Skeletal System Part 2 Flashcards
Concentric bony lamellae laid down by successive layers of
osteoblasts
Osteoblasts become trapped in lacunaein osteoid matrix & mature into
osteocytes
Osteocytes connected by minute canals (canaliculi) containing — —
cytoplasmic extensions
canaliculi communicate with each other via
gap junctions
Within center of each osteon is
Haversian canal (canal of Havers)
Haversian canal contains (2)
blood vessels & Nn
Longitudinal Haversian canals are connected by
transverse Volkmann’s canals
Exchange of waste & nutrients occurs via
Haversian vessels
Haversian systems oriented parallel to
long axis of bone
Inactive Haversian systems known as
interstitial systems
Spongy & woven bone lack
Haversian system
Haversian system is present only in
compact lamellar bone
Outer periphery of cortical bone arranged in
circumferential lamellae
Covered by dense connective tissue called
periosteum
bone growth is controlled by (3)
growth hormone, thyroid hormone, & sex hormones
Endochondral ossification
replacement of cartilage precursor by bone
Resulting woven bone is extensively remodeled by (2)
resorption & appostional growth
resorption & appostional growth result in =
lamellar bone (e.g., long bones, vertebrae, pelvis, & base of skull)
Intramembranous ossification
direct replacement of mesenchyme by bone
in intramembranous ossification there is no — precursor
no cartilage precursor
Mesenchymal cells differentiate into —, produce —, later mineralizes into —
osteoblasts
osteoid
bone (e.g., vault of skull)
Precursor of long bone formed of
hyaline cartilage
1’ center of ossification occurs in
mid-diaphysis
Osteoprogenitor cells and osteoblasts secrete osteoid, which mineralizes, forming
periosteal cuff
Calcification of cartilage matrix inhibits diffusion of nutrients resulting in (2)
death of chondrocytes & spread of osteoblasts
Osteoprogenitor cells from periosteum migrate into —, along with — — —
medulla
growing blood vessels
Two 2’ centers of ossification occur in
epiphyses
mineralization spreads across
cartilage matrix
Epiphyseal plate in region of metaphysis remains “—” (i.e., unmineralized)
open
Allows continuous
longitudinal growth
At maturity, hormonal changes decreases — — & cartilage plate is replaced by —
cartilage proliferation
bone
what does the epiphyseal growth plate consist of
several distinct zones in transition from cartilage to bone
Zone of Reserve Cartilage
hyaline cartilage with clusters of chondrocytes
proliferation in zone of reserve cartilage
no cell proliferation
Zone of Proliferation
successive mitotic division of chondrocytes, which results in columns of chondrocytes
Zone of Maturation
division ceases
in the zone of maturation, chondrocytes…
increase in size
Zone of Hypertrophy (& Calcification) (3)
chondrocytes greatly enlarge, contain large amounts of glycogen, become vacuolated & calcify
Zone of (Cartilage) Degeneration
capillaries of marrow cavity grow from diaphysis into growth plate
in the zone of degeneration, chondrocytes degenerate; lacunae invaded by
osteogenic cells
Zone of Ossification
blood vessels from marrow cavity grow into cartilage mass
Osteogenic cells differentiate into osteoblasts, congregate on spicules of calcified cartilage matrix to form bony
trabeculae
Mesenchymal cells differentiate directly into
osteoblasts
mesenchymal cells begin synthesizing osteoid at multiple sites, (multiple centers of ossification) within
membrane—no cartilage precursor
Mineralization follows with subsequent fusion of adjacent
centers of ossification
Osteoblasts trapped within lacunae of osteoid, become
osteocytes
Osteoprogenitor cells at periphery continue to divide, provide
replacements
Bone produced is woven bone—later remodeled by osteoclasts & osteoblasts to form
compact bone
Simple or closed fracture
no break in skin
Compound or open fracture
damage to skin exposing bone
Comminuted fracture
bone broken in several pieces
Blood fills fracture site, resulting in
hematoma
immediately after fracture, inflammatory response develops—(4)
pain, swelling, redness, & heat
In acute phase (first few days) — first to arrive, infiltrate hematoma, then —, (both phagocytic) to clean up site of injury
neutrophils
macrophages
After ~1 wk, (2) proliferate & grow into site
fibroblasts & capillaries
bone repair forms
granulation tissue (vascular collagenous tissue)
granulation tissue becomes progressively more fibrous in chronic phase, forms
fibrous granulation tissue
