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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?

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?

24
Q

In what shape do osteoclasts remodel bone?

A

In a ‘cutting cone’ shape

25
Describe the pathology of type I primary osteoporosis. Which group is it most prevalent in?
An increase in the number of osteoclasts, as a result of oestrogen withdrawal - it is therefore most common in post-menopausal women
26
Between what years does bone mass peak?
25-35
27
What is the recommended daily intake of calcium for post-menopausal women?
800 mg/day
28
What is osteoporosis?
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
Between what years does bone mass peak?
25-35
30
What is the recommended daily intake of calcium for post-menopausal women?
800 mg/day
31
What is osteoporosis?
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
List the stages of intramembranous ossification.
- 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
What are osteocytes?
Osteoblasts that have become trapped in the extracellular matrix they were secreting (osteoid)
34
What is the role of osteoblasts?
They lay down osteoid, an unmineralised bone matrix consisting of type I collagen and ground substance
35
What does osteoid form when it is calcified?
It forms spicules - these aggregate to form trabeculae, which form cancellous (spongy) bone
36
What is the periosteum?
Dense irregular connective tissue that surrounds bone (except at synovial joints)
37
What is the main component of compact bone?
Lamellae
38
What makes up an osteon?
Several sheets of bone lamellae
39
Discuss the distribution of osteocytes in mature and immature bone.
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
What structure do osteocytes lie in?
Lacuna
41
What is the role of osteoclasts? Are they multi-nucleated?
Osteoclasts are involved with the re-absorption of bone matrix, breaking it down using H+ ions and lysosomes - they are multi-nucleated
42
How do the trabeculae of cancellous bone rice be their nutrients?
They receive their nutrients from the bone marrow that surrounds them
43
Briefly describe haematoma formation.
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
What is a fibrocartilaginous callus? How does this aid in bone fracture repair?
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
How is a bony callus formed from a fibrocartilaginous callus?
The fibrocartilaginous callus is calcified and converted to a bony callus, via endochondral ossification
46
What type of ossification converts a fibrocartilaginous callus to a bony callus in fracture repair?
Endochondral ossification
47
What happens to a bony callus in fracture repair?
It is remodelled, by osteoblasts and osteoclasts
48
Specifically, how does increased osteoclast activity relative to osteoblast activity lead to osteoporosis?
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
What is the difference between osteoporosis and osteomalacia?
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
What is osteomalacia known as in children?
Rickets
51
What is Perthes Disease?
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
Does type II osteoporosis occur in males or females?
Both

Body Logistics (13 decks)

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