Articulations

Objectives:

1. Distinguish between different types of joints and link anatomical design to joint function.
2. Describe the dynamic movements of the skeleton.
3. Describe the articulations between the vertebrae of the vertebral column.
4. Describe the structure and function of the joints of the upper extremity.
5. Describe the structure and function of the joints of the lower extremity.

Joints

1. Fixed Unions - Synarthrosis - Absence of movement - no joint cavity.
1. Fibrous CT - fibrous joint, sutures, gomphosis
2. Cartilage CT - Cartilaginous joint, synchondrosis
3. Bony fusion - synotosis, metopic suture of the frontal bone
2. Flexible unions -
1. Amphiarthrosis - some flexibility, Syndesmosis, symphysis
2. Diarthrosis - freely moveable joints, synovial joints

Joint types

1. Fibrous joints - bones are united by fibrous tissue.
1. Sutures - in skull
2. Fontanelles - among sutures
3. Syndesmosis - Fibrous sheet of tissue, Interosseous membrane
2. Cartilaginous joints
1. Primary cartilaginous joints - Synchondroses, hyaline cartilage to bone , cartilage persists, ribs to sternum
2. Secondary synchondroses - Symphysis, covered by hyaline cartilage and united by fibrous tissue
• Symphysis pubis
• Intervertebral discs
• Manubriosternal joint
3. Synovial Joints
1. Joint cavity of dense connective tissue on outside connected to periosteum
2. Synovial membrane lines cavity
3. Synovial membrane secretes synovial fluid
4. Hyaline cartilage tips the bones adjacent to the joint (no perichondrium)

Joint from Cartilagenous Template

Synovial Joint

Hyaline cartilage of endochondrial bone formation template condenses into articulate disk of mesenchyme or the primitive joint plate, the synovial joit cavity develops around this and is stabilized by ligaments and the muscles/tendons.

Shoulder Articulation

Muscle and Joint

.

.
synovial membrane
.
ligament
.
hyaline cartilage
.
.

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joint cavity filled with synovial fluid which serves to both protects and nourishes the cartilageacts as lubricant

Terminology

Strain is an overstretched ligament
Bursa - protective sac between structures out pouching of synovial membrane - relieves the pressure
Bursitis - inflammation of the bursa

Types of Synovial joints

1. Uniaxial - hinge joint
2. Pivot joint - rotates about a long axis -
1. Radius to humerus
2. Axis to atlas
3. Saddle joint - two axis
1. Trapezium to metacarpal of thumb
4. Gliding joint - two axis
1. Clavicle to manubrium
5. Ellipsoidal joint - two axis
1. Radius to scaphoid
6. Ball and socket - three axis
1. Humerus to scapula
2. Femur to os coxa

Kinds of movement

Joint Movements

1. Flexion
2. Extension
3. Adduction
4. Abduction
5. Rotation
6. Circumduction
7. Supination/Pronation
8. Inversion/Eversion

Arthritis

1. Gouty arthritis - due to excess uric acid accumulation and crystallization in the synovial cavity.
2. Osteoarthritis - degenerative joint disease resulting from cumulative wear and tear on joint surfaces, often with genetic predisposition. 25% of women and 15 % of men over 60 are affected.
3. Rheumatoid arthritis - inflammatory arthritis affecting 2.5 % of adults. Cause uncertain, believed to be associated with auto-immune response, swelling and inflammation of the synovial membrane.

When articular cartilage has been damaged, the matrix begins to break down, and the exposed cartilage changes from a slick, smooth gliding surface to a rough feltwork of bristly collagen fibers. This increases friction, leading to further damage, exposure of underlying bone, and the union of bone by collagen fibers, later converted to bone, ankylosis.