The Skeletal System

The Skeletal System Articulations (Joints)

Articulations • Joints between bones • Classified according to degree of movement • 3 types • Synarthrotic – immovable • Amphiarthrotic – slightly movable • Diarthrotic – highly movable

1. Synarthrotic • Immovable • Suture

2. Amphiarthrotic • Slightly movable pubic symphysis intervertebral joint

3. Diarthrotic • Highly movable • Most common of all 3 joints • Ankle • Wrist • Finger • Shoulder • Hip

Characteristics ofDiarthrotic joints • All have same 3 characteristics

1. Articular cartilages Prevents opposing bones from making direct contact

2. Joint (articular) capsule • Dense CT connecting opposing bones • Encloses entire joint

3. Synovial membrane • Lines inside of joint capsule • Comprised of a few layers of cells • Produce synovial fluid • Provides lubrication • Nourishes CT • Shock absorber • Fills entire joint • Held in by capsule • Increase in volume when joint is injured

Synovial joint and fluid fluid

Joint Movements • Synovial joints have to be able to bend in equal and opposite ways

1. Abduction vs Adduction Abduction – movement away from center axis in frontal plane Adduction – movement back to center axis

2. Flexion vs Extension Flexion -- bending a joint Extension – straightening a joint Hyperextension – Continued extension beyond anatomical position

3. Rotation (head)

3. Rotation (limbs) Medial rotation – anterior surface facing medially Lateral rotation – back to anatomical position

4. Inversion vs Eversion (ankle) lateral medial turns sole outward turns sole inward

Dorsiflexion vs Plantar flexion (ankle) • Dosiflexion – toes pointing up • Plantar flexion – toes pointing down

6. Pronation vs Supination (wrist) Pronation – palm facing posterior Supination – palm facing anterior • Pronation – palms facing posterior • Supination – palms facing anterior

7. Elevation vs Depression • Elevation – shoulder shrug • Depression – return to anatomical position

The Skeletal System