Anatomy: Intro to Joints

Three types of skeletal joints:

fibrous, cartilaginous, synovial

The structural classification of joints:

Describe how bones connect to each other

The functional classification of joints:

Degree of movement between joints

Fibrous joints (synarthoroses) are united by:

Fibrous tissue that is rich in collagen, has little or no movement

Cartilaginous joints (amphiarthroses) are united by:

Hyaline or fibrocartilage with some movement

Two types of amphiarthroses joints:

Primary cartilaginous (synchrondroses) and secondary cartilaginous (symphyses)

What is primary cartilaginous joints joined by and their purpose?

Joined by hyaline cartilage; there is a slight bending in early life and is usually temporary unions as seen in development of bones

What is secondary cartilaginous joints joined by and their purpose?

Joined by fibrocartilage; they are strong and slightly moveable and act for strength, flexibility, and shock absorption

4 Characteristics of Synovial Joints (diarthroses)

1. Joint cavity

2. Synovial membrane and fluid

3. Articular cartilage

4. Fibrous capsule

Most common joint category:

Synovial Joints

Plane or gliding joints:

one bone glides over the other, uniaxial, usually small (ex: acromioclavicular joint)

Ball and socket joint:

ball of one joint fits into socket of the other bone, multiaxial joint (ex: hip and shoulder joint)

Hinge joint:

like a hinge on a door, uniaxial joint, sagittal around an axis that runs transversely (ex: interphalangeal joints)

Pivot joint:

allows rotation around an axis, uniaxial (ex: atlantoaxial joint)

Condyloid joint:

ovoid surface, condyle into elliptical cavity, biaxial (ex: radiocarpal joint)

Saddle joint:

similar to condyloid but no axial rotation, biaxial, concave/convex (ex: carpometacarpal joint)

In the fibrous capsule, strength is provided by ligaments, what are intrinsic ligaments of the wrist?

Seen between carpal bones alone

In the fibrous capsule, strength is provided by ligaments, what are extrinsic ligaments of the wrist?

Seen between carpals and metacarpals

In the fibrous capsule, strength is provided by ligaments, what are intra-articular ligaments?

Housed within but separate from the joint capsule (ex: cruciate ligaments of the knee)

In the fibrous capsule, strength is provided by ligaments, what are extra-articular ligaments?

Separate from and outside the joint capsule (ex: collateral ligaments of the knee)

Three types of cartilage:

hyaline, elastic, fibrocartilage

Hyaline cartilage:

Found lining articular surfaces, and in the nasal septum, tracheal rings, costal cartilages, and the epiphyseal cartilage of growing bone; most widespread

Fibrocartilage:

Found in intervertebral discs, the pubic symphysis, in menisci of joints, and often occurs where tendon and ligament are joined to bones

Elastic:

Found in the ear and epiglottis, where it provides a rigid but elastic, framework, usually springy and yellow

Main cell type of cartilage:

Ground substance of cartilage:

Fibrous sheath of cartilage:

Chondrocytes

Chondroitin sulfate

Perichondrium

How do the joints receive a blood supply?

Through articular arteries that arise from vessels around the joint, arteries are often anastomose to form networks to ensure a blood supply in any position assumed by the joint

What are articular nerves?

The nerve supply to the joints, which arise from branches of cutaneous nerves supplying overlying skin; HOWEVER most articular nerves are branches of nerves that supply the muscles that cross and therefore move the joint

What is Hilton's law?

Nerves supplying a joint also supply the muscles moving the joint and the skin covering their attachments