Cartilage & Bone

Question 1

what are the similarities of bone and cartilage?

Answer 1

both contain cells embedded in an ECM that they have produced

Question 2

what is the thin layer of dense irregular connective tissue covered on cartilage and bone?

Answer 2

cartilage: perichondrium
bone: periosteum

Question 3

stem cells

Answer 3

can create more stem cells + differentiate into specialized cell lineage

Question 4

potency

Answer 4

refers to the possible cell types that a given stem cell can generate

Question 5

what are some main differences between cartilage and bone? (in terms of hydration and mineralization)

Answer 5

cartilage: very hydrated and squishy not mineralized
bone: rigid and mineralized

Question 6

perichondrium

Answer 6

layer of connective tissue that surrounds cartilage

Question 7

periosteum

Answer 7

layer of connective tissue that surrounds bone

Question 8

progenitors

Answer 8

• in perichondrium/periosteum
• stem-like, proliferate
• lineage-restricted

Question 9

blast

Answer 9

• some proliferation
• start to differentiate
• lay down matrix

Question 10

cytes

Answer 10

• terminally differentiated
• trapped in matrix = lacunae

Question 11

function of synovial membrane

Answer 11

lubricated joints, reduces friction

Question 12

articular cartilage

Answer 12

• located at the ends of bones
• provide smooth cushioned surface to reduce friction

Question 13

what colour is the bone and cartilage with histochemical stain?

Answer 13

bone: red
collagen: blue

Question 14

blood vessels in bone vs cartilage

Answer 14

cartilage: avascular (no blood vessels)
bone: richly vascularized

Question 15

how does avascular cartilage affects its regeneration?

Answer 15

lower regenerative capacity due to the lack of blood vessels, hydration, and fewer stem cells

Question 16

hyaline cartilage

Answer 16

• most abundant type of cartilage; found in joints, nose, trachea, bronchii
• entirely organic ECM (not mineralized)
• mainly composed of: water, collagen, proteoglycan

Question 17

how does proteoglycan affect hydration and compression?

Answer 17

proteoglycans are negatively charged -> attract sodium and water -> increases diffusion index and keeps it hydrated and moderately compressible

Question 18

elastic vs hyaline cartilage

Answer 18

elastic: greater flexibility, more abundant and larger chondrocytes
hyaline: less matrix

Question 19

chondrocytes

Answer 19

mature cells found in cartilage for maintenance and repair

Question 20

osteocytes

Answer 20

mature bone cells located in lacunae that help maintain bone health and regulate its growth

Question 21

characteristics of fibrocartilage

Answer 21

• contains type I collagen
• not distinct perichondrium
• found in intervertebral disk
• high tensile strength
• little to no ability to regenerate

Question 22

annulus fibrosis

Answer 22

outer ring of fibrocartilage protects and confines nucleus pulposus

Question 23

nucleus pulposus

Answer 23

embryonic remnant of mesenchymal ‘notochord’; very few cells, high hyaluronic acid and water content; allow disc to compress and expand

Question 24

osteoarthritis

Answer 24

• defects in articular/hyaline cartilage within joints
• cartilage has little regenerative potential

Question 25

what happens when fibrocartilaginous repair occur initially in wounded articular cartilage of mobile synovial joints?

Answer 25

- mesenchymal stem cells can migrate from bone marrow into wounded articular/hyaline cartilage - within the wound stem cells differentiate into 'fibro' chondrocytes (more collagen I, less proteoglycan) - due to high mobility in joints, the fibrocartilage eventually worn away - then its replaced by bone on joint surfaces

Question 26

organic component = osteoid in ECM of bone

Answer 26

- low amount of ground substance, some proteoglycan and glycoprotein - high amount of type I collagen fiber - low amount of diffusion - deposited first by osteoblasts

Question 27

inorganic component = mineralized in ECM of bone

Answer 27

- consist of crystals - very low amount of diffusion - deposited late, by osteoblasts and osteocytes

Question 28

periosteum layers

Answer 28

- outer fibrous layer, dense irregular CT - inner cambium layer, osteoprogenitors and osteoblasts

Question 29

how does mineralization occur?

Answer 29

- collagen fiber - outside the cell - alkaline phosphate (enzyme) is secreted - form crystals outside the cell and mineralizes

Question 30

osteoblasts

Answer 30

cuboidal shape, matrix secreting machinery directed to attached surface of the cell; prominent RER

Question 31

osteocytes

Answer 31

stellate shape, located in lacunae (small space in matrix); send out processes through canaliculi and communicate via gap junctions

Question 32

osteoclasts

Answer 32

- large *multinucleate* cell - derived from hematopoietic - can digest/destroy bone matrix - control blood levels of Ca2+

Question 33

what is osteoclast stimulated and inhibited by?

Answer 33

parathyroid hormone, calcitonin & bisphosphonates

Question 34

what are the 2 types of bone?

Answer 34

spongy and compact bones

Question 35

what cartilage is in growth plate?

Answer 35

hyaline cartilage

Question 36

osteoporosis

Answer 36

increase in bone porosity -> increased risk of fracture (greater resorption in bone remodelling)