Exam 4 - Bone 1 Flashcards
Functions of bone
- Support
- Protection: skull around brain; ribs, sternum, vertebrae, protect organs of thoracic cavity
- Movement
- Storage of Ca and P
- Blood cell production
- Enhances insulin effects
Osteocalcin
Secreted from osteoblasts
- increases number of beta cells in pancreas
- increases sensitivity in tissues to insulin WHILE INHIBITING WEIGHT GAIN
Dry weight of bone
1/3 organic
2/3 inorganic matter
Organic matter of bone
collagen
glycosaminoglycans
proteoglycans
glycoproteins
inorganic matter of bone
85% hydroxyapatite
10% calcium carbonate
other minerals (fluoride, potassium, magnesium)
Combination of organic and inorganic materials of bone
Provides strength and resilience
- minerals resist COMPRESSION; collagen resist TENSION
- bone adapts by varying proportions
If mineral is removed
bone is too bendable
if collagen is removed
bone is too brittle
osteogenic cells in endostium and periosteum…
give rise to NEW OSTEOBLASTS which arise from embryonic FIBROBLASTS
produce and may help mineralize organic matter of matrix
Osteoblasts
Osteoblasts trapped in the matrix they formed
OsteoCYTES
Other information about osteocytes
- cells in lacunae connected by gap junctions inside canaliculi
- CONTRIBUTE TO HEMOSTATIC MAINTENANCE OF BONE DENSITY and blood concentrations of calcium and phosphates
- strain sensors: flow of extracellular fluid of lacunae and canaliculi results in remodeling if needed
Spaces occupied by osteocyte cell body
Lacunae
Canals occupied by osteocyte cell processes
Canaliculi
Share no common origin w/ other bone cells
OsteoCLASTS
basic structural unit of bone
osteon / Harvesian system
run PARALLEL to long axis
Central / Harvesian canals
Concentric layers of compact bone tissue that surround central canal
Lamellae
Perforating / Volkmann’s canal
- runs PERPENDICULAR to long axis
- both perforating and central canals contain blood vessels
- DIRECT FLOW OF NUTRIENTS FROM VESSELS THROUGH CELL PROCESSES OF OSTEOBLASTS AND FROM ONE CELL TO THE NEXT
Outer layer is fibrous
Periosteum
Inner layer of periosteum
- consist of SINGLE LAYER OF CELLS including osteoblasts, osteoclasts, and osteochondral progenitor cells
Fibers of tendons become continuous w/ fibers of …?
Periosteum
Sharpey’s fibers
some periosteal fibers that penetrate through the periosteum and into the bone
- strengthen attachment of tendon to bone
Endosteum
- similar to INNER LAYER OF PERIOSTEUM
- lines all lateral spaces including spaces in cancellous bone
When you break a bone, what do you actually break?
Periosteum, the bone itself doesn’t have innervation for you to feel
How do osteoclasts develop?
by fusion of 3-10 stem cells
- develop from bone marrow stem cells
- osteogenic cells, osteoblasts, and osteocytes come from same cell lineage (MESENCHYME) BUT OSTEOCLASTS HAVE INDEPENDENT AND DIFFERENT ORIGIN
Osteoclast responsibility
Resorption of bone
- H+ ions pumped across membrane which eats away bone
- Enzymes released that digest the bone
Woven bone
- collagen fibers randomly oriented
- FORMED DURING FETAL DEVELOPMENT AND FRACTURE REPAIR
Remodelling
- removing old bone and adding new
- woven bone is “remodeled” into lamellar bone
Lamellar bone
- mature bone in sheets called LAMELLAE
- fibers are oriented in one direction in each layer, but in different directions in different layers for strength
Spongy bone
Spongelike appearance formed by plates of bone called TRABECULAE
- SPACES FILLED W/ RED BONE MARROW
Have few osteons or central canals
Trabeculae; no osteocyte is far from blood of bone marrow
Develop along bone’s lines of stress
Trabeculae; provides strength w/ little weight
Shaft comprised of COMPACT BONE
Diaphysis
End of the bone comprised of CANCELLOUS BONE (SPONGY)
Epiphysis
Comprised of hyaline cartilage; PRESENT UNTIL GROWTH STOPS
Epiphyseal plate
In children _____ is filled w/ red bone marrow.
medullary cavity
Endochondrial ossification takes place in…?
cartilage
Intramembranous ossification takes place in…?
connective tissue “membrane” similar to the dermis
- as such sometimes called DERMAL BONES (flat bones of skull, clavicle) because membrane looks similar to dermis
Clinical relevance of intramembranous ossification
there are some bones that are produced by this ossification; when someone has growth hormone excess, they growth in width and those bones are prone to growing more w/ this excess
both methods of ossification:
- produce WOVEN BONE THAT IS THEN REMODELED
- produce bone that is, AFTER REMODELING, INDISTINGUISHABLE as forming from one method or the other
Revew slides
16-18 on powerpoint
