Bone tissue and Microscopic Structure Flashcards
Bone has cells…
as well as a calcified extra-cellular matrix
How do bones change depending on how we use our body?
Bone cells respond to external forces and remodels and can change shape through your life to reflect how you are using your skeleton.
When a bone is broken..
Bone tissue will form and reform to connect those bits of bone that are broken from one another.
Why do bone cells respond to trauma
To unite broken parts
What are majority of bones made out of
They are made out of a matrix not cells
What is the inorganic portion of the extracellular component of the bone
The inorganic portion is made out of mineral which makes the bone hard and unique among other tissues
What is the organic portion of the extracellular component of the bone
What are the two extracellular components of the bone
Organic and inorganic
What is the function of the connective tissue of the bone
It supports other tissues or organs and helps it maintain its form
What percentage of the extracellular component of the bone is organic
33%
What allows bones to have flexibility?
Collagen fibres which criss cross across the organic matrix
If the bone did not have some level of flexibility,
putting pressure on it will break it
When the collage from a bone is removed,
it breaks easily and is very brittle
Why is the organic component of bones important
To have flexibility and take the weight
What percentage of the bone’s extracellular component is inorganic
67%
What is the purpose of the mineral components in a bone?
It makes the bone hard and resistant to compression
What happens when the bone’s inorganic components are removed?
The bone will be too flexible because of the lack of the inorganic components replaced with only the collagen.
What are the minerals that make a bone inorganic?
Hydroxyapatite and other Calcium minerals or mineral salts
What percentage does the cellular component of the bone make up by weight?
2%
What are the mature bone cells
Osteocytes
What are the four types of cells
- Osteogenic cells
-Osteoblasts
-Osteocytes
-Osteoclasts
The same amount of bone must be maintained/balanced during childhood
True
2/3 of the matrix is…
inorganic
What do osteoblasts do?
These bone cells work in teams to produce new bone called osteoid. They control calcium and mineral deposition, secreting out the matrix of bone.
1/3 of the matrix is ..
organic
What do osteocytes do?
Osteocytes are what osteoblasts turn into when they have stopped making bone. They stay within the bone matrix and they maintain the bone by recycling proteins and minerals from our matrix and communicate with other cells whether more bone should be formed or destroyed.
What are osteoclasts?
They are the destructive cells. They take bone matrix away when it is either too old or not providing the service that they used to.
What are the two types of bone tissue?
Compact and cancellous
Compact and cancellous bones are…
made out of the same things but are structured differently.
what is the structure of compact bones?
Osteon structure which is when they ar like cylinders that pack really tightly together to make the dense compact bone.
What is the structure of cancellous bones?
Trabecullar structure which is where it branches out.
what is the periosteum
Outside surface of a bone
What are the holes in the compact bone called?
Foramina
Microscopically, there is a structure that allows blood supply to get in, and to be distributed with our cells. What is that called for compact bones?
They are called osteons
Why do we need blood supply in our bones?
We require holes in our bones because there are living cells in them, and we need to get the nutrients in them. There are nerve supplies in our bones because the cells need to communicate with one another.
What are osteons?
They are the longitudinal unit within a compact bone.
What is the function of osteons?
They provide a pathway for nutrients to get to cells in the extracellular matrix.
What is the lamellae
Lamellae are the series of cylinders formed of extracellular matrix around the central canal. They are made out of the inorganic materials.
What is the central canal?
They contain blood vessels and nerves
What forms the shape of the osteon?
lamellae
What are canaliculi
They are channels for the osteocytes. They allows blood and nerves to pass through.
Describe the lacunae.
In between the lamellae are dark circles called the lacunae, where the osteocyte are found.
Describe the bone using the terminology learned
There is a dense outer surface and inside are cylindrical osteon structures that have blood supply flowing through it. The canaliculi that connect the blood supply to the lacunae where the osteocytes are living allowing them to get nutrients and communicate with one another.
Describe the bone structure of the cancellous bone
They are made out of this branching bone structure that goes out in different directions, with spaces between them. The trabeculae are surrounded by red marrow where the red blood cell formation is normally occurring.
What forms each one of the struts of the cancellous bone
The lamellae structure or the rings of bone
Where are osteocytes housed?
In the lacuna in between the lamellae/ on the surface.
The cancellous bone does not have…
a central canal
Why does the cancellous bone not have a central canal?
The branches for this type of bone are really thin and they are in direct contact with blood supply all around them where the red marrow is. That means that the canaliculi will open up to the surface and blood can go from the surface and into the centre to supply the osteocytes with the nutrients that it needs. It is easy enough for these bones to get their nutrients from the outside due to their shape alone.
Why is the trabecullar bone/ or the branching structure important or helpful in our bodies?
Because the structure resists force from multiple directions, collecting force from multiple directions and transmitting it into a single direction down the shaft where the compact bone is.
The criss cross structure of the trabecular bone..
The criss cross structure of the trabecular bone shows that the areas where the bone is most dense and most prolific gathers the force and pushes it down in one direction.
If we are forming bone on the outside,
the hollow bit of the bone should also be lighter.
What is appositional growth?
As our bone widens, bone is taken away from the inside of the bone.
What happens during bone remodelling?
The osteoblasts are communicated with by the osteocytes. They form extra lamellae on the outside of the bone. At the same time, the osteoclasts which are on the inside of the bone next to the medullar cavity, remove the inside of the bone to ensure that our bones do not get really heavy and dense.
as our legs grow,
it gets longer and just a little bit wider.
medullar cavity…
gets wider as grow into an adult.
How is bone homeostasis formed
By achieving a balance between osteoblast and osteoclast activity
The bone is constantly…
being destroyed and formed.
Why are bones constantly being formed and destroyed?
The body is storing nutrients that we need in our bones. so when they are destroyed, the useful things we need are mobilised into the bloodstream and only then can our body use them.
What is the purpose of bone remodelling?
It allows our bones to slightly change shape and to rejuvenate our bones.
We can only have homeostasis…
if we give our body what it needs to achieve it, through either adequate calcium in diet and exercise.
Without the requirements to maintain homeostasis,
there will be an imbalance in osteoblastic and osteoclastic activity.
In the conditions of osteoporosis and/or osteopenia
Instead of having wide and dense compact bones, the bone is thinning and won’t be able to take on weight as well as it used to.
What is osteoporosis?
It is the loss of cortical bone. The cancellous bone trabecullae become thinner and when that happens, we get compression fracture where the bones weaken and crumple. We are more prone to this on our vertebrae.
Why are lifestyle factors important in our chances of getting osteoporosis?
because lack of exercise and nutritional factors like too much salt can increase our chances of getting the disease.
Why are biological females more at risk at getting ostoporosis?
Biological females are more at risk due to the loss of estrogen post menopause.
When is our peak bone mass?
In our 20s
