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MS1422017S2 > Musculoskeletal System > Flashcards

Musculoskeletal System Flashcards

1
Q

What are the 6 functions of bone?

A 
Support
Protection
Movement
Calcium and phosphorous reserve
Haemopoiesis  - red BM
Fat storage - yellow BM
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2
Q

What are the 3 main functions of the axial skeleton?

A

Support
Protection
Heamopoiesis - Red BM

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3
Q

What are the 3 main functions of the appendicular skeleton?

A

Movement
Fat storage
Yellow bone marrow

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4
Q

What part of the bone forms the joint?

A

Epiphysis

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5
Q

What part of the bone forms the junction?

A

Metaphysis

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6
Q

What part of the bone forms the shaft of the bone?

A

Diaphysis

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7
Q

Describe the structure of the epiphysis:

A

On the outside is articular cartilage, then compact bone, then spongy bone. There are blood vessels inside the compact bone and in between the trabeculae which are plates and rods in the spongy bone that are covered in endosteum. The spaces in between the spongy bone are called the medullary cavity and are most likely to become red bone marrow

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8
Q

Describe the structure of the diaphysis:

A

It is a cylinder with a hollow centre called the medullary cavity where bone marrow is found. It is lined with endosteum which is a thin inner fibro-cellular layer. Then there is a layer of compact bone. Then a layer of periosteum which contains blood vessels, nerves and sharpeys fibres (collagen fibres) that blend with the endosteum

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9
Q

Why is there such a difference in shape between the epiphysis and the diaphysis?

A

The forces on the epiphysis are perpindicular to the surface so it doesn’t need a hard shell, but it needs trabeculae for extra support. The forces in the diaphysis are parallel so there is no need for trabeculae but they need a hard outer layer.

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10
Q

What is the extracellular matrix of bones made up of?

A 
Fibres (organic) 1/3 DW
Ground substance (inorganic) 2/DW
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11
Q

What are the fibres (organic) of bone and what forces do they resist?

A 
Collagen fibres (type 1 and 5) which is thick and strong
Resists tension - stretching/pulling
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12
Q

What is the ground substance of bone and what forces does it resist?

A

Hydroxyapatite - calcium and phsophorus

Resists compression - squeezing/crushing

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13
Q

What are the cells in bone and what forces do they resist?

A 
Osteogenic
Osteoblasts
Osteocytes
Osteoclasts 
Resist torsion (twisting)
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14
Q

What is the precursor for osteogenic cells?

A

Unspecialised stem cells (mesenchyme embryonic CT)

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15
Q

What is the precursor for osteoblasts?

A

Osteogenic cells

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16
Q

What is the precursor for osteocytes?

A

Osteoblasts

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17
Q

What is the precursor for osteoclasts?

A

Fusion of many monocytes (WBC) progenitor cells (syncitium)

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18
Q

What is the location of osteogenic cells?

A

The surface of bone in the periosteum and endosteum. Also found in the central canals of compact bone

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19
Q

What is the location of osteoblasts?

A

Usually in a layer under the active periosteum or endosteum. Found where new bone is being formed

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20
Q

What is the location of osteocytes?

A

Trapped within laccunae of bone. They can communicate with neighbouring cells through their long cellular processes through canniliculi

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21
Q

What is the location of osteoclasts?

A

At sites where bone reabsorption is occurring

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22
Q

What is the function of osteogenic cells?

A

Normally dormant but can divide and supply developing bones with bone forming cells

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23
Q

What is the function of osteoblasts?

A

Synthesis, deposition and calcification of osteoid

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24
Q

What is the function of osteocytes?

A

Bone tissue maintenance. They are a live lattice inside bones, localised minor repair and rapid Ca2+ exchange

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25
Q

What is the function of osteoclasts?

A

Secrets acid and enzymes. Dissolves the mineral and organic components of bone. They have a ruffled border to increase SA and seals on to create a microenvironment and destroy

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26
Q

Bone remodelling = ?

A

Apositional growth (+) + bone reabsorption (-)

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27
Q

How do long bones grow?

