Bone Flashcards
Functions of bone
Support, lever for effective movement, protection of internal organs, calcium store and haemopoiesis
How much calcium is found within bone
About 95% of total body calcium
Composition of bone
65% biopatite, 23% collagen, 10% water, and 2% non-collagen proteins
Fibrous connective tissue surrounding bone is known as
Periosteum
What are the two types of bone
Cortical bone and cancellous bone
What type of bone makes up the shaft
Cortical bone
What type of bone makes up the ends of bone
Cancellous bone
What is the main difference between the morphology of cortical and cancellous bone
The presence of spaces, known as marrow cavities, adjacent to cancellous bone
Bone that is made up from layers is known as
Lamellar bone
What is within the small canals in bone
Blood vessels and nerves
What are the cells living within bone called
Osteocytes
Characteristics of trabecular bone
- Has osteocytes
- Lamellar in nature
- Haversian canals are uncommon
The outer layers of bone are organised in lamellae that run around the bone and are called
Outer circumferential lamellae
What are the cells found within bone
Osteoprogenitor cells, osteoblasts, osteocytes and osteoclasts
Osteoprogenitor cells
- Located on bone surfaces under the periosteum
- Reserve pool of osteoblasts
Osteoblasts
- Bone forming cells
- Found in the surface of developing bone
- Plentiful RER and prominent mitochondria
Osteocytes
A bone cell trapped within the matrix
Osteoclasts
- Large multinucleate cells
- Found on the surface of bone
- Responsible for bone resorption
How do osteoblasts produce new bone
They actively secrete a matrix onto the top of pre-existing bone
What is the main make up of the mineral of bone
Calcium phosphate crystals
What do osteoblasts secrete
Collagen, GAGs, proteoglycans, and other organic compounds
What is osteoblast secretion known as
Osteoid
Other than osteoid, what else do osteoblasts secrete
Matrix vesicles
What do matrix vesicles contain
Enzymes which produce phosphates and accumulate calcium phosphate salts
What type of bone is laid down after a break
Woven bone
How does woven bone differ to lamellar bone
In lamellar bone the collagen fibres are orientated in one diffraction but in woven bone they are laid down in a haphazard fashion
Characteristics of woven bone
- Not as strong as lamellar
- Eventually remodelled into lamellar bone by being broken down by osteoclasts and reformed by osteoblasts
Osteoclasts
- Derived from macrophage lineage
- Several will fuse and form a single giant multinucleated cell
What is the collection of osteoclasts and osteoblast that particiapate in bone remodelling at a particular site called
The basic multicellular unit (BMU)
How is bone remodelled
- A number of osteoclasts congregate and begin to drill into bone forming a tunnel
- A blood vessel grows into the tunnel and brings osteoblasts with it
- Osteoblasts line the tunnel and begin laying down new bone
- Process continues until only the Haversian canal is left
Lines around an osteon
Cement lines
What are interstitial lamellae
Lamellae between old osteons that are the remnants of old osteons
Periosteum
- Dense connective sheath around bone
- Has two layers
Types of ossification
Intramembranous and endochondral
Intramembranous ossification
- Mesenchymal cells differentiate into osteoblast and begin to synthesis and secrete osteoid
- This process begins at the centres of ossification
How does endochondral ossification begin
With a hyaline cartilage model of the bone to be formed
Examples of bones produced from endochondral ossification
Most long bones, base of skull, and the medial and lateral ends of the clavicle
Characteristics of bone
- Rigid
- Non-permeable
- Appositional growth
- Cells within bone nourished by blood vessels that pervade the matrix
