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1 - PBS2 > 94 - Histology of Bones and Joints > Flashcards

94 - Histology of Bones and Joints Flashcards

1
Q

Most common type of cartilage

A

Hyaline

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2
Q

Components of hyaline cartilage ECM

1-4

A

– Collagen type II (mainly)
– aggrecans (large GAGs including chondroitin
sulphate and heparan sulphate)
– hyaluronic acid
– chondronectin (glycoprotein, binds collagen, aggrecans and integrins)

Surrounded by perichondrium

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3
Q

Cellular component of hyaline cartilage

A

Chondrocytes

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4
Q

Components of elastic cartilage

A

Hyaline cartilage with elastin.

Surrounded by perichondrium.

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5
Q

Where is elastic cartilage found?

A

In the ear, ear canals, epiglottis, larynx.

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6
Q

Role of fibrocartilage

A

Binds solid joints, forms menisci and IV discs

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7
Q

Composition of fibrocartilage

A

Mixture of dense connective tissue and isolated islands of cartilage

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8
Q

Location of fibrocartilage

A

In joints, in the form of menisci, in IV discs, where bones fuse

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9
Q

Composition of fibrocartilage

A

No perichondrium.
Type 1 collagen
Chondrocytes (that have differentiated from fibroblasts)

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10
Q

Composition of IV discs

A 
External ring of fibrocartilage (annulus fibrosis)
Nucleus pulposis (form gelatinous centre with collagen type II, replaced with fibrocartilage around age 20)
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11
Q

Structure of cortical bone

A

Concentric layers (cylindrical modules of bone, concentrically surrounding artery). These are called Haversian systems.

Outermost part of bone is made up of layers of cortical bone, not Haversian systems

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12
Q

Structure of trabecular bone

1-4

A

1) Open structure braces joints
2) Spaces are continuous and full of marrow and blood vessels
3) Made up of lamellae
4) Osteocytes are in contract with the marrow cavity and vessels via their processes

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13
Q

Differences between yellow and red marrow

A

Yellow marrow is mostly fat cells, red marrow is mostly haemopoietic cells.
In early life, red marrow predominates, in later life yellow marrow predominates.
Yellow marrow retains some haemopoietic cells, can become actively haemopoietic if required.

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14
Q

Blood supply in bone marrow that is unusual

A

Blood vessels include sinusoids (large, open capillaries with pores in the walls).

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15
Q

Periosteum

A

Thin layer of connective tissue that surrounds bony surface

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16
Q

Layers of periosteum
1
2

A

Outer layer is fibrous (fibroblasts, blood vessels, more collagen)
Inner layer is more cellular (osteoprogenitor cells, which can give rise to osteoblasts)

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17
Q

Components of endosteum

A

Bone lining inner marrow cavity covered by endosteum

thinner than periosteum, still contains osteoprogenitor cells

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18
Q

Components of where tendons and ligaments attach to bone

A

Collagen is parallel to surface of compact bone.
At tendon connection, bone collagen is continuous with collagen of ligament or tendon.
Collagen fibres penetrate bone surface (these are Sharpey’s fibres)

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19
Q

Blood supply to bone

1-4

A

1) Arteries supply bones at discrete points
2) Branch in marrow cavity
3) Arteries supply shaft (diaphysis) and ends (epiphysis_ separately
4) Periosteum is separately supplied

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20
Q

How are bones innervated?

A

Nerves follow blood vessels

21
Q

Components of articular cartilage

A

Hyaline cartilage
Slippery, smooth, resistant to compression
No perichondrium in joints

22
Q

Problems with having no perichondrium in articular cartilage

A

Perichondrium contains cells to repair cartilage, so lacking it makes articular cartilage repair very slowly.

23
Q

Type of surface that synovial membrane is

A

A connective tissue structure that is very porous (it is not epithelium)

24
Q

Structure of synovial membrane

1-4

A

1) Not epithelial
2) Surface layer (intima) is two-three cells thick, a mix of fibroblast-like cells and macrophage-like cells
3) Sub-intimal layer is fibrous connective tissue
4) Synovial fluid is an ultrafiltrate of synovial blood vessels plus proteoglycans

25
Q

Cells embedded in Haversian systems

A

Osteocytes.

