Bone Flashcards
to accomodate changes related to mechanical stresses and demands on calcium homeostasis bones are in a dynamic state of ____ and _____ throughout life
growth and resorption
What provides the framework and necessary tensile strength of bones and who produces it?
collagen fibers produced by osteoblasts
what serves as a carrier for minerals?
osteoid = the extracellular matrix
What layer acts as a site of insertion of muscles, tendons and ligaments?
periosteum
What tissue layer lines the trabeculae of spongy bone?
endosteum
osteocytes originate from _____
osteoblasts
osteoblasts secrete what type of collagen?
type 1
What cells are found in a single layer external to the osteoid matrix? Where do they originate?
osteoblasts (immature bone cells)
from osteoprogenitor cells
What bone cell is responsible for the synthesis and secretion of collagen and osteoids?
osteoblast
When the osteoid mineralizes, osteoblasts are entrapped as _______
osteocytes
How do osteoclasts decalcify bone?
When they are activated and in contact with bony surface, they release acid and lysosomal enzymes
What kind of cells are occupied within lacunae? Are they mature or immature?
osteocytes = mature
How do osteocytes maintain contact with adjacent osteocytes?
filopodia connecting each other via canaliculi
how do osteocytes transfer nutritional needs to the next cell?
gap junctions
are osteocytes capable of undergoing mitosis?
no
Do osteoclasts have basophilic or acidophilic cytoplasm? What are they closely related to?
acidophilic
macrophages
Osteoclasts induce osteolysis in order to ____ in response to ______
maintain calcium homeostasis and remodel in response to growth or mechanical stresses
filopodia are extensions of ____
osteocyte cytoplasm
Where does intramembranous ossification occur? In what bones?
within membranes of condenses primitive mesenchymal tissue, in flat bones of the skull
Where does endochondral ossification occur?
At ossification centers in the diaphysis of bones. occurs in majority of bones in the skeleton (limbs, vertebral column, pelvis, base of the skull)
bone develops from what kind of cartilage?
hyaline cartilage
Can bone grow longitudinally in a mature animal?
no not when the growth plate is closed
What is woven bone and how are the collagen fibers arranged?
Immature bone present during fetal development and the early stages of bone repair.
Collagen fibers are crisscrossed or woven
What kind of bone is composed of successive concentric layers around a central canal?
lamellar bone = mature bone
What is the functional unit of mature bone?
osteons
What is in the center of each osteon?
Haversian canal
What hormone increases the recruitment/activity osteoclasts?
PTH
Where is articular cartilage found?
On the bone surfaces in a synovium
What happens with decreased production of synovial fluid?
Bones can rub against each other, arthritis
where are epitheliod cells found and what do they do?
lining the joint cavity. they secrete hyaluronic acid and phagocytize debris
Why are synovial cells epitheliod and not epithelial?
because they do not sit on a basement membrane or have intercellular junctions
What is the function of synovial fluid and what should it look like?
Clear and viscous. Functions include nutrition, lubrication and protection of articular surfaces
The structure of bones is designed for providing _____
maximum resistance to mechanical stress while gaining the least body mass
The organic matrix of bone is made up of mostly ____
collagen (95%)
The inorganic matrix of bone is composed of mainly ______ for the purpose of ______
hydroxyapitate crystals within collagen fibrils
enhance tensile strength
What is rickets?
vitamin d deficiency, bones curve
What type of cell digests bone to maintain Calcium homeostasis? And where do they originate?
osteoclasts
from pluripotent stem cells of the bone marrow
What kind of cytoplasm do osteoblasts have?
basophilic
Can osteocytes undergo mitosis?
no. they are mature
The circumferential zone is associated with what kind of bone cells?
osteoclasts
What kind of ossification is characterized by subsequently replacing osseous tissue at ossification centers? Where does it occur
endochondral
at growth plates (epiphysis)
