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Bone Microanatomy
LECOM Yr 1
76
Anatomy
Graduate
08/05/2011

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Cards

Term
what are osteoblasts?
Definition
cuboidal to columnar bone building cells
Term
what do osteoblasts deposit which becomes calcified bone?
Definition
osteoid
Term
what are osteocytes?
Definition
mature bone maintaining cells trapped in lacunae
Term
what are osteoclasts?
Definition
large multinucleated cells responsible for bone resorption
Term
what 3 hormones regulate calcium phosphate homeostasis?
Definition
PTH, calcitonin, calcitriol (vitamin D)
Term
what effect does PTH have on bone resorption?
Definition
increases bone resorption, raises serum calcium levels (has also been seen to lower bone resorption but mechanism is unknown)
Term
how does PTH increase bone resorption?
Definition
binds to receptors on osteoblasts. osteoblasts then secrete osteoclast stimulating factor which binds to osteoclasts and activates them
Term
what effect does calcitonin have on bone resorption?
Definition
inhibits osteoclasts so decreased bone resorption which prevents calcium release from bone (decreased serum calcium)
Term
what effect does vitamin D have on calcium?
Definition
increases calcium absorption in the gut, increases bone resorption taking calcium and phosphate from old bone in order to mineralize new bone
Term
effect of calcitriol on bone?
Definition
bone resorption
Term
effect of calcitriol of kidney?
Definition
reduced excretion of calcium
Term
effect of calcitriol on gut?
Definition
absorption of calcium and phosphate
Term
who is at greatest risk of osteoporosis?
Definition
postmenopausal women
Term
what effect does estrogen have on bone?
Definition
maintains bone density in both sexes, it inhibits bone resoprtion
Term
what is the predominant structural protein in bone?
Definition
type I collagen
Term
what is the form of calcium and phosphate in the collagen and ground substance of bone?
Definition
hydroxyapatite crystals
Term
what do bone morphogenic proteins (BMPs) do?
Definition
induce the differentiation of mesenchymal cells into osteoblasts
Term
what is the shaft of the long bone termed?
Definition
diaphysis
Term
what are the proximal and distal ends of the long bone termed?
Definition
epiphysis
Term
where is the epiphyseal line?
Definition
between the metaphysis and the epiphysis
Term
what is the periosteum?
Definition
a fibrous connective tissue that surrounds the outer surface of the non articulating parts of the bone
Term
what is the source of the pain from a bone fracture?
Definition
periosteal nerve
Term
nutrient vessels enter the bone through what?
Definition
nutrient foramina
Term
where is red bone marrow typically found in adults?
Definition
the sternum and iliac crest
Term
what are the sternum and iliac crest typically used for clinically?
Definition
sites for biopsy and marrow transplantation
Term
what is yellow bone marrow?
Definition
fatty marrow that can convert to red marrow if need be
Term
concentric lamellae and the haversion canal constitutes the?
Definition
osteon
Term
what are the result of bone remodeling and lie between complete osteons?
Definition
interstial lamellae
Term
what are the two parts of the periosteum?
Definition
out fibrous layer (dence CT) and inner cellular layer (osteoprogenitor cells)
Term
where does the endosteum line?
Definition
internal surfaces; has a thin layer of osteoprogenitor cells
Term
what are sharpey's fibers?
Definition
collagen fibers found at the site of a tendon insertion into bone; these fibers run through the periosteum and are continuous with the collagen fibers of bone tissue
Term
what are caniculi and how do they communicate?
Definition
small canals allowing extended cytoplasmic processes of an osteocyte trapped in lacunae to make contact with other osteocytes and communicate via gap junctions
Term
what is the center of the haversion system lined with?
Definition
endosteum
Term
what is the orientation of haversion systems?
Definition
longitudinal
Term
what is the orientation of volkman's canals?
Definition
perpendicular
Term
where is the outer circumferential lamellae located?
Definition
under the periosteum
Term
where is the inner circumferential lamellae located?
Definition
around marrow cavity
Term
describe the difference between immature (woven) bone and mature (lamellar) bone
Definition
immature has more cells and the matrix is not layered while mature has fewer osteocytes per unit area and has osteons with concentric lalellae with the presence of interstital lamella
Term
where is primary bone typically found in adults?
