Bones Flashcards
Give four functions of bone and an example of each
Mechanical - support and attachment for muscles, tendons, ligaments and joints
Protective - protects internal organs
Metabolic - mineral reservoir for calcium and phosphate homeostasis
Haematopoiesis - support blood formation
Describe the development of bone as a result of endochondral ossification
- bone forms as cartilage first during third month of development
- blood vessels and osteogenic cells invade the cartilage framework
- the cartilage remains as growth plates
- growth plates fuse at approx. 18 in females and 21 in males
Describe the development of bone as a result of intramembranous ossification
- bone forms as a fibrous plate
- bone cells differentiate from fibroblasts and haemopoietic precursers
- no cartilaginous phase
Describe the composition of bone
- 20% water
- 35% protein - collagen type I (provides toughness), growth factor proteins, other organic matrix proteins
- minerals - hydroxyapatite (provides rigidity)
The epiphyses of long bones are composed of
trabecular (spongy) bone - acts as a softer interface at joints
The diaphysis of long bones is made up of
cortical bone
Cortical bone is
- denser
- arranged into Haversian Systems from the way the collagen molecules form fibrils which then form fibres and finally sheets
- structure gives the bone its strength
Give the two main cells involved in bone maintenance and renewal
- osteoclasts
- osteoblasts
Osteoclasts are
- the bone resorbing cells
- derived from haemopoietic lineage
Osteoblasts are
- responsible for laying down more come
- derived from mesenchymal lineage
Bones are constantly monitored and remodelled to
keep them at peak strength
Osteoclasts will absorb any area of bone that has been
damaged
When damaged areas of bone have been absorbed, osteoblasts will
lay down new bone in the same area
Osteocytes act as sensors of
mechanical pressure and damage
