1. Basic Concepts In MSK - Bone Flashcards

1
Q

What are the three major components of the MSK?

A

Bone, skeletal muscle, connective tissues`

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2
Q

From which of the germ layers do the three major components of the MSK derive from?

A

Mesoderm

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3
Q

What are the 6 functions of bone?`

A
• Support
• Protection
• Metabolic
• Storage
• Movement (i.e.
joints)
• Haematopoiesis
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4
Q

Describe the function of bone to support

A

The skeleton provides the framework for maintaining our body posture, with the limbs acting as pillars to support the trunk in space, and the rib cage supporting the thoracic wall.

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5
Q

Describe the function of bone as protection

A
  • The ribs protect the lungs and heart;
  • the skull protects the brain;
  • the vertebrae protect the spinal cord
  • the pelvic structures are protected by the bony pelvis
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6
Q

Describe the metabolic function of bone

A
  • Bone is a living, actively-metabolising tissue; it is not inert.
  • The metabolic functions of bone largely involve the homeostasis of calcium and phosphate.
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7
Q

Describe the storage function of bone

A
  • the skeleton is the main body reservoir for calcium and phosphate.
  • bone also contains a large amount of protein (e.g. collagen) and the bone marrow is rich in fat.
  • The skeleton is the primary site of storage of some growth factors and cytokines e.g. insulin like growth factors, transforming growth factors and bone morphogenetic proteins (BMPs).
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8
Q

Describe the function of bone in movement

A

• Movement occurs at joints between bones.
• The bones act as an attachment site for the muscles and tendons, which use the bones as levers.
• The shape of the articulating surfaces determines the range of
motion.

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9
Q

Describe the haemopoietic function of bone, including where it occurs in children and adults

A

• This takes place within the cavities of the bones.
• In children, the long bones such as the femur and
tibia are important sites of haematopoiesis
• in the adult the residual sites are mainly the pelvis, skull, vertebrae and the sternum.

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10
Q

What are the 6 functions of skeletal muscle?

A

1) LOCOMOTION: Contraction of muscles acting across a joint lead to movement of that joint
2) POSTURE: Postural muscles enable us to maintain equilibrium e.g. when standing upright
3) METABOLIC: fast-twitch and slow-twitch
4) VENOUS RETURN: The muscles in the leg compress deep veins and help to propel venous blood back up towards the heart.
5) HEAT PRODUCTION: Shivering results in an increase in the metabolic rate of muscle, which in turn results in the generation of heat (thermogenesis) and an increase in body temperature
6) CONTINENCE: The muscles of the pelvic floor are responsible for the maintenance of urinary and faecal continence

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11
Q

What are the different types of connective tissue?

A
Tendons
Ligaments
Fascia
Cartilage - hyaline/elastic/fibrocartilage
Synovial membrane
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12
Q

What are the functions of tendons?

A

Tendons connect muscle to bone.

Their role is force-transmission from the contracting the muscle to the bone to which they are attached.

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13
Q

Through what are tendons anchored to bone?

A

Sharpey’s fibres

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14
Q

Why do tendons heal slowly?

A

Relatively poor blood supply

Low water content - limits diffusion of nutrients

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15
Q

Why don’t tendons stretch too much when pulled?

A

Contain lots of collagen but little elastin - minimal waste of energy transfer

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16
Q

What are the functions of ligaments?

A

Ligaments connect bone to bone.

They support joints and prevent an excessive range of movement

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17
Q

Why is ligament healing compromised?

A

Relatively poor blood supply

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18
Q

What are ligaments composed of?

A

Dense regular bundles of connective tissue protected by dense irregular connective tissue sheaths

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19
Q

What do peri-articular (capsular) ligaments comprise of and what do they do? Give an example

A

Comprise of thickening of the capsule that surrounds synovial joints

Act as mechanical reinforcements

E.g. anterior and posterior cruciate ligaments of the knee

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20
Q

What is fascia and what is its function?

A

Fascia is sheets of connective tissue. One of the major functions of fascia is to envelop groups of muscles and divide body parts (e.g. the arm) into anatomical compartments. Some sheets of fascia are very tough (e.g. fascia lata in the thigh) and therefore also serve a protective function for the underlying structures.

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21
Q

What is superficial fascia?

