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 llength > width Short mmore equal dimensions u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’d Medullary Canal center of diaphysis hollow → decreases weight contains marrow, passage for nutrient arteries Endosteum lines medullary canal

Bone Anatomy Cont’d Periosteum 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 Structure Compact / Cortical Bone: hhard / dense w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’d Cancellous/ 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 cartilage  Steps: - 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 skull Steps: Development of ossification center → formation of bone matrix → formation of trabeculae & periosteum → formation of bone collar & red marrow

Endochondral Ossification

Joint Types Fibrous : 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), 1 st 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 Joints Plane : gliding motion Example : * inter tarsal * intercarpal

Synovial Joints Pivot : rotation Example: * proximal radioulnar jt. * atlantoaxial jt.

Synovial Joints Hinge : flexion/extension Example: * elbow * knee

Synovial Joints Condyloid : flexion/extension abduction/adduction Example: * wrist * metacarpalphalangeal jt.( MP )

Synovial Joints Saddle : flexion/extension abduction/ adduction rotation (accessory) Example: * carpometacarpal jt. (thumb)

Synovial Joints Ball & Socket: flexion/ extension abduction/ adduction rotation Example: * hip * glenohumeral jt. (GH)

Synovial Jt. Structure Ligaments :  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’d Hyaline 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’d Synovial 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