Histology of Bone Flashcards
what cells do bone originate from?
mesenchyme stem cells
What are osteoblasts?
bone generating cells
What are the gaps called between the bone of a babies skull before they are sutures?
fontanel
What is intramembranous ossification?
Bone development then occurs within the mesenchyme from these cells (mainly osteoblasts)
between different bone
What is endochondral ossification?
Bone development then occurs within the mesenchyme from these cells (mainly osteoblasts)
within the bone
What is immature bone called? (not mineralsied)
osteoid bone
What are the 3 names for immature bone?
IMMATURE
WOVEN
OSTEOID
What inogranic salts mineralise the immature bone to mature bone?
calcium hydroxyapatite crystals - mineralised, rigid, hard
Where do osteoclasts come from?
blood stream
What is the matrix of bone occupied by?
Matrix occupied by collagen fibres and specialized bone cells – osteoblasts, osteocytes and osteoclasts.
What is cortical bone?
dense and solid and surrounds the marrow space
Is this compact or spongy bone?
compact
What is lamellae?
concentric layer of bone
Is this compact or spongy bone?
spongy
What is the central canal of an osteon called?
Haversian canal
What is an Haversian system also known as?
osteon
What is at the central canal of an osteon?
blood vessels
What are other names for spongy bone?
trabecular
cancellous
What do you find in the marrow cavity of bone?
formation of blood - Hematopoiesis
fat (adipose tissue)
Where are osteocytes found in compact bone?
lacunae (trapped)
What factors can change the composition of bone?
age and metabolic status
Is bone a dynamic tissue?
yes, Composition changes with age and metabolic status
In adults, when would pre-mineralised/immature bone be found?
Organic component (pre-mineralised/immature bone) is called osteoid/woven bone. In adults only found where bone remodelling is occurring
What are the components of the ECM of bone?
60-70% inorganic salts, 30-40% collagen and remainder (@5%) is protein and carbohydrate
What collagen fibre dominates in collagen?
type I
What do the gaps between collagen i the ECM provide?
Gaps’ provide space for bone salt crystals (up to 50% of calcium hydroxyapatite crystals within fibres)
What glycoproteins are associated with the ECM of bone?
osteonectin
what is the role of osteonectin in bone?
Glycoproteins associated with matrix include osteonectin which acts as an adhesive between the collagen, hydroxyapatite crystals and cells
What synthesises collagen?
osteoblasts
How do collagen fibres increase the strength of bone?
Collagen fibres have differing orientations within bone to enhance strength
What do Sharpey’s fibres connect?
Sharpey’s fibres connect periosteum (P) to cortical bone. Tendons and ligaments also insert into bone by means of collagen fibres
What is the precursor of osteoblasts?
osteoprojenitor cells
What do osteoblasts release to initiate mineralisation of the bone?
release of vesicles rich in alkaline phosphatase
and make calcium hydroxyapatite
What do osteoblasts become when surrounded by mineralised bone?
osteocytes
What is a canaliculi?
a minute canal in a bodily structure: as. a. : one of the hairlike channels ramifying a Haversian system in bone and linking the lacunae with one another and with the Haversian canal.
connect lacunae to each other and central canal
Name structures A and B
A = canaliculi
B = lacuna
What cells are shown here?
osteoclats
next to resorption bone
What cell is multi-nucleated?
osteoclasts
What is the role of osteoclasts?
Found on the surface of the bone undergoing resorption/ remodelling
What cell is involved in calcium homeostasis?
osteoclasts
parathyroid hormone stimulates, calcitonin depresses their activity
What is shown here?
resorption pit/bay
showing osteoclasts also
What is the resorption pit also called?
Howship’s lacuna
Where is a ruffled border found?
In EM numerous folds seen in the cytoplasm of the osteoclast – “ruffled border” at the surface of resorption bay/pit (Howship’s lacuna)
What is found in the cytoplasm of the osteoclasts?
Cytoplasm of cell contain numerous mitochondria, Golgi and lysosomes (=active cells) associated with resorption and degradation of bone
How would you describe the bone of the alveolar bone?
modified compact bone
What is the difference between the alveolar bone and compact bone?
Is similar to compact bone but has many perforating collagen fibres (Sharpey’s fibres)
What bone surrounds the alveolar bone?
normal compact bone and spongy bone
Name the bone types at the red, blue and yellow arrows
red = modified compact bone
blue = normal compact bone
yellow = spongy bone
What type of bone is shown here?
spongy bone
What does anastonise mean?
the meeting of ‘mouths’ / connecting
What bone diseases shown here?
osteoporosis
How are the lamallae arranged within the trabeculum?
parallel to one another
What can cause the different orientations of trabeculae?
Different orientations of trabeculae occur in response to stress requirements
