Injury and healing Flashcards
Some functions of the skeleton
Protects organs, store of calcium and phosphate and produces blood cells.
What are mesenchymal stem cells?
Stem cells that can give rise to different connective tissue cells.
What are the two types of bone formation?
Intramembranous and endochondral.
What kind of ossification forms flat bones?
Intramembranous ossification.
What kind of ossification forms long bones?
Endochondral ossification.
Key difference between intramembranous and endochondral ossification?
Intramembranous produced bone from fibrous membrane (straight from mesenchymal cells) while endochondral produces bone from hyaline cartilage model.
How does intramembrous ossification occur?
MSC’s form osteoblasts. Osteoblasts cluster together and secrete osteoid which traps osteoblasts to form osteocytes. MSC’s form periosteum and formation of trabecular matrix occurs. Crowded red blood cells condense into red bone marrow.
How is bone marrow anatomically positioned differently in flat bones and long bones?
Bone marrow is present in a cavity in a long bone but in a flat bone it isn’t.
What are osteons and where are they located?
Osteons are the units that make up cortical bone.
What are the structures and cells present in an osteon?
Haversian canal, bone matrix and osteocytes, osteoblasts, volkmann’s canal.
What is the haversian canal?
Structure present in the centre of an osteon; contains blood vessels, nerves and lymph vessels.
What are the concentric lamellae in an osteon?
Rings of bone matrix.
What are the lacunae in an osteon?
Between rings, contain osteocytes.
What are the interstitial lamella?
Spaces inbetween osteons.
Where would you find osteoblasts in an osteon?
Outer part of the osteon.
What is a volkmann’s canal and where would you find it?
Transverse canals that are inbetween haversian canals or emerge from periosteum that contain blood vessels.
What is trabeculae?
Makes up cancellous bone (spongy bone) and has honeycomb structure.
Osteoblasts function
Forms bone by secreting osteoid and catalysing mineralisation of osteoid.
What is osteoid?
Organic bone matrix (unmineralised).
What proteins are present in osteoid?
Collagen type I, proteoglycans and glycoproteins
What makes up the ground substance in osteoid?
Proteoglycans and glycoproteins.
Osteocyte function
Senses mechanical strain to direct osteoblasts and osteoclast activity.
What connects osteocytes and what’s the function of these connections?
Canaliculi. Exchange of nutrients.
Osteoclast function
Degrade bone by phagocytosis.
What are osteoclasts derived from?
Bone marrow.
What converts osteoblast to osteocytes?
When osteoblasts get embedded in osteoid.
What is inorganic bone matrix made up of?
Calcium hydroxyapatite and osteocalcium phosphate.
What are osteogenic cells?
Bone stem cells derived from MSC’s.
Where would you find osteogenic cells?
Periosteum.
Where would you find osteoblasts?
Periosteum and endosteum.
What is the endosteum?
Membrane that lines medullary cavity.
Where would you find osteocytes?
Bone matrix.
Where would you find osteoclasts?
Sites of old and injured bone.
Can you describe the process of endochondral ossification?
Bone collar forms around diaphysis of the hyaline cartilage model. Cartilage calcifies in the center of the diaphysis and then develops cavities. Blood vessel of periosteal bud invades internal cavities and formation of cancellous bone occurs. Diaphysis elongates and medullary cavity forms. Secondary ossification center develops after birth at the epiphysis. Ossification occurs at epiphysis; cartilage is replaced by bone. Eventually only cartilage left is at epiphyseal plate and articular cartilage.
What is the diaphysis?
Central part of long bone.
What does invasion of periosteal bud mean?
A periosteal bud, which consists of blood vessels, lymph vessels and nerves, invades the cavity left by the chondrocytes.
What cell types does the periosteal bud contain?
The vascularization utlimately carries hemopoietic cells, osteoblasts and osteoclasts inside the cavity. The hemopoietic cells will later form the bone marrow.
How is the bone collar formed in endochondral ossification?
The osteoblasts secretes osteoid against the shaft of the cartilage model.
What is articular cartilage?
Cartilage present on the surface of the bone at the joint only.
What is the epiphysis?
Zone between epiphyseal plate and joint.
What cells break down cartilage?
Osteoclasts.
What is the periosteum?
Connective tissue covering of bone.
What is the outer cortex made up of?
Cortical bone.
Where is cancellous bone located in long bone?
Epiphysis.