Structures Of A Synovial Joint

Question 1

Synovial fluid

Answer 1

3 Primary functions:
 - Lubrication
 - Nutrient distribution 
 - Shock absorption
Found in synovial cavity, which is space enclosed by the articular capsule. It’s nutritional abilities are vital for healthy cartilage, which has a very poor blood supple so relies on diffusion form the synovial fluid.

Question 2

Articular Capsule

Answer 2

Fibrous capsule which is continuous with the periosteum of the articulating bones. Has 2 Layers:

• Outer fibrous layer: made up of white fibrous tissue, called the capsular ligament. This holds together articulating bones and supports the synovium
• Inner synovial layer (synovium) - A highly vascularised layer of connective tissue. It absorbs and secretes synovial fluid and is responsible for the mediation of nutrient exchange bw blood and joint.

Question 3

Articular cartilage

Answer 3

The bones of a synovial joint are covered by a thin layer of hyaline cartilage which serves to line the epiphysis (end) of the bone.
The smooth surface it provides has 2 functions: It minimizes friction upon joint movement and. Absorbs shock

Question 4

Accessory ligaments

Answer 4

Separate ligaments part of the joint capsule. Made up of bundles of dense regular connective tissue, which are adaptive to resisting strain. This prevents any extreme movements that may damage the joint.

Question 5

Bursae

Answer 5

Small sac lined by synovial membrane and filled with synovial fluid. They are placed at key points of friction in a joint, providing the joint with free movement.

They can become inflamed following infection or irritation by over use of the joint (bursitis)
Eg of friction points is where tendons run over the joint.

Question 6

Innervation

Answer 6

Joints have a rich nerve supply provided by articular nerves.

Hilton’s law: the nerves supplying the joint also supply the muscles moving the joint and the skin covering their distal attachments.

The nerves of a joint transmit impulses which play a key role in proprioception

Question 7

Vasculature

Answer 7

Joints receive blood via articular arteries which arise from the vessels around the joint. The articular arteries are located within the joint capsule, mostly in the synovial membrane

A feature of the articular arterial supply is frequent anastomoses (communications) in order to ensure a blood supply to and across the joint regardless of position. This usually means arteries are above and below a joint, curving around each side and joining via small connecting vessels.

Articular veins accompany the articular arteries and are also found in the synovial membrane.

Question 8

Osteoarthritis

Answer 8

Most common form of joint inflammation. Stems from heavy use of articular joints over time which can result in wearing away of articular cartilage and often erosion of the underlying articular surfaces of the bones.
The changes which occur are irreversible and degenerative. Decreasing effectiveness of articular cartilage as a shock absorber and lubricated surface, as well as the roughened edges causing further damage.
Repeated friction can cause symptoms of joint pain, stiffness and discomfort. Most frequent in joints that support full body weigh such as hips and knees.
Arthritis can also be caused by infection, auto inflammatory causes (rheumatoid arthritis) and infection but not of the joint itself (reactive arthritis)