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LOCOMOTOR > Locomotor Histology > Flashcards

Locomotor Histology Flashcards

1
Q

Describe the composition of the osteoid (bone ECM)

A

Type I collagen fibres, ground substance, structural glycoproteins

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2
Q

Which cells form the osteoid?

A

Osteoblasts

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3
Q

Describe structure of woven bone

A

Random collagen fibre organisation

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4
Q

Describe structure of lamellar bone

A

Highly ordered, layered collagen fibres

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5
Q

Describe the structure of long bones

A

Thick compact bone on their shafts (strength), towards centre and at ends have spongy/trabecular bone (has spaces filled with bone marrow –> lighter)

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6
Q

What is present at the ends of long bone?

A

Articular cartilage (if located at joint) or thin layer of compact bone

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7
Q

What is present in the centre of the shaft of long bones?

A

Medullary cavity filled with bone marrow

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8
Q

Describe the structure of short, flat and irregular bones

A

Outer surface is compact bone, inner bone is cancellous/spongy

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9
Q

In what type of bone does most blood cell production in adults occur and why?

A

Flat bones, have greater proportion of red bone marrow where haematopoiesis takes place

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10
Q

What is yellow bone marrow?

A

Mainly adipose tissue

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11
Q

Why does bone stain a bright pink colour?

A

Due to presence of type I collagen

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12
Q

Where do osteocytes obtain their nutrients in trabecular bone?

A

Blood sinusoids in the bone marrow

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13
Q

What lines the surface of the trabeculae?

A

Endosteum

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14
Q

What is the endosteum comprised of?

A

Layer of osteoprogenitor cells

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15
Q

What is the purpose of osteoprogenitor cells

A

Stem cells that are derived from mesenchymal cells which can differentiate into osteoblasts and are important for bone remodelling as well as repair following damage

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16
Q

What are Haversian systems/osteons?

A

Lengthwise bony coluns in compact bone, where concentric bony lamella surround a neurovascular bundle (Haversian canal)

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17
Q

What is a Haversian canal?

A

Neurovascular channel in compact bone surrounded by concentric lamellae (Haversian system)

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18
Q

What are Volkmann’s canals?

A

Neurovascular supply that runs perpendicular to the Haversian canals, and is involved in bringing the neurovascular supply into the compact bone and distributing it to the Haversian systems/osteons

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19
Q

What forms the most outer surface of compact bone?

A

Several layers of circumferential lamellae

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20
Q

Where is endosteum located in compact bone?

A

Inside of Haversian system

21
Q

How do osteocytes distinguish the lamellae of compact bone?

A

They are arranged in rows, organisation allows you to clearly distinguish between different osteons

22
Q

Describe osteoclasts

A

Multinucleate, macrophage-like cells that resorb bong in response to blood calcium requirements and changing mechanical stresses

23
Q

What are resorption canals?

A

Tunnels through bone created by osteoclasts

24
Q

How do osteoblasts respond to a resorption canal?

A

Build a new osteon there (deposition)

25
Q

What is an intact osteon indicative of?

A

Being most recently formed by osteoblasts, as there hasn’t been an opportunity for osteoclast degeneration yet

26
Q

What are canaliculi in bone?

A

A system of tiny canals that allow osteocytes to be able to access the nutrients carried in the capillaries of the Haversian canals or from marrow spaces in trabecular bone - appear as fine lines in ground bone extending from capillaries to osteocytes in their matrix

27
Q

How are osteocytes interconnected?

A

By canaliculi through which they send fine cytoplasmic processes and communicate via gap junctions

28
Q

What is the periosteum?

A

Fibrous capsule that covers the outer surface of a bone

29
Q

What is the function of the periosteum?

A

Carries a blood and neural supply to the bone

30
Q

Describe the structure of the periosteum

A

Periosteal blood vessels penetrate into bone from the fibrocollagenous layer and the inner periosteum is lined by osteoprogenitor cells (stem cells –> osteoblasts)

31
Q

What are the two types of ossification?

