Bone Histo Lecture

Question 1

Components of compact bone

Answer 1

Net positive charge
Attracts negative stains
Hypocellular
No clusters of osteocytes

Question 2

Cartilage vs bone cell type and location

Answer 2

Cartilage: large round cells in clusters in the ECM
Bone: ellipsoid, isolated cells in mineral, more hypocellular

Question 3

Cartilage vs bone texture

Answer 3

Cartilage: firm, gel-like, high tensile strength, resilience, elasticity
Bone: mineralized and hard

Question 4

Cartilage vs bone vascularization

Answer 4

Cartilage: avascular

Bone: vascular

Question 5

Cartilage vs bone metabolism

Answer 5

Cartilage: low metabolic rate

Bone: high metabolic rate

Question 6

Cartilage vs Bone ECM

Answer 6

Cartilage: type 2 collagen and Aggrecan\

Bone: type 1 collagen, small PG and glycoproteins

Question 7

Cartilage vs bone permeability

Answer 7

Cartilage: permeable

Bone: impermeable

Question 8

Cartilage vs bone growth

Answer 8

Cartilage: capacity for continued growth

Bone: complex structure with capacity for remodeling

Question 9

Osteoprogenitors

Answer 9

Stem cells for bone; spindle shaped, found near bone surface in periosteum and endosteum

Question 10

Bone lining cells

Answer 10

Flattened, line bone surfaces; likely are quiescent osteoblasts

Question 11

Osteoblasts

Answer 11

Bone-forming cells, proliferation, cuboidal, appear as sheets on bone surfaces; deposit Osteoid

Question 12

Osteocytes

Answer 12

Mature bone cells, non-proliferative, encased in mineral, filopodia for monitoring calcium levels

Question 13

Osteoclasts

Answer 13

Break down or resort bone, large, multinucleate, found on bone surfaces, not Mesenchymal

Question 14

Matrix composition of bone: 2 phases

Answer 14

Inorganic phase and organic phase

Question 15

Inorganic phase of bone ECM

Answer 15

Mineralized and make up 75%

Question 16

Organic phase of bone

Answer 16

Type 1 collagen (90%)
Small PG and glycoproteins (10%)

Total makes up 25%

Living

Question 17

Quarter staggered arrangements of type 1 collagen molecules into collagen fibril results in

Answer 17

Hole zones and cross striations of fibrils

Question 18

What happens in the hole zones

Answer 18

Calcium-binding molecules bind to collagen and mineral deposition occurs

Question 19

Mineral deposition in hole zones causes mineral plates to form which allows bone to

Answer 19

Bend

Question 20

Products of EO

Answer 20

Axial and appendicular skeleton and certain cranial bones

Question 21

Products of IO

Answer 21

Most cranial bones and periosteal bones

Question 22

Summary of Intramembranous ossification

Answer 22

Involves a direct differentiation of Mesenchymal or osteoprogenitor cells to osteoblasts, which secret a bone matrix. Bone forms through Apositional growth and the end result of IO is compact or cortical or dense bone without marrow cavity

Question 23

Trabecular bone has high surface area to sequester

Answer 23

Calcium

Question 24

IO summary steps

Answer 24

Mesenchymal cells and osteoids

Osteoids are mineralized and Mesenchymal cells become osteoblasts

Osteoblasts are trapped by mineral

Osteoblasts become osteocytes and create a mineralized bone matrix

Question 25

Osteocytes sends how much pressure bone is under and can sense …. Concentration

Answer 25

Calcium concentration

Question 26

When calcium is too low, what happens

Answer 26

Degradation

Question 27

When calcium is too high, what happens

Answer 27

Sequestering

Question 28

Osteocyte in its lacunae is encased by a mineralized osteoid matrix. Filopodia of the osteocytes extend into the canaliculi of the matrix in order to

Answer 28

Contact adjacent cells

Question 29

Osteoclasts are not Mesenchymal. They are of hematopoietic lineage and come from

Answer 29

Monocytes

Question 30

Primary bone

Answer 30

The first bone laid down, regardless of EO or IO, and represents a temporary immature skeleton

Question 31

Primary bone organization

Answer 31

Not well organized and greater cell-to-matrix ratio than mature bone

Question 32

Primary bone is replaced by ….. through

Answer 32

Primary bone is replaced by secondary bone through modeling and remodeling

Question 33

By the time the skeleton stops growing, all bone is

Answer 33

Secondary, lamellar bone

Question 34

In IO-derived bone, lamellar bone is organized in functional units called

Answer 34

Osteons

Question 35

Osteons consist of

Answer 35

Central Haversian canal with blood vessels and nerves, concentric lamellae of bone matrix, and inhabiting cells

Question 36

Bone remodeling steps

Answer 36

Osteoclasts degrade bone and create respiration pits Blood vessels inside pits and import osteoprogenitors which differentiate into osteoblasts Osteoblasts align along the exposed bone surface and secrete osteoid in lamellae around the central Haversian canal

Question 37

Bone modeling and remodeling occurs in all stages of life and depends on what 2 cells

Answer 37

Osteoclasts and osteoblasts

Question 38

Skeletogenesis modeling

Answer 38

Bones change width and shape Primary to secondary bone

Question 39

Adult homeostasis remodeling

Answer 39

Means for bone to adapt to mechanical pressure Calcium storage and release mechanism

Question 40

Pathology remodeling

Answer 40

Fracture repair, calcium imbalance, osteoblasts/osteoclasts dysfunction