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Clinical Anatomy Skeletal System 2 > CLASSIFICATION OF BONES BASED ON MICROSCOPIC STRUCTURE > Flashcards

CLASSIFICATION OF BONES BASED ON MICROSCOPIC STRUCTURE Flashcards

1
Q

What is lamellar? (3)

A
  1. Mature/secondary bone tissue
  2. layers in an osteon (sheets of mineralized matrix layers)
  3. Contains collagen fibers (highly organized; adds strength)
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2
Q

What is woven bone?

A
  1. fibrous/immature bone (not mineralized)
  2. First type of bone formed during fetal development
  3. Then replaced by lamellar bone(which is mineralized)
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3
Q

What does a lamellar make?

A
  1. Compact bone
  2. Trabecular bone
    * In adults
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4
Q

What is Secondary osteon?

A
  • Haversian system
  • Concentric lamellae
  • Surrounding a Haversian canal
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5
Q

What is the outer boundary of the Haversian system?

A
  • Cement line (Evidence of a previous remodeling process.)
  • Marks the limit of resorption
  • Cement line results from bone remodeling
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6
Q

What is primary osteon? (3)

A
  1. Lamellae around a Haversian canal
  2. Does not replace old bone
  3. Cement line is not formed
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7
Q

What is lacunae?

A
  1. Small cavities in bone that contains osteocytes
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8
Q

What is canaliculi? (2)

A
  1. Connect lacunae with each other in the Haversian canals

2. Transport nutrients from Haversian canal to cells in the osteon

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9
Q

What is the Haversian canal?

A
  1. Lines the endosteum(membrane covering internal surface of bone)
  2. Contains blood, lymph vessels, nerves, and loose connective tissue
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10
Q

What is Volkmann’s canal? (3)

A
  1. Perforate the lamellae (perpendicular to haversian canal)
  2. Connects Haversian canal with the Bone Marrow Cavity and Periosteum
  3. Provides channels for the neurovascular system
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11
Q

What is bone matrix in woven bone? (5)

A
  1. mineral content is low but the deposition of the minerals is faster than lamellar bone (because we don’t do nothing with soft bone)
  2. Contains collagen fibers(randomly oriented “woven”)
  3. No lamellae
  4. Strength is equal in all directions
  5. Cells are embedded in the matrix (around blood vessels penetrating the bone and on the surface )
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12
Q

Where is woven bone located after birth? (3)

A
  1. Near sutures of flat bones of the skull
  2. Tooth sockets
  3. Insertion site of some tendons
    * Also found in fractures, tumors, and infections
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13
Q

What are two types of ossification?

A
  1. intramembranous ossification
  2. endochondral ossification
  • Refers to the mechanisms by which bone is formed.
  • Woven bone is produced first and then replaced by stronger lamellar bone
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14
Q

What occurs in intramembranous ossification?

A
  1. Forms directly within condensations of highly vascularized mesenchymal tissue
  2. Formation of bone starts at the primary ossification center
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15
Q

What is osteoprogenitor cells?

A
  1. Are mesenchymal cells at primary ossification center

* Are immature cells that become osteoblasts

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16
Q

What happens to osteoblasts in intramembranous ossification? (4)

A
  1. Organize around developing capillaries
  2. Start synthesis of osteoid
  3. Mineralizes, creating small areas of bone with trabeculae and surrounds the osteoblasts, which become osteocytes
  4. Collagen fibers become randomly oriented and lamellae not present YET

*osteoid (bone that is not mineralized YET)

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17
Q

What occurs in intramembranous ossification when secretion of osteoid begins?

A
  1. Mineralization

2. Trabecular growth (Growth in the small bony areas)

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18
Q

What happens in ossification centers in intramembranous ossification? (4)

A
  1. Grow
  2. Fuse
  3. Replacement of Connective Tissue mesenchyme
  4. Produce compact bone that encloses the cancellous bone
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19
Q

How are Periosteum and endosteum form in intramembranous ossification?

A

Layers of Connective Tissue mesenchyme do not undergo ossification, which then creates periosteum and endosteum

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20
Q

What bones does intramembranous ossification make?

