Joints (Articulations)

Ligaments Connect bone to bone Composed of dense connective tissue that contains collagen and elastin fibers Cannot be regenerated naturally Some ligaments allow movement while others limit or prevent movements Some ligaments also function in stability and reinforcement. Ligaments gradually strain when under tension and return to their original position Some people have more elastic ligaments which results in hypermobility.

Joints (Articulations) Sites where 2 or more bones meet. 2 functions: Hold bones together securely Give the rigid skeleton mobility

Joints are classified in 2 ways: Functionally: amount of movement Structurally: how bones are articulated

Functional Synarthroses: immovable Amphiarthroses: slightly moveable Diarthroses: freely moveable

Synarthroses & Amphiarthroses joints are found in the axial skeleton and make up regions that function in protection Diarthroses joints are found in the limbs of the appendicular and make up regions that function in movement.

Structural Fibrous: immovable Cartilaginous: slightly moveable Synovial: freely moveable

Fibrous Fibrous tissue forms joints Short connecting fibers form sutures in the skull Long connecting fibers are called syndesmoses which allow for more give are found in the connection of the tibia to fibula. Gomphoses are immovable joints in the shape of a socket (teeth)

Cartilaginous Bones are connected by fibrocartilage Slightly moveable examples: Pubic symphysis of the pelvis Intervertebral disks of the spinal column Immovable (synchondroses) examples: Epiphyseal plates Joints between the first ribs and the sternum

Synovial Joint cavity containing synovial fluid All joints of the limbs All have 4 features: Articular hyaline cartilage at the ends of bones Articular capsule Joint cavity that contains synovial fluid Reinforcing ligaments

Synovial Cont. May have bursae & tendon sheaths Both are bags of lubricant that reduce friction Bursae: flattened sac of synovial fluid; common where ligaments, muscles, skin, tendons, or bones rub together. Tendon sheath: elongated bursae the wraps completely around a tendon

Types of Synovial Joints Shapes of articulating bone surfaces determine the movements that are allowed. Plane Hinge Pivot Condylar Saddle Ball & Socket

Plane Articular surfaces are flat Only short slipping or gliding movements are allowed There is no rotation around any axis Intercarpal joints of the wrist

Hinge Cylindrical end of one bone fits into a trough shaped surface of another Movement is allowed in one plane Elbow, knee, ankle, joints between phalanges of fingers

Pivot Rounded end of a bone fits into a sleeve or ring of a bone A rotating bone turns around its long axis. The bone rotates around another bone Radioulnar joint and between the atlas and axis of the vertebral column.

Condylar Knuckle like Egg shaped surface of one bone fits into an oval cavity of another Allow movement of bone from side to side and back and forth Bone cannot rotate Knuckle (between metacarpals and phalanges) joints

Saddle Each surface has concave and convex areas just like a saddle Same movements as condylar Joint between carpal and metacarpal of the thumb

Ball and Socket Spherical head of one bone fits into a round socket of another. Allows movement in all directions Most freely moving Shoulder and Hip