block 5 lecture 3 building the skeleton Flashcards
what do bones do?
protect organs, provide support for limbs, haematopoeisis
what signals determines the form of the skeleton?
genetic and functional signals
what are the two embryonic sources of the skeleton?
mesoderm and neural crest cells
what models do the long bones and ribs form in?
cartileginous models
bones of the skull and face form in a membrane derived from what?
neural crest
what days of the embryo do you get the development of somites?
21-25
what do vertebrae develop from in the embryo?
somites
what group of genes determine the shape of the individual vertebrae?
hox genes
what are the structures described as during limb development?
paddle-like structures
which limbs develop first?
for limbs
how do you form digits?
programmed cell death, cells in the paddle like structures die
what sends signals to the developing limb bud to identify elements of the limbs?
epithelium surrounding the limb
signalling from the route of the limb to the tip of the limb is done by what?
apical epidermic ridge
what is the signalling of limbs from side to side done by?
epidermic cap - zone of polarizing activity
what are the two types of ossification?
endrochondral ossification in cartilage and intramembranous ossification
what is the ossification center at the end of bones called?
epiphysis
which end is the epiphysis located?
articular end
what is the physis? and its other name?
epiphysial growth plate
the thin cartilage that separates the the epiphysis from bone, where growth occurs for length
what is the metaphysis?
broad part of the bone at the end of the shaft
what is the long part of the shaft of the bone called?
diaphysis
in endochondral ossification do genetic signals form?
cartilaginous models
how does cartilage ossify in endochondral ossification?
invaded by blood vessels
where does ossification begin along the shaft in in endochondral ossification?
middle
what is between the end of the long bone and the shaft?
epiphysial plate
how do bones increase in lengthin endochondral ossification?
cartilage at the epiphysial plate expands and drives the epiphys and diaphysis away
what is the epiphysis covered with?
articular cartilage that the bone was formed in
what stops the bone growingin endochondral ossification?
sex hormones are released during puberty which stops the cartilage from growing and ossifies the cartilage
what is the cell of cartilage?
chondrocyte
what are chondrocytes derived from?
chondroblasts
how are chondroblasts converted to chondrocytes?
the chondroblasts secrete a matrix which inttumes its self
what are the holes chondrocytes sit in called?
lacuna
how do bones grow in diameter?
laying cells on the outersurface under the peristoneum
how do the cells of bone act to make the bone bigger?
they proliferate forming layers and expand
what is the outer shell of long bones called?
cortex
what is at the end of long bones under the joints surface?
spongy network
features of the cortex of long bones?
compact
not porus
what are the long tubes forming in the compact regions of long bones called and what do they contain?
osteons and they contain minerals and collagen
shape of osteocytes?
they have long processes which penetrate the bone and have a central nucleus
how do bones adapt?
the processes of osteocytes stretch and contract which send signals to osteoblasts to deposit bone
how is bone removed?
acid secretion by osteoclasts
what is the formation when the cortex is first laid down?
woven
what is different about the layers of collagen in an osteon? and what is good about this?
the different layers go in different directions, strength
where is cancellous bone found?
ends of long bones
what is the woven structure of bone converted to?
lamellar
what is osteoporosis?
deposition and resorption is out of balance
what are the types of joints?
fibrous - sutures and between long bones
cartileginous - ribs
synovial
what is the synovial membrane?
thin sheet of connective tissue that secrets synovial fluid
what are synovial joints supported by?
ligaments
what are the five stages of healing?
haematoma, subperiostel and endosteal cell proliferation, callus, consolidation and remodelling
