Lecture 13 - Bone Flashcards

1
Q

What is ossification?

A

The formation of bone

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2
Q

How many types of ossification are there?

A

2

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3
Q

What are the 2 types of ossification?

A

Endochondral ossification
Intra-membranous ossification

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4
Q

What is EndoCHONDRAL Ossification?

A

Formation of LONG BONES from a Hyaline CARTILAGE TEMPLATE

CHONDRAL = Cartilage

Continued growth and lengthening at epiphyseal plate (appositional growth)

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5
Q

So what is Appositional Growth and therefore Endochondral Ossification?

A

Chondrocytes at epiphyseal plate secrete new bone matrix/tissue at the surface of the bone.

Bone gets added to existing surface

This causes the bone to grow outwards expanding and widening

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6
Q

What is Intra-membranous ossification?

A

Formation of bone from clusters of Mesenchymal Stem Cells (MSC) in the centre of the bone

Interstitial growth (growth in middle)

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7
Q

What Bones does Endochondral Ossification form?

A

Long Bones (E.g):
Tibia, fibula, femur, metatarsals and phalanges of LOWER LIMB

Humerus, radius, ulna, metacarpals and phalanges of UPPER LIMB

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8
Q

What bones does Intra-membranous ossification form?

A

Flat Bones of the skull and face
Most Cranial Bones (Part of Skull)
Clavicle

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9
Q

How many bones in the body?

A

206

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10
Q

Bone functions

A

Support body
Protect Organs
Storage/reserviour of inorganic substances (CALCIUM and PHOSPHORUS)
Haemopoiesis
Fat storage (yellow marrow)
Acid-base homeostasis (Calcium is alkali)

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11
Q

What type of tissue is Bone?

A

CONNECTIVE Tissue

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12
Q

If Bone is a connective tissue what is it made up of?

A

Cells (Osteoblasts, osteocytes and osteoclasts)
Collagenous fibres
Hard calcified matrix (only other body parts with a hard matrix is teeth

So the extracellular matrix = Collagenous fibres and calcified matrix

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13
Q

What 2 parts are the skeleton split into?

A

Axial Skeleton
Appendicular Skeleton

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14
Q

How many bones in Axial skeleton and what is its function?

A

80
The main supporting/foundation bones
The bones down the middle

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15
Q

Examples of bones in the Axial skeleton

A

Bones of skull
RIbs
Vertebrae

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16
Q

How many bones in the Apendicular Skeleton and its function

A

126
All other bones not in Axial Skeleton
Needed to help movement

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17
Q

Examples of Appendicular Skeleton bones

A

Upper Limbs
Lower LImbs
Pelvic Girdle

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18
Q

What are the 2 forms of Bone?

A

Compact/dense (Cortical Bone)
Spongy (Cancellous or medullary Bone)

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19
Q

Where is Compact/Cortical bone found?

A

Shafts of long bones
Forms plates of flat bones

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20
Q

Where is spongy bone found?

A

Ends of long bones (In epiphyses)
Centre of flat bones
Centre of Irregular Bones

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21
Q

What is found in central cavity and in spaces of spongy bone in Long Bones?

A

Red bone marrow (Haemopoiesis)
Yellow bone marrow ( Adipose tissue for energy source)

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22
Q

What is special about yellow bone marrow?

A

It can convert to red bone marrow in times of severe stress

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23
Q

What is Periosteum?

A

The tough DENSE vascular fibrous connective tissue layer that surrounds the bone.

It supplies blood (nutrients),lymphatic vessels and nerves to the Osteons via the Haversian canal

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24
Q

What is the Endosteum?

A

Thin cellular layer lining the inside of the marrow cavity of the bone

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25
Q

What is the function of Cortical bone?

A

Provides mechanical strength and protects organs

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26
Q

Spongy Bone function and where is it found?

A

End of long bones and centre of flat and irregular bones

Gives space for red marrow to grow and develop

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27
Q

What is the strucutre and function of the Central cavity of long bones?

A

Has spaces of spongy bone (yellow marrow can be here)

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28
Q

What is the Epiphyses in long bone?

