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πš™πš‘πš’πšœπš’πš˜πš•πš˜πšπš’ 𝟸 : πš–πšžπšœπšŒπšžπš•πš˜-πšœπš”πšŽπš•πšŽπšπšŠπš• > Cellular Structure Of Bone > Flashcards

Cellular Structure Of Bone Flashcards

1
Q

What are the 5 functions of bone?

A 
β†’ Support and movement 
β†’ Protection for internal organs 
β†’ Bone marrow store
β†’ Mineral reservoir 
β†’ Endocrine
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2
Q

Where is cortical compact bone found?

A

β†’ On the outside

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3
Q

How is cortical bone organised?

A

β†’ In sheet like structures

β†’ Surrounding a hollow structure called the Haversian canal

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4
Q

What are the repeating units of cortical bone?

A

β†’ Osteons

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5
Q

What are lacunae?

A

β†’ cell sized holes within the bone matrix

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6
Q

What are the function of Haversian canals?

A

β†’ Allow for blood vessel penetration

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7
Q

Where is trabecular bone found?

A

β†’ Near the head of the bone

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8
Q

What is the structure of trabecular bone?

A

β†’ spongy

β†’ interlocking struts with spaces inbetween

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9
Q

What is the function of trabecular bone?

A

β†’ Makes bone lighter

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10
Q

What is the composition of bone in %s?

A

β†’ Protein : organic osteoid matrix 25%
β†’ Mineral : 75%
β†’ Cells

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11
Q

What is the function of the organic protein matrix?

A

β†’ Gives flexibility and tensile strength

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12
Q

What is bone mineral?

A

β†’ Hydroxyapatite

β†’ Calcium and Phosphate

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13
Q

What is the function of bone mineral?

A

β†’ Gives bone rigidity and compressive strength

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14
Q

What are the 4 types of bone cells?

A

β†’ Osteoblasts
β†’ Osteoclasts
β†’ Osteocytes
β†’ Bone marrow cells

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15
Q

What are the two subtypes of bone marrow cells?

A

β†’ Mesenchymal cells

β†’ Haematopoietic cells

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16
Q

What do mesenchymal stem cells make?

A

β†’ Osteoblasts and osteocytes

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17
Q

Where are osteoblasts found?

A

β†’ Lining the inner surface of bone

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18
Q

Where are osteocytes found?

A

β†’ Encased within the bone matrix

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19
Q

What do haematopoietic stem cells give rise to?

A

β†’ Lymphoid lineage - lymphocytes

β†’ Myeloid lineage - RBC and macrophages

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20
Q

What are the 3 functions of osteoblasts?

A

β†’ Bone forming cells
β†’ Secrete osteoid collagen matrix of bone
β†’ Promote mineralisation of the osteoid

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21
Q

What are the 2 functions of osteoclasts?

A

β†’ Bone reabsorbing - digest old bone

β†’ Dissolve bone mineral and have enzymes to digest the organic matrix

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22
Q

What is the life cycle of osteoclasts controlled by?

A

β†’ Apoptosis

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23
Q

What is a protease that osteoclasts secrete?

A

β†’ Cathepsin K

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24
Q

What do osteoclasts secrete?

A

β†’ Acid and proteases that are active in acidic environments

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25
Q

What do osteoclasts look like?

A

β†’ They are large and multinucleate

26
Q

What are osteocytes?

A

β†’ Terminally differentiated osteoblasts

27
Q

What do osteocytes do?

A

β†’ They lay down bone matrix (organic material that becomes mineralised)

28
Q

How do osteocytes extend?

A

β†’ Via multiple dendrites via minute canals in the bone matrix

29
Q

What is the function of the lacunocanalicular system?

A

β†’ Maintains communication between the bone surface and blood vessels

30
Q

How is bone continually renewed?

A

β†’ Old bone is continually resorbed and new bone is laid down
β†’ Cycle between osteoclasts digesting old bone and osteoblasts laying down new bone

31
Q

How does bone remodelling occur?