Mesenchymal cells differentiate into chondroblasts, secrete
matrix
matrix secretion results in progressive replacement of granulation tissue by
hyaline cartilage
progressive replacement of granulation tissue by hyaline cartilage
provisional callous
Next, osteoprogenitor cells & osteoblasts from endosteum & periosteum at edge of wound grow —
inward
produce meshwork of woven bone within provisional callous, deposit calcium salts in
collagen matrix
Transforms into
bony callous
bony callous helps (2) fracture together
stabilize & bind fracture together
Important to realign & stabilize, or “set” fracture — this happens
before
When fracture site completely bridged by woven bone
bony union
Bony callous progressively remodelled
mature lamellar bone
Process takes ~ 6-12 wks, depending on (2)
severity & location
Synovial—characterized by
extensive movement
synovial joint is also known as
diarthroses
synovial joint/diarthroses are surrounded by
connective tissue capsule
connective tissue capsule
joint capsule
Lined by thin, discontinuous layer of cells,
synovium
synovium secretes
synovial fluid
synovial fluid bathes the
articular surface
No basement membrane, so not a
true epithelium
synovial “epithelia” is made of up to 4 cell layers of
synovial cells of mesenchymal origin
Two types of cells
A & B
Type A (2)
synoviocytes
resemble Mφ
Type B
resemble fibroblasts
Nonsynovial
limited movement; joined by dense connective tissue, lacks articular surface
Syndesmosis
dense fibrous tissue between bones In skull, progressively replaced by bone to become synostosis(aka “sutures”)
Synchondrosis
(1’ cartilage joint) contains single layer of hyaline cartilage
what unites first rib with sternum?
synchondrosis
only one in human adult
Symphysis
(2’cartilage joint), contains two hyaline cartilage surfaces connected by fibrocartilage plate
Intervertebral joints are a special type of
symphysis
Contain intervertebral discs, evolutionarily derived from — in chordates
notochord
Formed of concentric layers of
fibrocartilage
Forms annulus fibrosus around central core of viscous ground substance,
nucleus pulposus
Damage to annulus fibrosus causes nucleus pulposus to
herniate
Damage to annulus fibrosus causes nucleus pulposus to herniate, resulting in a
herniated disc
inflammationof joints
arthritis
Osteoarthritis (2)
progressive degeneration & loss of articular cartilage
Leads to eburnation, pitting, erosion resulting in (3)
pain, swelling, thickening of joint capsule
Osteophytes
production of irregular new bone at edges of articular surfaces; aka “bone spurs”
Limits range of
motion
Progressive build-up of osteophytes, osteoarthritis or trauma can lead to
ankylosis
ankylosis
bony fusion of joint with loss of mobility
Rheumatoid arthritis
local, autoimmune rxn in joints => body produces Ab’s that attack joints => pain, damage to articular cartilage; thickening, inflammation of synovial membrane
pannus
replacement of articular cartilage with fibrovascular tissue
Gout
deposit of urates & uric acid crystals in joints (especially fingers & toes)
gout is extremely painful, associated with consumption of large quantities of (2)
red wine, meat
gout is also caused by certain vegetables—(4)
asparagus, broccoli, cauliflower, Brussel’s sprouts
All represent new plant growth, high in (2)
protein & [N]
Some diuretics used to treat hypertension can also cause
gout
Rickets
bone matrix doesn’t calcify normally in children during growth
rickets results in
soft, deformed bones
rickets can be
permanent
rickets are due to insufficient dietary (2)
Ca or Vit D
In adults, insufficient Ca & Vit D can lead to
osteomalacia
osteomalacia
failure of mineralization, softening of bone
Osteoporosis
loss of bone mass
Resorption by osteoclasts exceeds deposition by
osteoblasts
Common problem in post-menopausal women, possibly due to
decreased estrogen levels
Tx with oral Ca supplementation & Vit D for increased
Ca absorption
chondroitin, glucosamine, gelatin also helpful
Newer osteoporosis meds, e.g., Fosamax, bind phosphates in GI tract, minimize
absorption
Possible side effects include
mandibular necrosis
— necessary for synthesis of collagen
Vit C
Vit C deficiency results in
scurvy
scurvy
bone matrix not calcified
Can also lead to weakening of collagen in
ligaments
especially periodontal ligament, resulting in
loose teeth
Breakdown of scars/ old wounds, which (2)
break open & bleed
Tx with fruits & vegetables high in
Vit C
e.g., citrus fruits—oranges, lemons, limes; also guavas
