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2017 - medsci 2/2 > Musculoskeletal - Bones > Flashcards

Musculoskeletal - Bones Flashcards

1
Q

What can bone be classified as? Explain

A
  • It can be considered an organ: it is made of multiple types of tissue (i.e. endothelial, smooth muscle, cartilage…)
  • It can be considered connective tissue: it is the tissue that holds all the other tissues within the skeleton (i.e. bones and skeleton are different)
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2
Q

What are the functions of the skeletal system?

A

Support

Protection

Movement

Calcium and phosphorous reserve

Haemopoiesis

Fat storage

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3
Q

What are haemopoises and fat storage contained in?

A

Bone marrow

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4
Q

What are the two types of bone marrow? What do they do?

A

Red = haemopoises

Yellow = Fat storage

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5
Q

In adult form, how many bones are there in the body? How does this change with age?

A

Adults (i.e. 20) have ~206 bones

As a new born you have 270 and as you get older you have less bones (as they fuse)

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6
Q

Why does the number of bones change with age?

A

The body is always trying to fuse bones so as you age the bones fuse therefore decrease

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7
Q

What are the two parts of the skeleton? Describe them

A

Axial skeleton are the bones of the trunk (i.e. spinal cord, skull, rib cage)

Appendicular skeleton are the bones of the extremities (i.e. arms and legs)

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8
Q

What is the main emphasis of the axial skeleton?

A

Support and protect internal organs and perform haemopoiesis

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9
Q

What is the main emphasis of the appendicular skeleton?

A

Facilitate movement and store fat

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10
Q

How does the composition of the bone marrow change as you move towards the extremities?

A

The bone marrow develops a higher yellow marrow composition

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11
Q

Label the diagram, what kind of bone is this?

A

Long bone

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12
Q

Why is the shape of the bone cylindrical? Why not solid?

A

It is for its weight the strongest, a solid bone though stronger would be much heavier

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13
Q

Label the diagram, what segment of the bone is this taken from?

A

It is from the Epiphysis

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14
Q

Label the diagram, what segment of the bone is this taken from?

A

It is from the Diaphysis

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15
Q

In the bone the blood vessels run through the bone, what runs alongs the blood vessels?

A

Nerve fibres

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16
Q

What is the function of the Perforating fibres? What makes them good at this function?

A

Anchor the ligament and tendons to the bone

They blend with the periosteum (outer sheath of the bone) and the collage that makes up the bone creating a very strong connection (FYI when you pull a ligament more often than not you are ripping the collagen, not the Perforating fibres –> that is how strong they are)

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17
Q

What part of the musculoskeletal system are long bones found most in?

A

The appendicular skeleton

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18
Q

Where is the bone marrow found in a long bone?

A

In the medulla cavity

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19
Q

In the long bone, how does the type of bone marrow vary within the medulla cavity? Why?

A

In the medullary cavity of the epiphysis it is likely to be red bone marrow because it is likely closer to the axial skeleton

In the medullary cavity oft he diaphysis it is likely to be yellow one marrow because it is further away form the axial skeleton

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20
Q

What does the periosteum cover?

A

The entire outside of the bone EXCEPT the articular cartilage of the epiphysis

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21
Q

Why is the structure of the long bone different through the bone (i.e. epiphysis vs diaphysis)?

A

The epiphysis in a long bone is in a ball and socket joint and the forces need to be transferred perpendicularly therefore the spherical structure. Also the forces are evenly distributed throughout this structure so it is filled with spongy bone to distribute the pressure across a thinner outside (i.e. beam and rod like structures take the load, not the outside)

The diaphysis doesn’t receive forces from multiple directions, instead it transfers the forces so it has a straight structures. It also doesn’t need to evenly distribute forces so instead it has a thicker outer wall to take larger directional loads

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22
Q

What are the two parts of connective tissue? What are their roles?

A

Cells: secrete and maintain the extracellular tissue

Extracellular matrix: the material that gives the properties of the tissue (anything that is not the cells)

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23
Q

How does bone meet the classification as a connective tissue?

A

It has cells embedded in an extracellular matrix

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24
Q

What is the extracellular matrix of the bone?

A

Collagen fibres (fibres) and hydroxyapatite (ground substance)

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25
Q

What are the cells of the bone?

A

Ostegenic, osteoblast, osteocyte, osteoclast

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26
Q

What is the function of the collagen fibres?

A

It resists tension

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27
Q

What is the function of each type of bone cell?

