The Skeletal System: Articulations Unit 02 The Skeletal System: Articulations Frederic Martini Michael Timmons Robert Tallitsch

Introduction Joints, or articulations, are connections between bones that may or may not permit movement. Cartilage, fluid, or dense connective tissues is usually involved in holding joints together. Joints are classified functionally by the amount of movement they allow. Immoveable or slightly moveable joints tend to be in the axial skeleton. Freely moveable joints are more common in the appendicular skeleton.

Synarthroses (Immovable Joints) Sutures are joints found only in the skull. Bony edges interlock and short dense connective tissue fiber hold the bones together. A gomphosis is the joint between a tooth and the alveolar fossa of the maxillae or mandible. Periodontal ligaments hold the tooth to the bone in the gomphosis. A synchondrosis is a joint in which hyaline cartilage separates the ends of the bones involved in the joint. A synostosis occurs if bones fuse together to form one bone.

Amphiarthroses (Slightly Movable Joints) A syndesmosis occurs when to bones are connected by relatively long connective tissue ligaments. Connecting bones using a fibrocartilage pad forms a symphysis. 

Diarthroses (Freely Movable Joints) Synovial joints are typically found at the ends of long bones in the upper and lower limbs. All synovial joints have six basic characteristics: A joint capsule Articular cartilages A joint cavity filled with synovial fluid A synovial membrane lining the joint capsule Accessory structures Sensory nerves and blood vessels

Synovial Joints Structure of a Synovial Joint

Synovial fluid has three functions: Lubricates the surfaces of the articular cartilages on the ends of the bones. Nourishes the chondrocytes by entering and exiting the articular cartilages due to the forces acting on the joint. Acts as a shock absorber.

Types of Movements Angular movements Rotation

Movements at the ankle include: Special Movements Movements at the ankle include: Eversion/inversion Dorsiflexion/plantar flexion Movement of the vertebral column includes: Lateral flexion Movement of the pollex (thumb): Opposition/reposition

Movements that occur at many joints include: Special Movements Movements that occur at many joints include: Protraction: anterior movement in the horizontal plane Retraction: posterior movement in the horizontal plane Elevation: cranial movement in the vertical axis Depression: caudal movement in the vertical axis

Structural Classification of Synovial Joints Plane joints:   Nonaxial or multiaxial Hinge joints: flexion and extension Pivot joints: rotational movements

Structural Classification of Synovial Joints Condylar joints: flexion/extension and abduction/adduction Saddle joints: biaxial joints that also allow circumduction Ball and socket joints: triaxial joints

The Temporomandibular Joint The Temporomandibular Joint (TMJ)

Intervertebral Articulations Anterior Vertebral Column Lateral Vertebral Column

There are four possible movements of the vertebral column: Vertebral Movements There are four possible movements of the vertebral column: Anterior flexion, or bending forward Extension, or bending backward Lateral flexion, or bending to the side Rotation–twisting

The Sternoclavicular Joint

The Shoulder Joint The Anterior Shoulder The Lateral Shoulder

The Shoulder Joint Sectional Shoulder Superior Shoulder

The Elbow Joint Medial Elbow Longitudinal Elbow

The Wrist Wrist Joints Wrist Ligaments

The Joints of the Hand Joints of the Hand

The Hip Joint Lateral Hip Posterior Hip

The Hip Joint Anterior Hip Sectional Hip

The Knee Anterior Knee Parasagittal Knee

The Knee Posterior Superficial Posterior Deep

The Knee Anterior Knee

The Ankle and Foot Ankle and Foot Ankle and Foot MRI