Bone

Question 1

What is hyaline cartilage and where do you find it?

Answer 1

Most common type of cartilage, find in ribs, trachea, joints
ECM consists of collagen TYPE 2, aggrecans, hyalyronic acid and chondronectin
- is incompressible

Question 2

What is elastic cartilage and where do you find it?

Answer 2

Hyaline cartilage with the addition of elastin

• present in ears, ear canals, epiglottis and larynx
• very flexible, maintains shape

Question 3

What is fibrocartilage and where do you find it?

Answer 3

Binds solid joints, forms meniscus and IV discs - to minimise movement at joints

• is a mixture of dense connective tissues and isolated islands of cartilage with NO perichondrium
• made of TYPE 1 collagen

Question 4

What is the basic structure of bone?

Answer 4

Bone is hollow with a “dense wall” of compact bone surrounding a “spongy interior of cancellous/trabecular bone

Question 5

What is the composition of compact bone?

Answer 5

Is on the outside of bone and forms the shaft of long bones

Formed by a repeating module (Haversian systems)

Question 6

What is the composition of trabecular bone?

Answer 6

Open structure that braces joints

- the spaces are continuous and full of marrow and blood vessels

Question 7

What is the medullary cavity?

Answer 7

Contains marrow, yellow or red

• yellow is mainly fat cells and is a major fat storage organ
• red is mainly haemopoietic cells - making blood cells
• red early in life, replaced by yellow

Question 8

What are sharpey’s fibres?

Answer 8

At tendon/ligament connections, collagen fibres penetrate the bone surface

Question 9

What is articular cartilage?

Answer 9

Hyaline cartilage which forms joint surface –> slippery, smooth and resistant to compression
is AVASCULAR

Question 10

What is special about the synovial membrane?

Answer 10

It is NOT an epithelium as it lacks a basement membrane - very leaky
- synovial fluid is an ultrafiltrate of synovial blood vessels plus proteoglycans

Question 11

What are osteoprogenitor cells?

Answer 11

In the periosteum and endosteum, flattened cells that are usually resting/quiescent but can give rise to new osteoblasts to grow or repair bone
- renewed from stem cells in bone marrow

Question 12

What are osteoblasts?

Answer 12

Work on bone surface to make bone –> add another layer, stay on the outside all the time

• makes osteoid (organic ECM of bone)
• inactive osteoblasts are flattened cells like osteoprogenitor cells

Question 13

What are osteocytes?

Answer 13

Surrounded by bone, maintain bone in response to loading

• loss of osteocytes leads to bone resorption
• capable of destroying local bone to free calcium

Question 14

What are osteoclasts?

Answer 14

Destroy bone in growth, repair and normal turnover

- giant multinuclear cells, seal itself to bone around the edge and secretes H+, Cl- and proteases

Question 15

What are the two types of bone formation?

Answer 15

Intermembranous bone formation and endochondral bone formation

Question 16

Describe intramembranous bone formation

Answer 16

Membrane bone forms directly from mesenchyme

- eg the skull, flat bones of the face, the mandible and clavicles

Question 17

Describe endochondral bone formation

Answer 17

A cartilage model of the bone is produced and the cartilage is replaced by bone

• build the shaft first (diaphysis) and then ossification centres in the epiphysis
• zones of ossification grow together but leave a thin zone of cartilage –> the growth plate, which enables long bones to grow and is present until about 21-22 years before it fuses

Question 18

What are the layers of the growth plate?

Answer 18

Distally to proximally

• Resting zone - normal hyaline cartilage
• Proliferation zone - dividing chondrocytes
• Maturation zone - mature chondrocytes
• Hypertrophic zone - dying (hypertrophic) chondrocytes
• Finally the degenerating cartilage is destroyed and bone laid down on its surface

Question 19

What is woven bone?

Answer 19

New bone that is made during development or repair - more cellular, more collagen with no Haversian systems –> weaker

Question 20

What are the constituents of osteoid?

Answer 20

• organic, unmineralised bone matrix
• collagen type 1
• proteoglycans, osteocalcin, osteonectin

Question 21

Describe the process of osteoclastogenesis

Answer 21

• cellular dependent with osteoblasts
• osteoclasts have RANK-R, stimulation via RANK-L (from osteoblasts) stimulates the osteoclastic precursor to begin differentiating and drives the differentiation and multinucleation to form the giant mature osteoclast