Unit 13 - Bone disorders Flashcards
What are 5 functions of the skeletal system?
- Structural support
- Storage of minerals and lipids
- Blood cell production
- Protection of delicate tissues and organs
- Leverage
What are the two components of bone?
- Cells (only 2% of composition!)
2. Matrix
What are the two different materials of the bone matrix?
- Hydroxyapatite (66%)
2. Collagen fibres (33%)
What is the role of hydroxyapatite in the bone matrix?
Makes bones rigid
What is the role of collagen fibres in the bone matrix?
Provides flexibility to bone
- prevents bones from snapping
True or False:
When we are young, there is a lot more hydroxyapatite compared to collagen fibres
False
- there is more collagen fibres in bones when we are young compared to hydroxyapatite
What are the 4 cells of bone tissue?
- Osteoblasts
- Osteocytes
- Osteoclasts
- Osteoprogenitor cells
What cells produce hydroxyapatite?
Osteoblasts
What are osteoprogenitor cells?
Stem cells
What is the functional role of osteoblasts?
- Form bone through ossification or osteogensis
2. Secrete collagen and hydroxyapatite (mainly this)
What are osteocytes and what do they do?
Mature bone cells
- make small amounts of matrix to maintain it
What kind of bone cell matures to form osteocytes?
Osteoblasts
What are osteoclasts related to? Why?
Related to macrophages (WBCs)
- secrete acids and enzymes in order to break down bone
What kind of bone cell is HUGE and is multi-nucleated?
Osteoclasts
What are osteoclasts derived from?
Monocytes
What is the function of osteoclasts?
Breakdown (resorption) of bone
What is broken down by acids and what is broken down by enzymes?
Hydroxyapatite = broken down by acids
Collagen fibres = broken down by enzymes
What are the stem cells of bone cells?
Osteoprogenitor cells
What do osteoprogenitor cells differentiate into?
Osteoblasts
True or False:
Bones are not highly vascularized (ie - they don’t have a lot of blood supply)
False
- bones ARE highly vascularized
- they have a LARGE blood supply
What is the periosteum?
Sheath around bones
- it has two layers
What is the endosteum?
Lines all the internal spaces of the bone
- contains same cells as periosteum
What are the 3 key hormones that are involved in the regulation of bone growth and remodeling?
- Parathyroid hormone
- Vitamin D
- Calcitonin
What do you need to have in order to absorb calcium in the GI tract?
Vitamin D
What is the process of vitamin D activation?
- Vitamin D synthesis in skin
- Then in liver
- Then in kidneys
When is parathyroid hormone released?
When blood calcium levels become too low
What are the three ways that parathyroid hormone increases blood calcium levels?
- From bone = release of calcium from bone
- From kidneys = increases reabsorption
- From intestines = promotes absorption via activated vitamin D
True or False:
African people have low levels of vitamin D
True
Why would someone have weak bones if they had a lung tumor that secreted parathyroid hormone?
High levels of PTH in circulation stimulates osteoclasts to break down bone
- bones are weak (thinning)
Why would someone in complete kidney failure have weak bone?
Kidneys produce ACTIVE vitamin D
- if the kidney function is suffering, production of active vitamin D is suffering
- if active vitamin D is low = low absorption of calcium
- low calcium = weak bones (b/c of low deposition of calcium into bone)
What is released from the thyroid gland when blood calcium is too high?
Calcitonin
What function does calcitonin perform?
Inhibits the release of calcium from bone
- reduces osteoclast activity
When is calcitonin most active?
In children
- when bones are growing
Why does calcitonin inhibit vitamin D activation by the kidneys and inhibit calcium reabsorption by the kidneys?
Calcitonin is released by blood calcium levels are HIGH
- therefore, it decreases overall blood calcium levels by preventing the absorption of new calcium and preventing the reaborption by the kidneys
When is bone mass the highest?