A

The ends of the bone containing Cancellous or spongy bone

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29
Q

What is the diaphyses in long bone?

A

The hollow region of bone made up of cortical bone found between the 2 epiphyses, contains Bone marrow

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30
Q

What is an osteoblast?

A

Bone producing cell
It lays down substance called osteoid

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31
Q

What is osteoid?

A

Collagen 1
Enzymes
Ground substance

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32
Q

What is an Osteocyte?

A

An osteoblast which has been surrounded in MINERALISED OSTEOID = BONE SUBSTANCE

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33
Q

What is an osteoclast?

A

Multinucleated cell that contains macrophages which breaks down bone.

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34
Q

What is an Osteon/Haversian system?
Osteon and Haversian system are interchangeable terms

A

The Functional Unit of the Cortical Bone
The Structures that cortical bone is composed of

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35
Q

What is Lacunae?

A

Spaces which contain osteocytes

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36
Q

What is lamellae in the Osteon?

A

The concentric rings of matrix which surround the Haversian Canal

37
Q

What is the Haversian Canal?

A

The central part of the Osteon that contains:
-Nutrient Providing Blood Vessels
-Lymphatic Vessels
-Nerves

These supply the osteocytes with blood nutrients from the periosteum.

38
Q

What are Volkmann’s Canals?

A

Haversian canals that branch horizontally to adjacent Osteons.
They help blood to flow from the periosteum to all of the Osteons

39
Q

What is found within the lamellae?

A

Lacunae (Contain osteocytes)

40
Q

What are canaliculi in Osteons?

A

Small channels running between all of the lacunae, supply the osteocytes with substances and nervous impulses

41
Q

What is Spongy (cancellous bone) made up of?

A

Network of Beams of Bone called Trabeculae

42
Q

Cancellous bone has gaps between its Trabeculae.
What is found here?

A

Red Bone Marrow

43
Q

How does Osteoid become mineralised?

A

Calcium and phosphate deposited into osteoid forms strong crystals called hydroxyapatite

44
Q

Why is vitamin D important for bones?

A

Vitamin D is necessary to absorb calcium
Low Vit D = low calcium = poor bone mineralisation = weak bones

45
Q

What is an osteoblast called that is trapped in bone lamellae?

A

Osteocyte

46
Q

Which cells produce alkaline phosphatase?

A

Osteoblasts

47
Q

What is the function of alkaline phosphatase?

A

MAKES HYDROXYAPATITE
Changes the osteoid pH by adding hydroxide and bicarbonate ions to calcium phosphate leading to the deposition of hydroxyapatite (mineralisation)

48
Q

What is the cement line?

A

The boundary between newly formed bone tissue and non bone tissue

49
Q

How is the periosteum connected to the bone?

A

Via collagen fibres called Sharpeys fibres

50
Q

What is the function of the inner layer of sharpeys fibres?

A

Contains Osteoprogenitor cells that differentiate into Osteoblasts

51
Q

What are the cavities called which osteocytes occupy?

A

Lacunae

52
Q

How is bone lamellae arranged in cortical bone to form an Osteon?

A

In concentric rings running 45º to each other

Protects against torsion damage

53
Q

How are the collagen fibres arranged in a bone lamellae?

A

Running in same direction

54
Q

What is bone resorption?

A

When osteoclasts release collagen digesting enzyme and acidic mixture to dissolve Calcium phosphate in the bone returning it to the blood

55
Q

What is bone remodelling?

A

Constant formation, breakdown and replacement of bone

56
Q

What is Osteomyelitis?

A

Infection within bone

57
Q

What is osteopathy?

A

Disease of the bone

58
Q

What is Osteoporosois?

A

Weak bone

59
Q

What is Osteosarcoma?

A

Cancer originating from bone forming cells

60
Q

What is the middle of a bone called?

A

Diaphyses

61
Q

What are the 2 ends of a bone called?

A

Epiphyses

62
Q

What are the 2 steps to bone remodelling?