26
Q

Cells of bone

1-4

A

Make bone:
Osteoprogenitor cells
Osteoblasts
Osteocytes

Degrade bone:
Osteoclasts

27
Q

Osteoprogenitor cell location

A

In periosteum, endosteum

28
Q

Features of osteoprogenitor cells

1-3

A

Normally resting or quiescent
Can give rise to new osteoblasts to grow or repair bone.
Renewed from stem cells in bone marrow

29
Q

Features of osteoblasts
1
2
3

A

Works on bone surface to make bone.
Makes osteoid (organic ECM of bone, which is type I and bone matrix proteins).
Inactive osteoblasts are flattened cells that look like osteoprogenitor cells

30
Q

Markers of osteoblast activity

A

Osteocalcin (Ca2+ binding protein) and alkaline phosphatase

31
Q

Osteocyte location

A

Present within bony matrix (not on surface like osteoprogenitor cells and osteoblasts).

32
Q

Role of osteocytes

A

Maintain bone in response to loading.

Can destroy local bone to free Ca2+

33
Q

Effect of loss of osteocytes

A

Bone resorption

34
Q

Morphology of osteoclasrts

A

Giant multinuclear cells (different progenitors to osteoprogenitor cells/osteoblasts/osteocytes)

35
Q

Role of osteoclasts

A

Destroy bones in growth, repair and normal turnover.

36
Q

How do osteoclasts resorb bone?

A

Seals itself to bone around edge.
Secretes HCl, to degrade mineral component.
Secretes proteases to degrade organic component.

37
Q

Marker of osteoclast activity

A

Tartrate-resistance acid phosphatase

38
Q

Progenitors of osteoclasts

A

Related to granulocytes (macrophages, neutrophils, etc).

39
Q

What regulates osteoclast activity?

A

Parathyroid hormone increases activity, calcitonin (form thyroid) decreases activity.

40
Q

Bone development

A

During bone development, bone is laid down as either membrane bone or endochondral bone.

Membrane bone forms directly from mesenchyme (EG: skull, flat bones of the face, mandible, clavicles form this way)

Endochondral bone (EG: weight-bearing bones, bones of the extremities) forms in hyaline cartilage. A cartilage structure of skeleton is replaced by bone.

41
Q

How does endochondral bone form?

A

It is not cartilage converted to bone (calcified cartilage is a pathology).

Bone first forms in diaphysis (shaft) of hyaline cartilage. Things can’t diffuse across bone, so cartilage around bone is starved of nutrients and starts dying off. Bone forms where the cartilage dies off.

Then bone starts forming within epiphyses.

Growth plate is remnant of cartilage between diaphysis bone formation and epiphysis bone formations.

42
Q

Number of centres of ossification in endochondral bone

A

Three normally.

One in diaphysis, one in each epiphysis.

43
Q

When do growth plates in humans fuse?

A

Around 21-22 years

44
Q 
Structure of growth plate 
1
2
3
4
5
A

Layers.
Distally is normal hyaline cartilage (resting zone)
Line of dividing chondrocytes (proliferation zone)
Region of mature chondrocytes (maturation zone)
Zone of hypertrophic (dying) chondrocytes (hypertrophy zone)
Degenerating cartilage is degraded, bone is laid down on its surface

45
Q

Type of bone that is newly-made

A

Woven bone (a special type of bone).

46
Q

Features of woven bone

1-4

A

No Haversian systems.
More collagen.
More cellular.
Woven bone is soon remodelled by osteoblasts and osteoclasts.

47
Q

How is woven bone remodelled?

A

Osteoclasts focally degrade woven bone (form tunnels).
Tunnels formed along stress axis of bone.
Blood vessels and osteoprogenitor cells (endosteum) invade tunnels.
These form Haversian systems

48
Q

Haversian system formation

A

Form in tunnels formed by osteoclasts in woven bone.
Osteoblasts lay layers of bone with the collagen alternating in direction (one layer is clockwise, other is anticlockwise)
Final layer leaves a final space for blood vessel.

1 - PBS2 (96 decks)

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