The Skeletal System II

Besides bone, what else do we have in the skeletal system?

Connective tissue, such as neural tissue, and often complex structures such as synovial joints.

What are the different classifications of joint?

Structural and functional.

What is the functional classification of joints based on?

Mobility.

What are the different joint types in the functional classification?

• Diarthrosis.

• Amphiathrosis.

• Synarthrosis.

What are diarthrosis joints?

Freely moveable joints, such as the elbow joint.

What are amphiarthrosis joints?

Slightly moveable joints, such as the joints between vertebral bodies.

What are synarthrosis joints?

Non-moveable joints, such as the suture joints of the skull.

What are the different structural classifications of joints?

• Synovial.

• Cartilaginous.

• Fibrous.

What are synovial joints?

These include the elbow joint.

What are cartilaginous joints?

These include joints between vertebral bodies.

What are fibrous joints?

These include the suture joints of the skull.

What are two examples of cartilagibous joints?

• Synchondrosis.

• Symphysis.

What is synchondrosis?

• Made of hyaline cartilage.

• Permanent.

• Temporary,

• Usually slightly mobile.

What is symphysis?

• Made of fibrocartilage.

• Permanent.

• Usually slightly mobile

What are two examples of fibrous joints?

Syndemoses.

Sutures.

What are syndemoseses?

• They support some long bones.

• Are very strong.

• Usually slightly mobile.

What are sutures?

• Very tight.

• Very strong.

• Virtually immobile.

What are the key features of synovial joints?

• Joint cavity contains synovial fluid.

• Nerve and blood supply.

• Articular hylaine cartilage

• Two layer capsule:

  • Inner: synovial membrane.

  • Outer: fibrous later. Tough connective tissue

What are additonal key features of synovial fluid?

• Produced by synovial membrane - viscous, straw colour.

• Friction reduction - lubricin acts as a lubricant, and hyaluronic acid acts as a gelling agent.

• Non-newtonian.

• Cells - chondrocytes/osteoblasts/fibroblasts/macrophages/neutrophils.

What are the six types of synovial joint?

• Ball and socket.

• Hinge.

• Saddle.

• Pivot.

• Gliding/plane.

• Condyloid.

What are the accesory structures to synovial joints?

• Bursae.

• Fat pads.

• Ligaments and tendons.

• Menisci.

What is bursae?

Fibrous sacs of synovial fluid, usually outisde joint capsule.

What is the role of bursae?

They reduce friction between tendons, bones & joints.

What are fat pads?

They are highly innervated and protective (contain adipose tissue).

What are ligaments?

They are made of dense regular connective tissue. They are essential support for capsules and joints.

What are menisci?

They are made of fibrocartilage, and act as shock absorbers. They improve the congruence of fit.

What are tendon sheaths?

They are like bursae: they act to reduce friction and wear of tissues surrounding the tendon.

What are the different features of bone ageing?

• Altered bone remodelling.

• Loss of bone mass.

• Changes in bone microarchitecture.

• Changes in bone fibres.

• Delayed fracture healing.

• Increased marrow fat.

What is altered bone remodelling?

• Decline in estrogen (especially post-menopause) and testosterone.

• Imbalance between osteoblast (bone-forming) and osteoclast (bone reabsorbing) activity.

What is loss of bone mass (osteopenia/osteoperois)?

• Reduced bone mineral density/reduced mechanical strength/increased risk of fractures.

What are changes in bone microarchitecture?

Thinning of trabeculae (spongy bone)/increased porosity of cortical bone.

What are changes in bone fibre?

Reduced collagen quality and elasticity.

What is delayed fracture healing?

Slower regeneration and repair processes.

What is increased marrow fat?

Replacement of hematopoetic tissue with adipose tissue.