A

loose connective tissue and fat underlying the skin - subcutaneous fatty layer

Also surrounds organs and glands and neurovascular bundles

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22
Q

What is the purpose of superficial fascia?

A
  • storage of fat and water
  • passageway for lymphatics, nerves and blood vessels
  • protective padding for organs
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23
Q

What is deep fascia?

A
  • Deep fascia is a layer of dense connective tissue that can surround individual muscles and groups of muscles to separate into fascial compartments.
  • This fibrous connective tissue interpenetrates and surrounds the muscles, bones, nerves, and blood vessels of the body.
  • Comprises of collagen bundles and elastin fibres orientated in a wavy pattern parallel to the direction of pull
  • Flexible and able to resist great unidirectional forces
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24
Q

What is the purpose of articular/hyaline cartilage?

A

• the cartilage found on the ends of bones contributing to joints. It is very smooth and helps to create almost
frictionless motion at the joint
• shock-ansorber

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25
Q

What is the purpose of fibrocartilage?

A

• Fibrocartilage has a higher collagen content than hyaline cartilage.
• involved in shock absorption
• increase bony congruity at joints (congruity = creating a complementary shape of bony surfaces to improve stability).
• The menisci of the knee are made of
fibrocartilage

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26
Q

What is the purpose of the synovial membrane and where is it found?

A
  • This tissue is found within joints, bursae and tendon sheaths.
  • It produces synovial fluid which lubricates the joints.
  • act as a shock absorber
  • transport nutrients to (and remove waste from) the articular cartilage of the joint as articular cartilage is avascular and synovial joints are surrounded by a plexus of arteries so have a rich blood supply
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27
Q

What does synovial fluid contain?

A

hyaluronic acid and lubricin, proteinases and collagenases

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28
Q

What is the nature of synovial fluid?

A

Clear/pale yellow, viscous, slightly alkaline at rest

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29
Q

What are bursae?

A
  • A bursa is a small sac lined by synovial membrane and containing a thin layer of synovial fluid.
  • It provides a cushion between bones and tendons and/or muscles around a joint.
  • This helps to reduce friction between the bones and allows free movement.
  • They can either be communicating or non communicating with the joint cavity.
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30
Q

What are tendon sheaths?

A

Tendon sheaths are elongated bursae that wrap around a tendon and reduce the friction associated with movement of the tendon.

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31
Q

What is the major component that differentiates bone from other connective tissue?

A

The presence of calcium phosphate (CaPO4)/ hydroxyapatite which mineralises the extracellular matrix conferring rigidity into the bone

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32
Q

What are the two divisions of bone?

A

Bone is divided into cellular and non-cellular components

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33
Q

What are the cellular components of bone?

A

The cellular components of bone are predominantly osteocytes, osteoblasts and osteoclasts. There are also fibroblasts, macrophages, mast cells and adipocytes
within bone.

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34
Q

What does the ECM of the bone contain?

A

Fibres: collagen(mainly) and elastic(small amounts)

Ground substance: water, GAGs, PGs

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35
Q

What are the 2 major components that give bone its mechanical properties?

A

The two major components giving bone its mechanical properties are collagen and calcium phosphate. The calcium phosphate confers great compressive strength
and the collagen confers great tensile strength to the bone.

36
Q

Why are bones calcified?

A

Makes them more rigid and gives it strength under compression

37
Q

How many bones in adult skeleton? Where are they found?

A

206 total
26 vertebrae
64 upper limbs (32 each side)
62 lower limbs

38
Q

What are the 2 divisions of the skeleton

A

The axial (longitudinal axis of the body) and the appendicular (compromises the bones of the upper and lower limbs)

39
Q

What is the function of osteoblasts?

A

Osteoblasts are responsible for synthesising new bone. They migrate over the matrix and synthesise and deposit osteoid, the matrix protein of bone.The osteoblasts then deposit calcium phosphate into the osteoid to make bone

40
Q

What does osteoid contain?

A

Osteoid contains collagen as its major protein and specialised proteins in smaller quantities, including osteocalcin and osteopontin

41
Q

What are osteoclasts and what is their function?

A

Osteoclasts are multinucleate cells formed by fusion of progenitor cells of thev monocyte/macrophage lineage. Role in resorbing bone -bone breakdown and mineral uptake

42
Q

How is resorption carried out by osteoclasts?

