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Y3 Musculoskeletal pathology > Musculoskeletal Bone 1 > Flashcards

Musculoskeletal Bone 1 Flashcards

1
Q

Name the 3 parts of bone

A

Epiphysis = end
Metaphysis
Diaphysis = middle

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2
Q

The bone is covered almost all around by …?

A

Periosteum = connective tissue

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3
Q

What covers the extrmities in long bones?

A

Cartilage

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4
Q

If you slice through a long bone you will find?

A

Bone marrow in the middle:

  • a cortex of compact bone (very strong)
  • spongy bone, which isn’t strong itself, but it is very important in redistributing strength within the bone as a whole
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5
Q

How is the structure of flat bones different to long bones?

A
  • They still have a periosteum covering

- There is spongy bone within two laminae of compact bone

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6
Q

Why is the metaphysis of bone very important?

A

It is the part that is still ‘alive’ when you have bone growth and it allows the bone to grow in length. (This part is not present in flat bones)

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7
Q

What are the two histological types of bone tissue?

A
  • Lamellar

- Woven

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8
Q

Describe the features of lamellar bone

A
  • Layered
  • Mature
  • Compact/Dense -> Osteonal bone (specific type)
    … or
  • Spongy/ Cancellous/ Trabecular
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9
Q

Describe the features of woven bone

A
  • Haphazard
  • Immature
  • New bone formation is always woven
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10
Q

Describe cancellous bone?

A
  • Composed of interconnected fenestrated plates of bone
  • Is porous and has less than 30% density
  • Acts as the “shock absorber” for the bone organ
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11
Q

Describe the three primary germ layers

A
  1. Ectoderm: Skin and Appendages (barrier function)
  2. Mesoderm: Skeleton, Connective Tissues, Vascular System, Linings of Thorax & Abdomen & Pelvis
  3. Entoderm: Pharynx, Respiratory System, GI System, Urinary Bladder and Urethra (barrier function)
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12
Q

From which of the 3 germ layers does bone originate from?

A

Mesoderm

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13
Q

Which bone types are seen:

  • in embryo
  • in juveniles
  • in adults
A
  • Woven bone
  • Woven and lamellar bone
  • Lamellar bone
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14
Q

Describe the mechanism of formation and growth in flat bones

A
  • Intramembranous Ossification: appositional growth, woven bone is replaced by lamellar bone
  • Membranous ossification :a group of mesenchymal cells differentiate into the periosteum (outer layer), the spindle cells get more plump as they become osteoblasts which produce bone
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15
Q

By which mechanism do long bones form and grow?

A

Endochondral ossification

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16
Q

Describe the process of Endochondral ossification

A
  • Long bones develop from cartilage models within the axis of limbs in the absence of a capillary bed, -> primary, secondary ossification centres
  • The fibrous perichondrium is continuous with the fibrous layer of the joint capsule
  • Bone develops from cartilage due to an influx of blood
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17
Q

Joint cavities develop via which mechanism?

A

Apoptosis (cell death)

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18
Q

Describe how joint cavities develop via Apoptosis (cell death)

A

Cystic degeneration of mesenchyme between ends of bones leads to joint formation.

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19
Q

Describe the system of width growth in long bones

A

Intramembranous ossification from the periosteum with apposition of bone – this is very slow

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20
Q

Describe the system of length growth in long bones

A

Occurs at the metaphysis by endochondral ossification

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21
Q

If you look down a microscope at the area of the metaphysis, there is another similar area underneath the articular cartilage = ?

A

Articular epiphyseal complex (AEC)

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22
Q

Describe the structure of the cells/zones in the growth plate (metaphysis)

A 
Cartilage - Chondrocytes (cells of cartilage) are arranged in columns 
• Resting zone: reserve cells
• Proliferating/maturing zone 
• Hypertrophy
• Apoptosis
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23
Q

Reserve cells grow under the effects of what molecules?

A

IgF I and II

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24
Q

Which cells are important in bone mineralisation?

A

Osteoblasts and osteoclasts (found in the areas of hypertrophy)
– the cells that produce or reabsorb bone, they work together in a balance

25
Q

Describe spongiosa and how it develops

A

Primary spongiosa (Bone spicules with cartilage core from endochondral ossification) -> Secondary spongiosa (Bone spicules without cartilage core)

26
Q

Which cells are found in bone?

A
  • Osteoblasts
  • Osteoclasts
  • Chondroblasts
  • Mesenchymal Stem Cells
  • Bone Matrix (Acellular)
27
Q

Describe the two types of osteoblasts and how they appear and function

A
  • Can either be resting or active
  • Resting appear flat and stay on the surface of mineralised bone and are protecting from reabsorption
  • While they are active they are plump and they produce and secrete material that is the precursor of bone itself
28
Q

What is the structure and function of osteoclasts?

