6.3 Bone Histology Flashcards
what is the bone matrix?
non-cellular/interstitial organic and inorganic material
what are the 3 main components of bone matrix?
hydroxyapatite (Ca++ PO4) inoranic, 65%
collagen and proteoglycans, organic material
what are the 3 types of bone cells?
osteoblasts
osteocytes
osteoclasts
what do osteoblasts do?
make new matrix: make organic material and help lay down Ca++ and PO4 that can combine to make mineral matrix
for growth repair and development
i.e. ossification/osteogenesis
when does an osteocyte form?
once an osteoblast becomes surrounded by matrix
what do osteocytes do?
less active than osteoblasts, just maintain matrix
where do osteocytes live?
lacunae and extensions of cytoplasm in canaliculi
what is the purpose of the cell-to-cell connections of the osteocytes and where are they located?
located in canaliculi
nutrients and gases move by diffusion from cell-to-cell
describe an osteoclast
multinucleated
responsible for bone breakdown/resorption
how do osteoclasts work and when do they work?
use H+ (acid to decalcify) and enzyme to digest proteins in the matrix
used to resculpt bone (as in a break or growth) or to release Ca++ for bl Ca++ levels
what is the origin of an osteoclast?
marrow
what is the origin of an osteocyte?
mature form of osteoblast
what is the origin of an osteoblast?
osteochondral progenitor cells
where are osteochondral progenitor cells located?
inner layer of periosteum
inner layer of perichondrium
endosteum
describe woven bone
woven bone is the temporary bone of the fetal skeleton or repaired areas
random arrangement of collagen
describe lamellar bone
replaces woven bone in mature bone
organized arrangement of sheets of bone and fibers (osteon)
what is the organizational unit of lamellar bone?
lamella arranged in osteons
what is a lamellae?
the matrix organizational unit of lamellar bone
thin sheets of mature bone matrix in which the collagen fibers lie parallel to each other
what is the arrangement of collagen fibers in lamellar bone?
parallel within the lamella but at an angle to the arrangement in adjacent lamellae
describe an osteon
a blood vessel within a central canal surrounded by concentric lamellae (sheaths of matrix)
layers of osteocytes connected by cannaliculi
what fills in between the circular osteons?
interstitial lamellae
what fills in the space between osteons on the periphery of the bone (just underneath the periosteum)
circumferential lamellae
what are the 2 types of mature lamellar bone?
cancellous (spongy) and compact
describe cancellous bone
contains a lot of “space”
aka spongy bone
made of interconnected trabeculae
spaces filled with marrow, vessels
describe trabeculae
the “beams” of cancellous bone
alternating layers of lamella and osteocytes
“exposed” surfaces covered with osteoblasts
describe compact bone
dense lamellar formation
osteon is functional unit
Draw a long bone
Do it
