Cartilage and Bone

Question 1

What is cartilage and bone?

Answer 1

Skeletal connective tissues

Question 2

What are the functions of bone?

Answer 2

• Structural support
• Protection
• Locomotion
• Mineral reservoir
• Blood cell production

Question 3

What are the functions of cartilage?

Answer 3

• Locomotion - smooth surface at bone ends
• Structural support
• Template for new bone formation

Question 4

What are the 2 different types of bone?

Answer 4

• Flat bone

- Long bones

Question 5

What is periosteum in bone?

Answer 5

Connective tissue surrounding outer surface

Question 6

What is cortical bone?

Answer 6

Dense outer layer

Question 7

What is cancellous/trabecular/spongy bone?

Answer 7

Inner layer of interconnected trabeculae

Question 8

What is red/yellow bone marrow?

Answer 8

Haematopoiesis and energy storage

Question 9

What is endosteum in bone?

Answer 9

Inner membrane, separates bone from marrow

Question 10

What is haematopoiesis?

Answer 10

The growth and maturation of the blood cells and other formed blood elements in the bone marrow

Question 11

What are osteoblasts?

Answer 11

Synthesise and secrete bone tissue

Question 12

What are osteocytes?

Answer 12

Maintain mineralised bone tissue

Question 13

What are osteoclasts?

Answer 13

Resorbs bone

Question 14

What is an osteogenic/osteoprogenitor cell?

Answer 14

• Bone cell precursor

- Gives rise to osteoblasts

Question 15

What is the process of mineralisation of bone (deposition of hydroxyapatite)?

Answer 15

• Osteoblasts secrete collagen and matrix vesicles
• Matrix vesicles direct the deposition of hydroxyapatite crystals
• Hydroxyapatite crystals continue to be deposited and coalesce leading to confluent mineralisation

Question 16

What structural units is cortical bone composed of?

Answer 16

Osteon

Question 17

What is an osteon composed of?

Answer 17

Layers of lamellae

Question 18

What does the central canal of an osteon contain?

Answer 18

Nerves, capillaries and lymphatics

Question 19

What is the process of osteon development?

Answer 19

1. Osteoclasts resorb a wide channel
2. Nerves, capillaries and lymphatics grow into the canal
3. Osteoblasts line the channel and lay down osteoid
4. As osteoid is mineralised, osteoblasts get trapped as osteocytes in lacunae (tiny spaces)
5. Concentric lamellae (circular layers of bone)
6. Interstitial lamellae
7. Circumferential lamellae (around the outside of bone)

Question 20

What are the 2 layers of periosteum?

Answer 20

1. Outer layer of dense, irregular fibrous tissue
   * contains blood, lymph and nerves
2. Inner cellular layer adjacent to bone surface
   * osteogenic cells
   * osteoblasts

Question 21

What is the function of periosteum?

Answer 21

• Site of bone synthesis

- Give rise to circumferential lamellae

Question 22

What is the structure of trabecular bone?

Answer 22

• Contains lamellar bone - osteocytes housed in lacunae
• Lattice-like network of rods called trabeculae
• Orientated to provide maximum strength for minimum mass
• Spaces between trabeculae occupied by red and yellow marrow
• Lined externally by endosteum

Question 23

What does bone remodelling occur in response to?

Answer 23

Growth and changing mechanical stresses upon the skeleton

Question 24

What external factors is bone remodelling influenced by?

Answer 24

• Hormonal: calcium homeostasis
• Neuronal
• Immunological

Question 25

What are the 3 types of cartilage?

Answer 25

- Hyaline cartilage - Fibrocartilage - Elastic cartilage

Question 26

What can cartilage be described as and what does it provide to the body?

Answer 26

- It is an avascular flexible connective tissue | - Provides strength and cushioning

Question 27

What is a chondroblast?

Answer 27

- Cells that synthesise and secrete ECM of cartilage | - Can divide to form small clusters of mature chondrocytes

Question 28

Where are chondroblasts found?

Answer 28

Become trapped in lacunae, within cartilaginous chondrocytes

Question 29

What are chondrocytes?

Answer 29

- Mature cartilage cells | - Maintain the integrity of cartilage

Question 30

As there are no blood vessels in cartilage, how do cells receive their nutrients?

Answer 30

- By diffusion of metabolites through the cartilaginous matrix

Question 31

Where is hyaline cartilage found?

Answer 31

- Nasal septum, larynx, tracheal rings and most articular surfaces

Question 32

What is the ground substance like in hyaline cartilage?

Answer 32

- Gel-like | - Provides a smooth, firm and slightly flexible surface as it contains some fibre

Question 33

What are the properties of perichondrium and what can this lead to?

Answer 33

- No capacity to repair following damage | - Wear and tear can eventually lead to arthritis

Question 34

Which type of hyaline cartilage does not contain any perichondrium?

Answer 34

Articular cartilage

Question 35

Where is fibrocartilage found?

Answer 35

- In vertebral discs and as a component of joint capsule

Question 36

What property does abundant collagen fibres provide?

Answer 36

Strength

Question 37

Where is elastic cartilage found?

Answer 37

- External ear, epiglottis and larynx

Question 38

What does abundant elastic fibres in elastic cartilage provide?

Answer 38

Flexibility

Question 39

What are elastic fibres synthesised by?

Answer 39

Chondrocytes

Question 40

In what 2 ways can a fracture of bone and cartilage occur?

Answer 40

- Due to trauma | - Due to pathologically weakened bone

Question 41

What is Osteomalacia?

Answer 41

- Failure of osteoid to mineralise adequately | - Bones become weakened and are prone to fracture

Question 42

What is Osteomalacia associated with?

Answer 42

- Lack of calcium and/or phosphate - Lack of vitamin D - Associated with dental abnormalities * Adults: weak jaw --> loss of teeth * Children: Severe forms of enamel disruption

Question 43

What is osteoarthritis?

Answer 43

- Degenerative disease of synovial joints - Cartilage eroded sue to wear and tear - Bone ends in direct contract

Question 44

What is rheumatoid arthritis?

Answer 44

- Destructive auto-immune disease of synovial joints - Immune cell infiltration - Cartilage destroyed and replaced by fibrous tissue - Immune mediated uncoupling of bone remodelling - Increased osteoclastogenesis (bone resorption)

Question 45

What is periodontitis?

Answer 45

- Destructive inflammatory disease - Chronic immune response to oral bacteria leads to destruction of host tissues - Immune mediated uncoupling of bone remodelling - Increased osteoclastogenesis (bone resorption) - Destruction of alveolar bone and subsequent tooth loss