embrogology Flashcards
Common terms for limb malformations
amelia: absence if limbs
meromelia: absence part of limbs
adactyly: sbsence dgigts on a limb
arachnodactyly; elogonation of digits
bracydactlyl ( shortnede fingers of toes
Polydactycly: more than 5 toes
syndactly( fingers joined together)
Limb Variations and what causes it
cruical 4th and 5th week
genetics, environemntal ,mechanincal
Rotation of the limbs
8th week the limbs rotate in opposite directions to reach anamtoical position
upper limbs laterall and dorsally
lower limbs roatet ,meidally and ventrally
How are dermatomes supplied
they dvelope from the dermatome part of the somite which forms the dermis of the skin
How are myotomes formed
each somite pair gives group of skeletal mm supplied by specifc sgemental spinal nerve
4-th to 8th hand and foot process
hylaine cartilage mdoels limb bones
develops distal end
mesenchymal tissue forms digitasl rays
apoptosis ruslts in reomval of cells b/w digital rays resulting is seprate digits
No aopotosis, syndactyly occurs, meaning webbing of figers
week 8: alll components of upper and loweer limb are distnct.
endochondral ossifcation starts whcihc marks the end of the embryhonic period and the beginnig of foetal period
hand and feet development order
limb buds, paddle-shaped hand and foot plates, digital raysm, nothces b/w digital rays, webbed fingers and toes, seperate digits
hand and foot development
upper limb buds 24 levels c5-8
lower limb L3-L5
Limp developemnt
during 4th week
Apical ectodermalridges induce mesoderm and ectoderm to create limb buds
2 upper 2 lower upper limb 2 dyas before
somites, functioning parts
dermatome: forms dermis
myotome mm
sclerotome: vertebra,rips
Specilaistaion of Mesoderm
end of week 3 first pair of somited form, 3 pairs a day unti 30 when 44 pairs exitts
humand left with 37 pairs
Neurulation: endoderm forms primitive nervous system
late week 3 nuerlation forms nervous systems
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notochord induces part of ectoderm to thciken and form neural plate.
neural plate forms nerual groove with a neural fold.
gorup of cells called neural crest is formed to form the PNS
End of weel 4 neural fold fuse together to form neural tube whcihc will become the rbain and pinal cord (CnNS)
Week 4: organogenenis begins
3 germ layers give rise to body systems
ectoderm: CNS, PNS, hair nails, epidermis of skin
mesoderm: bones, mm, blood vessels
endoderm: epithelial lining of gastrointestinal, respiratory& urinary systems
Embryonic Folding from Trilaminar Disc to 3d embryo
Cranicaudally gives c shaoe with distinct head and tail
laterally whcih creates the cylindrical body cavity
endoerm inner most layer: role of inner systems
mesoderms form body tissues b/w layers. bones, mm, connective tissue, blood vessels
Ectoderm encirlces other 2 layers formng outer layer and coveig of the embryo(epidermis)
Notochord AXIAL SUPPORT OF EMBRYO
mesodermal c3ells beneath prmitve streak form a rod called ntochord( SEPeartes left and right)
ntochord will induce cells in the ectodermnto differientiate nervous tissue.