Definition
tooth sockets, near the sutures of the flat bones of the skull and the insertions of some tendons
Term
what is the purpose of the ruffled border made by the osteoclast?
Definition
dramatically increases surface area
Term
the depression made in bone by the osteoclast is termed what?
Definition
howship's lacunae
Term
what is contained in the organic (osteoid) region of bone matrix?
Definition
collagen type I fibers, proteoglycans, and glycoproteins (these play a role in binding calcium)
Term
what is typically found in the inorganic region of bone matrix?
Definition
calcium and phosporus in the form of hydroxyapatite crystals
Term
what enzyme does the osteoclast use to help lower the pH of the microenvironment?
Definition
carbonic anhydrase
Term
what is it clinically termed when the mineralization of the bone matrix is impaired (soft bones) due to vitamin D deficiency?
Definition
osteomalacia
Term
in children, what is growing bone vitamin D deficiency termed?
Definition
Rickets
Term
what is osteogenesis imperfecta (Brittle Bone disease)?
Definition
genetic disorder of type I collagen characterized by repeated fractures after minor trauma
Term
what is osteoporosis?
Definition
decreased bone mass; rate of minerals to organic matrix is normal; bone is characterized by spicules that are thinner than normal bone
Term
what are the two ways in which bones can develop?
Definition
intramembranous ossification and endochondral ossification
Term
what is typical of intramembranous ossification?
Definition
numerous osteoblasts on surface of newly deposited bone, bone spicules interconnect forming trabeculae, no previous cartilage model, and the early periosteum is forming from cellular connective tissue
Term
how does intramembranous ossification begin?
Definition
by condensation of mesenchymal cells
Term
the site of osteoblast formation in intramembranous ossification is termed?
Definition
primary ossification center
Term
what are the 2 phases of endochondral ossification?
Definition
hypertrophy and degeneration of chondrocytes, and osteogenic bud of osteoprogenitor cells and blood vessels penetrate the space left by the dead chondrocytes
Term
if a bone collar is present, what type of ossification is indicated?
Definition
endochondral ossification
Term
where does the secondary ossification center arise later in endochondral ossification?
Definition
the epiphyses
Term
describe the sequence of events in endochondral ossification
Definition
bone collar forms, cartilage hypertrophy, osteogenic bud of blood vessels, osteoblasts differentiate, and primary ossification center expands
Term
what are the 5 zones of the epiphyseal plate?
Definition
zones of reserve, proliferation, hypertrophy, calcification, resorption
Term
bone formation is take place at what surface(s) of the epiphyseal plate?
Definition
the epiphyseal and diaphyseal surface
Term
describe the cutting cone in the bone remodeling unit
Definition
advances and resorbs bone
Term
what does the closing cone in the bone remodeling unit do?
Definition
deposits new bone
Term
what is the purpose of bone remodeling?
Definition
maintains shape of bone during growth
Term
the deficiency of growth hormone during the developing years that leads to failure of bone growth is termed what?
Definition
Pituitary dwarfism
Term
excess growth hormone during the developing years that leads to an abnormal increase in the length of bones is termed what?
Definition
gigantism
Term
excess growth hormone in adulthood that leads to thickening of the bones since the growth plates have already closed is termed what?
Definition
acromegaly
Term
what are the seven steps in fracture repair?
Definition
blood cot forms, periosteum and endosteum proliferate, hyaline cartilage forms, primary bone forms, bone callus unites fracture temporarily, osteoblasts form and deposit new bone, remodeling occurs
Term
Articular Surfaces
Definition
contact area two bones
Term
osteoprogenitor cells
Definition
mesenchymal stem cells, can give rise to osteoblasts
Term
osteoblast
Definition
secrete ECM
Term
Periosteal Cells
Definition
bone lining cells on external bone
Term
Endosteal Cells
Definition
bone lining cells on internal bone
Term
Osteoid
Definition
Uncalcified bone matrix
Term
Osteocalcin
Definition
Calcium binding protein, vit K dependent, in ECM
Term
Metaphysial Arteries
Definition
arise from periosteal vessels
Term
Endosteum
Definition
lines internal surface with osteoprogenital cells
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