A

• They migrate over the surface of the bone matrix and secrete acidic chemicals to dissolve it, forming a pit on the surface of the cortical bone
• As an osteoclast becomes active, the surface that is in contact with the bone becomes ruffled.
• This increases the surface area for absorption of minerals such as calcium and phosphate.
• The minerals in their ionic form are absorbed into the
osteoclast, which later releases them into the extracellular fluid, from where they enter the blood.

43
Q

What are osteocytes and what is their job?

A
  • Osteoblasts can become trapped within the bone matrix where they transform into osteocytes (figure 1.4).
  • They are trapped inside lacunae and become involved in signalling processes inside the bone.
  • Important for detecting strain/ stress on bone and sending information to osteoblasts/clasts for remodelling - maintains bone
44
Q

Explain the 2 types of bone

A

COMPACT BONE: dense outer layer of bone

CANELLOUS/SPONGEY: interior of bone, mesh like trabeculae, filled with bone marrow

45
Q

What are the classifications of bone?

A
 Long
 Flat
 Short
 Irregular
 Sesamoid
46
Q

What is the function of long bones?

A

They are longer than they are wide. These bones act as rigid levers and are positioned in space by the action of the muscles.

47
Q

Where are long bones found?

A

They are mostly found in the appendicular skeleton.

E.g. the femur and humerus

48
Q

What is the diaphysis?

A

shaft of a long bone

49
Q

Where does the metaphysis and epiphysis lie?

A

The diaphysis flares out at each end into the metaphysis, which lies adjacent to the growth plate. On the other side of the growth plate is the epiphysis.

structure:
Proximal epiphyses
metaphyses
diaphyses
metaphyses
distal epiphyses
50
Q

What is the medullary cavity of bone lined with?

A

Endosteum

51
Q

What does the medullary cavity contain in children?

A

Red marrow - which is actively involved in haematopoiesis

52
Q

What does the medullary cavity contain in adults?

A

High fat content and yellow marrow

53
Q

How is blood supplied to bones?

A

Epiphyseal arteries
Major nutrient artery
Periosteal arteries

When development is finished, the growth plates fuse and the epiphyseal vessels shrivel and become insignificant

Some bones have metaphysical arteries which enter at the site of attachment of the capsule. In a child these don’t cross the growth plate so the secondary ossification centre is dependent on the epiphyseal artery. In adulthood, when the epiphysis fuses, an anastomosis is formed between the epiphyseal and metaphyseal arteries

54
Q

How is blood supplied to long bones?

A

The nutrient artery supplies the marrow and enters the bone through a nutrient foramen, usually near the middle of the diaphysis

55
Q

Describe short bones, including their function and location

A
  • approximately as long as they are wide.
  • short bones provide stability and, when working together, they facilitate a great range of movement (e.g. at the wrist).
  • The carpal bones in the wrist and the tarsal bones in the ankles are examples of short bones
56
Q

Describe flat bones, including their function and location

A

• in the skull, the thoracic cage (sternum and ribs),
and the pelvis (ilium, ischium, and pubis).
• The function of flat bones is to protect the internal organs such as the brain, heart, and pelvic organs.
• Flat bones can also provide large areas of attachment for muscles.

57
Q

Describe irregular bones, including their function and location

A

• vary in shape and structure and therefore do not fit
into any other category (flat, short, long, or sesamoid).
• They often have a complex shape, which helps protect internal organs.
• For example, the vertebrae protect the spinal cord.

58
Q

Describe sesamoid bones, including their function and location

A
  • bones embedded in tendons.
  • main function is to protect the tendons from stress and wear, but they also provide mechanical advantage by acting as a fulcrum for a muscle crossing a joint with a wide range of movement.
  • commonly found in the tendons of the hands, knees, and feet. The patella (kneecap), is an example of a sesamoid bone; it is found within the quadriceps tendon and provides mechanical advantage to the quadriceps muscles.
59
Q

how are Short, flat, sesamoid and irregular bones different from long bones?

A
  • Short, flat, sesamoid and irregular bones consist of two layers of compact bone with a layer of spongy bone between them.
  • These bones have no growth plate or epiphysis.
60
Q

What are processes (in relation to bones)? What are they divided into?

A

Prominent projections of a bone.

Divided into articulating and non-articulating.

61
Q

Which are the articulating processes?

