development and growth of bone

Question 1

what are the 5 functions of bone?

Answer 1

• mechanical support for framework of the body
• acts as a level system for muscles of body
• protection of internal organs of body
• production of blood cells
• store for minerals

Question 2

what gives the bone cable like resistance to tension?

Answer 2

• due to osteoid component of bone

- collagen fibres laid parallel to one another

Question 3

what gives the bone pillar like resistance to compression?

Answer 3

due to impregnation of the osteoid with hydroxyapatite

Question 4

what is woven bone?

Answer 4

• immature bone
• collagen fibres randomly orientated, not organised
• not very resistant to tension
• very weak

Question 5

where is woven bone found?

Answer 5

• all foetal bones are woven, eventually replaces by mature bones
• type of bone found in new fractures that are healing
• Paget’s disease

Question 6

what is lamellar bone?

Answer 6

• lamellar bone

- collagen fibres organised in parallel layers which make them strong

Question 7

what is the epiphysis?

Answer 7

head of a long bone

Question 8

what is the diaphysis?

Answer 8

shaft of a long bone

Question 9

what is the metaphysis?

Answer 9

area between epiphysis and diaphysis

where the growth plate is

Question 10

where is compact bone found?

Answer 10

type of bone found in diaphysis

Question 11

what is the periosteum?

Answer 11

layer of fibrous tissue surrounding bone

Question 12

where is trabecular bone found?

Answer 12

• type of bone found in epiphysis

- spongy bone

Question 13

how is trabecular bone different to woven bone?

Answer 13

• it is mature

- has ordered arrangement of collagen

Question 14

what is the medullary cavity?

Answer 14

space in the centre of the diaphysis where the marrow lies

Question 15

how is lamellar bone organised?

Answer 15

into osteons

Question 16

what are osteons?

Answer 16

• section of concentric lamellae

- have a vascular bundle and lymphatic drainage in central canal

Question 17

where do the blood vessels that supply the osteons come from?

Answer 17

branches of periosteal arteries that enter through perforating canals

Question 18

what are the structures of trabeculae?

Answer 18

sections of lamellae that are not organised concentrically

they have a layer of osteoblasts lining the trabeculae

Question 19

what is the epiphysis supplied by?

Answer 19

epiphyseal vessels

Question 20

what is the metaphysis supplied by?

Answer 20

metaphyseal vessels

Question 21

what is the diaphysis supplied by?

Answer 21

perforating branches of the periosteal vessels

Question 22

what is the marrow cavity supplied by?

Answer 22

nutrient vessels that perforate nutrient foramina

Question 23

what are the layers of the periosteum?

Answer 23

cellular and fibrous layer

very important in growth of bone

Question 24

describe the general progression of bone cells

Answer 24

• osteogenic cells become osteoblasts that deposit bone
• these then become osteocytes which maintain bone
• other type = osteoclasts (involved in bone resorption)

Question 25

what is intramembranous ossification?

Answer 25

- when bone ossification occurs n existing vascular connective tissue - bone matrix (ostein) is deposited around collagen and mineralises to fotm woven bone - this is then rearranged to form lamellar bone

Question 26

what is endochondral ossification?

Answer 26

- when ossification occurs in presence of cartilage - chondrocytes die and cartilage calcifies - periosteal osteoclasts cut out a path for vessels to enter bone - osteoblasts enter with blood vessels to grow the bone

Question 27

when does the bone stop growing?

Answer 27

when the growth plate is over run by ossification

Question 28

describe bone adaptability

Answer 28

- can grow and change without compromising its support functions - inc. or dec. bulk and density

Question 29

what gives bone these adaptability properties?

Answer 29

- osteocytes which activate osteoblasts, osteoclasts | - rich vascular supply

Question 30

what is apposition?

Answer 30

- growth of the diameter of bone | - osteoblasts and osteocyte create grooves and ridges on the bone surface for vessels on the periosteum

Question 31

how does this then create a new osteon?

Answer 31

- periosteum grows around these vessels creating a tunnel around them lined by endosteum - endosteum contains osteoblasts which create concentric lamellae around new vessels - they resorb reflected bone to create a new osteon

Question 32

what are the stages of fracture repair?

Answer 32

- initial haematoma formation - bony callus formation - woven bone formation and endochondral ossification - reorganisation into lamellar bone

Question 33

what is the role of bone in calcium control when there is high blood calcium?

Answer 33

- high blood calcium - calcitonin release - inhibits bone resorption - inc. bone matrix formation

Question 34

what is the role of bone in calcium control when blood calcium is low?

Answer 34

- low blood calcium - PTH released by chief cells of parathyroids - inc. bone resorption - inc. Ca resorption - inc. Ca reabsorption in kidneys