A

Osteoclasts cut large cutting cone

Osteoblasts make smaller tunnel of cortical bone called the closing cone

63
Q

What can affect the activity of osteoblasts?

A

Simulated by:
-calcitonin
-GH
-Thyroid hormones
-Vit A
-OESTTROGEN AND TESTOSTERONE

64
Q

What can affect the activity of osteoclasts?

A

Increased activity by PTH - so more Ca2+ released into blood

Decreased by calcitonin (block action of PTH at PTH receptor)

65
Q

What nutrients affect bone stability and why?

A

Vitamin D (makes Calcitriol needed for Ca2+ absorption so poor mineralisation of bone if deficient)

Vitamin C (synthesising strong collagen, is a cofactor for prolyl hydroxylase needed to hydroxylate proline so many strong hydrogen bonds can form)
Vitamins K and B12 - needed to make bone proteins

66
Q

What does a decrease in bone mass of trabecular bone leave patients vulnerable to?

A

Increased susceptibility to fracture

67
Q

What is Osteogenesis imperfecta?

A

Brittlel bone disease to a gene mutation

68
Q

What gene is mutated in Osteogenesis imperfecta?

A

COL1A1

69
Q

What is the affect of the mutated COL1A gene in Osteogenesis imperfecta?

A

Incorrect Collagen 1 production
Not enough made or collagen made does not knit together well

70
Q

What are the signs and symptoms of Osteogenesis imperfecta?

A

BLUE SCLERA
Short stature
Weak bones (fractures)
Poor teeth development
Loose joints and flat or arched feet

71
Q

What are the 2 bone diseases that occur as a result of Vitamin D deficiency?

A

Rickets
Osteomalacia

72
Q

Which of the Vitamin D deficiencies affects children?

A

Rickets

73
Q

What are the signs and symptoms of Rickets in children?

A

BOWED LEGS
Soft bones
Painful to walk
Short height and stature

74
Q

How does a lack of vitamin D cause weak soft bones?

A

Vitamin D needed to make Calcitriol
Calcitriol needed to absorb calcium
Lack of calcium leads to reduced formation of Hydroxyapatite so reduced/ineffective bone mineralisation

75
Q

What is Osteomalacia?

A

Rickets in adults
Vitamin D deficiency

76
Q

What are the 2 types of Primary Osteoporosis?

A

Type 1 = post menopausal women

Type 2 = older men and women (senile osteoporosis)

77
Q

How does Primary Type 1 osteoporosis occur in post menopausal women?

A

Decreased oestrogen levels causes decreased activity of OSTEOBLASTS and INCREASED amounts of OSTEOCLASTS

78
Q

What happens in Primary Type 2 osteoporosis?

A

As people get older, osteoblasts lose their function

79
Q

What is secondary Osteoporosis?

A

Caused by drug therapy, malnutrition, prolonged immobilisation, metabolic bone diseases

80
Q

In terms of bone strength and amounts, what happens in osteoporosis?

A

Loss of bone matrix
Loss of structural density
Demineralisation

81
Q

How can poor bone strength/demineralisation be detected?

A

Measure bone density

82
Q

In terms of resorption bays, what happens in osteoporosis associated with aging?

A

INcomplete filling of the bays

83
Q

How can osteoporosis be prevented/delayed?

A

Sufficient calcium intake
Exercise
Not smoking

84
Q

Which type of bone is affected most by osteoporosis?

A

Trabecular/cancellous bone

85
Q

What type of mutation causes Achondroplasia?

A

Autosomal dominant POINT mutation

86
Q

Which gene is affected in Achondroplasia?

A

FGFR3

87
Q

What is the function of the FGFR3 gene?

A

Prodces fibroblast growth factor
This stimulates Chondrocytes to lay down new cartilage

88
Q

What happens when the FGFR3 gene is mutated?

A

FGF is not made
Reduced Endochondral ossification

89
Q

What are the signs of achondroplasia?

A

Short stature (normal head and torso)

Long bones cant form properly (Endochondral ossification affected since cartilage affected, Intramembranous ossification normal)