A

Endochondral ossification

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28
Q

Describe the 4 steps of bone remodelling:

A
  1. Resting periosteum (only osteogenic cells)w/ nerves and blood vessels. Osteocytes are in the lacunae w/ cellular processes in caniliculi
  2. Periosteum is now active. Osteogenic cells divide forming osteoblasts which deposit osteoid. Monocyte progenitor cells leave BV and fuse on bone surface
  3. Some osteoblasts become trapped in lacunae eventually becomin osteocytes. Osteoclasts form and start dissolving bone
  4. When growth stops, osteoblasts can convert back to osteogenic cells or die. The osteoid is fully calcified. Osteoclasts die (apoptosis) so reabsorption stops. Blood vessels grow into the new space.
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29
Q

What is rickets?

A

A disease in which children do not get enough calcium or vit D. They cannot correctly calcify their bones. It is called osteomalacia in adults

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30
Q

Describe mature or lamella bone:

A

As new bone is put down by osteoblasts, they do so in layers or sheets. The collagen fibres are typically put down in the same direction within a layer but they can alternate up to 90 degrees out of phase between the layers. This enables it to be able to withstand forces from different directions

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31
Q

What are the 2 forms of mature/lamella bone?

A

Spongy

Compact

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32
Q

Why in spongy bone can an osteocyte not be more than 0.2mm away from blood vessels?

A

Because the nutrients is passed down through the caniliculi, once it gets to the middle where the osteocyte is there needs to be enough otherwise it will die and osteoclasts will com along and form 2 trabeculae from the orginal one - we dont want this to happen

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33
Q

What is the turnover rate for spongy bone compared to compact?

A

5:1

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34
Q

What is found in between osteons in compact bone?

A

Interstitial lamallae or circumferential lamallae

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35
Q

What covers the outside of an osteon?

A

Endosteum

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36
Q

In a osteon where is the blood vessels found?

A

In the central/haversian canal

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37
Q

What are the horizontal canals called in compact bone?

A

Perforating or volksmann canals

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38
Q

Describe primary osteon formation:

A

Osteoblasts in the active periosteum either side of a blood vessel put down new bone, forming ridges. As the bone continues to grow the ridges come together and form a tunnel around a blood vessel. The tunnel is now lined with endosteum. The osteoblasts in the endosteum build concentric lamallae on the wall of the tunnel and fills it in. The bone continues to grow outwards as the osteoblasts in the periosteum build new circumferential lamallae

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39
Q

Describe how secondary osteons are formed:

A

A group of osteoclasts begin boring their way through existing bone. This is called the cutting cone. Osteoblasts line the tunnel wall and move in behind the cutting cone and start depositing osteoid onto the wall. The osteoid layer is then calcified forming the new lamalla. A new blood vessel grows into the space to supply it. The active area behind the cutting cone is the closing cone. Some osteoblasts become trapped and form new osteocytes. Some die and some become osteogenic cells

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40
Q

What is the cement line?

A

A line between the new osteon and the pre existing older bone

41
Q

For spongy and compact bone, what are the units?

A

Spongy: Trabeculae
Compact: Osteon

42
Q

For spongy and compact bone, how are the units formed?

A

Spongy: grows outwards
Compact: grows inwards

43
Q

For spongy and compact bone, what is the blood supply?

A

Spongy: blood vessels in the medullary cavity
Compact: blood vessels in haversian and volksmann canals

44
Q

What are the 3 functions of joints?

A

Movement, force transmission, growth

45
Q

Describe the following type of joint: synathrosis

A

Overtime they fuse (ankylosis. They are immovable joints that are very stable and are for growth and force. They are found in the axial skeleton.

46
Q

Describe the following type of joint: amphiarthosis

A

They are slightly movable and help with force

47
Q

Describe the following type of joint: diathrosis

A

Freely movable joint with little stability. Mainly found in appendicular skeleton. They are the most injured. E.g synovial joints

48
Q

Describe synovial joints:

A

They are freely movable and they are not restricted by the properties of the specific tissues that hold the ends of the bones together. They have a wide range of motion but are relatively unstable

49
Q

What type of tissue is articular cartilage?

A

A specialised form of connective tissue (hyaline cartilage)

50
Q

What is the main function of articular cartilage?

A

To protect the ends of bones that come together. It can absorb shock, support heavy loads for long periods of time and provide a smooth near frictionless surface when combined with synovial fluid

51
Q

The degredation of articular cartilage leads to….

