Bone Tissue - Downing Flashcards
What are the 2 steps of bone formation by osteoblasts?
Synthesis of organix matrix (osteoid)
Deposition of inorganix components
Where do you find osteoblassts?
They are located on bone surfaces (have an epitheliod appearance
What cells form osteocytes?
Osteoblasts that end up getting trapped in the bony matrix
How is osteoclast activity regulated?
Osteoblasts have surface receptors for parathyroid hormone (PTH)
Osteoblasts bind PTH
Release ‘osteoclast stimulating factor’
This stimulates osteoclasts to break down bone
How do osteocytes communicate?
They have processes that extend out and communicate through gap junctions
(Think prisoners in solitary confinement that communicate through passing notes through hole in the wall)
What are canaliculi?
The small passages through the bony matrix that the osteocyte processes travel to communicate, and through which the nutrients and waste materials can travel.
Function of the ruffled border of the osteoclast?
The part of the osteoclast that sticks to the bony surface
REMOVE ORGANIC AND INORGANIC PARTS OF THE BONE
INORGANIC
Membranes pump H+ into sub-osteoclastic compartment
-lowers pH and mineral is liberated
-Minerals enter osteoclast and are then delivered to nearby capillaries
ORGANIC
- Osteoclast secretes lysosomal hydrolases, collagenase, and gelatinase into sub-osteoclastic compartment
- Degrade organic components of decalcified bone matrix
- Degradation products are endocytosed by osteoclast
- Broken down into amino acids, monosaccharides, and disaccharides and released into capillaries
What is the region of resorbed bony matrix containing an osteoclast called?
Howship’s lacunae
What is the important part of the inorganic portion of bone?
*Calcium* Calcium phosphate Hydroxyapatite crystals -Hydrophilic -Facilitate exchange between crystals and body fluids
What are 3 glyoproteins are
colelctveily capable of binding together the cell and matrix components of bone?
Osteocalcin
Osteopontin
Osteonectin
Compare Cancellous bone with compact bone:
Cancellous (spongy bone)
- Spicules or trabeculae of bone united to form a network
- Found in interior of bone
Compact (dense bone)
- Found on bone exteriors
- Dense, thick layers
Compare Primary vs Secondary bone:
Primary bone
-First bone tissue to appear during growth & repair
“Woven bone”
-Irregular array of collagen fibers
Secondary bone
- Replaces primary bone
- Parallel arrays of collagen
- Lamellar deposition of matrix
- Production of Haversian systems
What are the two layers of periosteum?
Fibrous (outer) layer
- Fibroblasts; collagen; elastin
- Protection of bone
- Connection for ligaments
Osteogenic (inner) layer
- Osteoblasts adjacent to bone surface
- Osteoprogenitor cells - precursors to osteoblasts
- Osteoclasts if remodeling is occurring
What are Sharpey’s fibers for?
anchor the periosteum to bone!
What are heversian and volkmann’s canals?
Haversian canals run parallell with the bone tissue
Volkmann’s canals run perpendicular (or radially) to connect haversian canals and bring arterial connections into the bone
Both types of ossification processes (Intramembranous bone formation and
Endochondral bone formation) result in compact and cancellous bone tissue being formed. What are the important differences though?
Intramembranous Ossification
- Embryonic connective tissue precursor
- Connective tissue is well vascularized
- Gives rise to ‘membrane’ bones
- *Bones of skull; mandible; maxilla; clavicles
Endochondral Ossification
- Hyaline cartilage precursor/template
- Cartilage is avascular
- Calcified cartilage matrix removed
- Examples: long bones of body
List from distal to proximal in reference to the middle of the long bone, the layers of the epiphysis:
The resting zone
The proliferative zone (looks like pancake stack)
Zone of hypertrophy (cells look swollen)
Zone of calcification (darkening area in histology)
Zone of ossification (merges into the zone of calcification
Give me an example of stress-induced remodeling in bone!
Braces!
How can disuse adversely affect the bones?
weakening of the bones
How can hormonal changes affect bone plasticity?
PTH
Osteoblast has PTH receptors
Osteoblasts then secrete osteoclast-stimualting factor
rate of bone resorption increases
What hromrone rpomotes calcium deposition by inhibiting osteoclast activity and increasing matrix deposition of Ca?
Calcitonin
What disorder did children get when working long hours in factories with no natural light? and why?
Rickets
Vit D deficiency
- Leads to improper absorption of calcium from the intestinal mucosa and hence individuals have a calcium deficiency
- Incomplete bone matrix calcification
- Spicules distort under strain –> bone deformation
Osteomalacia is what?
Sometimes called adult rickets
Prolonged deficiency of vitamin D Calcium deficiency in adults Deficient calcification of new bone Decalcification of existing bone No bone distortion
What is osteoporosis?
Most common in post-menopausal women
Bone tissue diminished
More rapid destruction of bone tissue by osteoclasts than osteoblast formation of bone
1 out of 40 men will suffer an osteoporotic fracture
1 out of 2 women will suffer an osteoporotic fracture
Estrogen therapy helps alleviate this tendency
Which cells secrete synovial fluid? What does this fluid do for the synovial joint?
Fibroblasts = type B cells
Synovial fluid
- Lubricates joint
- Provides nutrients for articular cartilages
