Bones Flashcards
Function of bone
- support of body shape
- system of levers for muscle action
- internal organ protection
- blood cell formation site
- mineral storage pool
Bone mechanical properties
- Cable-like flexibility and resistance to tension because of collagen framework (plus other proteins)
- Pillar-like stiffness and resistance to compression conferred by impregnation of collagen with crystalline mineral (hydroxyapatite=complex calcium hydroxyphosphate)
Two main types of bone tissue
WOVEN BONE -immature -only found in repairing fractures in adults or in bone disease (Paget's) LAMELLAR BONE -mature -structure= concentric rings of cells
Lamellar bone arrangment
- outer hard layer of compact lamellar bone (cortical bone)
- inner layer of interlacing struts (cancellous/spongy/trabecular bone)
Trabecular bone
- trabeculae are irregularly arranged and made of lamellar bone
- otherwise known as cancellous bone
Epiphysis (long bone)
-end of a long bone
Metaphysis (long bone)
-portion between the epiphysis and the diaphysis
Diaphysis (long bone)
-shaft of a long bone
Bone blood supply
- rich blood supply
- fracturing bones can cause lots of bleeding
- nutrient foramina (tunnel through cortex of long bone) allows nutrient artery to pass into the bone
Periosteum
- outer surface of bone
- consists of a fibrous and cellular layer
- key roles in bone growth and repair, vascular effects and has a good sensory nerve supply
Bone development
-skeleton starts to form at 6 weeks of fetal life and growth continues in some bones until individual is 25 years old
Intramembranous ossification
- in existing vascular connective tissue
- bone matrix (ostein) deposited around collagen
- mineralises to form woven bone
- remodels to lamellar bone
Endochondral ossification
- within existing fetal cartilage models
- cartilage calcifies and chondrocytes die
- periosteal osteoclasts cut channels for sprouting vessels
- osteoblasts enter with vessels to build bone round them
Endochondral ossification and bone length growth
-most long bones must support large forces whilst growing which would disrupt terminal appositional growth
TO STOP THIS:
- the shaft ossifies first, followed by the epiphyses
- growth continues by ossification at growing cartilage plate between them
- growth cessation when cartilage growth ceases and plate is over-run by ossification
Age-related changes in the appearance of normal bones
- In a child’s wrist, epiphyses ossify in the 2nd year
- Epiphyseal plates remain cartilaginous until growth ceases after puberty