4.4 Bone Flashcards
what are the 4 functions of bone?
Protection, support, locomotion, mineral reservoir (Ca2+, PO4, Mg2+)
bone is _____ vascular and ____ inntervated
Highly, IS
composition of bone ECM?
50% organic, 50% inorganic
inorganic components of bone ECM (3)
- Hydroxyapatite crystals
- Citrate and carbonate ions
- Mg2+, K2+, Na2+
organic components of bone ECM (2)
- collagenous proteins (90%)
- non-collagenous proteins (10%)
what are 2 examples of collagenous proteins in bones?
type 1 and V collagen
______ are glycosaminoglycan side chains + core protein
Proteoglycans
_______ mediate matrix assembly/mineralization (DMP1, OPN, BSP)
Sibling proteins
________ capture calcium from plasma (ex:osteocalcin)
Bone specific vitamin-K dependent proteins
____ is a thin CT layer that lines all _____ surfaces
and Contains bone forming cells
Endosteum, inner
______ is the dense CT layer that is attached to bone via Sharpey’s layers
Periosteum
the inner osteogenic layer of the periosteum contains _______ and the outer fibrous layer contains ______
bone forming cells, fibroblasts
_______ are the source of new osteoblasts that are located on or near free surface
Osteoprogenitor cells (Opc)
where do osteoprogenitor cells come from?
mesenchymal cells in bone marrow
______ synthesize/secrete osteoid (Os), release matrix vesicles, and are found in actively forming bone surfaces
osteoblasts
what are osteoblasts originated from?
Osteoprogenitor cells
______ are mechanosensors and orchestrators of the bone remodeling process that communicate with osteoblasts via Canalicuae. They are located ________
- osteocytes
- within lacunae surrounded by mineralized bone
Osteocytes are derived from ____
osteoblasts
______ function in bone reabsorption and are loated in pits in the bone surface which are called resorption bays (Howship’s lacunae)
Osteoclasts
Osteoblasts have a ___ amount of golgi, RER and mitochondria and secrete a large amount of _____
Large, ECM
differences between Quiescent, Formative, and resorptive osteocytes??
- Quiescent
- Surrounded by bone matrix
- Filopodia extend away from cell body, links cells by gap jxns
- Decreased golgi/ER - Formative (right pic)
- Contain RER/golgi
- Small amt osteoid visible in space surrounding cell
- Un-mineralized collagen fibrils present in osteoid - Resorptive
- Many mitochondria
- Lysosomes containing enzymes in cytoplasm
- dissolve/chew away bone
- NO fibrils in pericellular space
- Large Golgi
______ are giant multinucleated cells that have many golgi/lysosomes, a ruffled border facing the bone surface, and communicate via _____
osteoclasts
gap jxns
_______ are the spaces between lamellae containing an osteocyte
Lacunae
____ are the tiny canals that connect all lacunae
Canaliculi
______ are thin, actin-rich plasma-membrane protrusions that function as antennae for cells to probe their environment
filopedia
______ are any of the tiny depressions, pits, or irregular grooves in bone that is being resorbed by osteoclasts
Howship’s lacunae
________ are the chief structural unit of compact (cortical) bone, consisting of concentric bone layers called lamellae, which surround a long hollow passageway, the Haversian canal
Haversian systems
_______ are any of the minute tubes which form a network in bone and contain blood vessels
Haversian canals
___________ are the layers around haversians canal
Haversian (concentric) lamellae
_________ fill the spaces between osteons
Interstitial lamellae
______ run around the circumference of bone
Circumferential lamellae:
_______ are any of the small channels in the bone that transmit blood vessels from the periosteum into the bone and that communicate with the haversian canals.
Volkmann’s canals
______ are small (20-200 nm) spherical bodies observed in the pre-mineralized matrix of dentin, cartilage and bone.
Matrix vesicles
what are the 3 kinds of intramembraneous ossification?
embryonic, sutural, periosteal
_______ drive intramembranous ossification. Is there a cartilagenous intermediate?
extrinsinc forces
NO
what are the 2 kinds of endochondral ossifcation?
embryonic, growth plate/synchondrosal/postnatal expansion
difference between intramembranous ossification and endochondral ossification?
