CH 7 Bone formation and remodeling

Question 1

Ossification

Answer 1

Formation of bone a.k.a. osteogenesis

Question 2

Two types of ossification

Answer 2

1. Intramembranous ossification
2. Endochondral ossification

Question 3

Intramembranous ossification: stage, types of bones, starting material

Answer 3

-Embryonic stage
-Produces flat bones of skull, clavicle, part of mandible
-Starting material is embryonic mesenchyme

Question 4

Stages of intramembranous ossification

Answer 4

1. Deposition of osteoid tissue
2. Calcification of osteoid tissue
3. Mesenchyme condensing
4. Formation of surface compact bone

Question 5

Intramembranous ossification:
Stage 1: Deposition of Osteoid tissue

Answer 5

Mesenchyme condenses; mesenchymal cells line blood vessels and become osteoblasts; they secrete pre-bone

Question 6

Collagenous osteoid tissue

Answer 6

Pre-bone; scaffolding of collagenous fibers

Question 7

Intramembranous ossification:
Stage 2. Calcification of osteoid tissue

Answer 7

-Calcium phosphate and hydroxyapatite crystallize on collagen fibers
-Osteoblasts trapped in lacuna and become osteocytes
-blood vessels compact to central location

Question 8

Intramembranous ossification:
Stage 3. Mesenchyme condensing

Answer 8

-Mesenchyme becomes periosteum around edges
-Formation of spongy bone (trabeculae)


Question 9

Trabeculae

Answer 9

 honeycomb shaped Slender calcification in spongy bone; from blood vessels getting trapped

Question 10

Intramembranous ossification:
4. Formation of compact bone at surface

Answer 10

Osteoblasts near periosteum deposit layers of compact bone; bone sandwich

Question 11

Bone sandwich in Stage four of intramembranous ossification

Answer 11

Mesenchyme
Periosteum
Compact bone
Spongy bone
Compact bone
Periosteum
Mesenchyme

Question 12

Endochondral ossification:
Develops from, bone types, plate?

Answer 12

-Cartilage to bone
-Most bones: long bones, vertebrae, ribs, sternum, pelvic girdle, etc.
-Epiphyseal plate on either side of bone


Question 13

Epiphyseal plate

Answer 13

Growth zone surrounded by metaphysis

Question 14

Stages of endochondral ossification

Answer 14

1. Hyaline cartilage formation
2. Formation of primary ossification center
3. Infiltration of blood vessels
4. Birth: formation of secondary marrow cavity
5. Child: filling of spongy bone
6. Late teen/adult: closing of epiphyseal plate

Question 15

Endochondral ossification stage one: hyaline cartilage formation

Answer 15

-Mesenchyme develops into hyaline cartilage
-Surrounded by Perichondrium (chondrocytes)

Question 16

Perichondrium

Answer 16

Fibrous outer shell that produces chondrocytes in stage one of endochondral ossification

Question 17

Endochondral ossification
stage 2: formation of primary ossification center

Answer 17

-Chondrocytes inflate and die= Primary ossification center
-Perichondrium turns into Periosteum starts producing osteoblasts and develops bony collar

Question 18

Primary ossification center and stage two of endochondral ossification

Answer 18

Lacuna join into one cavity; walls between calcify

Question 19

Bony collar

Answer 19

Periosteum produces osteoblasts that create bone around highland cartilage

Question 20

Endochondral ossification
Stage 3: vascularization of bone

Answer 20

-Blood vessels and osteoclasts invade primary ossification center (make Primary marrow cavity)
-Osteoblast deposit layers on bone
-Secondary ossification center as chondrocyte death push to epiphysis
-Metaphysis

Question 21

Metaphysis

Answer 21

Transitional Cartlidge to bone area; growth zone

Question 22

Endochondral ossification
Stage 4: formation of secondary marrow cavity (birth)

Answer 22

-Blood vessels infiltrate with osteoclasts and create secondary marrow cavity in epiphysis
-Osteoblasts continue laying out tissue; Primary marrow cavity and larges and creates diaphysis

Question 23

Endochondral ossification
Stage five: epiphysis fills with spongy bone (child)

Answer 23

-Creation of spongy bone in secondary marrow cavity from osteoblasts
-Cartilage left only at articular joints and Metaphysis surrounding epiphyseal plates

Question 24

Endochondral ossification
Stage six: closing of epiphyseal plate (late teen/adult)

Answer 24

-All remaining cartilage used up; gap closes into epiphyseal line
-Primary and secondary marrow cavity join together

Question 25

In bone growth and remodeling, Which directions can bones grow?

Answer 25

Growth: length Remodeling: width

Question 26

Bone elongation

Answer 26

Occurs at epiphyseal plate With metaphysis on each side

Question 27

Zones of metaphysis

Answer 27

1. Zone of reserve cartilage 2. Zone of proliferation 3. Zone of cell hypertrophy 4. Zone of calcification 5. Zone of bone deposition

Question 28

Zones of metaphysis: Zone 1, reserve cartilage

Answer 28

Closest to end of bone; has hyaline cartilage and chondrocytes

Question 29

Zone of metaphysis: Zone 2, Proliferation

Answer 29

Chondrocytes multiplying and dividing into lacuna

Question 30

Zones of metaphysis: Zone 3. Cell Hypertrophy

Answer 30

Chondrocytes get bigger and start to die

Question 31

Zones of metaphysis Zone 4. Calcification

Answer 31

As chondrocytes die, calcification of matrix around lacuna where chondrocytes are

Question 32

Zones of metaphysis Zone 5. Bone deposition

Answer 32

Full death of chondrocytes, breakdown of lacuna walls, bone put down by osteoblast, forming of trabeculae of spongy bone which Remains for life Subject to lifelong remodeling; all zones in epiphysis turn into zone five

Question 33

How does growth occur in adolescents?

Answer 33

Multiplication of chondrocytes in metaphysis zone two and hypertrophy of chondrocytes in zone three push zone one towards the end of the bone= elongation

Question 34

Epiphyseal line

Answer 34

Epiphyseal plate is closed; no more cartilage to elongate

Question 35

Appositional growth

Answer 35

Growth of bones in diameter and thickening along outer perimeter

Question 36

Which kind of ossification provides appositional growth?

Answer 36

Intramembranous ossification

Question 37

Bone remodeling

Answer 37

Continual process in which old bone is absorbed by osteoclasts and some osteocytes, while osteoblasts deposit new bone

Question 38

Three R’s for remodeling

Answer 38

1. Release minerals to blood 2. Reshape bone in response to use/disuse 3. Repair microfractures

Question 39

Wolff’s Law

Answer 39

Architecture of bone is determined by the mechanical stress placed on it More stress= more compact structuring by osteoblasts Less stress= less compact from osteoclasts