Bone Development

Question 1

What type of ossification directly develops from mesenchyme?

Answer 1

Intramembranous ossification (never has a cartilage stage)

Question 2

What type of ossification has a cartilage precursor?

Answer 2

Endochondral ossification

Question 3

What is the process depicted in the image?

Answer 3

Intramembranous ossification

Question 4

What protein begins ossification?

Answer 4

BMP

Question 5

Locations of intramembranous ossification

Answer 5

Flat bones of skull and face and the scapula

Question 6

Locations of endochondral ossification

Answer 6

Arms and legs, vertebral column, base of skull (skull is a composite of both types)

Question 7

How many ossification centers do long bones have?

Answer 7

2: primary (forms in the center of the bone) and secondary (forms in the epiphysis)

Question 8

How many ossification centers do short bones have?

Answer 8

1: primary

Question 9

Endochondral Ossification Steps

Answer 9

• fetal hyaline cartilage develops
• cartilage calcifies and periosteal bone collar forms around diaphysis
• primary ossification center forms in diaphysis
• secondary ossification center forms in epiphysis
• bone replaces cartilage (except articular and epiphyseal plates)
• epiphyseal plates ossify and form epiphyseal lines

Question 10

What are the 6 long bones?

Answer 10

• femur
• tibia
• fibula
• humerus
• radius
• ulna

Question 11

Endochondral bone growth: lengthening

Answer 11

Interstitial growth in the epiphyseal plate

Question 12

Endochondral bone growth: thickening

Answer 12

Appositional a little growth under the periosteum

Question 13

What is a mixed spicule?

Answer 13

A transition area that possesses both cartilage and bone

Question 14

Mixed spicule labeled components

Answer 14

Question 15

ID

Answer 15

Mixed spicule

Question 16

ID

Answer 16

short bone (phalanges)

Question 17

ID

Answer 17

long bone

Question 18

Where is the epiphyseal/growth plate located?

Answer 18

Between the primary and secondary ossification centers

Question 19

ID

Answer 19

Growth plate

Question 20

Growth plate labeled zones and functions

Answer 20

Question 21

What zone are mixed spicules located?

Answer 21

Ossification zone

Question 22

Epiphyseal plate vs epiphyseal line

Answer 22

Children have a plate and adults have a line

Question 23

Why is the jaw an exception to intramembranous ossification?

Answer 23

Because it develops secondary cartilage for the condyle
*It is considered intramembranous, but with a growth plate

Question 24

If cartilage is eroded in a joint, can it be replaced?

Answer 24

No

Question 25

Since there is no periosteum in joints, where do they receive their nutrients?

Answer 25

Synovial fluid

Question 26

How long does it take to remodel bones?

Answer 26

3-7 years

Question 27

How long does bone resorption take?

Answer 27

2-3 weeks

Question 28

How long does bone deposition take?

Answer 28

2 months

Question 29

What produces RANKL in bone?

Answer 29

PTH produces RANKL

Question 30

In bone remodeling, what are the two cones?

Answer 30

-Cutting cone, area of remodeling bone (osteoclasts) -Closing cone, area of depositing bone (osteoblasts)

Question 31

What is a moderate loss of bone density referred to?

Answer 31

Osteopenia

Question 32

What is a severe loss of bone density referred to?

Answer 32

Osteoporosis

Question 33

What causes osteoporosis?

Answer 33

An imbalance between osteoblasts and osteoclasts

Question 34

T1 Osteoporosis

Answer 34

- post‐menopausal women due to decreased estrogen

Question 35

T2 Osteoporosis

Answer 35

- elderly individuals usually 70+ and older (affects everyone)

Question 36

T3 Osteoporosis

Answer 36

- secondary to drug therapy (corticosteriod) or diseases

Question 37

Normal bone vs osteoporosis

Answer 37

Question 38

Peak bone density age (men and woman)

Answer 38

20s-40s

Question 39

Are osteoids mineralized?

Answer 39

NO

Question 40

What secretes matrix vesicles

Answer 40

Osteoblasts

Question 41

What is rickets and what causes it

Answer 41

- Defective mineralization of developing bones in kids - Vitamin D or calcium deficiencies

Question 42

What is osteomalasia and what causes it

Answer 42

- Defective mineralization of developing bones in adults - Makes bones soft

Question 43

How many steps in fracture repair?

Answer 43

4

Question 44

What are the steps to fracture repair

Answer 44

- Hematoma formation: mass of clotted blood - Callus formation: soft callus (cartilaginous) splint - Bony callus formation: hard callus (spongy/bony) splint - Bone remodeling: replace spongy bone with compact bone

Question 45

What is the mediator between osteoblast and osteoclast?

Answer 45

RANKL