In intramembranous ossification, bone develops directly from sheets of mesenchymal connective tissue. In endochondral ossification, bone develops by replacing hyaline cartilage.
what are the steps of embryonic endochondral ossification?
mesenchymal blastema formation → formation of hyaline cartilage model of bone → hypertrophy and destruction of chondrocytes and calcification of cartilage → cartilage replaced by bone → bone osteoid deposition and mineralization of calcified cartilage spicules
postnatal growth is driven by ______
growth plates
what are the different zones of post-natal expansion?
resting zone, proliferation zone, hypertrophy, zone of calcified cartilage, zone of ossification
______ is where progenitor cartilage cells rest, and the cells are smaller
Resting zone
_______ is where cells start rapidly dividing, expanding growth plate, stack in direction of bone axis
Proliferation zone
______ is where cells swell and bubble, pushes ECM to condense and calcify them
Hypertrophyzone
_________ is the blue matrix; scaffold for osteoblasts to lay down bone matrix
Zone of calcified cartilage
______ is the Pink matrix, comes from osteoids by osteoblast, and uses calcified cartilage as template
Zone of ossification
Endochondral ossification has ______ growth potential. Does it have cartilagenous growth plates?
INTRINSIC, yes
______ is growth formed around the trabeculae by differentiating mesenchymal cells.
Periosteal growth
______ growth produces new bone at the sutural edges of the bone fronts in response to external stimuli, such as signals arising from the expanding neurocranium
Sutral intramembranous bone
__________ is the part of a long bone where new bone growth takes place
Epiphyseal disc (growth plate)
______ is unmineralized bone tissue and is a key structure in the development of mature mineralized bone.
Osteoid
______ is the first bone laid down. It is formed from osteoblasts producing osteoid rapidly in fetal bones
Woven/primary/immature bone
_______ is the main type of bone in mature skeleton. It comes from aligned rows of osteoblasts working in unison
Lamellar (secondary, mature) bone
what is woven bone made of?
coarse, interwoven collagen fibers, increased numbers of osteocytes
what does lamellar bone contain?
collagen fibers arranged in concentric layers; multiple series of osteoblast passes creating multiple layers of lamellae
what are the 2 types of lamellar bone?
- cancellous/spongy/trabecular
- compact/dense/cortical
______ is a 3D lattice of spicules, trabeculae and plates that has spaces that contain red and yellow marrow
cancellous bone
______ is a solid mass of bone tissue that is highly organized around blood vessels
Compact bone
________ is a layer of hard connective tissue between the hyaline articular cartilage and subchondral bone. It gets calcified due to the deposition of insoluble calcium salts in the bone matrix.
Calcified cartilage:
______ is chemically similar to the mineral component of bone and hard tissues in mammals.
Hydroxyapatite
what does hydroxyapatite do?
support bone ingrowth and osseointegration
what is mineralization?
process by which organic bone matrix becomes filled with calcium phosphate nanocrystals
mechanisms of mineralization? (5 steps)
- Small membrane bound vesicles bud off osteoblasts
- they contain phosphoserine, CA2+ PO4- cAMP, ATP, ATPase, CaBP, alkaline phosphatase
- Ca2+ pumps cause influx of Ca2+
- crystallization occurs, crystals break open vesicles
- Crystal formation continues in absence of vesicles
mineralization is a highly _______and _____ process
organized and controlled
primary vs secondary cartilage
Primary Cartilage
- develop early, known as “synchondrosis
- Function: protects your joints and bones, shock absorber throughout your body, reduces friction and prevents bones from rubbing together when you use your joints
- Composition: Collagen Type II
- Examples: growth plates between ossification centers in long bones
- Growth: Interstitial cell proliferation
Secondary cartilage:
- delayed in initiation, known as “symphysis”
- Function: only allow slight movement (found at skeletal midline)
- Composition: fibrocartilage, collagen types I and II
- Location EX: intermaxillary suture cartilage, angular cartilage, fracture callus; forms adjacent to intramembranous bone
- Origin: not derived from primary cartilaginous skeleton; formed from bipotential cells or periosteal origin
- Growth: appositional proliferation
