MSK Histology Flashcards
What is the first stage of long bone formation?
The first stage in the process of long bone formation is the creation of cartilaginous models or proformers. These are then converted into bone.
When are long bones fully developed?
a) At birth
b) 2-3 years
c) Onset of puberty?
d) After puberty
After puberty
At birth and untill then, the cartilage persists as the growth plates
Which cells synthesize the hyaline cartilage of the proformers?
a) Osteoblasts
b) Osteocysts
c) Chondroblasts
d) Chondrocytes
Chondroblasts
Where is the primary centre of ossification established?
The central part of each developing bone
- Occurs in prenatal development
- Involves the erosion of the proformer cartilage and the formation of primary bone.
- Collar penetrated by blood vessels = more osteoprogenitor
cells -> osteoblasts and lay down bone
As the primary and secondary centres expand the amount of cartilage is reduced. Which area is it restricted to?
It becomes restricted to the epiphyseal growth plates that separate the diaphysis from the epiphyses (and to the articular surfaces of bones).
What is epiphyseal cartilage responsive to?
Growth hormone and sex hormones
- Exists beyond puberty
- Growth plates are largely responsible for the growth of bones during childhood and puberty
What cells are these?
a) Chondroblasts
b) Chondrocytes
c) Osteocytes
d) Osteoblasts
Chondrocytes
This is hyaline cartilage taken from the head of a growing long bone.
The dark-stainging chondrocytes are trapped within the amorphous matrix
Where does the following occur: The chondrocytes of the resting cartilage first divide creating columns of progeny
a) Zone of hyperplasia
b) Zone of hypertrophy
c) Zone of ossification
Zone of hyperplasia
Progeny = offspring
Hyperplasia = increase in organic tissue
Where does the following occur: Newly synthesised cells erode the cartilage as they expand.
a) Zone of hyperplasia
b) Zone of hypertrophy
c) Zone of ossification
Zone of hypertrophy
Hypertrophy = increase in volume due to enlargement of cells
Where does the following occur: The remnant strands of cartilage then become calcified and serve as a substrate to which osteoblasts become attached. These osteoblasts then lay down primary bone
a) Zone of hyperplasia
b) Zone of hypertrophy
c) Zone of ossification
Zone of ossification
Ossification = bone modeling and the process of laying down new bone
Which long bones have only a single epiphyseal growth plate?
The distal phalanges of the fingers and toes
What is this?
Developing membrane bone growing in a primative mesenchyme
Which type of ossification occurs in the flat bones of the skull?
intramembranous ossification
More direct
No cartilage proformer
Explain the process of intramembranous ossification.
Small clusters of progenitor cells within mesenchyme -> osteoblasts
Deposit isolated islands of bone
Islands and coalesce - meshwork of bone
Osteoblasts continue till mesh filled = primary plate of bone
later eroded and replaced with more organised lamellar secondary bone
What is synthesised by the blue staining cells?
Osteoid
Blue/purple cells are osteoblasts lining the holes. They stain blue to large amounts of RER
What is this?
Compact mineralised bone
Mature secondary bone
What is hydroxyapatite?
Hard crystalline calcium salt
5% of compact mineralised bone
What are volksmann’s canals?
Volkmann’s canals are cross sections between haversian canals of neighbouring osteons
What is this?
Mature decalcified bone
Compact lamellar secondary bone stains bright pink (collagen matrix of bone)
Trapped within bone are osteocytes
- surrounded by periosteum
What is this and where is it found?
Cellular bone marrow in the core of long bones
Describe the periosteum
The periosteum:
Outer fibrous layer
Inner cellular layer (paler) - contains osteoblasts - lay down new bone = appositional growth
Where are osteoprogenitor cells found?
The periosteum
After a fracture - they are stimulated to differentiate into chondroblasts for cartilage production which then undergoes endochondral ossification
What is articular cartilage?
After the growth plate closes cartilage persists as articular cartilage
