Skeletal System
Function :
Protection of vital organs
Muscle attachment & leverage
Blood cell formation
Mineral storage
Types of Skeletons Axial (green)
80 bones skull, vertebral column, ribs, &
sternum
Appendicular (purple) 126 bones Upper extremities {includes clavicles &
scapula} Lower extremities { includes pelvis}
Bone Types Lippert p. 15, Table 2-2
Long length > width
Short more equal dimensions usually articulate w/ more
than one bone
Flat:** broad, curved surfaces** site for red blood cell formation
Irregular: varied shapes
Sesamoid: ** located where tendons cross a joint
protection from excessive wear
mechanical advantage
Bone Anatomy
Epiphysis• distal & proximal• wider than shaft• cancellous bone
Epiphyseal Plate cartilaginous in growing
bone
Metaphysis• flared ends of diaphysis• cancellous bone• supports epiphysis
Diaphysis• shaft • compact bone
Bone Anatomy Cont’dMedullary Canal
• center of diaphysis• hollow → decreases
weight• contains marrow, passage for nutrient arteries
Endosteum• lines medullary canal
Bone Anatomy Cont’dPeriosteum
• thin, fibrous membrane• covers all bone except
articular surfaces• contains nerves & blood
vessels• attachment point for tendons & ligaments
Bone Structure Overview
Periosteum = Superficial layer Compact bone = Middle Cancellous bone = Deep
Bone StructureCompact / Cortical Bone: hard / dense weight bearing
Osteon : - structural unit of compact
bone - “weight bearing pillars”Lamella :
- layered, hollow tubes - collagen of each layered tube
runs in opposite directions
Central Canal : - runs vertically through center - contain nerves & blood vessels
Perforating Canal : - runs horizontally
- connects blood & nerve supply
periosteum → central canal of osteon
Bone Structure cont’dCancellous/ Trabecular Bone:
“little beams”
no osteons present
Lamella = hollow tubes
irregularly arranged
surrounded by endosteum
filled w/ marrow
bone weight
shock absorption
found at articular ends of bones
Bone Development
formation of long bones formed from cartilageSteps:
- Development of primary ossification center
- bone collar formation
- calcification
- cancellous bone formation
- formation of medullary cavity
- development of secondary ossification center
Endochondral ossification
Intramembranous ossification
formed from mesenchyme tissue occurs during formation of the
flat bones of the skullSteps: Development of ossification center → formation of bone matrix→ formation of trabeculae & periosteum→ formation of bone collar & red marrow
Endochondral Ossification
Joint TypesFibrous : thin layer of fibrous periosteum between 2 bones, no cavity
1. Synarthrosis : ( suture jt.) ; no motion ; Ex. Skull
2. Syndesmosis: (ligamentous jt.); minimal motion- depends on length of
connecting fibers; Ex. distal tibiofibular jt. distal radioulnar jt.
3. Gomphosis: (peg-in-socket); no motion; Ex. Tooth in socket of mandible/maxilla
Cartilaginous (Amphiarthrosis): bones united by cartilage, limited motion (bending ,twisting, compression)
1. Synchondrosis: hyaline cartilage; Ex. ephipyseal plate (children), 1st sternocostal jt.
2. Symphysis : fibrocartilage ; shock absorber; Ex. intervertebral discs, pubic symphysis
Joint Types cont’d
Synovial (Diarthrosis) :
fluid filled jt. cavity
free motion w/ decreased stability
Stability determined by :
1.) Shape of articular surface
2.) Number/position of ligaments
3.) Muscles & tendons crossing
the jt.
{Lippert p. 19}
Synovial JointsPlane: gliding motion Example : * inter tarsal * intercarpal
Synovial Joints Pivot : rotation
Example: * proximal radioulnar jt. * atlantoaxial jt.
Synovial JointsHinge : flexion/extension
Example: * elbow
* knee
Synovial JointsCondyloid :
flexion/extensionabduction/adduction
Example: * wrist * metacarpalphalangeal jt.( MP)
Synovial JointsSaddle :
flexion/extension abduction/ adduction rotation (accessory)
Example: * carpometacarpal jt. (thumb)
Synovial JointsBall & Socket: flexion/ extension abduction/ adduction rotation
Example: * hip * glenohumeral jt. (GH)
Synovial Jt. StructureLigaments :
bone approximation prevent excessive motion; stability attachment for cartilage, fascia, &
muscle
Capsule : surrounds joint protects articular surfaces 2 layers : -- Outer = fibrous; reinforced by capsular ligaments -- Inner = synovial membrane sensory nerve ending =
proprioception rich supply of blood vessels =
nutrition
Synovial Jt. Structure cont’d
Joint Cavity: “free space”
Synovial Jt. Structure cont’dHyaline Cartilage (articular) :
provides smooth articulating surface
no blood or nerve supply → unable to repair itself if damaged
Fibrocartilage : shock absorption in weight bearing
joints *knee – menisci : improve stability
vs. shock absorption
*intervertebral discs : shock absorption
*sternoclavicular jt. : shock absorption betwn. clavicle & sternum
Synovial Jt. Structure cont’dSynovial Membrane :
inner layer thick & vascular secretes synovial fluid
Synovial Fluid: found in jt. cavity & w/in articular cartilage primarily from filtration of blood through
capillaries of synovial membrane clear, viscous consistency due to
hyaluronic acid content becomes less viscous w/ ↑ jt. motion / temp.
reduces friction shock absorption
Nutrition: ** weight bearing → jt. compression →
forcing synovial fluid out of cartilage → compression removed → synovial fluid seeps back into cartilage
( Weeping Lubrication)
Synovial Jt. Degeneration
Synovial Joint Degeneration