Bone

Question 1

Steps of intramembranous ossification?

Answer 1

1. Small cluster of mesenchymal stem cells differentiate into osteoblasts 2. These then lay down EM (type I collagen-osteoid) 3. Osteoid mineralises to form a spicule 4. Spicule form a trabeculae 5. These merge to form a woven bone

Question 2

Endochondral ossification steps?

Answer 2

Hyaline cartilage ossified to bone in columns- lengthens shaft

Question 3

Fracture repair steps?

Answer 3

1. Broken blood vessels causes formation of haematoma, bone cells at end die and are phagocytosed 2. New blood vessels infiltrate and fibrocartilgenous callus formed when fibroblasts lay down collagen 3. Endochondral Ossified to bone 4. Remodelled by osteoblasts and clasts

Question 4

What causes Osteogenesis imperfecta?

Answer 4

Autosomal dominant Mutation in gene for type 1 collagen