Bones Flashcards
What are the functions of a bone:
Must be good at regulating themselves in order to:
Provide structure
Mobility
Support
Protection for the body
Storehouse for essential minerals
Typical long bone
What is found at either end?
Distal epiphysis and proximal epiphysis
Both contain articular cartilage
Typical long bone
Shaft of bone is-
What is found in the bone?
Shaft of bone is the diaphysis. Outer part is covered in compact bone which makes the bone strong
In the Bone is the medullary cavity. Endosteum (sheath) contains lots of cells and a bit of connective tissue, bone marrow and blood vessels
Typical long bone
What is the metaphysis?
A widened area connecting both proximal and distal epiphysis to the diaphysis
This separates the epiphyseal plate. This is where bone growth occurs
Typical long bone
What is the periosteum?
Periosteum surrounds the entire bone and has both an outer and inner layer
Outer - tendons and ligaments will attach
Inner - has cells
Bone as a connective tissue (CT)
What makes up the matrix?
Collagen fibres for flexibility and ground substance which gives firmness
25% water, 25% collagen 50% crystallised mineral salts - calcium hydroxyapatite.
Bone as a CT
Organisation of osseous tissue:
1) compact (cortical)
2) spongy (trabecular/canellous)
Types of osseous tissue
1) compact -
80% of total mass - denser than spongy but less flexible
Gives bone strength
Solid hard layer external layer of ALL bones
Osteon - concentric rings (lamellae) of calcified matrix surrounding vertically orientated blood vessels - lay next to each other along a vertical axis
More lamellae found between each osteon
Extra cellular fluid and bone cells found between lamellae
Canaicular projects at bone cells and have a role in nutrient regulation.
Takes vertical impact better than lateral and transverse impact
Types of osseous tissue:
2) spongy
20% of total mass - gives bone lightness and is a good shock absorber
Found in inner parts of axial skeleton and epiphyses of long bones
Lattice like structure
Well organised along lines of stress - giving strength and resisting stress and forces without breaking
Osteocyctes (bone cells) in lacunae (pit/lake) on the surface of the trabeculae
Nutrients directly from the blood in the medullary cavities
Helps withstand stresses from multiple directions
Blood vessels aren’t in the matrix
Cell types of bone
1) osteogenic/osteoprogenitor -
Undifferentiated cells
They wait to receive information about making a new bone
These cells can divide when stimulated - the daughter cells produced are osteoblasts
These are the ONLY bone cell that can divide
Cell types of Bone
2)osteoblasts -
These are affected by age
Build matrix and collagen fibres. Come from osteogenic cells and form bone tissue
Cells become trapped in own system of bone, they are then referred to as osteocytes
Osteoblasts sit on outside of bone whereas osteocytes sit inside
Cell types of bones:
3) osteocytes -
Mature bone cells
Have to maintain the bone and monitor nutrients. Sit inside bone
Cell types of bone:
4) osteoclasts -
Clear bone cells. Largest bone cell
Functions in reabsorption - the destruction of the bone matrix
Have a ruffed border - stick themselves to bone and release enzymes to destroy it
Minerals like calcium will be given to the rest of the body.
Where are the different types of bone cells located?
Osteogenic - endostium in inner layers of periostium
Osteoblasts - surface of bone
Osteocytes - lacunae of compact and spongy bone
Osteoblasts - surface of bone
How does bone grow?
Grows in length as cartilage grows on epiphyseal side of plate
And old cartilage underneath is replaced by bone (it calcifies)
18-25 this will stop
Growing shaft is remodelled width ways by blood vessels in bone stimulating osteoblasts to make more bone to increase width
This is called appositional growth
Length and width MUST grow at same time
What can go wrong and affect bone growth?
Osteoporosis (low bone density)
Osteogenesis imperfecta - genetic disorder whereby you don’t produce enough collagen therefore bones become brittle
Paget’s disease of bone whereby bone is replaced faster than usual and not made properly so is weak
Bone cancer
Bone infections
Where do different vessels supply in bones
Periosteal arteries -
Nutrient arteries -
Periosteal - periosteum and outer osteons of compact bones
Nutrient - medullary cavity and osteons of inner compact bone
Where do different vessels supply in bones
Metaphyseal arteries -
Epiphyseal arteries -
Metaphyseal - spongy bone and marrow in this area
Epiphyseal - spongy bone and marrow in this area
Dynamic skeleton
Bone remodelling affected by:
Age
Mechanical stress
Genetics and environment - black people have increased bone density whereas Asian most have decreased density
Calcium and phosphate levels - calcium deficiency results in bones being broken in order to obtain calcium
Hormones
Why does age has a big impact on bone remodelling ?
Demineralisation from the age of 40 - osteopenia
Reduces by 1% each year
Worse in woman
HRT can be given to keep oestrogen levels up to help prevent osteoporosis
Mechanical stress and impact on bone remodelling:
Weight bearing - so important for bone development and healing
Lack of activity results in loss of bone
Weight bearing activities build bone
Lack of mechanical stress reduces bone density
Bone disorders of development:
Agenesis - limb doesn’t/only partially forms
Osteogenesis imperfecta - genetic disorder - brittle
Spina bifida - spinal processes don’t form
Achondroplasia - long bones don’t form properly - dwarfism
Bone disorders of remodelling:
Age
Hormone levels
Calcium and phosphate level
Mechanical stress
Bone endocrine disorders:
Gigantism - produce too much growth hormones (childhood)
Acromegaly - bones increase in density and not length (adulthood)
Pituitary dwarfism
Hyper/hypoparthyroidism
Post menopausal osteoporosis
Bone disorders nutritional problems:
Rickets (Vit D)
Osteomalacia
Scurvy (Vit C)
Disorders linked to aging:
Osteopenia -
Osteoporosis -
Osteopenia - inadequate ossification. Osteoblasts activity decreases from 30-40 years
Jaw, vertebrae and epiphyseal areas are most commonly affected
Osteoporosis - decrease in bone mass greater for age/gender than expected
Mainly females and over 70
Low activity therefore not weight bearing puts you at really high risk
Osteoporosis
Primary -
Secondary -
Primary - simple form in elderly. Accelerated bone loss but within normal range for patients age/gender
Secondary - has a different cause rather than age or post menopause eg metabolic bone disease or serve malnutrition or some steroids
Fractures - named according to
1) severity (6 types) -
Open/compound - bone breaks skin
Impacted - one fragment driven into another
Comminuted - breaks into loads of pieces
Closed/simple - less soft tissue involvement
Displaced - fragments moved from original position
Compressed