A

β†’ The leading edge is where cells differentiate into osteoclasts
β†’ Behind that the new osteoblasts differentiate into new bone
β†’ As the osteoblasts lay down the new bone some of them will stay in it where they are encased in lacunae

32
Q

What are the 3 phases of bone remodelling?

A

β†’ Activation : promotion of differentiation of new osteoclasts
β†’ Resorption : duration of osteoclast activity
β†’ Reversal : osteoclast apoptosis, terminating activity

33
Q

What are the 3 factors that control bone remodelling?

A

β†’ Load bearing exercise
β†’ Cytokines and local signals
β†’ Endocrine

34
Q

What is the role of estrogen in bone remodelling?

A

β†’inhibits osteocyte apoptosis
β†’ Promotes osteoclast apoptosis
β†’ essential for skeletal health

35
Q

What does process does estrogen favor?

A

β†’ Formation over resorption

36
Q

What is osteoporosis?

A

β†’ Loss of bone mass above a certain threshold

37
Q

In what gender is osteoporosis more common in?

A

β†’ Women

38
Q

Why is osteoporosis more common in women?

A

β†’ dramatic loss of estrogen due to menopause

39
Q

What is delayed skeletal growth in men linked to?

A

β†’ Aromatase deficiency

40
Q

What is RANK?

A

β†’ A surface receptor on pre-osteoclasts that stimulates osteoclast differentiation

41
Q

What is the RANK ligand produced by and what does it do?

A

β†’ Produced by pre-osteoblasts, osteoblasts and osteocytes

β†’ binds to RANK and stimulates osteoclast differentiation

42
Q

In what two forms can the RANK ligand exist in?

A

β†’ Surface bounds

β†’ Soluble form that is secreted from osteocytes

43
Q

What does the RANK receptor binding promote?

A

β†’ osteoclast differentiation

44
Q

What is OPG?

A

β†’ A soluble protein produced by osteocytes

45
Q

What does OPG do?

A

β†’ Acts as an antagonist

β†’ binds to RANK ligand and prevents it from binding to the receptor

46
Q

What ratio controls osteoclast differentiation?

A

β†’ Ratio of RANK ligand to OPG

47
Q

What are the steps for activating Wnt?

A

β†’ The frizzled receptor

β†’ and the co-receptor called LRP5/6 have to interace

48
Q

What is the effector of the Wnt pathway?

A

β†’ beta catenin

49
Q

What happens after the Wnt pathway is activated?

A

β†’ beta catenin is translocated to the nucleus where it causes transcription

50
Q

What is the Wnt pathway regulated by?

A

β†’ DKK and Sclerostin

51
Q

Where is sclerostin expressed and what does it do?

A

β†’ Expressed in osteocytes

β†’ stops osteoblast differentiation

52
Q

What do OPG and NO do?

A

β†’ Inhibit the differentiation of osteoclasts

53
Q

What does the RANK ligand promote?

A

β†’ Promotes the differentiation of osteoclasts

54
Q

What do PGE2, NO and ATP promote?

A

β†’ Differentiation of osteoblasts

55
Q

What do sclerostin, DDK and SFRP1 inhibit?

A

β†’ Inhibit the differentiation of osteoblasts

56
Q

What is a common bone disease?

A

β†’ Osteoporosis

57
Q

What is a rare bone disease?

A

β†’ Osteomalacia

58
Q

What is sclerosteosis caused by?

A

β†’ Mutation of the SOST gene

β†’ Inactivating sclerostin protein

59
Q

What is osteopetrosis caused by?

A

β†’ Inactivating the RANK ligand

β†’ overgrowth of bone

60
Q

What 2 changes occur during osteoporosis?

A

β†’ Thinning of the cortical bone

β†’ Widening of the trabecular bone

πš™πš‘πš’πšœπš’πš˜πš•πš˜πšπš’ 𝟸 : πš–πšžπšœπšŒπšžπš•πš˜-πšœπš”πšŽπš•πšŽπšπšŠπš• (4 decks)

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