bone and ossification histo Flashcards
makes up the greater portion of the matrix
Inorganic elements – calcium, magnesium, and sodium
Ground substance is calcified – becomes hard and brittle
bone
organic elements of bone
(collagen, protein polysaccharide and chondroitin sulfate)
functions of bone
Internal support of the body
Attachment of muscles and tendons for locomotion
Contains the bone marrows – blood forming elements
Protects vital organs of the cranial and thoracic cavities
For storage of calcium in the body
types of bone based on the organization of its type I collagen fibers
lamellar
woven
type of bone
collagen fibers are arranged in an irregular feltwork
fabricated during periods of rapid bone growth
woven
type of bone
hypercellular, with large osteocytes and lacunae, distributed in a haphazard fashion, long axes follow the direction of the neighboring collagen fibers
woven
type of bone
higher mineral content than that of lamellar bone; deposited outside of collagen fibers
woven
type of bone
resist forces equally in all directions; weaker, less rigid, more flexible than lamellar bone (greenstick fracture)
woven
type of bone
collagen fibers are deposited in parallel arrays
lamellar
type of bone
synthesized more slowly, less cellular, smaller osteocytes and lacunae, distributed in a more organized fashion along the more regular collagen lamellae
lamellar
type of bone
process of mineralization occurs more slowly and continues long after the organic matrix is initially deposited
lamellar
type of bone
has greater rigidity and tensile strength, less elasticity than woven bone.
lamellar
FORMS OF LAMELLAR BONES
Cancellous or Spongy bone (substancia spongiosa)
Compact bone (substancia compacta)
LONG BONE
– thick walled hollow cylinder w/ a central medullary cavity containing the bone marrow
Shaft
LONG BONE
ends of long bones made up of spongy bone covered by a thin cortex of compact bone
Epiphysis –
LONG BONE
– separates the epiphysis from the diaphysis
Epiphyseal plate
LONG BONE
a transitional region connecting the epiphyseal plate to the diaphysis
Metaphysis
long bone
a layer of specialized CT w/ osteogenic potential
Periosteum
long bone
a thin cellular layer w/ osteogenic properties covering the marrow cavity
Endosteum
Found in the flat bones of the face and skull
Layer of spongy bone between 2 layers of compact bone forming an outer and inner table
diploe
bone cells
Osteoprogenitor cells
- Osteoblasts
- Osteocytes
- Osteoclasts
type of bone cells
Undifferentiated cells
On free bony surfaces,
endosteum, periosteum,
lining of the Haversian
canal, epiphyseal plate
With pale staining
nucleus and faintly
basophilic cytoplasm
Osteoprogenitor cells
type of osteoprogenitor cells
Divide – (bone - forming cells)
osteoblasts
type of osteoprogenitor cells
Unite – (bone - destroying cells)
osteoclasts
Bone forming cells responsible for the development of the bony matrix
Location: surfaces of developing bones
Arranged in an epitheloid layer of cuboidal cells
osteoblasts
Cells of fully formed bones in the lacunae of calcified matrix
An osteoblast is surrounded by bone matrix in its development
Flattened cell body inside the lacunae
osteocytes
Giant multinucleated cells closely associated with areas of resorption
Found in shallow concavities of the bone surface called Lacuna of Howship
osteoclasts
osteoclasts are found in shallow concavities of the bone surface called
Lacuna of Howship
Active in bone resorption
Ruffled border – radial striations found close to the bone
osteoclasts
Irregular branching bony spicules forming a network of interconnecting spaces containing bone marrow
With thin trabeculae made up of irregular lamellae of bone with lacunae containing osteocytes
spongy bone
Absence of haversian system
Trabeculae lined by endosteum containing osteoprogenitor cells, osteoblasts & osteoclasts
spongy bone
Parallel columns made up of concentric bony layers surrounding the haversian canal
Compact bone:
haversian channel with the concentric bony lamellae
Haversian system -
at right angle to the haversian canal
Volkmann’s channel -
numerous minute interconnecting canals
Canaliculi -
found between Haversian systems formed as a result of the continuous resorption and redeposition of bone
Interstitial lamellae -
– found at the outermost portion of the compact bone that extends around the circumference of the shaft
Periosteal / External Circumferential Lamellae
surrounds the central medullary cavity
Endosteal / Inner Circumferential Lamellae –
fibrous tissue covering the outersurface of the bone; bound to the underlying bone by Sharpey’s fibers
Periosteum –
lines the central medullary cavity
Endosteum –
Between lamellae are _________ in lacuna
osteocytes
histogenesis of bone
Intramembranous Ossification – occurs directly in primitive CT
- Intracartilaginous / Endochondral Ossification – replacement of cartilage by bone
histogenesis of bone
occurs directly in primitive CT
Intramembranous Ossification –
histogenesis of bone
replacement of cartilage by bone
- Intracartilaginous / Endochondral Ossification –
when bone arises in tissues not belonging to the skeletal system or in CT w/o osteogenic properties
Ectopic bone formation –
Bone formation occurs directly in primitive CT w/o cartilage formation
Commonly seen in the flat bones of the face & skull
Intramembranous Ossification
Involves the replacement of a cartilage model by bone
Cartilage destruction is a pre-requisite
Involves the bones of the entire skeletal system except the bones of the face & skull
Intracartilaginous / Endochondral Ossification
Occurs later & appears at birth
Sequence of changes similar to that in the diaphyses
Less bone destruction & no formation of a single marrow cavity
What remains is spongy / cancellous bone with a thin plate of compact bone surrounding it
EPIPHYSEAL OSSIFICATION
Imbalance between bone resorption and bone formation.
Reduced bone mineral density
Increased bone fragility & incidence of fracture
OSTEOPOROSIS
Blood clot replaced by vascularized granulation tissues
Initial formation of provisional callus (hyaline cartilage) from granulation tissues
Provisional callus transformed into temporary callus that unites the fractured bone
bone repair
Temporary callus is replaced by woven bone leading to a bony union of the fracture
Woven bone is transformed into compact bone and excess bone is resorbed.
bone repair
Found in the marrow cavity of the diaphysis of long bones
Abundant fat cells – yellow color
Not active in hemopoiesis
yellow bone marrow
