Bone Flashcards
What are the two ossification types?
Endochondrial ossification
- The formation of long bones from a cartilage template
- Continues lengthening is by ossification at epiphyseal plates (= appositional growth –> growth at edges)
Intra-membranous Ossification
- The formation of bone from clusters of MSC in the centre of bone –> trabecular (cancellous) bone
eg. interstitial growth (growth in the middle)
How does bone form in utero?
At 14 weeks gestation;
- Flat bone develops from mesenchymal tissue, by intra-membranous ossification
- Long bones require a cartilage template in order to develop by endochondrial ossification
How does the parietal bone develop in utero?
- Mineral deposits within the many trabeculae radiate outward from a central point (the earlier ossicifation centre)
In postnatal development how does the compact bone of the skull develop?
Volkmann’s canals connect osteon to osteon
What are the common characteristics of bone disease? Examples of bone disease
Depletion of bone mass always characterises disease. Loss of mass within the trabecular bone is particularly relevant to increased suseptability to fractures.
- Osteogenesis imperfecta
- Rickets and osteomalacia
- Osteoporosis
- Achondroplasia
What is Osteogenesis Imperfecta and what causes it?
- “Brittle Bone Disease”
- Mutation in COL1A gene
- Incorrect production of collagen 1 fibres
- Weak bones and increased fracture risk
- Shortened height and stature
- Mainly affects neonates and children
What is Rickets and what causes it?
- Mainly affects children
- Caused by Vitamin D deficiency
- Ineffective mineralisation leading to weakened bone development
- Soft bones leading to characteristic bowed legs
- Shortened height and stature
- Painful to walk
What is osteomalacia and what causes it?
- Rickets in adults
- Vitamin D deficiency
- Lower mineralisation
- Increased osteoid
- Increased calcium resorption
- Kidney disease: activates vitamin D
- Protection from sunlight: produces vitamin D
- Surgery: stomach and intestine
- Drugs: phenytoin prevents vitamin D absorption
What is Achondroplasia?
- Inherited mutation in the FGF3 gene
- FGF promotes collagen formation from cartilage (endochondrial ossification affected; intramembranous ossification unaffected)
- Results in short stature but normal sized head and torso (long bones cannot lengthen properly)
What are the 5 types of bone?
- Long
- Short
- Flat
- Irregular
- Sesamoid
What are long bones? Where are they found?
- Longer than wide eg. femur, metacarpals
- Mostly located in the appendicular skeleton
FUNCTION: Support body weight and facilitate movement
What are short bones? Where are they found?
- As long as they wide eg. carpals and tarsals
FUNCTION: Provide stability and some movement
What are flat bones and where are they found?
- Somewhat flattened and roughly parallel opposite edges, eg. occipital bone of skull, sternum and ribs, scapulae
FUNCTION: Protects internal organs and provides large area for attachment for muscles
What are irregular bones and where are they found?
- Vary in shape and structure so don’t fit into any other categories
- Complex shape
FUNCTION: Protect internal organs (eg. vertebrae protect spinal cord, Sacrum protects organs in the pelvic cavity) and provide anchor points for muscle groups
What are sesamoid bones and where are they found?
- Seed-like shape
- Embedded in tendons, eg. patella
FUNCTIONS: Protect tendons from stress and damage from repeated wear and tear
