Bone Structure, Function And Healing Flashcards
What do the bones of the skeleton provide?
Structural formation Mobility Support Protection of the body Storehouse
Describe bone
Connective tissue
Matrix of collagen fibres and a ground substance
Hard yet brittle
Consists of four types of cells
2 types of tissue in the bone - compact and spongy
What are the two types of bone tissue?
Compact and spongy
Describe characteristics of compact bone
80% of our total bone mass All cells squished together Solid hard layer Gives strength down the long axis of a bone - lateral impact could damage it Denser, less flexible - then spongy
Describe the appearance and structure on compact bone
Osteoblasts lay down collagen fibres in a criss cross fashion
Creates lots of ring like structures, around blood vessels = called lamellae.
You get lots of these side by side making a spiral like structure of rings and rings = Osteon aka. Haversian system.
Formed of concentric calcified rings, surrounding blood vessels
Lots of osteons lay next to each other along the long axis of your diaphysis. - can withstand great pressure
Between each osteon is more lamellae
Separating the lamellae is a Lacunae
A lake made of extracellular fluid and more cells known as osteocytes.
Describe characteristics of spongy bone
20% of a bones total mass
Composed of a honey comb network
Found in ends of all long bones - in the epiphseal where compressive forces are found
It redistributes the stress down the shaft
Light weight, good shock absorber
Distributes pressure and stress
Describe the appearance and structure of spongy bone
Laid down by osteoblasts in a lattice like structure along lines of stress
Beams and haphazard structure of the bone gives it this spongy look with gaps.
The gaps are filled with blood vessels, extracellular fluid, red and yellow bone marrow etc.
Nutrients are derived from the medullary cavities
What are the 4 types of bone cells?
Osteoprogenitor cells
Osteoblasts
Osteocytes
Osteoclasts
Describe osteoprogenitor cells
Undifferentiated cells
No distinguishing feature in this form
Sit and wait to receive information to be stimulated into making new bone
Once stimulated, they divide
The daughter cells produced are osteoblasts
Located in the endosteum and inner periosteum
Describe osteoblasts cells
Build the matrix and collagen fibres
Can’t divide
Come from osteoprogenitor cells
Once made, they remain in this form
Become trapped in their own system of bone.
Once trapped after being laid down, they are known as osteocytes
Located on the surface of bones and in the lacunae of built bone
Describe osteocyte cells
Mature cells
They maintain the bone
Have projections that communicate with other cells
Located in the lacunae, maintain the bone matrix
Provide information about how much building or breakdown of bone needs to be done
Also regulate nutrients
Describe osteoclast cells
Clear bone cells
A lot bigger than the other 3 types
Come from a monocytes
Clear up debris and dead bone
Have a ruffled border - easily stick to bone surface
Release enzymes and acids to destroy the bone underneath
Reabsorb this and release minerals back into the blood
Only respond to what osteocytes say
located on the surface of bones
What is Coupling?
The amount of bone being laid down and the amount broken down and reabsorbed is done at the right rate.
What is uncoupling?
Too much loss or gain of bone.
Osteoporosis is associated with this.
What is remodelling?
An ongoing process in the bone throughout our life.
Continually modelled throughout childhood and adolescence
Lots of removal and replacement at the same site.
Leads to strong, healthy bones.
What can go wrong with bone growth?
Low bone density - more brittle and weaker so more likely to break
Bone cancer
Bone infections - due to trauma or surgery
Osteogenesis imperfecta - an inherited disorder of extreme bone fragility, don’t produce enough collagen, very susceptible to fractures and don’t produce cartilage at the epiphyseal plates
What are the four arteries that supply bones with blood?
Periosteum arteries
Nutrient arteries
Metaphysical arteries
Epiphyseal arteries
Where does the periosteal arteries go?
Penetrates the periosteum through Vulcan canals
Supplies blood to the outer osteons of compact bone marrow
Where does the nutrient arteries go?
Enters through the diaphysis, through the nutrient foramen
Supplies the medullary cavity and osteons of inner compact bone
Where does the metaphyseal arteries go?