A

Osteogenic: acts as the stem cell reserve

Osteoblast: Aids in bone formation

Osteocyte: aids in bone maintenance

Osteoclast: aids in bone destruction

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28
Q

What are the components of the extracellular matrix of the bone?

A

Type I collagen (organic) and hydroxyapatite (inorganic)

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29
Q

What is the function of the type I collage fibres?

A

Resists tension/pulling

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30
Q

What is the function of the hydroxyapatite

A

Resists compression

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31
Q

What is a special trait of the connective tissue of bone?

A

It is made of only 25% water (normally it is much higher)

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32
Q

What is a major component of hydroxyapatite? What does this make it?

A

High amounts of calcium and phosphorous make it a good reserve of these elements

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33
Q

What type of force does the combined ability of organic and inorganic CT in the bone resist?

A

Torsion

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34
Q

What kind of cell is this?

What is the precursor of this cell?

What is its location?

What is its function?

A

This is an Osteogenic cell

The precursor is unspecialised stem cells from mesenchyme (connective embryonic tissue)

It is located in the surface of the bone in the periosteum and the endosteum and the central canals of compact bone

It can divide and produce bone developing cells

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35
Q

What kind of cell is this?

What is the precursor of this cell?

What is its location?

What is its function?

A

This cell is an Osteoblast

The precursor is an osteogenic cell

It is normally located in a layer under the periosteum but moves into the endosteum bone forming new bone

It function is to synthesis, deposit and calcify osteoid’s (unmineralised components of the bone that when mineralised forms the bone)

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36
Q

What kind of cell is this?

What is the precursor of this cell? How does it form?

What is its location?

What is its function?

A

This is an osteocyte

Its precursor is the osteoblast and forms when the osteoblast becomes imbedded within its own secreted osteoid

It is located within the lacunae of the bone

It maintains tissue by monitoring bone health, performs local minor repairs and facilitating rapid Ca2+ and phosphorous excahnge

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37
Q

What kind of cell is this?

What is the precursor of this cell?

What is its location?

What is its function?

A

This is an osteoclast

It is formed by the fusion of a monocyte (i.e. white blood cell) with many progenitor cell (cell that would normally turn into white blood cell)

It forms at sites where bone resorption is occurring

It secretes acid and enzymes dissolving the mineral and organic components of the bone

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38
Q

What is osteoid and what is it made of? What happens to it during bone formation?

A

An extracellular matrix which is 70% collagen + proteoglycans, other proteins etc.

This then becomes infiltrated with hydroxyapatite in a classification process making the bone strong

39
Q

How does the rate of classification of osteoid change with time? Why?

A

As it calcifies it takes the rate of nutrient exchange decreases. This is because it displaces water which means that fluids cannot diffuse freely through it

40
Q

What are lacunae?

A

A gap within the bone where osteocytes reside

41
Q

How do osteocytes communicate with each other?

A

They connect with each others lacunae by canaliculi

42
Q

What is the name of a cell that is made of fusion of many cells? What is an example of this in the bone?

A

Syncytium, an example is an osteoclast

43
Q

What is the Howship’s Lacunae?

A

The pit that is made while the osteoclast breaks down the bone

44
Q

What are the Ruffled borders that are formed during osteoclast function? How do these help the osteoclast?

A

They are the borders that are at the edge of the osteoclast which are rippled

The rippled structure increases the surface area of the border for increased absorption of the bone

45
Q

What does the osteoclast do with bone tissue?

A

It secretes acid to activate digestive enzymes that break down the bone underneath the ruffled border. The cell then absorbs the dissolved bone tissue by endocytosis and neutralises it then excretes it by exocytosis

46
Q

What is the function of the clear zone on a osteoclast?

A

They help to contain the destructive enzymes to just the target area of the bone

47
Q

What is the difference between active and resting periosteum?

A

Resting periosteum is when the periosteum (outside sheath of bone FYI) has only osteogenic cells (stem cells FYI)

Active periosteum is when there are osteogenic cells and osteoblasts in the periosteum layer

48
Q

When bones grow from childhood to adulthood, how does the bone generally change? What is this process called?

A

It becomes longer and thicker by appositional growth

49
Q

Explain what appositional growth is

A

It is where the bone becomes wider and thicker by adding bone to the periosteum and taking away bone from the endosteum

50
Q

Label the cells in this diagram. Explain what is being shown in this diagram and explain the steps

A

In this diagram it is showing the outward growth of the bone during appositional growth (i.e. the top part of the bone where new bone is added)

1 - Osteogenic cells divide forming osteoblasts which become secretory cells and produce osteoid

2 - Some of the osteoblasts become trapped in the osteoid that it deposits and become osteocytes

3 - When the growth stops the osteoblasts either convert back into osteogenic cells or die

4 - the osteoid fully calcifies completing the growth

51
Q

What does osteoid vs osteoblast look like?

