Bones Flashcards
What is the function of bone?
Weight bearing / Support
Protection
Mineral store
Blood formation
What are the different types of bone ?
Flat bone Sutural bone Short bone irregular bone Sesamoid bone Long bone
What are the 5 things which make up bone ?
Compact and spongy bone Blood vessels medullary cavity Bone marrow Membranes
What is another name for compact bone ?
Cortical bone
What is another name for spongy bone ?
Trabecular bone
What are the names of the two membranes found in bone ?
Periosteum
Endosteum
Where is the periosteum found ?
One the outsider of the bone
Where is the endosteum found ?
On the inside on the bone lining the medullary cavity
Describe the structure of compact bone
Compact bone has a structure called haversian system or osteons. This structure contains concentric circles (lamellae) with an haversian canal at the centre. The lamellae rings contain osteocytes which are connected by tiny channels called canaliculi.
Haversian canals are vertical cylinders containing blood vessels. Compact bone also has horizontal blood vessels containing canals called Volkmann’s channels.
Describe the structure of spongy bone
Also called cancellous or trabecular bone or diploe. It is less dense than compact bone. It forms a network of lamellated trabeculae filled with bone marrow and there are no haversian systems. The orientations of the trabeculae reflects the main directional of mechanical forces.
What kind of bone marrow fills spongy bone ?
Red
What are the names of the different cells which make up bone ?
Osteoclasts
Osteoblasts
Osteocytes
What is the extracellular matrix of bone made up of ?
Hydroxyapatite crystals
Collagen
Water
Describe the Hydroxyapatite crystals
Make bone stiff and able to support other structures
High strength under compression
Describe the collagen found in the ECM of bone
Some flexibility and reduces risk of fracture
High strength under tension
What are two properties of bone which make it so amazing ?
- Good regenerative power - It is able to heal itself
- Good adaptive power - Able to change depending on the demands placed on it.
What is bone turnover ?
The constant process which happens even in adults of bone being broken down and remade
What cells remove bone ?
Osteoclasts
What cells make new bone ?
Osteoblasts
What is important about healthy bone ?
It will have the correct balance of bone removal and formation
Describe the actions of osteoclasts
They are large multinucleated cells which are derived from haematopoietic stem cells.
They are found on the bone surface and there function it to resorb bone matrix.
They released acid to dissolve bone and create a ruffled boarder. The pit that is creaeted is called a Howships lacunae.
Describe the actions of the osteoblasts
Osteoblasts are immature bone cells created from osteoprogenitor cells int he periosteum and endosteum. They produce bone matrix. They produce an osteoid the unmineralized matrix and then initiate calcification. The osteoblasts become osteocytes once’s surrounded by matrix.
Describe the role of osteocytes
They are mature bone cells found in the lacunae.
They are connected by canaliculi which they use to communicate with each other.
What are some disorders which can arise when bone remodelling goes wrong ?
Osteoporosis when Resorption > formation. Very problematic for spongy bone.
Pagets disease where resorption and formation are both increased. Leads to deformed bones.
Osteopetrosis where formation > resorption. Bones become like rock, dense and brittle. Can compress nerves and give rise to neurological problems.
Describe what happens to bone mass as you age
It decreases especially quickly after the menopause. because oestrogen inhibits the osteoclasts, when oestrogen levels drop then more bone removal happens
What are the names of the two types of bone formation ?
Endochondral
Intramembranous
What is endochondral bone formation ?
Occurs inside cartilage. Cartilage model is made It is invaded by blood vessels. cartilage is replaced by bone (Apart from epiphyseal growth plate) Growth plate ossifies
What is intramembranous bone formation ?
Does not involve cartilage.
Mesenchymal cells develop into osteoprogenitor cells which mature into osteoblasts and start producing bone.
Mesenchymal cells develop into blood vessel and bone marrow.
occurs even in adults
What are the two types of bone growth ?
Appositional growth - Outward growth
Interstitial growth - Lengthening i.e. using the growth plates
Describe the process by which bones cells mature
Mesenchymal cells
osteoprogenitor cells in periosteum or endosteum
Osteoblasts
Osteocytes
Recall points for bones
Functions Shapes Components of bone Compact and spongy bone Extracellular matrix Cells Formation and growth