Around 30
True or False:
Men have denser bones than females
True
- due to testosterone and greater weight
True or False:
The smaller the force on bone, the greater the increase in bone mass
False
- the greater the stress, the greater the increase in bone mass
How do we measure bone density?
By getting an xray
- Score = -1, considered normal
- Score = -2.5 < -1 = osteopenia
- Score = < -2.5 = osteoporosis
Define osteoporosis
Absolute reduction of the total bone mass
True or False:
Osteoporosis affects women more than men
True
- especially after menopause
True or False:
Age is NOT related to osteoporosis
False
- in patients > 85 years old, 33% will have osteoporosis
What are the risk factors for PRIMARY osteoporosis (4)?
- Low initial bone mass (small frame)
- Bad dietary habits (and smoking)
- Hormones (early menopause)
- Age-related changes in metabolism
Explain why smoking is a risk factor for PRIMARY osteoporosis
- Smoking is associated with lower bone density
- Smokers consume alcohol (linked with bad dietary habits)
- Smokers are thinner (less bone mass)
- Fractures take longer to heal in smokers
- Smokers secrete LESS ESTROGEN
What are the risk factors for SECONDARY osteoporosis (5)?
- Hormonal disturbances (excess cortisol)
- Dietary disorders
- Immobility
- Tumors
- Alcoholism
Why is excess cortisol a risk for osteoporosis?
Elevated cortisol levels interfere with osteoblast formation and dramatically decreases bone building
- resulting in reduced bone density.
Why are dietary disorders linked with secondary osteoporosis?
Malabsorption
- body cannot properly absorb calcium
- leads to deficiency in blood calcium levels
Why is immobility linked with secondary osteoporosis?
Bones are not exposed to any stress
- therefore, they do not increase in density
True or False:
All exercise is good for bone density
False
- in women that have small frames and involved in sporting activities
- can experience reduced ovarian activity = less estrogen
= risk for osteoporosis
What are the causes of osteoporosis (4)?
- Heredity (small frame)
- Excessive PTH
- Inactivity
- Aging
What are the consequences of osteoporosis?
- Fractures (distal radius - happens when someone is trying to catch their fall)
- Proximal femur - bone that carries the most weight
- Greater curvature of the spine - person will become shorter (thoracic curve will become deeper)
Why is a postmenopausal woman prone to osteoporosis?
Decreased estrogen
Why is an olympic figure skate who takes steroids to reduce joint inflammation prone to osteoporosis?
Smaller frame (figure skater) and corticosteriod use will decrease bone mass by stimulating osteoclasts
What is the etiology of vitamin D deficiency (4)?
- inadequate intake
- inadequate exposure to sunlight
- abnormal intestinal absorption
- kidney disease
What is osteomalacia?
Softening of bones as a result of inadequate mineralization of the organic matrix
- deposition of calcium is impaired
What is commonly seen in patients with osteomalacia?
Bone deformities and fractures
- rigidity of bone will be affected
- synthesis of collagen will not be compromised
What is rickets?
Osteomalacia in children
What is rickets characterized by?
- Bowlegs
- Widened costo=chondral junction
- Delayed dentition
Where is the costo-chondral junction?
Junction between the ribs and the sternum
- in rickets, results in weaken ribs because that space is wider
What is renal osteodystrophy caused by?
Chronic renal failure and compensatory hyperparathyroidism
Explain the link between chronic renal failure and bone loss
- Chronic renal failure
- Decrease vitamin D activation
- Decrease in vitamin D
- Decrease in absorption of calcium
- Decrease in blood calcium levels
- Increase in PTH
- PTH causes bone resorption
- Decreased bone mass to increase blood calcium levels
What is a simple incomplete fracture?
Break transverses across bone
- not all the way across
What is a simple complete fracture?
Break transverses across bone
- ALL the way across
What is a compound fracture?
Breaks the skin
- increased risk of infection!
What is a comminuted fracture?
Bone splinters into many pieces
What is a displaed fracture?
