Bone Physiology Flashcards
What is bone?
Rigid form of connective tissue
Collagen fibres, GAG’s, and mineral salts
What are osteocytes?
main cell found in bone, they are found in small spaces called lacunae, projections from the cell membrane spread through the caniculi to sense whats happening in the extracellular matrix
What is an osteogenic cell?
a cell that develops into an osteoblast
What is an osteoblast?
a cell that forms bone tissue
How do osteocytes communicate?
they communicate through gap junctions
How do osteoblasts form bone tissue?
They synthesize and secrete collagen and other components of the bone matrix
Where are the end products of bone degradation absorbed into/
into the osteoclasts
What do osteoclasts leave behind as they resorb bone?
they leave behind mitogens (growth factors) to
encourage osteoblasts to mature and lay down matrix
Where does the nutrient artery enter from?
through nutrient foramens
Where does the nutrient artery supply the bones from?
supplies the inner 2/3 of the bone from the endosteum
What supplies the outer third of the bone?
Periosteal vessels, via attachments of muscles and tendons
What is the endosteal side of the bone?
woven or cancellous bone that houses the bone marrow
What makes up 95% of the bone matrix?
collagen fibres
hydroxyapatite
filler between collagen fibres that provides strength
What is cortical bone also known as?
compact bone
Where does the osteocyte come from?
the mesenchymal stem cell line
What is osteoid?
The substance that is secreted from osteoblasts before it becomes mineralised bone
What are the two sides of bones?
endosteal and periosteal
What does the endosteal side of the bone contain?
It houses the bone marrow and the main blood supply
What does the periosteal side of the bone contain?
it is the outer bone surface that can also bring blood to the bone via soft tissue
What is endochondral ossification?
ossification that begins in the primary growth plate in the centre of long bones
What marks skeletal maturity?
When the growth plate closes
What is intramembranous ossification?
growth occurs in the membrane rather than in a cartilaginous structure (occurs in flat bones)
Where are collagen fibres embedded in bone?
They are embedded into GAG’S or glycosaminoglycans (mineral salts are also embedded)
What makes up the majority of long bones?
Dense cortical bone
What makes up the majority of irregular bones?
Cancellous bone
What makes up flat bones?
They are thin cortical plates with small amounts of cancellous bone in-between
What are canaliculli?
Small canals that connect adjacent lacunae
What are lacunae
small spaces in the mineralised matrix that house osteocytes
How do osteocytes communicate with each other?
Through gap junctions
What separates bone fluid from other fluids in the body?
bone cell layer (made up of endosteum periosteum and haversian canals)
What is osteoid?
the substance secreted by the osteoblasts
How does osteoid become mineralised bone?
mixes with calcium phosphate that is also secreted from osteoblasts
How do osteoclasts destroy the bone matrix?
They acidify their environment to dissolve the calcium phosphate, they also digest collagen and other matrix proteins
What parts of the bone does the nutrient artery supply?
The inner 2/3 of the bone from the endosteum
What supplies the outer 1/3 of the bone with blood?
Periosteal vessels
What is apositional growth?
Increase in the diameter of the bone (bone becomes thicker)
How does intamembranous growth work?
Osteoblasts between the membrane secrete osteoid (osteoblasts differentiate from mesenchymal cells) this then becomes woven bone, lamellar bone and the outer periosteum then forms
How does endochondral growth work?
Bones begin as hyaline cartilage, Chondrocytes die leaving open spaces in the cavity of the bone
Blood vessels enter the primary ossification centre, osteoblasts enter through the blood vessels and begin to produce spongy bone, which over time will become a medullary cavity
What are perforating canals?
(haversian) Canals that move horizontally through the bone
Where does the blood supply run in the endosteal side of bones?
Inside of a volkmanns canal