A

Osteoid’s look clearer because it is not fully calcified s osteoblasts which become trapped inside the calcified osteoid

52
Q

Besides monitoring the health of the skeletal system, how can osteocytes actively help maintain the health of it?

A

The lacunae which osteocytes are impeded in act as calcium stores so excess calcium can be stored and rapidly used when necessary

53
Q

What does the direction of canaliculi indicate? Why is this?

A

The direction of bone growth

This is because canaliculi can only be made as the bone is growing, osteocytes cannot bore into existing bone

54
Q

Label the cells in the diagram. Explain what is being shown in this diagram and explain the steps

A

In this diagram it is showing the inward removal of the bone during appositional growth (i.e. the bottom part of the bone where old bone is removed)

1 - Osteocytes signal for the monocyte precursor cells to leave the blood vessels and fuse onto the bone surface

2 - The monocyte precursor cells fuse and for osteoclasts which release enzymes and acids to break down the bone

3 - After a given period of time the osteoclasts undergo apoptosis (i.e. cells die by themselves)

4 - After the osteoclasts die capillaries grow into the space

55
Q

What causes the monocyte precursor cells to come from the blood vessel and onto the bone during appositional growth?

A

The osteocytes signal for the monocyte precursor cells

56
Q

What indicates if a cell is a syncytium cell?

A

It is multi-nucleated

57
Q

What is the normal way which most tissue grows? Explain this growth method. Why can’t bone grow like this?

A

Most tissue grows by interstitial growth

This is when the cells divide within the tissue

Bones can’t do this because they are too rigid (i.e. if the bone cells grow from within it would split the bone) so instead the bone has to grow by adding/removing layers (i.e. appositional growth)

58
Q

Appositional growth and bone resorption can occur at the same time independently of each other, what is this called? What is the purpose of this process?

A

Bone remodelling is the skeletal systems response to physical usage

59
Q

What is the process of bones growing longer called?

A

Endochondral ossification

60
Q

Explain how endochondral ossification works and how it causes bones to elongate. When does it stop? When it stops what does this determine?

A

When young, the epiphysis is not connected to the metaphysics, instead it is separated by hyaline cartilage. The hyaline cartilage grows interstitially causing the gap between the epiphysis and metaphysics to grow larger, but the cartilage also serves as the building block for the growth of the metaphysis. For bone growth to occur the rate of hyaline cartilage has to be equal to or greater than metaphysics growth/degeneration of the hyaline cartilage.

Bone growth stops when the hyaline division slows down allowing the metaphysis to fuse with the epiphysis

This is when bones fuse and determines the final height of a person

61
Q

How does the epiphyseal line relate to endochondral ossification?

A

it is the point where the epiphysis and metaphysis fused in an adult

62
Q

What are the two different types of structures of cartilage inside the bone? What are the differences in structure and function?

A

Woven bone - This is when you are young (< 3) and the cartilage is very wavy so the bone can flex a lot before the cartilage begins to resist the force

Mature/lamellar bone - organised in layers of alternating 90º orientation layers which makes them denser therefore stronger for better load bearing

63
Q

When would woven bone form in an adult? Why?

A

When there is a broken bone so that the body can rejoin bones as soon as possible

64
Q

Why does mature bone grow in 90º alternating layers?

A

This is so that when the bone is placed under stress there will always be fibres that are resisting the force preventing the hydroxyapatite (the ‘glue’/ground substance holding the fibres together) from being load bearing which they aren’t very good at

65
Q

Label the diagram, what is this a diagram of?

A

A cross-section of a trabecular (FYI the individual fibres of spongy bone)

66
Q

There are lots of osteoclasts in spongy bone, why? What does this mean?

A

Spongy bone have a very high surface area and are highly vascular. This means that monocytes very often leave the blood stream and find an attachment site on the bone

This means the trabecular are constantly remodelled

67
Q

How do osteoclasts influence osteoporosis? Why does this affect elderly woman in particular?

A

This is when osteoclasts become more common resulting in more bone degradation

Oestrogen helps to control osteoclast by turning them off, after menopause woman lose a lot of their oestrogen production so osteoclast are less controlled

68
Q

For trabecular growth, what is it limited by?

