Growth and Development - bone tissue growth

Question 1

What are the functions of the skeletal system?

Answer 1

• leverage for muscle action
• support against gravity
• protection of soft internal organs
• storage in bone –> calcium, phosphorous, fat
• blood cell production

Question 2

What are the 2 features of a typical long bone?

Answer 2

• diaphysis
• epiphyses

Question 3

Features of the diaphysis (shaft)

Answer 3

• compact (dense/cortical) bone
• medullary cavity

Question 4

Features of the epiphyses (ends)

Answer 4

• trabecular (spongy/cancellous) bone

Question 5

What 3 things is bone made of?

Answer 5

• ground substance
• protein
• bone cells

Question 6

What is ground substance?

Answer 6

• brittle
• 2/3 of bone matrix
• minerals, predominantly calcium salts

Question 7

What is the matrix?

Answer 7

extracellular material (outside)

Question 8

What is protein?

Answer 8

• 1/3 of bone matrix
• most abundant protein type 1 collagen fibres

Question 9

Bone cells in relation to what bones are made of?

Answer 9

• only 2% of bone mass

Question 10

What do osteoclasts do?

Answer 10

dissolves away old bone to be replaced by new bone

Question 11

What do osteoblasts do?

Answer 11

• bone building cells
• immature bone cell
• secretes matrix proteins

Question 12

What are osteocytes?

Answer 12

mature bone cell that maintains the bone matrix

Question 13

What is the role of canaliculis?

Answer 13

allows nutrients to transfer

Question 14

How do osteoclasts dissolve away bone?

Answer 14

as they are a multinucleate cell that secretes acids and enzymes to dissolve bone matrix

Question 15

What is the role of the osteon?

Answer 15

• basic functional unit
• columnar
• strong in long axis

Question 16

What is the role of the central canal?

Answer 16

• tunnel for blood vessels
• allows nutrients in
• allows calcium out

Question 17

What is the structure of an osteon?

Answer 17

• central canal
• concentric lamellae –> layers
• endosteum –> inner lining of bone

Question 18

Features of trabecular bone

Answer 18

• no osteons
• arches, rods, plates of bone
• branching network
• strong in many directions

Question 19

Why does trabecular bone not need osteons?

Answer 19

don’t need a central canal –> as can easily diffuse due to contact with red bone marrow

Question 20

What are the 3 types of bone formation and growth?

Answer 20

• intramembranous ossification
• endochondral ossification
• appositional bone growth

Question 21

What is intramembranous ossification?

Answer 21

flat bone formation
- occurs inside the bone

Question 22

What is endochondral ossification?

Answer 22

formation from cartilage model

Question 23

What is appositional bone growth?

Answer 23

growth in width
- adding bone to the outside

Question 24

Process of intramembranous ossification

Answer 24

1) mesenchymal stem cells differentiate into osteoblasts
2) ossification forms spicules of bone around blood vessels
3) trabecular bone formed
4) remodeled into compact bone

Question 25

Process of endochondral ossification

Answer 25

1) matrix starts to calcify - add Ca to harden 2) osteoblasts cover the shaft in a thin layer of bone 3) blood vessels and osteoblasts penetrate to form a primary ossification centre 4) primary ossification centre enlarges 5) secondary ossification centres formed at epiphyses both proximal and distal

Question 26

What are the 4 requirements for normal bone growth?

Answer 26

- minerals - vitamins - hormones - loading

Question 27

What minerals do we need for bone growth?

Answer 27

- calcium --> not enough can impair growth - phosphate

Question 28

What is the main vitamin we need for bone growth?

Answer 28

vitamin D3 --> absorbs calcium

Question 29

What hormones do we need for bone growth?

Answer 29

- growth hormone - sex hormones (particularly oestrogen)

Question 30

What does oestrogen do?

Answer 30

- aids bone strength - decreased oestrogen leads to bone loss

Question 31

What is loading?

Answer 31

bones adapt shape/size depending on what happens to them

Question 32

What does bone remodeling do?

Answer 32

1) continuous breakdown (resorption) and reforming (formation) of bone tissue 2) allows adaptation to applied loads 3) allows storage and release of calcium

Question 33

What is bone mineral content (BMC)?

Answer 33

mass of mineral in body/region (g)

Question 34

What is bone mineral density (BMD)?

Answer 34

mass of mineral per unit area (g/cm2)

Question 35

What age is typical peak bone mass?

Answer 35

30s

Question 36

What age do we start to see bone loss?

Answer 36

40s

Question 37

What does osteoporosis lead to?

Answer 37

- low bone mass - increased fracture risk

Question 38

What is the most common overuse activity?

Answer 38

bone stress injury

Question 39

What are the risk factors included in a bone stress injury?

Answer 39

- increased/high workload - low bone density or thin cortical bone in some studies - in women: menstrual disturbance/amenorrhoea