A

Arthritis

52
Q

What are the cells that make up articular cartilage?

A

Chrondrocytes - they live in lacunae and build and maintain cartilage. They can occur by themselves or in groups called nests.

53
Q

Describe the ground substance of the extracellular matrix of articular cartilage:

A

It is made of water and soluble ions. It is fluid compartment that can move in and out of the cells. Glycosaminoglycans (e.g hyalauronic acid, chondroitin sulfate) and proteoglycans (e.g aggrecan). These provide the swelling and hydrating mechanism for cartilage. The are part of the fixed solid compartment. The are large in (-ve) charge

54
Q

Describe the fibres of the extracellular matrix of articular cartilage:

A

They are mostly type II collagen. They provide the structural integrity of the tissue. There are specific zoning patterns. They are also part of the fixed solid compartment

55
Q

What makes up the fluid compartment of articular cartilage?

A

Water and soluble ions (ground substance)

56
Q

What forms the fixed solid component of articular cartilage?

A

Collagen fibres and PG

57
Q

Name all the layers of articular cartilage going from the joint space to the subchondral bone:

A 
Joint space
Surface zone
Middle zone
Deep zone
Tide mark
Calcified cartilage
Osteochondral junction
Subchondral bone
58
Q

What part of articular cartilage make up the functional layers of articular cartilage?

A

Surface zone
Middle zone
Deep zone

59
Q

What parts of articular cartilage makes up the calcified part?

A

Calcified cartilage

60
Q

For each zone describe the PG content, the collagen fibre orientation and the chondrocytes: surface zone

A

Low PG content, fibres are arranged horizontally, cells are flat

61
Q

For each zone describe the PG content, the collagen fibre orientation and the chondrocytes: middle zone

A

PG content is increasing, fibres are criss-crossed and chondrocytes are more sphere like

62
Q

For each zone describe the PG content, the collagen fibre orientation and the chondrocytes: deep zone

A

Highest PG content, collagen fibres are vertical and cells are arranged in nests (stacked on top of each other)

63
Q

For each zone describe the PG content, the collagen fibre orientation and the chondrocytes: calcified cartilage

A

Low in PG, high in hydroxyapatite, fibres are still vertical, cells are in a partially calcified lacunae

64
Q

Where is the cement line?

A

At the osteochondral junction

65
Q

If cartilage contains no blood vessel or nerves, how are chondrocytes nourished?

A

By diffusion only

66
Q

What makes up a proteoglycan complex?

A

Repeating disacchride units make up a glycosaminoglycan (e.g chondoitin sulfate or keratin sulfate). Many GAGs are attached to a protein core to make a proteoglycan e.g aggrecan. -ve charges repel each other. Many proteoglycans attached to a hylauronic acid = proteoglycan complex

67
Q

Describe the loading cycle:

A

-ve charges on repeating disaccaride units attracts positive ions into the cartilage from the joint space. This increase in ion conc creates an osmotic pressure so water and nutrients enter, causing the cell to swell. As it swells, the cartilage is placed under increasing tension. Eventually the swelling force = tension force and the cartilage stops swelling (unloaded equilibrium). When a load is introduced, the fluid compartment is squeezed out along with waste and CO2 back into the joint space. The loss of fluid reduces the volume of the cartilage = creep. Eventually the load is supported by the solid compartment (-ve charges). The cartilage will stop shrinking = loaded equilibrium

68
Q

What is the function of the articular capsule?

A

Not tightly hold the bones close together but to become tight at the extreme limits of the natural range of motion to protect from damage.

69
Q

What is the articular capsule perforated by?

A

Ligaments, blood vessels and nerves

70
Q

Where are the closest blood vessels to the articular cartilage?

A

In the articular capsule

71
Q

What are the 2 layers found in the articular capsule going from the joint cavity to outside the joint cavity?

A

Synovial membrane

Fibrous layer

72
Q

What type of connective tissue is in the fibrous layer of the articular capsule?

A

Dense regular and irregular

73
Q

What type of connective tissue is in the synovial membrane layer of the articular capsule?

A

Loose

74
Q

What makes up the fibrous layer and what is its purpose?