A
  • These cells live inside the bone
  • They have tiny cytoplasmic dendrites which are in contact with each other, this allows them to sense the pressure on the bone to communicate to the osteoblasts where more/less bone should be produced
29
Q

What is osteoid?

A
  • Precursor of bone itself

- Unmineralized bone matrix initially deposited by a layer of osteoblasts

30
Q

What are the components of osteoid?

A

90% Collagen Type I + chondroitin sulphate + osteocalcin

31
Q

10 days after osteoid formation you get?

A

Primary mineralisation
About 8-10 days after an osteoid seam (layer) is formed, the initial 70-75% of the total amount of bone mineral occurs relatively rapidly within a few days to a few weeks.

32
Q

Several months after primary mineralisation you get?

A

Secondary mineralisation

Completion of bone tissue mineralization to final bone density occurs slowly over a period of several months.

33
Q

Describe some features of the chemical composition of bone and cartilage

A
  • In bone there is collagen type I and type II
  • Cartilage contains a lot of water (70-85%)
  • Mineral salts
34
Q

What is the osteoid seam?

A

Name of the layer of superficial non mineralised osteoid

35
Q

What are osteoclasts, describe their appearance?

A
  • They are multinucleated, large cells
  • They are the joint venture of monocytes fusing together
  • They come from bone marrow
  • The rim of the cell is undulated
36
Q

What is the function of osteoclasts?

A

Osteoclasts are end-stage cells with specialized organelles that produce low pH acid in a resorption pit to dissolve bone salts and release proteolytic enzymes that dissolve osteoid matrix

37
Q

Where do osteoblasts originate?

A

Osteoblasts arise from mesenchyme adjacent to bone surfaces and bone marrow stromal cells

38
Q

Where do osteoclasts originate?

A

From fusion of cells of monomyelocytic stem cell origin, both local monocytic cells and those of blood origin

39
Q

What are peritrabecular stromal cells of bone marrow?

A

Connect to osteoblasts by cellular junctions and become osteoblasts during bone deposition

40
Q

What are the four Roles of Peritrabecular Bone Marrow Stromal Cells?

A
  1. Produce hematopoietic growth factors, e.g. Erythropoietin
  2. Are precursor cells of the osteoblasts
  3. React to Parathyroid Hormone stimulation
  4. Act as Strain Gauges and Activate Bone Remodelling
41
Q

What are the effects of parathyroid hormone stimulation in bone?

A
  • Attract and stimulate osteoclasts to remove bone

* Proliferate and form fibro-osseous matrix

42
Q

Name the round cells that sit in cartilage

A

Chondrocytes

43
Q

When osteoblasts go from resting to plump what happens?

A

Bone production
- They produce osteoid which is slowly mineralising, they can produce so much that they encapsulate themselves into the bone that they produce and they become osteocytes and the bone forms grows

44
Q

Bone is the only tissue that can do what?

A

Regrow exactly as it was before, following an injury

45
Q

What is the key cell in bone reabsorption?

A

Osteoclast

46
Q

How to resting osteoblasts prevent osteoclast action?

A

Resting osteoblasts cover the surface and prevent the attachment of osteoclasts when reabsorption is not needed

47
Q

What happens to osteoblasts when reabsorption is needed?

A

If reabsorption is needed the resting osteoblasts make space for attachment of the osteoclast

48
Q

On histology what does an acellular pink substance represent?

A

Osteoid - surrounded by osteoblasts

49
Q

Osteoblast precursor and osteoblasts produce which molecules?

A

RANK-L and OPG

50
Q

What is the function of RANK-L?

A

Stimulates the osteoclast precursor to differentiate into the multinucleated osteoclast (RANK-L increases bone reabsorption)

51
Q

What is the function of OPG?

A

Inhibits the differentiation of osteoclasts (opposite of RANK-L)

52
Q

Pressure on the bone causes?

A

More bone growth and less reabsorption

53
Q

Which hormone stimulates the production of RANK-L?

A

Parathormon (parathyroid hormone)

54
Q

What is the other function of Parathormon (parathyroid hormone)

A

Inhibits the transition of osteoblasts from their resting to active state
- stimulates bone reabsorption

55
Q

What is the function of calcitonin

A

Acts against parathormone by inducing death in the osteoclasts (apoptosis)

56
Q

What happens to bone when inflammation occurs?

A

Very often when inflammation occurs bone is remodelled (reabsorption/new bone formation)

57
Q

What is seen grossly that shows osteoblasts have recently produced such matrix and osteoblasts have remodelled it

A

Bone is woven and not properly formed

58
Q

What are resting lines?

A

A longitudinal straight basophilic line within the bone matrix is the evidence that at some point in the past, groups of osteoblasts were “resting” for a while during their bone forming activity

59
Q

What are reverse lines?

A

Scalloped lines are the evidence that in the past an osteoclast was actively reabsorbing the bone matrix in that site

Y3 Musculoskeletal pathology (5 decks)

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