_____ canals are the central canals that form in the center of osteon units. ____ essentially wrap around these vascular pores, forming the cortical bone around it.
Haversion
Lamellae
Trabeculae in heads of long bones, like the femur, take on an _____ formation that distributes the load the bone bears,
Arcade
At 26 days development, upper _____ buds appear, which are important for patterning of the musculoskeletal system.
Upper Limb Buds
At about 32 days development, first ______ contractions are observed, and are important for developing the proper function of joints.
Muscle
The cranium and shoulder girdle are formed from embryonic ____, the post cranial skeleton (the rest of the bones) is formed from embryonic _____.
Ectoderm
Mesoderm
Collagen synthesis begins with the generation of procollagen ____ chains with _____ ends, which are what allow the coiling of the collagen molecule into triple helicies. Once the collagen molecules are secreted out of the cell, the _____ ends are cleaved to allow for proper arrangement of the molecules into fibrillar structures which are reinforced by covalent cross-linking facilitated by the enzyme ____ oxidase.
Alpha chains
Propeptide
Propeptide
Lysyl oxidase
_____ are the cells primarily responsible for creation of cartilage. They are derived from _____ stromal cells. As it matures, it moves into the _____ (newly formed boned), and then differentiates into ______ as it moves into the mineralized bone.
Osteoblasts
Mesenchymal stromal cells
Osteoid
Osteocytes
Type ___ collagen is comprised of two alpha I strands and one alpha II strand. The 300nm periodicity of collagen “striping” is very important to the structure and function of the collagen fibers, allowing them to bend and kink. The overlapping region accounts for about ___% of the tropocollagen length. Together with the Lacunar region, this accounts for exactly ___nm.
Type I collagen
10%
67nm
Cartilage is comprised of Type ___ collagen.
Type II
The energy that it takes to cause bone to fail is termed _____.
Toughness
______ refers to cells’ ability to sense and respond to mechanical events. It has three main components:
- ______ –> cells’ detection of mechanical stimulus outside of cells and relay message inside.
- ______ –> biochemical and cytoskeletal relaying of the message within the cells.
- ______ –> signal reaches its target, the target is activated, causing alterations in cell behavior.
Mechanotransduction
- Mechanoreception
- Signal Transmission
- Target Activation
_____ are dynamic structures that grown and shrink. They are found in ____ and ____ and are often associated with molecular motors that transport intra-cellular vesicles.
Microtubules
Cilia and Flagella
_____ (actin filaments), are comprised of ____ and ____. They are more mechanical in structure, and are found adjacent to the cell _____.
Microfilaments
F-actin
G-actin
cell Membrane
_____ junctions connect cells in epithelial tissue, and are important in mechanical signal transduction between cells.
Adherens
_____, the “all purpose glue,” connects the cytoskeleton/nucleus to the ECM, allowing for mechanical signal transduction.
Fibronectin
_____ is a component of the ECM that helps retain _____, increasing cellular resistance to compression.
Proteoglycan
Water
_____ are transmembrane proteins that bind the cell to the ECM.
Integrins
Cellular response to mechanical signals begins with a _____ receiving the stimulus from the ECM –> the _____ relays the signal to the nucleus –> DNA is trancribed into RNA –> RNA is translated in the ____ –> proteins are assembled and modified in the _____ –> these proteins are secreted
Mechanoreceptor
Cytoskeleton
ER
Golgi
Osteocytes connect with one another via _____ protrusions, while their cell bodies reside in the ____.
Canalicular
Lacunae
_____ progenitor cells give rise to _____, while ______ progenitors give rise to all of the other orthopedic tissues (bone, muscle, cartilage, tendons/ligaments, and fat.)
Hematopoietic progenitors
Osteoclasts
Mesenchymal progenitors
Interestingly, pre-_____ give rise to both _____ and adipocytes.
pre-Osteoblasts
Osteoblasts
Deficiency of BRM-SWI/SNF favors _____ lineage of MSCs and confers resistance to _______.
Osteoblast
Osteoporosis
Remember that osteoclasts are _____-nucleate.
Multi-nucleate
In order to resorb the mineralized bone, osteoclasts secrete hydrogen and _____, which is prevented from leaking out laterally by an _____ ring.
Chloride
Actin
HSCs congregate in niches within bone marrow and associate with _____ cells (particular osteoblasts.) They mobilize from _____ niches to _____ niches in response to fibroblast growth factor 4 (FGF4) and O2.
SNO cells
Endosteal niches
Stromal niches
VitD3, PTH, and IL-___, factors that drive the differentiation of HSCs to _____, are secreted by _____ and stromal cells. Also, M-CSF is produced by stromal cells, which causes HSCs to differentiate into monocyte/macrophage cells –> these bind to ____, which is produced and expressed on the stromal cell membrane –> causes differentiation into ______ precursors –> acted on by M-CSF to commit to _____ differentiation, but they are not considered _____ until they fuse and exhibit at least 3 nuclei.
IL-11
Osteoclasts
Osteoblasts
RANKL
Osteoclast
Osteoclast
Osteoclasts
____ is a factor secreted by osteoclasts that competitively inhibits monocyte/macrophage cells from binding ____, and thus from differentiating into osteoclasts.
OPG
RANKL
A factor necessary for MSC differentiation into pre-osteoblasts is _____. It also facilitates differentiation of pre-osteoblasts into osteoblasts. Another factor that does the latter is _____.
Runx2
Osx