A
  1. Patterns of ossification of flat bones that contribute to the growth of:
    - short bones
    - maxilla
    - mandible
    - clavicle
    - Thickening of long bones
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21
Q

What is Diploe?

A

Trabecular bone that remains at the center between two layers of compact bone
*Contain diploic veins

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22
Q

What occurs in cranial flat bone during intramembranous ossification?

A
  1. Bone formation predominates over bone resorption at both, internal and external surfaces of the compact bone
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23
Q

What are diploic veins?

A
  1. Thin-walled valveless veins that occupy channels in the diploe
  2. Connected with the intracranial and extracranial veins by emissary veins
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24
Q

What are Emissary veins?

A
  1. Valveless veins that pass through apertures in the cranial wall
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25
Q

What are the functions of diploic and emissary veins? (4)

A
  1. Help to equalize pressure in the intracranial and extracranial veins
  2. Act as safety collateral pathway during cerebral congestion or obstruction of veins
  3. Function in cooling blood before it enters the brain
  4. Serve as routes for the spread of infection from the extracranial veins to the intracranial veins
26
Q

Where does endochondral ossification take place?

A
  1. First occurs in Bone collar

2. Within hyaline cartilage

27
Q

What takes place in endochondral ossification?

A
  1. Mesenchymal cells differentiate into chondroblast

2. Chondroblast form an embryonic hyaline cartilage model of the bone with perichondrium

28
Q

What is bone collar in endochondral ossification? (3)

A
  1. Produced by osteoblasts that differentiate within the perichondrium, transitioning to periosteum
  2. Forms during late 1st trimester (beneath the perichondrium; around the diaphysis of the long bone cartilage model)
  3. Blocks nutrient and oxygen diffusion into underlying cartilage
29
Q

What occurs in chondrocytes hypertrophy in endochondral ossification? (6)

A
  1. Chondroblasts become chondrocytes that compress the surrounding matrix and initiate calcification that leads to Cartilage degeneration
  2. Hypertrophic chondrocytes degenerate and die, creating empty spaces within the calcified matrix
  3. Then are invaded by periosteal buds
  4. Osteoblasts move into the empty spaces and deposit osteoid
  5. Calcification occurs creating woven bone that is remodeled as compact bone
  6. This process occurs in the diaphysis that forms the primary ossification center
  • Cartilage IS REPLACED BY BONE NOT CONVERTED
30
Q

What are periosteal buds in endochondral ossification?

A
  1. Composed of blood capillaries and osteoprogenitor cells(become osteoblast)
31
Q

What happens to osteoclasts after the formation of primary ossification center in endochondral ossification? (3)

A
  1. Osteoclasts are activated
  2. Resorb the bone at the center
  3. Creates marrow cavity
32
Q

What happens in primary and secondary ossification centers in the endochondral ossification? (3)

A
  1. Expansion
  2. Undergoes remodeling and produces cavities that fuse with the initial marrow cavity that was created by osteoclast.
  3. Marrow cavity is filled with bone marrow and trabeculae

*Cartilage model is gradually replaced by bone EXCEPT for epiphyseal plate and articular cartilage

33
Q

What is Periosteum?

A

-CT, which is an external covering of bones (EXCEPT for articular surfaces of tendons, ligaments, and muscles that attach to bone using articular cartilage)

34
Q

How many layers are in Periosteum?

A
  • Two layers: Outer layer and Inner cellular layer
35
Q

What does the outer layer of periosteum contain? (4)

A
  1. Contains dense irregular connective tissue
  2. Contains collagen fibers
  3. Contains Sharpey’s fibers
  4. Contains blood vessels
36
Q

What is Sharpey’s fibers in Periosteum?

A
  • Bundles of collagen fibers that penetrate the bone matrix that anchor the periosteum to the bone
37
Q

What is the Inner cellular layer in periosteum?

A
  1. Immediately adjacent to the bone surface
  2. Contains Osteogenetic layer (consist of Osteoprogenitor cells, dense network of blood vessels, lymphatic vessels, and sensory nerves)

*Osteoprogenitor cells are the MOST immature cells that differentiate into osteoblast

38
Q

What is endosteum? (3)

A
  1. Lines the surface of the bone trabeculae
  2. Lines the walls of the medullary (bone marrow) cavity
  3. Lines the Haversian canals
39
Q

What is Endosteum composed of? (3)

A
  1. Osteoprogenitor cells
  2. Osteoblast and osteoclasts
  3. Small amount of loose irregular connective tissue
40
Q

What is the function of endosteum?