A
  • Head
  • Condyle
  • Facet
62
Q

What is an articular head?

A

Rounded articular projection supported by a neck (e.g.head of humerus)

63
Q

What is a condyle?

A

Large, knuckle-like, articular projection (e.g. medial condyle of the femur)

64
Q

What is a Facet?

A

Smooth flat surface (superior and inferior articulating facets of the vertebrae)

65
Q

What results in non articulating processes?

A

These are usually the result of traction on the developing bone by muscles, ligaments etc. The stronger the force exerted on the bone, the larger the
bony prominence that develops.

66
Q

Which are the non-articulating processes?

A
  • epicondyle
  • trochanter
  • tubercle
  • tuberosity
  • crest
  • line
  • spine
67
Q

What is an epicondyle?

A

Smaller projection above the condyle (usually attachment site for muscles and ligaments e.g. medial epicondyle of femur)

68
Q

What is a trochanter?

A
Blunt projection (only on femur; greater and lesser
trochanters of femur)
69
Q

What is a tubercle?

A

Small knob-like rounded process (e.g. greater tubercle of humerus)

70
Q

What is tuberosity?

A

Large, usually roughened, process (usually an attachment site e.g. tibial tuberosity)

71
Q

What is a crest?

A

Prominent border or ridge (e.g. iliac crest)

72
Q

What is a line?

A

Less prominent ridge than a crest (e.g. linea aspera)

73
Q

What is a spine?

A

Sharp slender process (e.g. spinous process of a vertebra)

74
Q

What are depressions on bone?

A

Depressions on the surface of bones provide for the passage of blood vessels and other soft tissues

75
Q

What are examples of depression on bone?

A
  • fovea
  • sulcus / groove
  • fossa
  • cavity
  • notch
76
Q

What is a fovea?

A

Pit-like depression (e.g. fovea capitis of femur)

77
Q

what is a sulcus / groove?

A

Furrow that accommodates soft tissue such as blood
vessels, nerves or tendons (e.g. intertubercular sulcus of
the humerus through which the tendon of the long head of biceps brachii passes)

78
Q

what is a fossa?

A

Basin-like depression (e.g. glenoid fossa at the shoulder)

79
Q

what is a cavity?

A

Spacious open area (e.g. acetabulum of pelvis)

80
Q

what is a notch?

A

a C- or U-shaped depression (e.g. femoral notch at the

knee)

81
Q

What are openings?

A

Openings occur primarily where blood vessels and nerves pass into or through the bone:
• fissure - Narrow slit-like opening between adjacent parts of bones through which blood vessels or nerves pass (e.g. superior orbital fissure of sphenoid bone in the skull)
• foramen - Hole or window in the bone (e.g. foramen magnum at the base of the skull, for passage of the spinal cord)
• canal - Tube-like passageway (e.g. optic canal in the skull, forpassage of the optic nerve)`

82
Q

Which are the 3 arteries that supply blood to bones? Where are they found?

A

Nutrient artery - enters diaphysis. Supplies marrow + cortex.
Periosteal arteries - within periosteum and supply the periosteum and the outer third of the cortex of the bone
Metaphysical arteries - in some bones eg femur. Enter at site of attachment of capsule

83
Q

How do metaphysical arteries differ in adults and children?

A

Children = metaphyseal arteries do not cross the growth plate so the secondary ossification centre in the epiphysis is completely dependent on the epiphyseal artery.

Adults = epiphysis fuses, an anastomosis is formed between the epiphyseal and metaphyseal arteries.

84
Q

What is anastomosis?

A

No capillary intermediate. Artery to artery communication.

85
Q

What is avascular necrosis?

A

death of bone tissue due to lack of blood supply

86
Q

What are causes of avascular necrosis?

A

The most common cause is a fracture, but other risk factors include alcoholism, excessive steroid use, other trauma (non-fracture), radiation, thrombosis (blood clot),
hypertension (high blood pressure) and decompression sickness (after deep sea diving).
Radiation exposure can lead to obliteration of small arteries. In decompression sickness, small bubbles of nitrogen form which can impede the blood supply to the bone

87
Q

When does bone remodeling occur?

A
  • in response to environmental factors e.g sustained application of a load due to a change in the balance in activity between osteoblasts and osteoclasts

E.g. humerus in dominant arm of cricketer is thicker