Bone Flashcards
what is bone comprised of?
How are bones organised?
what is bone marrow?
Tissue found within bone cavities.
what are the two types of marrow in humans?
Red
Yellow
role of Red marrow?
haemopoietic active and produces new blood cells.
what is yellow marrow comprised of?
mostly fat.
how does bone marrow change throughout life?
Proportion of red to yellow marrow changes
what is the structure of Haemopoeitic tissue?
are described as existing as cords.
Islands of lineage specific differentiation embedded in these cords.
where are Sinuses found and what are the function?
are lined in endothelial cells and are essential in controlling release of mature cells.
how can you view the Organisation of the red marrow?
Bone marrow is exceptionally cellular.
In order to view structure a biopsy must be taken.
Not a smear!
what does a bone marrow aspirate take as a sample?
semi-liquid bone marrow
what does a Trephine biopsy take as a sample?
solid bone marrow.
how is bone marrow transplant taken?
Sample is generally taken from the posterior iliac crest.
Patient receives local analgesia and anaesthetic at site of biopsy.
when are Bone marrow aspiration/biopsy used?
in diagnosis of a number of conditions, including leukaemia.
how can Bone marrow be used as a therapeutic?
Haemopoietic stem cells (HSC) found in bone marrow can be transplanted from patient to patient or harvested from a patient and saved for later.
how is bone marrow added to body?
Allogenic and autologous transplantation.
what different ways can these stem cells can be harvested?
Bone marrow harvest.
HSC apheresis.
Useful in the treatment of several diseases, name one.
Blood cancer.
what are the 2 types of bone?
how are they classified?
Compact bone
Spongy bone
are classified according to size and distribution of spaces macroscopically:
where is compact bone found?
Outer region of bones,
diaphysis of long bones,
outer & inner regions of flat bones.
function of compact bone?
Provides protection and support – mechanically strong.
what is The functional unit of compact bone?
osteson.
where is spongy bone found?
Found within the epiphysis of long bones
fills most irregular bones.
structure of spongy bone?
Large spaces filled with bone marrow – mechanically weak.
Irregular lattice of thin plates of bone (trabeculae) formed of lamellae (not arranged into osteon systems as in compact bone).
what are Osteoblasts derived from?
Derived from osteoprogenitor cells.
what adaptations do osteoblasts have?
Numerous mitochondria and extensive Golgi body apparatus.
what do osteoblasts secrete?
constituents of osteoid.
what are osteoblasts required for?
mineralization (calcification) of osteoid matrix.
osteoblasts have receptors for which hormones that acts to indirectly regulate osteoclasts?
calcitriol (active vitamin D) and PTH
how can Osteoblasts can be identified?
via inherent alkaline phosphatase activity.
Hydrolyses alpha napthyl into napthol (black staining deposit)
Osteoblasts are positive via IHC for which markers?
Oestrogen receptor. CD10 CD44 CD53 CD56
which identification method is preferred?
Immunohistochemistry markers are cheaper and easier to use to identify
where are osteocytes found?
osteoblasts are trapped in lacunae
function of osteoblasts?
Mature bone cells derived from osteoblasts
function of Canaliculi?
Communicate via fine cytoplasmic processes extending through canaliculi.
Osteocyte lacunar and canalicular remodeling to release calcium (Osteocytic Osteolysis).
Canaliculi allow for exchange of calcium from interior to exterior of bone and exchange of nutrients and waste.
what are Osteoclasts?
Giant, multinucleated highly mobile cells derived from monocytes.
what are adaptations of osteoclasts?
Numerous mitochondria and lysosomes.
what are osteoblasts Responsible for?
bone-resorption during growth and bone remodelling.
the Activity of osteoblasts is controlled by which various hormones?
Calcitonin inhibits osteoclast activity (high plasma Ca2+)
Stimulation is indirect via PTH and Calcitriol (low plasma Ca2+)
how is bone reabsorpted?
Release enzymes and acids into the extracellular space between the ruffled border and the bone matrix.
what happens After resorption is complete?
cells undergo apoptosis.
How can osteoblasts be identified?
Osteoclasts have an acid phosphatase (Tartarate Resistant Acid Phosphotase) which can be identified using enzyme histochemistry and confirmed using IHC.
Osteoclasts are also positive for what in IHC
CD13
CD31
CD54
Why is The processing of bone for histopathological examining challenging?
Bone requires decalcifying prior to processing and staining.
Which criteria should Decalcifying agents meets?
Be fast - Remove all calcium and quickly, Some take weeks
Be good- Some only penetrate so far
Do good - Shouldn’t cause complete destruction of bone sample. So changes seen are diagnostically significant not a result of the decalcifying agent
what is the most commonly used chelating agent?
EDTA.
which pH is preferred?
Neutral pH is preferred (~7) to prevent tissue degradation.
Why is EDTA Not suitable for emergencies?
Process is exceptionally slow but causes minimal tissue disruption.
what are mineral acids?
These tend to be very strong acid solutions derived from hydrochloric or nitric acids.
why are mineral acids used for decalcifying bone?
Extremely quick at decalcifying bone
downsides of mineral acids?
Tissue disruption is common.
Nuclear detail is lost - in image
what organic acids are widely used for decalcification?
Formic acid solutions are popular and are widely used for decalcification.
how is formic acid used?
Formic acid can be used as a simple 10% aqueous solution or combined with formalin or with a buffer.
what is the advantage of using formic acid?
Although it is slower than the strong acid agents it is much gentler in action and less likely to interfere with nuclear staining