A

Nutrient supply by the capillaries (in the medullar cavity)

69
Q

What is the limitation of growth of a trabecular? Explain why

A

A trabecular cannot grow more than 0.4 mm in diameter (but can grow as long or wide as it want FYI)

This is because the blood vessel run on the outside of the trabecular and for the nutrients to diffuse, an osteocyte cannot be any further than 0.2 mm from a blood supply or else the diffusion is no longer effective throughout the calcified material

70
Q

Label the diagram, what kind of bone is this showing primarily?

A

It is primarily compact/cortical bone

71
Q

What does the osteon make up?

A

The Haversian system which is the same thing as the functional unit of the bone

72
Q

What is the normal thickness of the spongy and compact bone?

A

Spongy < 0.4mm

Compact > 0.4mm

73
Q

What allows the compact bone to get much thicker than the spongy bone?

A

It has blood vessels that run throughout the bone

74
Q

What is the name of the blood canal that supply blood through the compact bone?

A

Perforation/Volkmann’s canal

75
Q

What is the orientation of the lamellae on the osteon? How do they respond to stress (for repetitive directional and random)?

A

The layers of lamella are alternating

If stress is applied randomly (over a long period of time FYI) then the fibres become less aligned (for greater force distribution from multiple directions)

If stress is repetitive (i.e. the stress occurs in the same way each time) the lamellae will become more aligned (as the force is more consistently in one direction the bone adapts to dealing with stress in a uniform direction)

76
Q

How can you identify spongy bone from compact bone?

A

There are not osteons in spongy bone

77
Q

What are circumferential lamellae? Where are they normally found?

A

Layers of bone which are not organised into osteons are normally found on the outer edge of the bone

78
Q

What are the two types of osteons?

A

Primary and secondary osteons

79
Q

Label the diagram and explain the first step in primary osteon bone formation

A
80
Q

Label and diagram and explain the second step in primary osteon bone formation

A
81
Q

Label the diagram and explain the third step in primary osteon bone formation

A
82
Q

Label the diagram and explain the fourth step in primary osteon bone formation

A
83
Q

How does the groove forming on the outer surface of growing bone during primary osteon formation occur?

A

The osteoblasts that are in the periosteum (top active layer of bone FYI) produce bone more rapidly than the osteoblasts underneath which causes the groove to form

84
Q

When does periosteum turn into endosteum?

A

When the ridges of the primary osteon fold over and periosteum is no longer exposed to the outside surface

85
Q

What causes the endosteum to go from being active (i.e. laying down new bone) to being resting?

A

When the bone grows around the blood vessel and there is no more space for the vessel

86
Q

What is the difference between primary and secondary osteons?

A

Primary osteons are created as the bone grows (harvesian canal made during appositional growth), secondary osteons are created inside already existing bones (harvesian canal bored through bone)

87
Q

What is the purpose of making secondary osteons?

A

Creating secondary osteons inside pre-existing bone is how it is remodelled as it allows for the fibres to realign to adapt to stress

88
Q

Label the cells and sections in the diagram and explain how secondary osteons form

A

1 - Osteoclasts form and gather in an area that needs to be remodelled then bore their way through the bone

2 - Osteoblasts move into this newly formed tunnel and active endosteum deposit osteoid onto the walls of the tunnel which calcifies and forms new lamella

3 - A new blood vessel grows in the tunnel and the osteoblasts deposit layers of new bone (i.e. concentric lamellae) until they enclose the blood vessel, some of the osteoblasts get trapped in the calcified osteoid and become osteocytes

4 - The endosteum becomes resting again and a new osteon is formed

89
Q

What controls the direction and initiation of the osteoclasts boring through the bone during secondary osteon remodelling?

A

The osteocytes in the current bone

90
Q

What would cause the osteocytes to initiate the formation of a secondary osteon?

A

If the bone becomes too damaged for repair

become old and brittle

osteocytes move too far away from a blood source

91
Q

What is the rate of boring during secondary osteon boring?

A

1mm per 20days

92
Q

What does the cement line indicate? Why is it called this?

A

It indicates the boundary of the new osteon

It is called this because it stains really well

93
Q

Why does the cement line stain really well?

A

Because it is full of proteoglycans

94
Q

What is the maximum diameter of the osteon? Why?

A

0.4mm because no osteocyte can be more than 0.2mm away from a blood supply due to limitation of diffusion through calcified material

2017 - medsci 2/2 (16 decks)

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