Building and maintaining the skeleton L3 Flashcards
Function of bones (2)
Protect organs
provide support and rigidity in limbs
How is the form of the skeleton determined
genetic & functional signals
What is bone formed from in the head
neural crest–>develops membrane, which then ossifies and forms bone
What is bone formed from in the body
Cartilaginous (made of cartilage models) apart from clavicle
Name three things migrated neural crest cells form
dorsal root ganglia
sympathetic chain ganglia
cells of the adrenal medulla
How do individual vertebrae know the identity they should become?
Patterning genes = hox genes
What are patterning genes called
hox genes
What do hox genes not control
Do not control the building of the vertebrae or any bones (just give the signal for what identity the bone should have)
When do limb buds develop?
4-5 weeks
Which limbs develop first?
The forelimb
What process forms the digits
programmed cell death
What does the apical ectodermal ridge control
signalling from the root to the tip of the limb
–> gives a signal to grow length wise
What does the zone of polarizing activity control
signalling from side-side on the limb
Endochondral ossification
develops in pre-existing cartilage (body of the skeleton)
intramembranous ossification
membrane models (skull and clavicle|)
Order of bone structure
Epiphysis
Physis (epiphyseal growth plate)
Metaphysis
Diaphysis
What causes a bone to ossify
the invading blood vessels
Where does ossification begin
the diaphysis
Where is the second ossification
At the end of long bones, under the influence of blood vessels
Where does cartilage expand
in the epiphyseal plate, driving the plates apart from the metaphysis.
What happens at puberty
sex hormones released cause cartilage to stop growing
What is left behind as a mark of bone growth
A epiphyseal line
What are bones and cartilages
connective tissue
What are chondrocytes
produce and maintain the cartilaginous matrix
What are chondrocytes derived from
chondroblasts
which secretes matrix and then tombs itself trapping itself, converting into a chondrocyte
Disadvantage of cartilage
it can’t adapt once laid down, avascular (v low blood supply)
What do chondrocytes lie in
lacuna
How do bones grow in diameter
laying bone on the outer surface, under the periosteum
How do bones grow in length
extensions at the cartilaginous growth plate
Cartilage proliferates from the epiphysis forcing apart the ends of the bone by stretching muscles and tendons that cross along the bone
Why is it hard to tell a fracture on a kid
they have growth plates
What do long bones consist of (2)
Cortex
Cancellous bone
What is the cortex
outer-shell of bone, made of compact bone, not very porous
What are circumferential lamellae called
osteons (layers and layers of bone with cells trapped between)
What is cancellous/trabecular bone
At the end of long bones—> spongy network of bony tissue
What is the middle off the shaft like in long bones
completely hollow
Bone made off (3)
Cells
Fibres
Mineralised ground substance
Osteoblasts
lay down unmineralised material (osteoid)
What is osteoid
Unmineralised material
Key feature about bone
it can adapt rapidly by altering the way you load it
What detects change in bone loading
osteocytes
What are osteoclasts
multi-cellular derived in similar way to macrophages
What do osteons drill through to create structure
woven bone
What is the canal formed in the middle of osteons
Haversian canal (surrounded by concentric lamellae, with osteocytes trapped in them)
What happens to bones when loading is less server
Cortical bone is made into less dense cancellous bone (particularly at the end of long bones)
Osteoclasts
destroy bone – resorption
Osteoporosis =
deposition & resorption out of balance –> bone thinning–> fracture
Three types of joints
fibrous
Cartilaginous
Synovial
Main issue of synovial joints
articular cartilage can be worn down easily
5 stages of fracture healing
Haematoma
Subperiosteal &; endosteal cell prolifertion
Callus- woven bone
Consolidation -(woven bone to lamellar bone)
Remodelling
