Bone I Flashcards
True or false: Bone is an organ system
True. It’s constantly being remodeled and must respond to changes in the
environment.
What are characteristics of woven bone? Does it have an ordered structure?
It’s primary bone and is the first bone to appear in embryonic development and in
fracture repair. It’s not ordered and is characterized by random disposition of collagen
fibers. It’s rich in osteocytes. It’s temporary and later replaced by secondary bone
(usually when the toddler starts walking).
Give details on lamellar bone
it’s also called secondary bone and is the type of bone usually found in adults. It has
an organized pattern (at approximately right angles) where lamellae are organized either
parallel to each other or concentrically around a vascular canal.
What are other names for trabecular bone?
Cancellous bone, spongy bone. Trabecular bone is an inner meshwork
What is another name for compact bone?
A: Cortical bone. Compact bone has a rigid outer shell
What is wrong in osteoporosis?
there’s a decrease in bone mass. Bone does not remodel very well with age. Also
some endocrine issues
What is still okay in osteoporosis?
the ratio of mineral to matrix is normal
What deficiency is there is osteogenesis imperfecta?
There’s a collagen type I deficiency
Name the four fundamental cells in bone. Give their roles as well.
Osteoprogenitor (stem), osteoblast (synthetic), osteocyte (maintenance, repair), and
osteoclast (dissolve, remodel).
What’s the only way bone can grow?
through appositional growth
Where are osteoprogenitor cells located?
they line the bone surface
What are some characteristics of osteoprogenitor cells?
They’re mesenchymal derived, mitotic (not synthetic), a pre-osteoblast cell type, spindle shaped (thin) and migratory
Are osteoblasts mitotic?
NO!! The suffix –blast is a misnomer. Instead, they are synthetic.
Which cells are responsible for synthesizing all the osteoid? Where are they located?
What are the shapes of these cells?
Osteoblasts. They are cuboidal in shape and secrete their materials at the base of the
cell. They are located at the surface of the bone matrix.
What is the effect of PTH on osteoblasts? What other effects does PTH have on these
cells?
PTH inhibits osteoblast. It also inhibits alkaline phosphatases and collagen synthesis.
How do osteoblasts communicate with each other?
A: Gap junctions
What is the primary function of osteocytes?
maintenance. They are reserve cells found within the calcified bone matrix in lacunae
Who are osteocytes derived from?
derived from osteoblasts that have been engulfed in the matrix
When are osteocytes “activated”?
They’re activated in repair (they can differentiate back into osteoblasts if there’s a
fracture). Also, they are mechanicoreceptors for bone remodeling.
What is the primary role of osteoclasts?
they dissolve bone and are thus involved in remodeling
What are osteoclasts derived from?
they are derived from mononuclear phagocytic system (similar to macrophage)
Which bone cells are large and multinucleated?
osteoclasts
Where do osteoclasts reside? How do they attach themselves there?
They reside on bone surfaces, attached via integrins and cadherins to osteopontin.
More specifically, they are found in depressions called “Howships’s Lacunae”.
How do osteoclasts exert their influence on bone?
A: secrete acid collagenases and acid phosphatases and other proteolytic enzymes that
decalcify bone and digests osteoid.
