CT 3 A Flashcards
Most extracellular matrix in bone is _____.
calcified and packed with dense parallel collagen fibers
Bone matrix also contains ____
negatively charged proteoglycans and other glycoproteins, but several of these are specific to bone.
Unlike most connective tissues, bone matrix is unique in containing:
large amounts of a crystallized form of Ca2+ and PO4 called hydroxyapatite, the crystals are found on collagen fibers, and in the ground substance
i.e. the matrix is mineralized or calcified.
Bone is _____
vascular and innervated.
Threading throughout the matrix of bone tissue are a large number of channels that contain both blood vessels and nerves.
Thus, relatively short distances of diffusion are needed for _____
nutrients to reach osteocytes within the bone matrix, and for transport of mobilized Ca2+ from the matrix to the bloodstream.
Haversian canals.
In long bones, channels that traverse the long axis through compact bone
Bone _____ tend to surround a Haversian canal in _____;
lamellae
concentric rings (like the rings of a tree)
Volkmann’s canals
link Haversian canals to each other and to the periosteum at the bone surface.
lamellae and their canal are frequently referred to as a unit called the _____.
osteon
The formation of cartilage and bone tissue are highly regulated processes that _____.
integrate cell proliferation and differentiation with the synthesis and transformation of extracellular matrix
The formation of long bones is directly tied to _______
formation of cartilage,
Both cartilage and bone formation begins in ____
embryogenesis.
Some complete bones are formed before birth.
Other bone tissue, particularly in the long bones of the extremities continue to be formed during post-natal growth.
formation of new bone tissue continues through the ____
remodeling of existing bone, and can be stimulated following severe injury (bone fracture).
Intramembranous ossification: occurs _____
In the absence of a pre-made cartilage tissue:
Intramembranous ossification occurs first when:
Within a sheet of connective tissue, groups of mesenchymal cells come together (a process called condensation), transform into osteoprogenitors, which then differentiate into osteoblasts.
The flat bones all form by
intramembranous ossification.
These islands of osteoblasts secrete ___.
osteoid
More cells at the periphery of these islands convert into ____
other osteoblasts adding to the mass of the developing bone; eventually “bone islands” join.
Calcification of the matrix is ____.
delayed relative to its initial formation.
initially: trabecular
then vessels grow in
Initially, the bone matrix is of _____.
woven bone
remodeling by osteoclasts and new bone deposition by ____
osteoblasts converts some of this bone to a compact lamellar form.
Endochondral ossification is made by:
In the embryo and fetus, cartilage tissue generates various structures of the skeleton that will become bone. Subsequently, some cells within the perichondrium are converted to osteoprogenitors. This sets in motion a series of events that cause the replacement of cartilage by bone.
Formation of the cartilage model:
Mesenchymal cells undergo division and differentiate to generate a group of chondrocytes. Chondrocytes begin to secrete the matrix typical of hyaline cartilage. As they secrete their matrix individual chondrocytes become encased in their lacuna. Eventually an elongate structure in the relative proportion of a long bone is formed
cartilage model then continues to grow in two different ways:
- appositional growth
2. interstitial growth
