Exam 2: Bone Flashcards
Pressure to bone results in
bone resorption (breakdown)
Tension to bone results in
bone deposition (addition)
Long bones
Contain 2 epiphyses, a diaphysis, marrow cavity in core
Epiphyses
2 bulbous ends of long bone
epiphyseal growth plate
consist of hyaline cartilage plates that allow bone growth in length. Disappear around age 18-20
Metaphysis
angulation between epiphyseal plate and diaphysis
Diaphysis
long cylindrical shaft between two epiphyses
Periosteum
external connective tissue capsule of bone - 2 layers outer fibrous and inner cellular
Does not cover articulating surfaces of bones and where tendons attach to bones
Outer fibrous layer
dense collangeous CT, blood vessels and nerves
Sharpey’s fibers
anchor periosteum to bone
Found in outer fibrous layer
Inner cellular layer
covers actively growing bone - contains osteoprogenitor cells
Endosteum
internal CT capsule of bone
thin CT layer with a single row of osteoprogenitor cells
Line bone marrow cavity, and Haversian and Volkman canals
Cover bony spicules and trabeculae of spongy bone
Bone Matrix is made of
inorganic minerals (hardness) and organic fibers/ground substance (prevent bone from becoming brittle)
Bone fibers are mainly
type I collagen (acidophilic)
Proteoglycans (with hyaluronan, chondroitin sulfate, and keratan sulfate)
bind growth factors
Osteonectin
serves as glue between collagen and hydroxyapatite crystals
sialoproteins (osteopontin and sialoproteins I & II)
bind cells to bone matrix
begins calcium phosphate formation during mineralization
osteocalcin
traps calcium from blood stream
stimulates osteoclasts to remodel bone
Osteoprogenitor cells
arise from mesenchymal stem cells
located in inner layer of mature periosteum and in endosteum
Differentiate into osteoblasts
Osteoblasts
arise from osteoprogenitor cells Cuboidal-columnar shaped basophilic synthesize organic component of bone matrix Has high levels of alkaline phosphatase
Osteoid
newly formed non-mineralized bone
collagen type I and bone matrix proteins
When bone is being synthesized, what is high in blood
alkaline phosphatase
Osteocytes
osteoblasts that are enclosed within matrix they produce
Enclosed in lacuna
Rickets
calcium or vitamin D deficiency
Bone softening
Osteoporosis
reduction in bone mass - porous bones that fracture easily
Bone-lining Cells
cover bone surface, protecting it from osteoclasts
nutritional support of osteocytes
Canaliculi
cytoplasmic processes that radiate from osteocytes
form gap junctions with other osteocytes to transfer nutrients
Osteocyte is surrounded by
fluid in periosteocytic space
The periosteocytic space is surrounded by
osteoid - nonmineralized bone matrix (osteoid is surrounded by mineralized bone)
Osteoclasts
motile, acidophilic due to lysosomes
derived from mononuclear hemopoietic progenitor cells in bone marrow
resorb bone
An osteoclast in the process of bone breakdown has what 3 regions?
ruffle border, clear zone, basolateral regions
ruffled border
associated with bone resorption
cell membrane is thickened with infoldings
exocytosis of hydrolytic enzymes and endocytosis of broken down bown
Clear zone
lacks organelles
has actin microfilaments
sealing zone that isolates acidic resorption compartment
Basolateral region
contains organelles
functions in exocytosis of broken down matrix
Compact Bone
dense, solid bone that forms a shell around the exterior of long bones
Contains Haversian systems
Skull cap consists of
an outer table of compact bone covered by periosteum and an inner table of compact bone that is lined by periosteal layer of cranial dura mater
Cancellous bone
spongy bone that lines marrow cavity of long bones
bony trabeculae and spicules protrude from inner surface of compact bone toward marrow cavity
Contains mainly an irregular arrangement of bone lamellae
Primary bone
forms during fetal development and bone repair
contains irregular bundles of collagen
Temporary tissue, resorbed by osteoclasts and replaced by secondary bone
Secondary Bone
parallel or concentric bone lamellae
collagen fibers parallel
more mineral content than primary bone
Outer circumferential lamellae
deep to periosteum
surround bone
Sharpe’s fibers anchor periosteum to underlying bone
Interstitial lamellae
lamellar fragments, remnants of former osteons
Haversian canal systems (osteons)
vascular space that encloses a neurovascular bundle - No Lymphatics!
Helical arrangement
Volkmann canals
connect osteons that are next to each other
not have to be concentric
Inner circumferential lamellae
around marrow cavity
Ankylosis (arthritis)
trauma induced to a joint that damages hyaline cartilage
Cartilage becomes calcified, die, then replaced by bone - two articulating bones fuse = no joint movement
Rheumatoid arthritis
autoimmune disease that attacks synovial joints, damaging articular cartilages, producing disfigurement of joints and severe pain
Gouty arthritis
accumulation of uric acid crystals in joints
Intramembranous ossification
bone forms directly within a membrane of highly vascular mesenchyme
Flat bones of skull, face, mandible, clavicle, and other flat bones form this way
The first bone laid down is
primary bone
The soft osteoid of primary bone undergoes
mineralization, trapping osteocytes in lacunae
Primary bone is resorbed by ____ and replaced with____
osteoclasts; secondary bone
Newly formed secondary bone occurs as
spongy bone, which can remain spongy or become compact bone
Endochondral Ossification
cartilage model of bone-to-be is formed first, than becomes calcified, eroded, and replaced by bone
Long bones and vertebrae of spine form via
Endochondral Ossification
Primary ossification center is located in
diaphysis (hyaline cartilage model of bone)
As bony collar forms in Endochondral ossification, cartilage cells
hypertrophy (accumulate glycogen and form vacuoles) and produce alkaline phosphatase - cartilage matrix becomes calcified
Secondary center of ossification is located in
the epiphysis, forms shortly after birth
Cartilage is continuously being replenished at _____ side of growth plates and being replaced by bone at the ______ side.
epiphyseal; diaphyseal
Zones of epiphyseal plate
Zone of Reserve Cartilage, Zone of proliferation, Zone of hypertrophy, zone of calcified cartilage, zone of resorption and ossification
Zone of reserve cartilage
hyaline cartilage
mitotically active
Zone of proliferation
intense mitosis here - chondrocytes produce new organic matrix - cartilage grows interstially
form parallel columns of isogenous cells
Chondrocytes appear in stacks (like pennies) parallel to long axis of bone
Zone of hypertrophy
chondrocytes accumulate glycogen and become vacuolated
Individual chondrocytes swell in size
Zone of Calcified cartilage
lacunae coalesce, calcification of cartilage matrix, chondrocytes die
Zone of resorption and ossification
calcified cartilage remnants form long spicules, blood vessels bringing osteoprogenitor cells invade, differentiate into osteoblasts
Calcified cartilage stains
blue - basophilic
Does not contain cells
Mineralized bone stains
pink - acidophilic
contains living cells
Bone growth in width occurs by
appositional growth - osteoblasts secrete bone matrix on subperiosteal bone surface
Neutrophils
arrive at site of bone injury first, then macrophages arrive to clean up debris
Soft callus
formed by granulation tissue and cartilage to cover injured bone, eventually dies and is replaced by bony callus
Achondroplasia
most common cause of dwarfism
Cartilage in growth plates is replaced by bone at a very slow rate - results in short bones in upper and lower limbs
