Exam #2: Bone Flashcards
What does pressure being applied to bone result in?
Bone resorption (breakdown)
What does tension being applied to bone result in?
Bone deposition (addition)
What percentage of Ca++ is stored in bone?
99%
Metaphysis
Angulation between the diaphysis & epiphysis
What is the difference between active/growing periosteum & inactive/ mature periosteum?
- Active (growing)= 2x distinct layers
- Inactive= mostly outer fibrous layer with a poorly defined inner layer
Characteristics of the Outer Fibrous Layer of Periosteum
- Dense collagenous CT
- Contains blood & lymphatic vessels, & nerves
- Anchored to bone via Sharpey’s Fibers
Sharpey’s Fibers
Bundles of collagenous fibers that anchor the outer fibrous periosteum to the bone
Characteristics of Inner Fibrous Layer of Periosteum
- Active= osteoprogenitor cells
- Inactive= periosteal cells
Characteristics of Endosteum
- Single row of osteoprogenitor cells
- Lines bone marrow cavity
- Lines Haversian & Volkman Canals
- Covers bony spicules & trabeculae of spongy bone
Inorganic Component of Bone Matrix
- Minerals that give bone its hardness
- 65% of the dry weight of bone
Organic Component of Bone Matrix
Consists of fibers & ground substance
Fibers
- Type I Collagen (acidophilic)
- Prevent bone from becoming brittle
Ground substance
- Proteoglycans w/ GAG side chains
- Multiadhesive Glycoproteins
- Bone specific proteins
- Growth Factors
Ground Substance Proteoglycans
- Hyaluronan
- Chondroitin Sulfate
- Keratin Sulfate
Function: Bind growth factors
Ground Substance Multiadhesive Glycoproteins
- Osteonectin
- Sialoproteins
Osteonectin
“glue” between collagen & hydroxyappetite crystals
Sialoproteins
- Osteopontin= binds cells to bone matrix
- Sialoproteins I & II= helps bind cells to bone matrix & begins calcium phosphate formation during mineralization
Bone -specific, Vitamin K-dependent proteins
Osteocalcin= traps Ca++ from the blood & stimulates osteoclasts to remodel bone
BMP
Bone Morphogenic Protein
- induce mesenchymal cells to differentiate into osteoblasts
- Used following surgery to stimulate bone formation
What are osteoprogentior cells in the inner layer of periosteum called?
Periosteal cells
What are osteoprogenitor cells in the endosteum called?
Endosteal cells
Osteoblast Characteristics
- Cuboidal Shaped
- Basophilic due to rER
- Synthesize organic component of bone matrix called osteoid
- Membranes contain a high level of alkaline phosphatase enzyme
Osteoid
- Organic component of bone matrix
- Non-mineralized
- Type I Collagen
- BMPs
When bone is being synthesized, what increases in the blood?
Alkaline phosphatase levels
Alkaline phosphatase enzyme
Mineralizes bone
How do osteoblasts communicate with other osteoblasts & osteocytes?
Gap junctions
Periosteocytic Space
Space between the osteocyte cell membrane & the lacuna & canaliculi
What surrounds an osteocyte?
1) Fluid in the periosteocytic space
2) Osteoid
3) Mineralized bone
Characteristics of osteoclasts
- Multinucleated
- Motile
- Acidophilic
- Very large
What are osteoclasts derived from?
Monocytes (mononuclear hemopoietic progenitor cells)
Ruffled Border
- Site of exocytosis of hydrolyitc enzymes
- Also the site of endocytosis of broken down bone & other products
Clear Zone
- NO organelles, but has actin ring
- Sealing zone that isolates the acidic, corrosive resorption compartment
Basolateral Region
- Contains organelles
- Functions in exocytosis of broken-down matrix
What breaks down the inorganic component of bone?
Acidic environment created by the osteoclasts (H+)
What breaks down the organic component of bone?
Lysosomal hydrolases & metalloproteinases
How do drugs that slow bone breakdown in osteoporosis work?
Accelerate osteoclast apoptosis
Compact Bone
- Dense solid bone that forms a shell around the exterior of long bones
- Contains Haversian systems (Osteons)
Cancellous Bone
- Spongy bone that lines the marrow cavity of long bones
- Contains an irregular arrangement of lamellae
Primary (Immature, Woven, Bundle) Bone
- Forms during fetal development & bone repair
- Temporary tissue that is resorbed by osteoclasts and then replaced by secondary bone
- Bone lining the alveolar sockets remains immature throughout life
Secondary Bone
- Contains parallel or concentric lamellae
- Collagen fibers are parallel within lamella
- Higher mineral content (stronger)
- May exist as spongy or compact bone
Haversian Canal
- Vascular space enclosing a neurovascular bundle
- Does NOT contain lymphatic vessels
What is the only bone tissue that contains lymphatic vessels?
Perichondrium
Rickets
- Ca++ Deficiency or Vitamin D deficiency in which bone does not mineralize properly, leading to bowing of the lower legs in infants
- Osteomalacia in adults
