Histo - Bone Ossification Flashcards
What is ossification?
AKA ____
ossification aka osteogenesis
is the development of bone tissue
What are the two steps in ossification (aka osteogenesis)
- development of primary bone (woven, immature) TEMPORARY
2. primary bone replaced by secondary bone (mature, lamellar) PERMANENT
Bone tissue is a type of ___
connective tissue
Bone tissue arises from connective tissue called ____
mesenchyme
What are the two types of ossification (osteogenesis)?
- intramembraneous ossification
2. endochondrial ossificatino
Which type of ossification has a hyaline cartilage model precursor?
endochondrial ossifiction
Which type of ossification follows this pattern:
mesenchyme -> bone
intramembraneous ossification
Which type of ossification follows this patterm:
mesenchyme -> hyaline -> hyaline cartilage -> bone
endochondrial ossification
Intramembraneous ossification leads to the production of which type of bones?
flat bones of skull and face
Which type of ossification leads to the production of flat bones of the skull and face?
intramembraneous ossification
Endochondrial ossification leads to the production of which type of bones?
short and long bones in the body
Which type of ossification leads to the production of short and long bones?
endochondrial ossification
When do intramembraneous ossification and endochondrial ossification each begin?
intramembraneous begins to occur ~8weeks gestation
endochondrial
- first hyaline cartilage visible ~6weeks gestation
- ossification centers are present in all long bones of limbs by 12th week gestation
What are the 4 steps of intramembranous ossification?
- development of ossification center
- calcification
- woven bone and periosteum develop
- replacement of woven bone
In intramembranous ossification, explain what happens histologically as mesenchymal cells differenate?
elongated, pale staining mesenchymal cell clusters differentiate into osteoprogenitor cells
they become more rounded
cytoplasm changes from acidophilic to basophilic
In intramembranous ossification, why does the cytoplasm change from acidophilic to basophilic as mesenchymal cell clusters differentiate into osteoprogenitor cells?
addition of rER
In intramembranous ossification, the osteoprogenitor cells differentiate into ____
osteoblasts
In intramembranous ossification, clusters of ___ create the ossification center.
these cells secrete ____
osteoblasts.
osteoblasts secrete organic ECM (osteoid)
In intramembranous ossification, what do osteoblasts secrete?
organic ecm (osteoid)
In intramembranous ossification, describe the calcification step.
Calcium and other mineral salts are deposited around the framework of collagen fibers in intramembranous ossification
In intramembranous ossification, during calcification, cells trapped in calcified osteoid are now called ____
osteoclasts in lacunae
In intramembranous ossification, when do osteoclasts form? How?
osteoclasts are trapped in the calcified osteoid during the calcification step
(calcification step = when calcium and other mineral salts are deposited around framework of collagen fibers)
What is appositional growth?
growth along the surface
In intramembranous ossification, how is woven bone produced?
produced in small, irregularly shaped pieces or spicules that increase in size by appositional growth
In intramembranous ossification, describe how appositional growth affects how woven bone is formed?
appositonal growth allows small patches of bone production to merge together to produce a labrynth of woven bone
In intramembranous ossification, what are spaces between bone spicules of woven bone filled with?
What does that differentiate into?
embryonic blood vessels
will differentiate into red bone marrow
In intramembranous ossification, where do embryonic blood vessels go?
What do they differentiate into?
between the bone spicules of woven bone development
will differentiate into red bone marrow
In intramembranous ossification, how does periosteum form?
mesenchyme at periphery of bone condenses to form periosteum
In intramembranous ossification, mesenchyme at periphery condenses to form ___
periosteum
In intramembranous ossification, what is woven bone replaced with?
lamellar bone
What are the 6 stages of endochondrial ossification?
- Development of fetal cartilage model
- Bone collar forms and cartilage begins to calcify
- Primary ossification center forms in diaphysis
- Secondary ossification center forms in epiphysis
- Hyaline cartilage retained for articular cartilage & epiphyseal plate
- Epiphyseal plate ossifies into line
In endochondrial ossification, mesenchyme differentiates into ____
chondroblasts
In endochondrial ossification, chondroblasts (differentiated from ___) secrete what? produces what?
chondroblasts are differentiated from mesenchyme
They secrete matrix (type II collagen)
Produces hyaline cartilage model
In endochondrial ossification, what specifically produces hyaline cartilage?
the chondroblasts (differentiated from mesenchyme) secrete matrix (type II collagen) and PRODUCE HYALINE CARTILAGE MODEL
In endochondrial ossification, hyaline cartilage continues to grow via what type of growth?
both appositional and interstitial growth.
interstitial growth because chondrocyte activity in lacunae
appositional growth because of chondroblasts activity at surface
In endochondrial ossification, how does hyaline cartilage grow via appositional growth?
chondroblast activity at surface
In endochondrial ossification, how does hyaline cartilage grow via interstitial growth?
chondrocyte activity in lacunae