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Body Logistics > Bone > Flashcards

Bone Flashcards

1
Q

Which process contributes to the thickening of long bones? Which process contributes to their lengthening?

A

Intramembranous ossification contributes to the thickening of a long bone, while endochondral ossification contributes to their lengthening

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2
Q

What is intramembranous ossification?

A

Bone growth within condensations of mesenchymal tissues (as opposed to replacement of hyaline cartilage)

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3
Q

What is the difference between an osteoblast and an osteoclast?

A

An osteoblast deposits and forms new bone, while an osteoclast breaks down existing or damaged bone

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4
Q

What are the 2 types of bone?

A

Cancellous and compact bone

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5
Q

What is cancellous bone?

A

A network of fine, bony columns filled with bone marrow

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6
Q

Where is compact bone found?

A

On the external surfaces of the bone

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7
Q

Describe the composition of bone.

A

65% mineral (calcium hydroxyapatite crystals)
23% type I collagen
10% water
2% non-collagen proteins

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8
Q

What structure makes up the majority of compact bone?

A

An osteon

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9
Q

What canals innervate an osteon of compact bone? In which direction do these vessels run?

A

A Harvesian canal runs parallel to an osteon, while a Volkman’s canal runs perpendicular

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10
Q

How are osteocytes arranged differently in mature and immature bone?

A

Osteocytes are arranged randomly in immature bone, while in mature bone the arranged in the concentric lamellae of osteons

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11
Q

Define what an autograft, homograft, and a heterograft are.

A

An autograft is where the donor is the recipient, a homograft is where the donor is of the same species (ie another human), and a heterograft is where the donor is a different species

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12
Q

Which is the most successful out of an autograft, homograft, and a heterograft?

A

Autograft

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13
Q

List the 4 stages of repair of a bone fracture.

A

1) haemotoma formation
2) fibrocartilaginous callus formation
3) bony callous formation
4) bone remodelling

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14
Q

From which germ line cell type does bone form in intramembranous ossification? What is the intermediate cell type between these and an osteoblast?

A

Bone forms from mesenchymal stem cells - these differentiate into osteoprogenitor cells, which then mature into osteoblasts

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15
Q

Which type of collagen do osteoblasts mainly lay down?

A

Type I collagen

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16
Q

What is osteoid?

A

Unmineralised bone matrix (hasn’t been calcified) composed of type I collagen and GAGs

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17
Q

Are osteoclasts uni-nucleated?

A

No, they are multi-nucleated

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18
Q

Biochemically, what does bone mineralisation specifically refer to?

A

The deposition of hydroxyapatite crystals

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19
Q

List the 5 zones apparent in endochondral ossification?

A 
Zone of resorption
Zone of calcified cartilage
Zone of hypertrophy 
Zone of proliferation
Zone of reserve cartilage
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20
Q

Name 3 bones that are formed by intramembranous ossification? What type of bones are these?

A

The skull, scapula, and clavicle - these are all flat bones

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21
Q

Once osteoid is calcified (mineralised), what does it become?

A

Spicules

22
Q

What do spicules combine to form? What are these then replaced by?

A

Trabeculae - these are replaced by lamellae

23
Q

Are there any blood vessels in the trabeculae of cancellous bone?

A

No

24
Q

In what shape do osteoclasts remodel bone?

A

In a ‘cutting cone’ shape

25
Q

Describe the pathology of type I primary osteoporosis. Which group is it most prevalent in?

A

An increase in the number of osteoclasts, as a result of oestrogen withdrawal - it is therefore most common in post-menopausal women

26
Q

Between what years does bone mass peak?

A

25-35

27
Q

What is the recommended daily intake of calcium for post-menopausal women?

A

800 mg/day

28
Q

What is osteoporosis?

A

Osteoporosis denotes decreased bone strength, due to osteoclasts reabsorbing more bone than osteoblasts are laying down - bones become more brittle and fragile, and an overall decrease in bone mass, to the point it no longer provides adequate strength and support

29
Q

Between what years does bone mass peak?

