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MBBCh 2- ANAT2020A > Specialized Connective Tissue: Bone > Flashcards

Specialized Connective Tissue: Bone Flashcards

1
Q

What is the difference between bone and bone tissue?

A
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2
Q

What is ECM? (2)

A
  • ECM is mineralized by calcium phosphate in the form of hydroxyapatite crystals
  • Serves as a storage site for calcium and phosphate and plays a role in homeostasis of blood
    calcium levels
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3
Q

What fibres are present in ECM?

A

o Mostly type 1 collagen (all collagen in the bone constitutes 90% of bone matrix protein mass)

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4
Q

What are the Ground substance proteins? (5)

A
  1. Proteoglycans
  2. GAGs
  3. Multi-adhesive glycoproteins
  4. Bone-specific vitamin K-dependent proteins
  5. Growth factors and cytokines
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5
Q
  • Matrix contains _____ containing an osteocyte
  • Osteocytes extend processes into small tunnels called ______
  • Canaliculi connect adjacent lacunae and allow for communication between _______
A

lacunae
canaliculi
osteocytes

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6
Q

Osteoprogenitor cells:
Description
Location
Function

A
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7
Q

Osteoblasts:
Description
Location
Function

A
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8
Q

Osteocytes:
Description
Location
Function

A
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9
Q

Bone-lining cells:
Description
Location
Function

A
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10
Q

Osteoclasts:
Description
Location
Function

A
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11
Q

What is Periosteum? (2)

A
  • Sheath of dense fibrous connective tissue containing osteoprogenitor cells
  • Absent on articular surfaces
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12
Q

What are the 2 layers of the Periosteum?

A

o Outer fibrous layer resembling dense connective tissue
o Inner cellular layer containing osteoprogenitor cells
* If active bone formation is not in progress, the inner layer is not well defined
* Collagen fibers of periosteum are arranged parallel to the surface of the bone

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13
Q

What is the Endosteum?

A
  • layer of connective tissue cells that contains osteoprogenitor cells
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14
Q

What is mature bone? (3)

A
  • Composed of structural units called osteons (Haversian systems)
  • Consists of concentric lamellae of bone matrix surrounding a central canal (Haversian canal)
  • Haversian canal consists of the nerve and vascular supply of the osteon
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15
Q

What are Canaliculi? (2)

A

o Contain the osteocyte processes are arranged in a radial pattern relative to the Haversian canal
o Serves for the passage of substances between the
osteocytes and blood vessels
* Interstitial lamellae- concentric around osteons
* Circumferential lamellae- follow the circumference of the shaft of the bone

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16
Q

What is Volkmann’s canal? (2)

A

o Channels which allow vessels and nerves to travel from periosteal and endosteal surfaces to the Haversian canals
o No concentric lamellae around the canal

17
Q

What are the features of mature spongy bone? (3)

A

o Tissue arranged in trabeculae
o Matrix of the bone is lamellated
o No Haversian systems

18
Q

What is immature (foetal) bone? (3)

A
  • Lack of organized lamellar appearance
  • More cells per unit area than mature bone that are randomly arranged
  • Has more ground substance and is not heavily mineralized
19
Q

How is bone formed? (3)

A
  • Bone is formed by differentiation of mesenchymal cells into osteoblasts
  • Occurs in flat bones, mandible and clavicle
  • Occurs around 8th week of gestation
20
Q

What is the process of Intramembranous Ossification? (11)

A
  1. Mesenchymal cells aggregate
  2. Blood vessels form and invade the mesenchymal cells —> primary ossification centre
  3. The cells increase in size and become rounder- osteoprogenitor cells
  4. Osteoprogenitor cells differentiate into osteoblasts
  5. Osteoblasts secrete bone matrix which forms the osteoid
  6. Osteoid is mineralized and trapped osteoblasts become osteocytes
  7. Initially, only a spicule is formed
  8. Osteoblasts lay down new osteoid on the spicule which later mineralizes to form bone
  9. Spicules grow by appositional growth around embryonic blood vessels randomly ® woven bone
  10. Vascularized mesenchyme condenses on the external surface of the woven bone ® periosteum
  11. Trabeculae just deep to the periosteum thicken and are later replaced by mature lamellar bone
21
Q

What is the process of Endochondral Ossification? (9)

A
  1. Cartilage forms in the shape of the bone and the model grows in length by interstitial growth and
    in width by appositional growth.
  2. The perichondral cells in the mid-region of the cartilage model stop giving rise to chondrocytes
    and osteoblasts are produced. The non-functional perichondrium is now the periosteum and a
    cuff of bone is produced around the mid-region
  3. Chondrocytes in the mid-region enlarge and become hypertrophic as the matrix calcifies
  4. Calcification inhibits nutrient diffusion causing the chondrocytes to die leaving lacunae empty. Lacunae fuse to form cavities
  5. Blood vessels grow through the thin bony collar to vascularize the cavity and mesenchymal stem
    cells migrate into the cavity and differentiate into osteoprogenitor cells
  6. When the osteoprogenitor cells come into contact with remaining calcified cartilage spicules they
    become osteoblasts
  7. Osteoblasts create osteoid ® primary ossification centre
  8. Cartilage near each epiphysis is replaced by shafts of bone
  9. Blood vessels invade the epiphyses and osteoblasts form secondary ossification centres
22
Q

What is the general growth process of Endochondral Bone? (3)

A
  • Growth in length of long bones depends on the presence of epiphyseal cartilage
  • As the diaphyseal marrow cavity enlarges, a distinct zonation can be seen in the cartilage on both
    ends of the cavity
  • The avascular cartilage is gradually replaced by vascularized bone
23
Q

What are the zones of Endochondral Bone? (5)

A
  1. Zone of reserve cartilage
  2. Zone of proliferation
  3. Zone of hypertrophy
  4. Zone of calcified cartilage
  5. Zone of resorption
24
Q

What is the Zone of reserve cartilage?

A

o Exhibits no cellular proliferation or active matrix production

25
Q

What is the Zone of proliferation? (3)

A

o Cartilage cells undergo division and organise into distinct columns
o These cells are larger than those in the previous zone
o Actively produce collagen and other matrix proteins

26
Q

What is the Zone of hypertrophy? (4)

A

o Greatly enlarged cartilage cells
o Clear cytoplasm shows presence of glycogen
o Metabolically active- secrete type I and X collagen, and VEGF (vascular endochondral growth
factor)
o Matrix is compressed to form linear bands between columns of hypertrophied cells

27
Q

What is the Zone of calcified cartilage? (2)

A

o Hypertrophied cells begin to degenerate and die
o Matrix becomes calcified

28
Q

What is the Zone of resorption? (4)

A

o Calcified cartilage is in direct contact with the connective tissue of marrow cavity
o Blood vessels invade the region occupied by dying chondrocytes
o Forms a series of spearheads, leaving the calcified cartilage as longitudinal spicules
o Invading blood vessels are the source of osteoprogenitor cells which differentiate to form
osteoblasts

MBBCh 2- ANAT2020A (60 decks)

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