Bone Flashcards
What forms the external surfaces of bones?
Compact bone
What forms the inside of bones?
Cancellous bone (spaces filled with bone marrow)
What are Haversian and Volkmann’s canals?
Go through compact bone and carry blood vessels, lymph vessels and nerves
How are osteocytes arranged in immature bone?
Randomly
How are osteocytes arranged in mature bone?
Concentric lamellae of osteons
What are Canaliculi?
Allow communication of cytoplasmic processes between adjacent osteocytes. They connect via gap junctions and connect with the central Haversian canal
What is the structure of cancellous bone?
Similar to compact bone, but there are no Haversian or Volkmann’s canals. There is also osteocytes between lamellae
What deposits bone?
Osteoblasts
What breaks down bone?
Osteoclasts
What do Osteoclasts release to break down bone?
H+
Lysosomal enzymes
How can bone resist fracture?
It has high tensile strength, but also the Lamellae can slip relative to one another to allow flexibility.
What initially happens when a bone fracture occurs?
Blood vessels break so a Haematoma forms (Mass of clotted blood)
Swelling
Inflammation
Bone cells at edge die
What happens after Haematoma formation in a bone fracture?
A fibrocartilaginous callus forms; Blood vessels infiltrate.
Procallus of granulation tissue forms
Fibroblasts produce collagen fibres
Spongy bone is starting to form.
What happens after Fibrocartilaginous callus formation in bone fracture?
Bone trabeculae appears in fibrocartilaginous callus
Converted to callus of cancellous bone by endochondrial and intermembranous ossification
What is the last stage in fracture repair?
Callus of spongy bone is remodelled into compact bone.
Osteoclasts break down material that bulges out of the bone
Final shape is same as original.