Enter the metaphysis
Supply spongy bone and bone marrow
Where do the epiphyseal arteries go?
Enter your epiphysis
Supply spongy bone and bone marrow
What can remodelling be affected by?
Age Mechanical stress Genetics and environment Hormones Nutrition
How does age affect remodelling?
Once at full height our bone density then begins to decrease.
Demineralisation from the age of 40
And continues to reduce at 1% each year
Due to menopause in women this can sometimes be worse
Remodelling in older people will take longer and may not heal properly or as fast
How does mechanical stress affect remodelling?
Weight bearing is important for development and healing
As your muscle pulls on a bone it causes mechanical stress which means the bone will remodel.
Increases the mineral and collagen production to keep bones strong and healthy
Weight bearing builds bone
Lack of activity results in loss of bone and decrease in density
How does genetics and the environment affect remodelling?
Genetically particular races such as black, have denser bones and are less likely to suffer from diseases such as osteoporosis.
Women’s bones are more affected than mens due to hormones
Cannot control genetics but can control environmental factors
Balanced diet, physical exercise
How does nutrition affect remodelling?
Deficits in calcium will cause your osteoblasts to send signals that we need more calcium = bones are broken down to re absorb more calcium into the body.
Need around 800-1000 mg of calcium a day
Other vitamins such as D are needed to help calcium be absorbed and K
A lack of calcium causes bone deterioration and too much can causes lots of bone building
How do hormones affect remodelling?
Menopause can cause women to become prone to uncoupling due to a change in hormone levels.
What are some bone disorders of development?
Spina bifida
Osteogenesis imperfecta
Agenesis
What are some bone disorders of remodelling?
Age
Hormone levels
Calcium levels
Mechanical stress
What are some endocrine bone disorders?
Gigantism - too much growth hormone
Pituitary dwarfism
Postmenopausal osteoporosis
What are some nutritional bone disorders?
Rickets - reduced amounts of vitamin D
Osteomalacia - bones become soft. Aka. Rickets in adults
What is osteopenia?
Medical condition where proteins and mineral content of bone tissue is reduced.
Bones become thinner with age
Affects your jaw, vertebrae and limbs
What is osteoporosis?
Medical condition in which the bones become brittle and fragile from loss of tissue.
Usually due to hormonal changes
More common in females
Over 70s
Early menopause or longer lasting menopause than normal can increase the risk.
More prone to fractures
What scan can be done to check for osteoporosis?
A Bone Density scan aka. Dexa Scan
The scanner cannot easily pass through dense bone so a low reading indicates high bone density.
A high reading indicates low bone density, as the scanner can easily pass through.
What are the two types of osteoporosis?
Primary and secondary
What is primary osteoporosis?
Simple form
In the older generation, predicted
Or after menopause
What is secondary osteoporosis?
Not related to age or time of life. Relegated to other factors such as: - bone diseases - cancerous illnesses - malnutrition - weightlessness - smoking - alcohol - lack of calcium All of the bottom 3 must be excessive and can be modified.
What is a fracture?
Breaks caused by mechanical stress applied on a particular location where the bone cannot support it.
What are some names of fractures?
Open Closed Displaced Comminuted Compressed Spiral Oblique Green stick Transverse Colle Potts Boxer Pathological
Describe the rate of healing
It depends on the type of fracture and where it is positioned - wither in the upper or lower limb.
Uber limb takes less time to heal than the lower as it is smaller.
What can affect the rate of healing?
Type of fracture Vascular supply Age Movement of fracture Infection Bone pathology
What are some clinical features of a fracture?
Pain and tenderness Swelling and bruising Deformity Impaired function Shock
How might a fracture be treated?
Sling, cast, splint
Open reduction internal fixation
Open reduction external fixation
Rehabilitation may also be provided to help healing. But this tends to be after its fixed, to re gain movement and strength.
What are some complication with fracture healing?
Delayed
Mal/non union - doesn’t heal in the correct alignment, may need to be re broke and re aligned
Compartment syndrome
Blood vessel damage
Fab embolus - causes a blockage of blood flow, preventing healing
Growth impairment
Osteoarthritis