Results in abnormal bone placement
When does a greenstick fracture occur?
When bone mineralization is LOW
- bone is very flexible (more than it should be)
- results from inadequate mineralization or vitamin D deficiency
True or False:
Greenstick fractures more commonly occur in children
True
- because they have more collagen compared to ossified bone
What is an Epiphyseal fracture?
Fracture occurs at epiphyseal plate (growth plate)
- bones will no longer be able to grow in lenth
When does a compression fracture of the vertebrae occur?
When the protection (discs) between the vertebrae become thinner
- bones grind against each other and CRACK - ouch!
What are the steps involved in a bone fracture repair?
- Fracture
- Hematoma
- Callus formation (stabilizes fracture)
- Callus ossification
- Remodelling (spongy bone is replaced with compact bone and thickness of bone will be slowly readjusted)
- Eventually the bone will look like new
True or False:
Rheumatoid arthritis and Gout have inflammation as an underlying cause, while osteoarthritis does not
True
What is the function of synovial fluid inside joints?
Reduces friction
What is the most common joint disease?
Osteoarthritis
True or False:
Osteoarthritis is a DEGENERATIVE joint disease
True
What are the two classifications of osteoarthritis?
- Primary
2. Secondary (related to another disease)
True or False:
Age is not a risk factor for osteoarthritis
False
- age is a risk factor
Describe what happens inside the joint during osteoarthritis
- Damage to articular cartilage
- Underlying bone is exposed to compression fractures
- Growth of bone where the compression fractures occur = makes bone spurs
- Spurs can grow long enough that they can lock into each other = VERY painful!
What are osteophytes?
Bone spurs
What happens to the articular capsule in osteoarthritis?
Articular capsule get inflamed
- becomes thicker
- becomes less flexible
What are the clinical manifestations of osteoarthritis (5)?
- Pain
- Crepitus
- Joint swelling and warmth
- Joint deformity
- Loss of mobility
What is crepitus?
Crackling sounds in joint
True or False:
Rheumatoid arthritis is a systemic autoimmune disease
True
What does RA cause?
Chronic inflammation of joints and other connective tissue
True or False:
Men are more affected by RA than women are
False
- women are more affected by 3:1 ratio
True or False:
Symptoms of RA exacerbate in pregnancy and lessen during postpartum period
False
- lessen during pregnancy
- exacerbate during postpartum
Describe what happens in the joint during RA
- Immune system produces antibodies that attack the synovial membrane
- Inflammation occurs
- Inflammation causes loss of mobility and joint pain
- Pannus is formed
- Ultimately, joint becomes FUSED
What is the treatment for RA?
Anti-inflammatories
True or False:
RA has high mortality and low morbidity
False
- RA has high morbidity
- RA has low mortality
What is gout defined as?
Systemic metabolic disorder often affecting the joints
What does gout involve (4)?
- Hyperuricemia
- Swelling and pain of big toe
- Subcutaneous tophi
- Uric acid urinary stones
Why does gout occur?
Because the body is creating too much uric acid or not able to clear away uric acid
What are tophi?
Uric acid crystals formed in the tissues, joints, and kidneys
Describe the pathogensis of gout
- Uric acid is high in blood
- Deposited into big toe
- WBCs infiltrate to get rid of deposited uric acid
- WBCs release cytokines
- Cytokines attract more WBCs
- Inflammation occurs
- Swelling and pain in the joint
True or False:
The presence of uric crystals is the cause of the pain in gout
False
- inflammation response causes the pain
- not the presence of uric crystals
What are the clinical features of acute gout?
Joint pain, swelling and inflammation
What are the clinical features of chronic gout?
Tophi, deposits of uric acid crystals in internal organs, urinary stones
True or False:
Osteoarthritis is localized while RA and Gout are systemic
True
True or False:
Osteoarthritis, RA and Gout are all inflammatory
False
- RA and Gout are inflammatory
