Bone Homesostasis Flashcards
Calcium has this effect on blood coagulation
Promotes it
3 organ systems involved in calcium balance
Bone, kidney, intestine
3 hormones involved in calcium balance
PTH, Vitamin D, Calcitonin
This is the primary mineral form in bone
Hydroxyapatite (Ca10(PO4)6(OH)2)
Osteoid is the protein matrix of bone, and the majority of it is made up of this
Type I collagen oriented in a tight triple helical structure
This provides site of nucleation of hydroxyapatite crystals with alignment along collagen fibers for tensile strength
Type 1 collagen oriented in tight triple helical structure in osteoid (bone matrix)
Type 1 collagen oriented in a tight triple helical structure within osteoid provides site of nucleation of this, with alignment along collagen fibers for tensile strength
Hydroxyapatite crystals
Cells the promote bone formation
Osteoblasts
Cells that promote bone resoprtion
Osteoclasts
Osteoblasts that localize to the bone during during mineralization and remain there
Osteocytes
Cells that sense mechanical stress on bone and secrete factors to stimulate osteoblasts
Osteocytes
Osteocytes are this type of cell that localize to the bone matrix during mineralization and remain there
Osteoblasts
Flat quinescent cells with barrier function
Bone lining cells
Mononuclear cells that seem to prepare areas for new bone deposition
“Reversal” cells
Osteoprogenitor cells arise from this
Mesenchymal stem cells
When these cells are stimulated by growth factors, daughter cells differentiate into osteoblasts
Osteoprogenitor cells
When osteoprogenitor cells are stimulated by growth factors, daughter cells differentiate into these
Osteoblasts
Osteoblasts are activated by this signaling
Wnt/beta-catenin
The Wnt/beta-catenin signaling pathway governs this
Differentiation of osteoprogenitor cells into osteoblasts
Cells that produce and deposit organic components to form matrix, and initiate the mineralization process
Osteoblasts
Osteoblasts remaining on bone surface transforming to these
Bone lining cells
Osteoblasts surrounded by new matrix differentiate to these
Osteocytes
Osteocytes communicate via this
Canaliculi
Regulators of bone remodeling that communicate via canaliculi
Osteocytes
Osteocytes secrete this which decreases bone formation
Wnt inhibitor sclerostin
What is sclerostin?
Wnt inhibitor secreted by osteocytes that decreases bone formation
Cells that secrete Wnt inhibitor sclerostin that decreases bone formation
Osteocytes
Mechanical forces induce signaling of these cells, leading to expression of growth factors that stimulate osteoblasts and bone formation
Osteocytes
What effect does osteocyte death have on bone?
Triggers remodeling
(apoptosis recruits osteoclasts, initiates resorption; lack of mechanical stimulation increases apoptosis, also aging and glucocorticoids)
What effect does mechanical force/stimulation have on bone?
Induces osteocyte signaling, leading to formation of growth factors that stimulate osteoblasts and bone formation
Lack of mechanical stimulation increases osteocyte apoptosis, triggering remodeling
Osteoclasts originate from these
Myeloid precursors that arise from hematopoietic stem cells
Macrophage colony stimulating factor (M-CSF/CSF1), IL-2, and TNF regulate these cells
Osteoclasts
Osteoclasts are regulated by cytokines and growth factors, including these 3
Macrophage colony stimulating factor (M-CSF/CSF1), IL-2, and TNF
Cells that originate from myeloid precursors that arise from hematopoietic stem cells
Osteoclast
Mature multinucleated osteoclasts (a fusion of 6-12 precursors) survive about this long
2 weeks
Cells that promote bone resorption
Osteoclasts
Osteoclasts promote this
Bone resorption
Cells that bind tightly to bone surface via integrins attachment to vitronectin
Osteoclasts
Osteoclasts bind tightly to bone surface via this attachment
Integrins attachment to vitronectin
Osteoclasts bind tightly to bone surface via integrins attachment to this
Vitronectin
Cells that dissolve minerals by acid (uses proton pump system) and organic elements by proteases
Osteoclasts
Osteoclasts dissolve minerals by this
Acid (proton pump system)
Osteoclasts dissolve organic elements by this
Proteases
Cells that when mature, are multinucleated due to fusion of 6-12 precursors
Osteoclasts
Paracrine factor expressed by osteoblasts that induces osteoclast precursor differentiation
CSF1