Physio of Bone Flashcards
Abreeivations 2 PGE2 Pi PPi PTH RANKL TNAP TNF
Prostagladin E2 inorganic phosphate pryophosphate parathyroid hormone RANK ligand tissue-nonspecific alkanine phospohoptae Tumor nerotic factor
Abreviations 1 ANKH CT I-1 M-CSF NPP1 OPG
Adensosine triphosphate
Calcitonin
Interlukin-1
macrophage-colony stimulating factor
ectonuceotide pyrophostphataese/phosphodiesterase
Osteoprotegerin (ostoclastic inhibiting factor)
Bone Functions
Structure Integrity
Movement of Limbs
Storage of Calcium and Phosphate
Hematopoeisis
Processes within Bone
Growth
Modeling
Remodeling
Repair
Bone - components
Collagen fibers (Type I) Calcium phosphate salts
_________ are responsible for building and maintaining bone tissue
cells
Bone modeling - define
altering the structure of a bone in response to the mechanical laods placed on it
Bone remodeling - define
repair of microdaamage that occurs
Blood flow in resting skeletal muscle v blood flow to bone
4 v 10 ml per 100/mn
Cells that make up bone
Osteoblasts
Osteocytes
Osteoclasts
Lining cells periosteal and endosteal
Osteoblasts - origin, location, function (details)
Mesenchyma Stem cells
Surface of the bone
Formation of bone - Lay down collagen fibers, deposit Ca2+ & PO43- in matrix
Osteocytes - origin, location, function (explain)
Osteoblasts
In bone channels or canaliculi
I) Sensing mechanical strain; II) Transport of Calcium and phosphate
I) (strain causes bone fluid movement in canaliculi. movement transduced into electrical signal. signal tells through osteocytes activates osteoblasts)
II) (osteocytes express PTH receptors. When Ca2+ decreases/PTH increases, osteocytic osteolysis begins. Osteocytes release Ca2+ into plasma compartment to maintain Ca2+ homeostasis. NOT bone resorption)
Lining cells - origin, location, function
Osteoblasts
Periosteal and endosteal surfaces of the bone
I) Regulate movement of calcium and phosphate into and out of the bone
II) can become an osteoblast again, if needed
Osteoclasts - origin, location, function
Hematopoietic stem cells
Surface of the bone
Breakdown/Resorption of bone - destroy matrix, fee Ca2+/PO43-
Osteoblasts and osteoclasts activity are stimulated by ….
Cytokines
Other chemical messengers
Vit D
Parathyroid hormone (PTH)
PTH def & activity
Primary endocrine regulator of bone remodeling. Secreted in response to decreased plasma Ca2+. Stimulates Osteoblastic activity and stimulates osteoclast activity INDIRECTLY. needs normal levels of VitD to have effect
Vit D
Acts to increase intestinal absorption of Ca2+
Osteoblast to osteocclast process simplified
Osteoblast release M-CSF. M-CSF induces osteoclasts precursors. M-CSF acts with RANKL. RANK (receptor on osteoclast precursor membrane) induces osteoclastogenesis. Osteoclasts dissolve calcified crystals and release Ca2+ and Pi ino blood.
Osteopontin
OPN
Acidic protein. when phosphorylated, generates strong negative charge
Binds strongly to Ca2+, inhibiting mineralization
Expression increased with hypocalcemia and hypophospatemia
Osteoclast
Bone Sialo protein
BSP
part of collagen - aids crystallization of hydroapatite
Osteoblasts
TNAP
Promotes precipitation by hydrolizing PPi into Pi.
Promotes Osteoblast activity (increase Mineralization)
NNP1
Uses ATP and ADP to form PPi , which inhibits matrix mineralization
hypophospatasia
An inborn error of metabolism caused by a deficiency in the TNAP isoenzyme
Diagnosed by a low serum TNAP level and accumulation of phosphocompunds (e.g. PPi)
epiphyses - def
ends of bones
epiphyseal plate - def.
layer of cartilage separating the head of the bone from the shaft
Bone remodeling - fxns, method
Contributes to Ca2+ regulation by moving calcium into or out of bone
Repairs micro-damage
Old bone reabsorbed (osteoclasts) then new bone deposited (osteoblasts) - Occurs @ surface
PTH - OB/OC effects
Inc OB
Inc OC
Paradox
Vit D
Inc OB
Inc OC
Paradox
Calcitonin (CT) - OB/OC effects
Dec OC
Estrogen - OB/OC effects
Dec OB
Dec OC
Testosterone - OB/OC effects
Dec OB
Dec OC
IGF - OB/OC effects
Inc OB
Inc OC
Thyroid Hormone - OB/OC effects
Inc OB
Inc OC
Cortisol - OB/OC effects
Inc OB
Dec OC
Bone repair process
Hematoma -> Soft callus -> Hard callus -> Bone
ANK
Decrease bone mineralization by increasing PPi
BSP
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