Bone Flashcards
Where does intramembranous ossification take place?
within condensations of meenchymal tissue- tissue that can differentiate into many types of cells
What kind of bones develop by intramembranous ossification?
Flat bones e.g. skull, clavicle, scapula and pelvic bone
What else does intramembranous ossification do?
Thickens long bones
What are the stages of intramembranous ossification?
- Small cluster of mesenchymal stem cells form a tight cluster of cells (nidus)
- MSCs become osteoprogenitor cells (more golgi and RER)
- Osteoprogenitor cells become osteoblasts
- Osteoblasts lay down extracellular matrix containing type I collagen (osteoid)
- Osteoid mineralises to form bone tissue spicules, surrounded by osteoblasts, contain osteocytes
- Spicules form trabeculae which form woven bone and is replaced by lamellae of mature compact bone
What is the difference between bone from intramembranous ossification and bone from endochondral ossification?
Intramembranous contains osteocytes, osteons, Haversians and Volkmanns canals
What is cancellous bone?
Spongy, network of fine bony columns, spaces filled with bone marrow
What is compact bone?
External surface of bones- 80% of skeletal mass
What do haversian and Volksmann canals do?
Carry blood vessels, lymph vessels and nerves
What is the difference between immature and mature bone?
Immature has osteocytes randomly arranged
matures osteoctes are arranged in concentric lamellae of osseous
Reabsoprtion canals in mature bone run parallel with osteon long axes
What are canaliculi?
Tiny interconnecting tunnels
What are gap junctions used for?
so nutrients can be passed between osteocytes
What is the trabeculae?
The bone part of cancellous bone, same as compact bone without haversian and volkmanns canals
How is cancellous bone remodelled?
A cutting cone contains Osteoclasts which release H+ and lysosomal enzymes and creates a tunnel
What can osteons do?
Branch and terminate
What are bones made up of?
Mineral, collagen, water, non-collagen proteins