Bone Development

Question 1

What are the 2 types of bone formation mechanisms?

Answer 1

Intramembranous

Endochondral

Question 2

Intramembranous Bone Formation:

1. Many [] bones and [] bones develop in this manner
2. Formed directly from [] cells without going through the cartilage stage

Answer 2

1. Flat bones and craniofacial develop intramembranously
2. Formed directly from mesenchymal cells

Question 3

What are the steps of Intramembranous Bone Formation from mesenchymal –> Bone?

Answer 3

1. Mesenchymal cells condense to form a membrane like structure and then differentiate into osteoprogenitor cells
2. OP cells become larger and then differentiate into osteoblasts
3. Osteoblasts grow the bone through appositional growth and laying down osteoid.

Question 4

Endochondral Bone Formation:

1. [] bones and [] skeleton develop from pre-existing [] model
2. Contains [] and [] ossification centers
3. Bone formation starts in the middle regions, or the [],
4. The cartilage that remains between the primary and secondary ossification centers is called the [] []

Answer 4

1. Long bones and axial skeleton develop from pre-existing cartilage model
2. Contains primary and secondary ossification centers
3. Bone formation starts in the middle regions, or the Diaphysis.
4. The cartilage that remains between the primary and secondary ossification centers is called the Epiphyseal Plate/Growth Plate

Question 5

Steps in the Formation of a Primary Ossification Center:

1. [] changes into periosteum, through osteoprogenitor cells
2. [] start to hypertrophy and die
3. The old matrix starts to []
4. [] vessel Invasion
   
   1. [] bud grows into calcified cartilage, brings in [], which differentiate into []
   2. [] remove clacified cartilage while [] deposit bone matrix to form mixed []

Answer 5

1. Perichondirum changes into periosteum, through osteoprogenitor cells
2. Chondrocytes start to hypertrophy and die
3. The old matrix starts to calcify
4. Blood vessel Invasion
   
   1. Periosteal bud grows into calcified cartilage, brings in Osteoprogenitors, which differentiate into Osteoblasts
   2. Osteoclasts remove clacified cartilage while Osteoblast deposit bone matrix to form mixed spicules

Question 6

T/F

The mixed spicules that are formed during bone formation are a permanent bone structure?

Answer 6

False

They will get replaced by osteoclasts.

Question 7

What are the 5 zones of secondary ossification growth?

Answer 7

1. Zone of reserve Cartilage
2. Zone of Proliferation: Chondrocytes get in stacks of coins
3. Zone of Hypertrophy: Chondrocyte Hypertrophy
4. Zone of Calcified Cartilage: COndrocytes degenerated
5. Zone of resorption: formation of mixed spicules

Question 8

Bone growth is associated with bone []

Answer 8

Remodeling

Question 9

How do bones grow?

Answer 9

• Appositional growth under periosteum and endosteal resorption for thickening

Question 10

The [] plate will grow until puberty and will grow twoards the center of the bone.

Answer 10

Epiphyseal Plate

Question 11

Bone Remodeling:

1. Replace [] bone and maintain [] shape
2. Commences in [] and continues throughout life
3. Involves [] resorption and [] of bone matrix
4. Carried out by bone remodeling units consiting of [] and []

Answer 11

1. immature bone and maintains original shape
2. Utero
3. selective resorption; deposition of bone matrix
4. Osteablast and osteoclast

Question 12

What are the 2 zones of a “bone remodeling” unit and what is the function of each zone?

Answer 12

1. Cutting Zone
   
   1. ​resoprtion by osteoclasts, ~200um in diamater
   2. Found at the tip of the unit
2. Closing Zone
   
   1. ​New bone formation by osteoblast

Question 13

T/F

New Haversion system will stain lighter than an aging osteon?

Answer 13

True!

Question 14

What does osteopotrosis result in?

Answer 14

• Genetic disorder reducing the activity of osteoclasts.
• Leads to hyperdense bone (stone bone, marble bone)

Question 15

What does osteogenesis imperfect result in?

Answer 15

• Collagen disorder
• Leads to osteoporosis –> slender diaphysis

Question 16

1. Rickets is derived from a deficiency in…
2. Scurvy is derived from a deficiency in…
3. Vitamin A deficiency results in the…

Answer 16

1. Ca2+
2. Vitamin C
3. suppression of endochondral bone formation, and the inhibition of bone formatino and remodeling

Question 17

Osteoporosis = bone []

Answer 17

Loss

Question 18

Hormonal Factors effecting Bone Growth

1. Growth Hormone - promotes [] cartilage and bone []
2. Thyroid Hormone - deficiency in kids can lead to [] stature, [] bone maturation, mental []
3. Parathyroid Hormone - promotes bone [] by osteocytes and osteoclasts
4. Calcitonin - []osteoclast activity and bone resorption
5. Estrogen (Androgen) - activates [] to produce and secrete bone matrix, [] osteoclast activation

Answer 18

1. Growth Hormone - promotes epiphyseal cartilage and bone growth
2. Thyroid Hormone - deficiency in kids can lead to short stature, delayed bone maturation, mental retardation
3. Parathyroid Hormone - promotes bone resorption by osteocytes and osteoclasts
4. Calcitonin - inhibits osteoclast activity and bone resorption
5. Estrogen (Androgen) - activates osteoblasts to produce and secrete bone matrix, inhibit osteoclast activation

Question 19

What are the hormonal factors of bone growth we learned?

Answer 19

Growth Hormone

Thyroid

Parathyroid

Calcitonin

Estrogen/Androgen