Bones Flashcards
What are the 5 bone types?
- Long
- Short
- Irregular
- Flat
- Sesamoid
Basic bone structure of a long bone (top to bottom)
Epiphysis Metaphysis Diaphysis Metaphysis Epiphysis
2 types of tissue in a bone? and characteristics
Compact bone is dense and is designed to withstand large amounts of compressive force.
Spongy bone has open spaces, it is supportive but also light in weight. designed to be ready for breakdown and remodeling by osteoclasts/blasts.
That sheath like structure surrounds the bone?
Periosteum
What us the medullary cavity?
The medullary cavity is the hollow part of bone that contains bone marrow.
What is an osteon?
The osteon consists of a central canal called the osteonic (haversian) canal, which is surrounded by rings called concentric lamellae. Lamellae are perpendicular to each other in order to resist twisting forces in multiple directions. Between the rings of matrix, the bone cells (osteocytes) are located in spaces called lacunae.
What runs down the center of an osteon?
Central canals contain blood vesicles, nerves and lymphatic vesicles which branch off at right angles through a perforating canal extending out to the periosteum and the endosteum.
What are the periosteum and the endosteum?
Thin layers of membrane of connective tissue that lines the inner surface of the medullary cavity of long bones.
The endosteum is also the lining of the central canal of the osteon allowing remodeling of osteons over time.
What is an osteocyte
Bone (osteo) cell (cyte)
Located in lacuna (spaces in the lamellae)
has canaliculi branching off connecting to other lacunae and with the central canal they can send nutrients to be transported into the osteocytes and waste transported out.
what is trabeculae?
The main product of spongy bone. They may look like a random structure where it in fact it forms along lines of stress to transport force to the compact bone
Why is spongy bone honeycombed in structure?
In order for the muscles to move it easier
Functional differences of bone types?
Compact Compact bone like a drinking straw Good at absorbing/transmitting forces in single direction Heavy
Spongy
Spongy absorb forces from multiple directions
Found where little force absorption or force from
many directions
Light weight
Support and protection for bone marrow cells
Bone matrix: 3 major components of bone and their approximated percentage?
Calcium phosphate 66% of total bone mass
Collagen fibres 33%
Bone cells 2%
Calcium phosphate
- Forms hydroxyapatite (naturally occurring mineral form of calcium apatite) through interaction with calcium hydroxide
- Bind calcium carbonate, sodium, magnesium, fluoride
- Provides compression strength
Collagen fibres
• Provides tensile strength
Bone cells
• Maintain the bone matrix
4 types of bone cells?
Osteoclasts
• Break down bone matrix
• Osteolysis
Osteoblasts
• Produce new bone substance
• Osteogenesis
Osteocytes
• Mature bone cells
Osteoprogenitor cells
• Mesenchymal cells
• Differentiate into osteoblasts
• Important in fracture & repair
5 characteristics of bone remodeling
- Normal process/constantly occurring
- Maintains structural integrity (strength)
- Balance of reabsorption and formation important
- Mechanism for shape change over time
- Remodel after a bony injury
What are factors that affect bone remodeling?
Dietary factors
• Calcium & phosphate
• Magnesium, citrate, carbonate & sodium
• Vit A, C & D
Hormonal factors • Parathyroid hormone • Calcitonin • GH & thyroxine • Sex hormones (estrogen & testosterone)
Strain • Loading through activity/exercise (or lack thereof) • Magnitude, rate and direction • Influenced by activity type • Immobilisation
Aging
Gender
• Hormonal factors (post-menopausal)
4 markers of bone strength
Bone mineral density (BMD)
Bone mineral content (BMC)
Size
Geometry
How is bone density measured?
Dual energy X-ray absorptiometry scan (DEXA or DXA)
Quantitative computed tomography (QCT)
What does different bone types look like in a DEXA scan?
Compact looks white and more solid whereas spongy bone looks grey and dull as it is less dense.
What information does a DEXA scan provide?
A detailed image on the scanned bone as well as detailed information of various tissues within the scanned areas such as fat mass, lean mass, fat percentage BMI score and BMC.
How are DEXA scans are compared?
Compared to young norms, compared with results of people with the same gender and race. This is how t scores are determined.
In regard to a DEXA scan what is a t score?
T score expresses the bone density in terms of standard
deviations below peak young adult bone mass. like averages and percentiles.
Using t scores how can you tell someone is at risk of osteoporosis?
-3 -2 -1 0 1 2 3
1 to -1: normal
-1 to -2.5: at risk of osteoporosis and low to medium fracture risk
-2.5 or lower: osteoporosis = fracture risk is high
What does QCT scan provide?
A calibrated references to materials of known density to compare the density of structures.
A more portable options for limbs.
3D image reconstruction
BMD and geometry
Trabecular & compact bone individually unlike DEXA scans.
What is bone in the bank?
Start exercising at a young age in order to build up bone before you stop building bone during adulthood.
10 acute fracture types
Greenstick Transverse Oblique Spiral Avulsion displaced 1 compound 2 comminuted Growth plate fracturing Epiphyseal Slippage (capital femoral)
2 types over use fractures +def
Periostitis (medial tibial stress syndrome)
Stress fracture
caused by repetitive forces without an appropriate time to heal.
Greenstick fracture characteristics
Tends to occur during growth. Breaks like a green branch (greenstick). Partial break through the bone which is not fully calcified.
Transverse fracture characteristics
Full break with a straight line going all the way across.
Oblique fracture characteristics
straight line on an angle of a long bone.
Spiral fracture characteristics
Twists around the bone shaft. Created from twisting force
comminuted fracture characteristics
Fracture into 2 pieces causing multiple bone fragments throughout tissue.
Compound fracture characteristics
When the bone breaches the skin
What are displaced fractures?
Compound and comminuted
Avulsion fracture characteristics
Where the part of the bone is broken off at the attachment site of the tendon or ligament.
Growth plate fracture characteristics
Can cause deformities as other bones are growing yet this bone is too busy healing.
Epiphyseal Slippage (capital femoral) fracture characteristics
A specific type of growth plate fracture where the head of the femur becomes displaced relative to the neck of the femur.
Periostitis (medial tibial stress syndrome) characteristics
Shin splints
occur during high impact sports and running
Stress fractures characteristics
Not giving injuries enough time to heal causes stress fractures to occur.
