction at joint surfaces

  • Structures of a Long BoneMedullary cavityCavity of the shaft lined by the endosteumContains yellow marrow (mostly fat) in adultsContains red marrow (for blood cell formation) in infantsFigure 5.2a

  • Bone MarkingsSurface features of bonesSites of attachments for muscles, tendons, and ligamentsPassages for nerves and blood vessels***You are responsible for the bone markings on your notes page***What they are and their function

  • JointsArticulations of bones exist wherever two bones meetFunctions of joints: strength & mobility

  • Structural Classification of JointsFibrous joints - Generally immovableCartilaginous joints - Immovable or slightly moveableSynovial joints - Freely moveable

  • Functional Classification of JointsSynarthroses immovable jointsAmphiarthroses slightly moveable jointsDiarthroses freely moveable joints

  • SynarthrosesBony edges are close together and may interlock Suture bones interlocked and bound together with dense connective tissue (skull)

  • Syndesmoses (fibrous)Allows more movement than sutures due to longer connective fibersThe joints have more giveDistal ends of the tibia and fibula

  • AmphiarthrosesSymphysis (cartilaginous): Bones connected by cartilage ExamplesPubic symphysisIntervertebral jointsFigure 5.27de

  • Diarthroses (Synovial Joints)Articulating bones are separated by a joint cavityTypically found at the ends of long bonesSynovial fluid is found in the joint cavityFigure 5.24fh

  • Features of Synovial JointsJoint surfaces are enclosed by a fibrous articular capsuleLigaments reinforce the joint

  • Features of Synovial JointsBursae small packets of connective tissue filled with synovial fluidShock absorber/ friction reducerFound where tendons or ligaments rub against other tissues

  • Features of Complex Synovial JointsMeniscus - shock absorbing fibrocartilage padFat pads protect the articular cartilages & act as filler

  • Types of Synovial Joints Based on ShapeFigure 5.29ac

  • Plane/Gliding JointArticular surfaces are flatShort slipping or gliding movements Nonaxial - no rotationCarpal and tarsal jointsEnds of clavicles

  • Hinge JointCylindrical end of one bone fits into a trough-shaped surface on the otherUniaxial movement around one axis Elbow & joints of the phalanges

  • Pivot JointUniaxial joints rounded end of one bone fits into a sleeve or ring of boneProximal radioulnar jointThe atlas and dens of the axis

  • Condyloid (ellipsoidal) JointBiaxial can rotate around two different axesOval shaped articular surface & concavityBone may travel from side to side & back and forthMetacarpophalangeal joints

  • Saddle JointsBiaxial Joint articulated surfaces have convex and concave surfacesJoint of the thumb

  • Ball-and-Socket JointOnly multiaxial joints spherical head of one bone fits into the round socket of anotherProvide greatest variation in motion

  • Inflammatory Conditions Associated with JointsBursitis inflammation of a bursa usually caused by a blow or frictionTendonitis inflammation of tendon sheaths

  • RheumatismGeneral term describing pain or stiffness arising in the muscular or skeletal system Several major forms of rheumatism:Arthritis inflammatory or degenerative diseases of jointsAlso known as degenerative joint disease (DJD)25% of women and 15 % of men over age 60 show signs of this disorderOver 100 different typesThe most widespread crippling disease in the United States

  • Clinical Forms of ArthritisOsteoarthritis: Most common chronic arthritisProbably related to normal aging processes softening, fraying and breakdown of the articular cartilageExposed bone thickens into spurs limits movement

  • Clinical Forms of ArthritisRheumatoid arthritisAn autoimmune disease the immune system attacks the jointsOften leads to deformities in hands and feet

  • Clinical Forms of ArthritisGouty Arthritis: Inflammation of joints is caused by a deposition of urate crystals from the bloodNeedle like crystals usually accumulate in one joint typically the big toeCan usually be controlled with diet

  • Review- Correctly label the types of joints

  • Review Correctly label the four types of bones and give an example of eachFigure 5.1

  • Review Label the main structures of a long bone

  • Microscopic Anatomy of BoneOsteon (Haversian System)A unit of bone

  • Microscopic Anatomy of BoneCentral (Haversian) canalOpening in the center of an osteonCarries blood vessels and nerves

  • Microscopic Anatomy of BonePerforating (Volkmans) canalCanal perpendicular to the central canalCarries blood vessels and nerves

  • Microscopic Anatomy of BoneLacunae: Cavities containing bone cells (osteocytes)Arranged in concentric ringsDetail of Figure 5.3

