bone growth Flashcards
What is the term for bone formation?
Ossification or osteogenesis
In which four situations does bone formation occur?
- Initially in embryo & foetus
- Growth
- Remodeling
- Repair of fractures
What are the two main mechanisms of bone formation?
- Intramembranous ossification
- Endochondral ossification
What is intramembranous ossification?
Bone forms directly in mesenchyme layers
What is the role of mesenchyme in bone formation?
Mesenchyme model is replaced with bone
When does endochondral ossification begin?
Around week 8 of development
Which bones are formed by endochondral ossification?
- All bones below the base of the skull
- Clavicles
What is the first step in endochondral ossification?
Bone collar forms around the diaphysis of the hyaline cartilage model
What happens during the second step of endochondral ossification?
Cartilage calcifies in the center of the diaphysis
What is the periosteal bud?
Contains nutrient artery, vein, nerve fibers, red marrow elements, osteoprogenitor cells, and osteoclasts
What occurs during postnatal bone growth?
- Bones grow in length and thickness
- Chondrocytes in the epiphyseal plate divide
What hormone controls bone growth during infancy and childhood?
Growth Hormone (GH)
At what age does epiphyseal plate closure typically occur in females?
18 years
What is the time required for the entire skeleton to be replaced in adults?
Every 10 years
What regulates blood levels of calcium?
Negative feedback loops
What is the effect of parathyroid hormone on bone?
Increases osteoclast activity and decreases loss in urine
What factors affect bone growth?
- Adequate minerals (Calcium, Magnesium, Phosphorus)
- Vitamins A, C, D
What is osteomalacia?
A disorder in which bones are poorly mineralized, soft, and weak in adults
What is osteoporosis?
A disease in which bone resorption exceeds bone formation
Which factors are risk factors for osteoporosis?
- Decreased sex hormones
- Insufficient bone stress
- Poor diet in calcium, Vitamin D, or protein
- Smoking and drinking
- Genetics
What are the types of fractures based on completeness?
- Complete
- Incomplete
What are the types of fractures based on penetration of skin?
- Open (compound)
- Closed (simple)
What is the typical cause of fractures in young individuals?
Trauma
What is the typical cause of fractures in older individuals?
Change in the property of bones
What vitamin is important for bone health and can be obtained from sunlight?
Vitamin D
