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