A

25-35

30
Q

What is the recommended daily intake of calcium for post-menopausal women?

A

800 mg/day

31
Q

What is osteoporosis?

A

Osteoporosis denotes decreased bone strength, due to osteoclasts reabsorbing more bone than osteoblasts are laying down - bones become more brittle and fragile, and an overall decrease in bone mass, to the point it no longer provides adequate strength and support

32
Q

List the stages of intramembranous ossification.

A
  • condensation of mesenchymal stem cells form a nidus
  • the mesenchymal cells differentiate into osteoprogenitor cells
  • osteoprogenitor cells differentiate into osteoblasts which lay osteoid
  • the osteoid mineralises and becomes bone spicules
  • bone spicules join to form trabeculae
  • trabeculae merge to form woven bone which is replaced by lamellae
33
Q

What are osteocytes?

A

Osteoblasts that have become trapped in the extracellular matrix they were secreting (osteoid)

34
Q

What is the role of osteoblasts?

A

They lay down osteoid, an unmineralised bone matrix consisting of type I collagen and ground substance

35
Q

What does osteoid form when it is calcified?

A

It forms spicules - these aggregate to form trabeculae, which form cancellous (spongy) bone

36
Q

What is the periosteum?

A

Dense irregular connective tissue that surrounds bone (except at synovial joints)

37
Q

What is the main component of compact bone?

A

Lamellae

38
Q

What makes up an osteon?

A

Several sheets of bone lamellae

39
Q

Discuss the distribution of osteocytes in mature and immature bone.

A

In immature bone, osteocytes (osteoblasts) are fairly randomly arranged as they are still laying down osteoid - in mature bone, the osteocytes have become trapped in their matrix which is now concentric layers of lamellae, which compose an osteon

40
Q

What structure do osteocytes lie in?

A

Lacuna

41
Q

What is the role of osteoclasts? Are they multi-nucleated?

A

Osteoclasts are involved with the re-absorption of bone matrix, breaking it down using H+ ions and lysosomes - they are multi-nucleated

42
Q

How do the trabeculae of cancellous bone rice be their nutrients?

A

They receive their nutrients from the bone marrow that surrounds them

43
Q

Briefly describe haematoma formation.

A

A bone break causes blood vessels to break - these form a clot called a haematoma - swelling and inflammation occurs - osteoclasts and macrophages remove dead and damaged tissue

44
Q

What is a fibrocartilaginous callus? How does this aid in bone fracture repair?

A

A procallus forms as as new vessels innervate the haematoma - fibroblasts then produce collagen, while others differentiate into chondrocytes which produce hyaline cartilage - this fibrocartilaginous matrix thus splints the bone fracture

45
Q

How is a bony callus formed from a fibrocartilaginous callus?

A

The fibrocartilaginous callus is calcified and converted to a bony callus, via endochondral ossification

46
Q

What type of ossification converts a fibrocartilaginous callus to a bony callus in fracture repair?

A

Endochondral ossification

47
Q

What happens to a bony callus in fracture repair?

A

It is remodelled, by osteoblasts and osteoclasts

48
Q

Specifically, how does increased osteoclast activity relative to osteoblast activity lead to osteoporosis?

A

There is incomplete filling of osteoclast absorption bays by osteoblast, meaning bone is not as thick (has a decreased mass) and as such is more brittle, and not as strong

49
Q

What is the difference between osteoporosis and osteomalacia?

A

Osteoporosis is a result of decreased bone mass, while osteomalacia is a result of the bodies inability to mineralise bone matrix (osteoid), due to a lack of vitamin D

50
Q

What is osteomalacia known as in children?

A

Rickets

51
Q

What is Perthes Disease?

A

Perthes disease is a childhood disease affecting the head of the femur, where the blood supply to the growth plate of the bone at the end of the femur is inadequate (avascular blood supply) - this causes necrosis, causing the bone to soften and break down

52
Q

Does type II osteoporosis occur in males or females?

A

Both

Body Logistics (13 decks)

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