Bone structure and function Flashcards
What is the function of bone
structural function, mobility and strength, support, protection for the body- skull protects brain, storehouse essential material- production and storing of minerals such as calcium, fat production and storage
Typical long bones- epiphysis
distal and proximal. These are covered with cartilage, and it is made up of spongy
Typical long bones- shaft/ diaphysis
this is covered with cpm[act bone, it has medullary cavity, inside this it has a endosteum and connective tissue, bone marrow and blood vessel
Typical long bones- metaphysis
the metaphysis attaches the diaphysis to the epiphysis
Typical long bones- periosteum
all the way around it is a periosteum- outer layer is were tendons and ligaments attach too, the inside has osteoprogenitor cells
Typical long bones- what is all away round long bones
a layer of compact cortical bone to make it strong
types of osseous tissue- compact
80% total mass, solid hard layer, external layer of all bones- strength down long axis, not strong down transverse or lateral impacts
types of osseous tissue- spongy
20%- honeycomb network, found in inner parts of axial skeleton and epiphyses of long bone, good shock absorber/ good at redisturbuting pressures and stressors
Compact (cortical) bone- structure
denser the spongy bone/ trabecular bone, but less flexible
Compact (cortical) bone- osteon
connective rings (lamellae) of calcified matrix surrounding vertically oriented blood vessel
Compact (cortical) bone- make up
made with artery and vein running down the middle, osteoblasts lay down collagen fibres in a criss- cross fashion- helps with strength, this leads to a ring of bone around the blood vessel
Compact (cortical) bone- rings
end up with lots of rings going in a spiral, this forms osteons, lots of these lay next to each other on the long axis of the diaphysis- means it can withstand great pressure down vertical axis, between each osteon is more lamelle
Compact (cortical) bone- what separates the lamellae
separating the lamellae is the lucunai , this is a pit/ lake, inside there is extracellular fluid and osteocytes (bone cells)
Compact (cortical) bone- osteocytes
osteocyte are mature bone cells, osteoblasts become trapped within itself and turns into an osteocyte
why are osteocytes important
they are important because they provide information about how much building/ breaking down needs to be done. Osteocytes form projection (canaliculi), branch out and receive information from other osteocytes in other lucane. they have a role in regulation nutrients
Spongy (trabecular/ cancellous) bone- structure
lattice like, light- less compact, collagen fibres laid down by osteocytes, laid down along lines of stress and this forms trabeculae
Spongy (trabecular/ cancellous) bone- lines of stress
well organised along lines of stress- gives strength and resisting stress and force without breaking- forces from different angle. It dissipates stress- lots of projection of bones to transfer stress through, bone marrow forms holes, within these holes- blood vessels and extracellular fluid
Spongy (trabecular/ cancellous) bone- osteocytes and nutrients
osteocytes in lacunae on the surface of trabeculae, nutrients directly from the blood in the medullary cavities
Cell types in bones- osteogenic/ osteoprogenitor cells
undifferentiated cells- sit and wait to receive information to be stimulated to make new bone- when stimulated they are able to divide into osteoblast. Found in endosteum and inner layer of periosteum.
Cell types in bones- Osteoblasts
build matrix and collagen fibres but cannot divide, they build bone and get trapped within their own system of bone. when they have built their surroundings, they are referred to as osteocytes.
Cell types in bones- osteocytes
mature cells, sit in lacunae. These maintain bone tissue and what we need through communication about nutrients needed (long branches)
Cell types in bones- osteoclasts
clear bone cells, bigger than other cells, forms monocytes- good at clearing up debris. Function is reabsorption, the destruction of bone matrix.