A

Intramembranous ossification and endochondral ossification

32
Q

What is intramembranous ossification?

A

Formation of bone from within a membrane of primitive mesenchymal tissue (occurs in flat bones)

33
Q

What is endochondral ossification?

A

Formation of bone from a cartilage model (typified by long bone development)

34
Q

Outline the 4 stages of intramembranous ossification

A

1) Within mesenchyme, mesenchymal cells –> osteoblasts and form numerous centres of ossification
2) Osteoblasts –> osteoid at centres –> mineralisation of osteoid –> spicules of bone
3) Ossification centres grow (due to osteoblast differentiation) –> grow around foetal blood vessels in mesenchymal membrane until centres meet –> fuse –> spongy bone –> mesenchyme condenses on outer surface –> vascularised periosteum
4) Further fusion of outer trabeculae and periosteum formation –> outermost bone –> continuous sheet of woven bone –> remodelling –> outer woven to lamellar compact –> inner bone –> lamellar trabecular, mesenchymal cells within spaces of spongy bone –> haemopoietic marrow cells

35
Q

What is a diaphysis?

A

Shaft of dumb-bell hyaline cartilage model

36
Q

What is an epiphysis?

A

End portions of dumb-bell shaped hyaline cartilage model

37
Q

Describe the formation of the primary ossification centre in endochondral ossification

A

1) Perichondrium around shaft of cartilage model –> periosteum –> mesenchymal cells here –> osteoblasts –> lay down collar of bone (sides of diaphysis)
2) Cartilage cells in centre of diaphysis hypertrophy –> thin intervening cartilage matrix –> matrix calcifies –> cells degenerate
3) Nutrient artery perforates bony collar around diaphysis –> carries primitive mesenchymal and osteoprogenitor cells –> osteoblasts –> osteoid –> form bone of calcified cartilage remnants –> trabecular bone formed in centre of diaphysis –> primary ossification centre

38
Q

What covers the dumb-bell shaped structure at the beginning of endochondral ossification?

A

Perichondrium

39
Q

What is the necessary precursor to endochondral ossification?

A

Hyaline cartilage model (dumb-bell shape)

40
Q

What is the primary ossification centre in endochondral ossification?

A

Trabecular bone in the centre of the diaphysis

41
Q

How does the diaphyseal bone grow in diameter?

A

By adding to the periosteal surface

42
Q

Describe the formation of the secondary ossification centre in endochondral ossification

A

At epiphyseal ends: cartilage cells hypertrophy and die, intervening matrix –> calcifies, epiphyseal arteries carry osteoprogenitor cells into area –> osteoblasts –> form trabecular bone in centre of epiphyses –> secondary ossification centres

43
Q

What is the secondary ossification centre in endochondral ossification

A

Trabecular bone in the centre of the epiphyses

44
Q

Describe the formation of the epiphyseal growth plate

A

Trabecular bone continues to replace cartilage in epiphysis –> cartilage only remains on articulating surfaces between diaphysis and epiphysis –> epiphyseal growth plate

45
Q

What is the role of the epiphyseal growth plate?

A

Allows bone to continue to grow in length until the end of puberty

46
Q

Describe appositional growth

A

More bone is laid down by osteoblasts in the periosteum and more cartilage is laid down on articulating surfaces by proliferation of surface chondroblasts and matrix expansion

47
Q

What are the 5 zones of endochondral ossification

A

1) Zone of resting/reserve cartilage
2) Zone of chondrocyte proliferation
3) Zone of maturation and hypertrophy
4) Zone of degeneration and calcification of matrix
5) Zone of osteogenesis (bone formation)

48
Q

Describe the histology of how muscles can be directly attached to bone

A

Collagen of endomysium of skeletal muscle interweaves with the collagen of the bone periosteum

49
Q

What are Sharpey’s fibres?

A

Dense collagen fibre bundles that are inserted into the bone matrix which attach the periosteum to the bone (extend deeply into bone at such sites)

LOCOMOTOR (21 decks)

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