Joints

Chapter 8, Section 1

The science of joints is called arthrology.

Joints, also called articulations, are functional junctions between two bones

Functions of joints1. Bind skeleton together2. Enable body movements3. Makes growth possible4. Permit changes in skeleton for childbirth

Classification of Joints

Classifications based on amount of movement1. Synarthrotic = immovable

2. Amphiarthrotic = slightly moveable

3. Diarthrotic = fully movable

Classifications by types of tissue:1. Fibrous joint = dense connective tissue

2. Cartilaginous joint = bones connected by cartilage

3. Synovial joint = contains a synovial membrane

Fibrous Joints

There are three (3) types of fibrous joints:• Syndesmosis• Suture• Gomphosis

1. Syndesmosis:Bones are connected by a sheet or bundle of fibrous tissue.

Examples include the interosseous membrane and interosseous ligaments between the tibia and fibula.

Interosseous membrane between tibia and fibula is a syndesmosis joint.

2. Suture:• Thin layer of dense

connective tissue

• Connects flat bones of the skull (sutural ligaments)

• Synarthrotic

Fibrous Joints

3. Gomphosis:• Cone-shaped bony process

in a bony socket

• Example includes a tooth anchored into a bony socket

Cartilaginous Joints

• There are two (2) types of cartilaginous joints:• Synchondrosis• Symphysis

1. Synchondrosis• Bones are united by a band of

hyaline cartilage.

• Located between manubrium of sternum & 1st rib

• Also located at epiphyseal plates of developing bone

• Movement is synarthrotic

2. Symphysis• A pad of fibrocartilage

between two bones

• Examples include the pubic symphysis and intervertebral discs

• Movement is amphiarthrotic.

Cartilaginous Joints

General Structure of Synovial Joints

Synovial Joints are Freely movable (Diarthrotic)

Structures include:• Articular cartilage

• Synovial membrane – secretes synovial fluid

• Joint cavity – filled with synovial fluid

• Joint capsule – dense connective tissue that stabilizes and protects joint

Figure 8.7 The generalized structure of a synovial joint.

General Structure of Synovial Joints

Structures include:• Ligaments – bundles of

collagenous fibers that reinforce the joint capsule

• Menisci (sing. Meniscus) – pad of fibrocartilage that separates some joints.

• Bursa – sac filled with synovial fluid. • Bursitis = inflammation

of bursa

Figure 8.8 Menisci separate the articulating surfaces of the femur and tibia. Several bursae are associated with the knee joint.

Types of Synovial Joints

1. Ball-and-socket • rounded head + cup-shaped socket.• Movement in all planes (multi-axial).• Allows for rotation• Includes hip joint and shoulder joint.

2. Condylar joint• Oval condyle + elliptical socket• Movements in most planes (bi-axial)• No rotational movement• Joints between metacarpals and

phalanges/

3. Plane (Gliding) Joint• Flattened bones slide across each

other• Includes carpals and tarsals• ribs 2-7 articulate with sternum

Types of Synovial Joints

4. Hinge joint• Increases or decreases angel

between bones• Includes elbow joint• Joints between phalanges

5. Pivot Joint• Rotation around a central axis

(uni-axial)• Joint between radius and ulna• Joint between atlas (C1) and

axis (C2).

Types of Synovial Joints

6. Saddle Joint• 2 concave bones positioned at

right angles• Includes metacarpal and carpal

of thumb

End of Chapter 8, Section 1