Lectures 15 & 16 - Bones and Joints Pathophysiology I & II Flashcards
5 functions of bones?
- Support: lower limbs, pelvis, spine, neck etc. support body structures
- Protection: of some organs
(e. g. brain, thoracic organs, spinal cord) - Movement: muscles move bones at joints
- Storage: calcium (99%) and phosphate (85%)
- Hematopoiesis: red bone marrow produces blood cells
What kind of tissue are bone and cartilage?
Types of specialized connective tissue: cells surrounded by ECM, in this case the ECM is ossified and encased
What are bones made of?
Contain a mixture of compact and spongy bone
Other name for compact bone?
Cortical bone
Other name for spongy bone?
Trabecular bone
Which type of bone contains bone marrow?
Spongy bone
What is found in long bones?
Medullary cavity with bone marrow
What is yellow bone marrow?
Inactive bone marrow in adults
Which bones grow?
Long bones elongate at growth plate during bone growth
3 types of bone cells? Describe each.
- Osteoblasts: build bone
- Osteoclasts: cells from macrophage lineage, break down bone
- Osteocytes: osteoblasts surrounded by mineralized bone matrix (less active than osteoblasts)
What are osteons?
Units of compact bone
Why does cartilage injury tend to heal more slowly than bone?
Because cartilage is not as well vascularized as bone
What provides tensile strength to bone?
Organic fibers, mainly type I collagen
What hardens bones?
Inorganic materials like calcium hydroxyapatite
Where are osteoblasts located?
Toward bone surface
How is bone remodeling regulated?
By cytokines, growth factors, and other signal molecules
What is bone resorption?
Osteoclasts release breakdown enzymes that degrade the bone matrix and release calcium into blood
What is bone remodeling important for? 4
- Normal bone health
- Blood calcium homeostasis
- To maintain bone shape after bone growth or in response to stress/exercise
- For bone healing after fracture
What are 2 hormones important for calcium homeostasis?
- PTH
2. Vitamin D
3 roles of PTH for calcium homeostasis?
- Release of calcium from bone stores and stimulates bone resorption
- Increase renal calcium reabsorption
- Increase vitamin D production
Role of vitamin D for calcium homeostasis?
Increases calcium absorption from GI
What is articular cartilage made of? 3
- Chondrocytes
- 70% water
- ECM: type II collagen, proteoglycans, and other proteins
Role of articular cartilage?
Functions as shock absorbed and decreases friction in joints
Name of cartilage in synovial joints? Where is it located?
Hyaline cartilage, lines bone at a joint
Does cartilage turn over like bone? What to note?
YUP - but not as frequently as with bone and it slows with age
4 components of synovial joints? Describe each.
- Articular cartilage: thin layer of hyaline cartilage that covers bone ends
- Joint/articular capsule: fibrous membrane that holds bones together and is made of dense connective tissue
- Synovial membrane: inner lining of capsule at the border of the synovial cavity
- Synovial fluid: lubricating fluid secreted by synovial membrane
3 ways of examining bones and joints? Which is best?
- Observation of bone/joint deformity: fracture, bowing, luxation, or signs of inflammation
- Specific exam for each joint including examining patency of structural ligaments, discs, etc. => range of motion, compromise of joint movement
- X-ray: best modality for initial bone imaging
4 signs of bone/joint inflammation?
- Heat
- Swelling
- Redness
- Pain
What is bone luxation?
Dislocation
2 bone diseases?
- Osteoporosis
2. Paget disease of bone
5 types of arthritis?
- Rheumatoid arthritis
- Osteoarthritis
- Seronegative spondyloarthropathy
- Gout and pseudogout
- Infectious arthritis
What is osteoporosis? 2 types? Which is more common?
Reduced bone mass and bone strength causing increased risk of fractures due to an imbalance between bone formation and resorption
- ***Primary: postmenopausal or senile
- Secondary to other conditions
When is peak bone mass achieved? What does this depend on? Implication?
Young adulthood
Based on gender (males>females), genetics, physical activity, diet => onset of osteoporosis will be affected by this peak bone mass
When does bone mass start declining? When is peak bone loss?
After 40s with each resorption/formation cycle, peak bone loss in 60s onward
Symptoms of osteoporosis?
None other than easier to fracture bones (compression fractures and due to falls)
5 contributing factors to osteoporosis?
- Changes with aging: osteoblasts from elderly have decreased ability to synthesize bone, decreased replicative activity of osteoprogenitor cells, decreased biologic activity of matrix-bound growth factors
- Reduced physical activity: bone formation increases with increased stress on bone (e.g. weight bearing exercise increases bone density and immobilized patients and astronauts have decreased bone mass)
- Genetic factors: vitamin D receptor type important for peak bone mass acquisition
- Environmental: calcium and vitamin D levels, smoking, steroid therapy
- Hormone levels: estrogen important for maintaining balanced resorption/formation cycles
Why are women at higher risk than osteoporosis then men?
Because of the significant drop in sex hormones at menopause vs a more gradual decline in men
How exactly does decreased estrogen cause osteoporosis at menopause? 2
- Causes cytokine activation of osteoclast activity > osteoblast activity
- RANK: receptor activator of nuclear factor that activates osteoclast differentiation
5 secondary causes of osteoporosis?
- Osteogenesis imperfecta (dysfunctional type I collagen)
- Drugs (e.g. steroids)
- Endocrine disorders (e.g. hyperparathyroidism)
- Neoplasia
- Malnutrition or malabsorption with vitamin deficiency