A

It is made of parallel but interlacing bundles of collagen fibres that are continuous with the periosteum of bone. Thicker sections are called capsular ligaments. They resist tensional forces. This layer supports the synovial membrane and the whole joint. The fibrous capsule is poorly vascularised but richly innervated.

75
Q

What are the 2 types of synovial membrane?

A

Intima and subintima

76
Q

Describe the intima of the synovial membrane of articular capsule:

A

It is thin and only 1-3 cell layers thick. The cells are called synoviocytes and they secrete some components found in synovial fluid

77
Q

Describe the subintima of the synovial membrane of articular capsule:

A

Highly vascular and contains macrophages, fat cells and fibroblasts which help to maintain and protect the articular capsule during normal movement

78
Q

What are the peripheral margins of the joint cavity filled with?

A

Collapsing and infolding of the synovial membrane (villi)

79
Q

What is the function of the synovial fluid?

A

Joint lubrication, shock absorption, chondrocyte metabolism and overall joint maintence

80
Q

Free cells are found in low concs of synovial fluid what are they?

A

Monocytes, lymphocytes, macrophages, synoviocytes

81
Q

What is synovial fluid?

A

A clear or yellowish ultrfiltrate of blood plasma that leaks out of blood vessels in the synovial membrane (subintima) into the joint space. Other components not found in blood plasma are secreted by the synoviocytes e.g hyalauronic acid

82
Q

What type of connective tissue is tendons made of?

A

Dense regular

83
Q

What is the order of layers in a muscle from skin to a myofibril?

A 
Skin
Superficial fascia
Deep fascia
Muscle
Epimysium
Perimysium
Fasicle
Endomysium
Myocyte
Myofibril
84
Q

What is a myofibril?

A

Many sarcomeres which is the contractile unit

85
Q

What is a myocyte/myofibre?

A

A bundle of myofibrils with variable diameters. In between the myofibrils is the sarcoplasm and the cell membrane is the sarcolemma. There are many nuclei and they can store O2 in myoglobin

86
Q

What are fascicles?

A

A bundle of myocytes which are surrounded by endomysium (loose irregular CT containing nerves and blood vessels). There is a thin basement membrane between the myocyte and endomysium

87
Q

What is a muscle?

A

A bundle of fasicles. Perimysium (dense irregular CT) surrouunds the fasicles. Epimysium (dense irregular CT) surrounds perimysium and entire muscle

88
Q

Describe deep fascia and muscle compartments:

A

Deep fascia is under the skin and subcutaneous tissue. The outer walls of a compartment are made of deep fascia. The deeper walls are investing fascia (intermuscular septa (between muscles)/ intersorrosus membrane (between bones). When investing fascia comes into contact with bone it blends with periosteum. The epimysium can slide under the deep fascia

89
Q

Can skeletal muscle undergo hyperplasia?

A

Noooo

90
Q

What is hypertrophy?

A

An increase in muscle size due to an increase in the size of myocytes (more myofibrils). It can be caused by repetitive contraction of muscles to max tension and anabolic steroids

91
Q

What is atrophy?

A

When muscle decreases in size due to the reduction of myofibrils in myocytes. Often caused by not using a limb etc or old age

92
Q

What is hypodisplasia?

A

Muscle loss due to loss of myocytes

93
Q

How are myocytes created?

A

The fusion of many myoblasts during embryonic stage of life. Because they are so large and have many nuclei they can’t just divide by mitosis.

94
Q

How are satallite cells formed?

A

During the formation of myocytes, not all of the myoblasts fuse, some remain as cells and become satallite cells.

95
Q

Where do satallite cells sit?

A

Beside the muscle fibres (myocytes), outside the sarcolemma but within the same basment membrane

96
Q

What is the function of satellite cells?

A

Repair any damage and they have a limited ability to replace muscle fibres that die from old age or injury

97
Q

What is desmin?

A

A protein that is found holding together the Z discs of adjacent sarcomeres which results in contraction in unison. This is why they appear striated.

98
Q

What is dystrophin?

A

A protein complex that connects a myocyte to the surrounding endomysium.

99
Q

What is muscular dystrophy?

A

A disease where the protein dystrophin is not transcribed properly or missing. This results in myocytes that have a weaker sarcolemma and tear easily - death of cell eventually

MS1422017S2 (8 decks)

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