What does the border of the osteoclasts allow
the rough border allows them to stick to surface of bone and release enzymes and acids that destroy bone, during the process they clear up and absorb debrie- able to release minerals back into blood system. they only do this based on what osteocytes signals are needed
what is remodelling of bone
absorption is an ongoing process for bones to keep them healthy- continually make new bone and break down old bone- called remodeling.
what is coupling (remodelling)
equilibrium between amount absorbed and amount broke down need stop be at right rate and each cell is doing the right amount- this is called coupling. if something goes wrong (net bone change), this system is called uncoupling
Ageing of osteoblasts and osteoclasts
osteoblasts age quicker than osteoclasts- more building less clearing at older age
Location of cells- osteocytes
found in lacunae of compact of spongy bone
Location of cells- osteoblasts
found on surface of bone
Location of cells- osteoprogenitor cells
found in endosteum and inner layers of periosteum
Location of cells- osteoclasts
found on surface of bone
process of modelling and remodelling
bones are continually modelling through childhood and adolescence, much of the cellular activity in a bone consist of removal and replacement at the same sit, this process is remodelling. Many things can interfere with the developments of strong and healthy skeleton, e.g. osteoporosis
how do bones get longer
new cartilage gets produced on the epiphyseal side on the plate , old cartilage calcified- turns into bone, cartilage grows, cartilage replaced by bone
how does bone stop growing in length
after a certain age epiphyseal plate stops producing cartilage and collagen, meaning the amount of bone being produced to lengthen stops, from 18-25
how do bones get wider
this is called appositional growth, the presents of the blood vessels within the bone stimulate the osteoblasts to make more bone. this makes bones wider.
what grows quicker length or width
the length and width need to grow at the same time (coupling), if length grows quicker than width then a think weak bone occur
What can go wrong with bone growing- osteoporosis
low bone density (low peak bone mass)- osteoporosis. Bones are weaker and are more likely to break
What can go wrong with bone growing- osteogenesis imperfecta
genetic disorder- don’t produce enough collagen= bones are weaker, and brittle. Doesn’t grow as quickly as it should, epithelial plates may be damaged
What can go wrong with bone growing- Paget’s disease of bone
bones replaced faster than usual (problem with bone regeneration), the bone isn’t made that well- meaning it i weaker
What can go wrong with bone growing- cancer
bone cancer
What can go wrong with bone growing- bone infection
usually after some form of trauma or surgery expose to bone
blood supply to bones- periosteal arteries
periosteum and outer osteons of compact bone- breaks through volkmann canals. Supplies blood to osteons and outer parts of bone
blood supply to bones- why do bones need good blood supply
large blood supply because of activity going on there. Constant remodelling and coupling- blood is supplied by many different areas. bone are important for overall health, therefore, the bones are able to communicate with the whole body.
blood supply to bones- nutrient arteries
medially cavity and osteons of inner compact bone, enters through diaphysis through the nutrient foramen
blood supply to bones- metaphyseal arteries
spongy bone and marrow in this rea, enter the metaphysis and they supply trabecular/ spongy bone
blood supply to bones- epiphyseal arteries
enter through epiphyseal, supplies spongy bone and marrow in this area
blood supply to bones- internal bleeding
when bones are broken, and fractures can lead to internal bleeding and damage of arteries. Bones can take longer to heal if damage to arteries occur, and can lead to parts of the bone dying. Femur is susceptible to this. Interruption to blood supply can take a while to fix
What is remodelling affected by
age- some cells slow down, mechanical stress, genetic and environment, calcium and phosphate levels- nutrition, hormones
effect of age on bones- Demineralisation
demineralisation from the age of 40 years- osteopenia. Reduces 1% per year. Worse in women- 40-45 years- hormone oestrogen and production is slower
effect of age on bones- osteoporosis prevention
HRT- hormone replace therapy to prevent osteoporosis
Why are weight bearing exercises important
Weight bearing exercise is important for developing and healing- to a certain degree. Relevant to weight bearing status of patient. Lack of weight bearing activity builds bones.
effect of lack of mechanical stress
lack of mechanical stress reduces bone density- if in cast for 12 weeks will half its normal levels. With activity bone density can be built up but can take up to 4 months before seeing good results. Elderly may never get back to full bone density- due to age related issues
effect on bone density- genetic and environmental
black people have greater bone density- asians have weakest bones
environment- it is important for children to have a good balance diet and get lots of exercise
effect on bone density- nutritional
calcium and phosphate- if there is a lack of calcium bones will be broken down due to signalling by the osteoblasts. Calcium is important in many stems in body such as blood clotting
effect on bone density- hormones
growth hormones and sex hormones, parthod hormones, calcitonin hormones
