Bone Development Flashcards
What type of ossification directly develops from mesenchyme?
Intramembranous ossification (never has a cartilage stage)
What type of ossification has a cartilage precursor?
Endochondral ossification
What is the process depicted in the image?
Intramembranous ossification
What protein begins ossification?
BMP
Locations of intramembranous ossification
Flat bones of skull and face and the scapula
Locations of endochondral ossification
Arms and legs, vertebral column, base of skull (skull is a composite of both types)
How many ossification centers do long bones have?
2: primary (forms in the center of the bone) and secondary (forms in the epiphysis)
How many ossification centers do short bones have?
1: primary
Endochondral Ossification Steps
- 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
What are the 6 long bones?
- femur
- tibia
- fibula
- humerus
- radius
- ulna
Endochondral bone growth: lengthening
Interstitial growth in the epiphyseal plate
Endochondral bone growth: thickening
Appositional a little growth under the periosteum
What is a mixed spicule?
A transition area that possesses both cartilage and bone
Mixed spicule labeled components
ID
Mixed spicule
ID
short bone (phalanges)
ID
long bone
Where is the epiphyseal/growth plate located?
Between the primary and secondary ossification centers
ID
Growth plate
Growth plate labeled zones and functions
What zone are mixed spicules located?
Ossification zone
Epiphyseal plate vs epiphyseal line
Children have a plate and adults have a line
Why is the jaw an exception to intramembranous ossification?
Because it develops secondary cartilage for the condyle
*It is considered intramembranous, but with a growth plate
If cartilage is eroded in a joint, can it be replaced?
No
Since there is no periosteum in joints, where do they receive their nutrients?
Synovial fluid
How long does it take to remodel bones?
3-7 years
How long does bone resorption take?
2-3 weeks
How long does bone deposition take?
2 months
What produces RANKL in bone?
PTH produces RANKL
In bone remodeling, what are the two cones?
-Cutting cone, area of remodeling bone (osteoclasts)
-Closing cone, area of depositing bone (osteoblasts)
What is a moderate loss of bone density referred to?
Osteopenia
What is a severe loss of bone density referred to?
Osteoporosis
What causes osteoporosis?
An imbalance between osteoblasts and osteoclasts
T1 Osteoporosis
- post‐menopausal women due to decreased estrogen
T2 Osteoporosis
- elderly individuals usually 70+ and older (affects everyone)
T3 Osteoporosis
- secondary to drug therapy (corticosteriod) or diseases
Normal bone vs osteoporosis
Peak bone density age (men and woman)
20s-40s
Are osteoids mineralized?
NO
What secretes matrix vesicles
Osteoblasts
What is rickets and what causes it
- Defective mineralization of developing bones in kids
- Vitamin D or calcium deficiencies
What is osteomalasia and what causes it
- Defective mineralization of developing bones in adults
- Makes bones soft
How many steps in fracture repair?
4
What are the steps to fracture repair
- 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
What is the mediator between osteoblast and osteoclast?
RANKL
