MSK Flashcards
Endochondral bone healing
- involves formation of a cartilaginous template that later gets replaced with bone
- a soft callus is initially formed
- chondrocytes in the callus transform into osteoblasts
- osteoblasts lay down bone matrix and the callus is replaced by hard bone tissue
- more common in long bones such as the femur
Intramembranous bone healing
- bone forms directly within a connective tissue membrane without the involvement of a cartilaginous template
- osteoblasts differentiate from mesenchymal stem cells
- osteoblasts produce and deposit bone matrix directly, forming woven bone
- woven bone remodelled to lamellar bone over time
- more common in flat bones such as in the skull
What bones undergo intramembranous bone formation
- flat bones such as the skull
- clavicles
Why has the patient got half a clavicle and expanded skull vault
Cleidocranial dysplasia develops when there is a problem with the RUNX2 gene.
RUNX2 plays a role in osteoblast formation and chondrocyte maturation.
This leads to underdeveloped bones.
Large cranial vault due to delay in closing the cranial vault sutures, allowing the skull to expand for a longer period of time.
The clavicle doesn’t fully form as the body can’t produce enough osteoblasts necessary for ossification
Anatomy of the hip
- hall and socket joint between head of femur and pelvic acetabulum
- designed for stability and weight bearing rather than providing a large range of movement
- hip bones are the ilium, pubis and ischium (fuse during teenage years)
- ligaments are present to provide stability, they are intra or extra capsular
- intracapsular: ligament of the head of the femur
- extracapsular: iliofemoral, pubofemprak and ischiofemoral
Blood supply to femoral head
Main blood supply from the medial femoral-circumflex artery and lateral femoral-circumflex artery
These are large branches of the femoral artery which is a branch of the external iliac artery
What are the different types of bone cells
Osteoblast, osteocyte, osteoclast, osteogenic cells
What hormones affect bone cells
Parathyroid hormone
Calcitrol
Calcitonin
What are osteoblasts
Immature bone cells that secrete organic components of matrix.
Responsible for making new bone and repairing old bone
What are osteocytes
Inactive osteoblasts that are trapped in their own matrix.
Maintain connections to other osteocytes and osteoblasts and are important for communication with bone tissue
What are osteoclasts
Multinucleate cells that break down bone by releasing enzymes and acids to dissolve bone matrix
What are osteogenic cells
Undifferentiated stem cells that differentiate into bone cells
What effect does parathyroid hormone have on bone cells
Stimulates bone formation by regulating osteoblast formation and increasing the number of osteoblasts
How does calcitrol affect bone cells
It is a hormone derived from vitamin D that stimulates the intestine to absorb enough calcium and phosphorus
How does calcitonin affect bone cells
Inhibits bone breakdown and therefore prevents excessive calcium levels in the blood