A

Bone remodeling

41
Q

Where does bone growth in length take place? (3)

A
  1. Takes place at the Epiphyseal plate
  2. On the epiphyseal side the chondrocytes proliferate
  3. On the diaphyseal side the chondrocytes degenerate and die. Replaced by bone
42
Q

Where does bone growth in width take place? (3)

A
  1. Occurs through appositional growth
  2. In Periosteal deposition it contributes to the overall growth of flat bones and thickening of long bones
  3. In Endosteal deposition it contributes to the growth of trabecular bones and endosteal cortex (Haversian system)
43
Q

What happens when bone deposition exceeds resorption?

A

There is an increase in bone mass

44
Q

What is the peak bone mass for an individual? (3)

A
  1. Maximum amount of bone matrix attained by an individual
  2. Reached at age 20-25 years.
  3. Bone mass begins to decline
45
Q

What is modeling in bone growth?(2)

A
  1. A process of bone reorganization that also occurs during bone growth.
  2. Changes in size and shape of the bones continue throughout life
46
Q

What is bone remodeling? (5)

A
  1. A continuous process throughout life to repair damaged bone
  2. Bone matrix constantly being removed and rebuilt
  3. Osteoclasts resorb old bone
  4. Osteoblasts deposit a layer of osteoid on the surface of pre-existing bone
  5. Ion homeostasis is maintained and the bone is reinforced for increased stress
47
Q

What is bone remodeling during childhood? (2)

A
  1. Process is very active

2. Bone synthesis exceeds bone resorption

48
Q

What is bone remodeling during adulthood?

A
  1. Remodeling begins with localized resorption
49
Q

What is bone remodeling in young adults?

A
  1. Bone synthesis and resorption are balanced
50
Q

Which bone has a higher rate of remodeling?

A

Trabecular bone has a higher rate of remodeling than compact bone

51
Q

What happens during bone remodeling in advancing age?

A
  1. A reduction in bone mass known as osteoporosis
52
Q

What is osteoporosis? (5)

A
  1. When bone resorption exceeds bone synthesis
  2. Creates a reduction in bone mass
  3. Disruption of trabecular network
  4. Thinning of trabeculae
  5. Possible osteoclastic perforation
  • This increases a risk of fracture
  • 5-10% bone turn over annually for healthy adults
  • Strict bed rest cause 1-2% trabecular bone turn over per week
53
Q

What is osteopenia?

A

Decrease rate of osteoid synthesis leads to the reduction in bone mass

54
Q

What is osteopenia?

A
  1. Occurs in adults

2. Ca absorption from GI tract is prevented that causes a deficiency of vitamin D

55
Q

What is Rickets?

A
  1. Occurs in children
  2. Osteoid synthesis is normal
  3. Ca salt are not deposited, which softens and weakens bone
56
Q

What occurs during fracture repair? (5)

A
  1. A hematoma is formed from the collection of blood from a fracture
  2. Hematoma is removed by macrophages and inflammatory leukocytes
  3. Replaced by a soft fibrocartilage that is rich in collagen and fibroblasts
  4. Fibrocartilage is replaced by woven bone
  5. Vasculature is reestablished
  • A scar is collagen buildup
57
Q

What are inflammatory leukocytes?

A
  1. Release inflammatory substances that cause cell proliferation and new blood vessel formation
58
Q

What is the blood and nerve supply of long bones?

A
  1. Nutrient artery
  2. Epiphyseal artery
  3. Metaphyseal artery
  4. Periosteal artery (provide blood to muscles)
59
Q

What is metaphysis?

A
  1. MOST vascular part of long bone

2. Where most bacterial infections occur

60
Q

What blood vessel are flat cranial and irregular bones supplied with?

A
  1. Periosteal vessels
61
Q

What blood vessel are flat bones (pelvic and shoulder girdle) supplied with?

A
  1. Periosteal artery

2. Nutrient artery

Clinical Anatomy Skeletal System 2 (4 decks)

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