Bone Flashcards
What type of tissue is bone?
specialized connective tissue
What are the support cells of bones?
osteoblasts and osteocytes
What are the non-mineralized organic matrix of collagen and GAGs?
osteoid
What are the inorganic mineral salts within matrix?
hydroxyapatite
What are the remodeling cells of bone?
osteoclast
What are the functions of bone?
-mechanical support
-locomotion
-protection
-metabolic reservoir of mineral salts
What type of bones are in limbs?
long bones
What is the shaft of long bones called?
diaphysis
Where is compact bone?
cortex
Where is spongy, cancellous/trabecular bone?
medullary cavity
-marrow
Where is red (hematopoietic) and yellow (fatty) bone marrow at?
medullary cavity
What are the ends of bones called and what are they made up of?
epiphyses
-spongey, cancellous/trabecular bone covered with hyaline articular cartilage
What are the flared regions between the epiphysis and diaphysis called?
metaphysis
Where is the epiphyseal plate?
metaphysis
What is an osteoid?
collagenous support tissue embedded in a GAG gel containing osteocalcin (binds calcium)
-has deposition of mineral salts to give bones rigidity and strength
What makes and maintains osteoids?
osteoblasts and osteocytes
What is woven bone?
haphazard organization of collagen fibers and is mechanically weak
-fast production of bone
What is lamellar bone?
regular, parallel alignment of collagen into sheets and is mechanically strong
What are the two major components of bones?
-outer cortical or compact bone
-inner trabecular or cancellous bone
What is the outer shell of the bone?
cortical bone
-resist deformation
What is the inner network of the bone?
trabecular network
What surrounds osteons?
concentric lamellae of compact bone with osteocytes
What acts as packing between adjacent Haversian systems?
interstitial bone lamellae
What horizontally links osteons?
Volkmann’s canal
What carries the blood vessels and nerves in osteons?
Volkmann’s canal
How do osteocytes communicate with one another?
canaliculi
What can cause abnormalities in bone architecture?
-damage to both cortical and trabecular bone due to fracture
-decreased cortical and trabecular bone due to osteoporosis
-destruction of trabecular bone due to cancer
-maldevelopment of bone
What is the endosteum?
membrane lining the inner surface of the bony wall also identified as the lining membrane of the bone marrow cavity
What does the endosteum line?
Haversian canals and all internal cavities of the bone
What makes up the endosteum?
a layer of flattened osteoprogenitor cells and a type III collagenous fibers
Which is thinner: endosteum or periosteum?
endosteum
What are the two layers of the periosteum?
outer fibrous membrane and inner cellular layer
What is the outer fibrous layer of periosteum?
irregular, dense connective tissue type with more collagenous matrix and fewer cells
What is the inner cellular layer of periosteum?
made of osteoprogenitor cells
-also known as osteogenic layer
contains osteoblasts in young developing bones (in adults, osteoblasts may be absent unless required)
-rich in vascular structure and many blood vessels
What are osteoprogenitor cells?
multipotent stem cells
-undergo mitotic division and differentiate into osteblasts
What are Sharpey’s fibers?
parallel bundles of collagen fibers
-extend from periosteum or muscle tendon and insert into superficial layer of bone
-provide anchorage and support
What are osteoblasts?
make osteoids and mineralized it by depositing hydroxyapatite
-only large and metabolically active when synthesizing/mineralizing
-polygonal, mesenchymal derived from osteoprogenitor cells
-basophilic due to organelles for making of large amounts of proteins and proteoglycans
What are osteocytes?
inactive cells trapped within bone matrix
What are osteoclasts?
multinucleate cells derived from monocytes
-reabsorb bone to release calcium and phosphate
-stimulated by parathyroid hormone in response to low serum calcium levels
What allows osteoblasts to calcify?
secretion of matrix vesicles
What is inside the matrix vesicles?
alkaline phosphatases
-cause precipitation of mineral salts in form of hydroxyapitate
Where do osteoblasts mature into osteocytes?
lacunae
What are the components of bone?
70% inorganic salts and 30% organic matrix
What is the organic matrix?
> 90% type 1 collagen
What GAGs are in the ground substance of bone?
hyaluronic acid, chondroitin sulfate, and keratan sulfate
What are the non-collagenous organic molecules in bone?
-osteocalcin
-osteonectin
-sialoproteins
What is osteocalcin?
binds intracellular Ca during mineralization
What is osteonectin?
bridges/binds collagen and minerals
What are sialoproteins
rich in sialic acid; concentrated in plasma
What does bone have high affinity for?
heavy metals (Pb and Hg) and radioactive isotopes
Where are osteoclasts normally found?
endosteal/periosteal surface in depressions called Howship’s lacunae or reabsorption bays
How do osteoclasts function in Ca homeostasis?
produce organic acids and lysozymes that digest bone
-secreted into ECS by ruffled border
What 2 antagonist hormones work to maintain calcium homeostasis?
parathyroid hormone and calcitonin
What is parathyroid hormone?
secreted by parathyroid hormone
-stimulate osteoclast activity
-increase blood Ca levels and decrease renal excretion by kidneys
What is calcitonin?
secreted by thyroid gland
-stimulate osteoblast activity
-inhibit osteoclasts
-decrease blood calcium levels
What is somatotropin?
pituitary growth hormone
-stimulates growth in epiphyseal cartilage and bone
-decrease bone calcium
-oversecretion can lead to gigantism or acromegaly
-undersecretion leads to pituitary dwarfism