  • Microscopic Anatomy of BoneLamellae: Rings around the central canalSites of lacunae

  • Microscopic Anatomy of BoneCanaliculi: Tiny canals that form a transport system between individual cellsRadiate from the central canal to lacunaeDetail of Figure 5.3

  • Types of Bone CellsOsteocytes - Mature bone cellsMaintain normal bone structureRecycle calcium saltsAssist in bone repair

  • Types of Bone CellsOsteoblasts: Responsible for osteogenesis (bone formation)Produce new bone matrix Promote the deposition of calcium salts in the bone matrixWhen completely surrounded by calcified matrix it will differentiate into an osteocyte

  • Types of Bone CellsOsteoclasts - Bone-destroying cellsProduce large amounts of acids and enzymesOsteolysis as bony matrix dissolves, stored minerals are releasedHelps regulate calcium and phosphate levels

  • Ossification & Bone GrowthSkeletal growth begins about 6 weeks after fertilizationAll skeletal components are initially composed of cartilageBone growth continues through adolescenceSome portions continue to grow until about age 25

  • OssificationProcess of replacing other tissues with boneIntramembranous bone develops within sheets or membranes of connective tissueEndochondral bone replaces existing hyaline cartilageMost bones are formed in this way

  • Long Bone Formation and GrowthFigure 5.4b

  • Bone Growth and RemodelingBones are remodeled and lengthened until growth stopsAppositional growth as the bones lengthen they also increase in diameterCells of the periosteum develop into osteoblasts and produce bone matrixInner surface eroded by osteoclasts increasing the diameter of the marrow cavity

  • Bone Growth and RemodelingReliable source of minerals needed for growth to occur absorbed from mother while developingMother often loses bone mass during pregnancyDiet must have adequate amounts of calcium, phosphates & Vitamin D3

  • Bone RemodelingNormal process of protein and mineral composition being removed and replaced About 18% each year in adultsCauses bones to change shapeMay change shape/size in response to stresses such as fractures, breaks or change in muscle massBone mass lost with disuse and age

  • Bone HealthBones become stronger in response to stressWhen we are inactive (no exercise) bones become weak and fragile

  • Areas That Do Not Undergo OssificationCartilage remains in isolated areasBridge of the noseLarynx Trachea Parts of ribsJoints

  • Skeletal DisordersHeterotopic Bones: abnormal development of osteoblasts in normal connective tissuesFibrodysplasia Ossificans Progressiva: rare genetic heterotopic disorderMuscles of the back, neck & upper limbs gradually replaced by bone

  • RicketsSoftening and bending of the bones due to Vitamin D3 deficiencyChildren get bowed legs as they bend under the weight of the bodyNo longer common (in US) due to dietary supplements

  • ScurvyVitamin C deficiency causes reduction in osteoblast activityWeak and brittle bonesCommon on ships

  • OsteopeniaBones become thinner and weaker with ageReduction in bone mass begins between ages 30 40Important to build strong bones as a child/ young adult

  • OsteopeniaOsteoblast activity declinesOsteoclast activity remains normalWomen lose about 8% and men about 3% of their bone mass every decade Epiphyses, vertebrae & jaws affected the mostFragile joints/limbs, height reduction and tooth loss

  • OsteoporosisBone-thinning disease that afflicts half of women over 65 and 20% of men over 70Bones are brittle and fracture easilyOften causes kyphosis due to vertebral collapseCaused partially by estrogen deficiency after menopauseOther factors include lack of calcium, protein and vitamin D in the diet, smoking and insufficient weight-bearing exercise

  • Osteoporosis

  • Bone FracturesA break in a boneTypes of bone fracturesClosed (simple) fracture break that does not penetrate the skinOpen (compound) fracture broken bone penetrates through the skin

  • Treating Bone FracturesBone fractures are treated by reduction and immobilizationRealignment of broken bone ends Closed reduction - bone ends coaxed back into place by physician's hands Open reduction - surgery, bone ends secured together with pins, wires or plates & screws

  • Types of Bone FracturesComminuted - bone fragments into many pieces Compression - bone is crushed ( due to porous bone) Depressed - broken bone is pressed inward (e.g. in skull) Transverse - break occurs across the long axis of a bone

  • Types of Bone FracturesImpacted - broken bone ends are forced into each other Spiral - ragged break as a result of excessive twisting of bone Epiphyseal - break occurring along epiphyseal line/plate Greenstick - bone breaks incompletely

  • Common Types of FracturesTable 5.2

  • Bone Remodeling After a Fracture

  • Review label the microscopic anatomy of the bone

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