Limb Developement (Movement / Embryology / Anatomy) Flashcards
When does limb developement occur?
5-8weeks
In what weeks are the limb buds visible as outpouchings from the ventrolateral body wall?
end of week 4
The mesoderm core of the limb bud differentiates into mesenchyme. What does this form in the limb/
Bones and connective tissue
What does the paraxial mesoderm form?
Paraxial mesoderm forms somites. The somites differentiate into structures - including skeletal muscle of limb.
The somites divide into the sclerotome and dermomyotome what do these give rise to?
Sclerotome = vertebral bodies
Dermomytome = skin and skeletal muscle
The epimere makes up the back muscles. What are they innervated by?
Dorsal rami of the spinal nerves
The hypomere makes up the muscles of the thoracic / abdo walls also muscles of the limbs. what are they innervated by?
ventral rami of the spinal nerves
Where does the limb musculature derive from?
Myotomt divides into epimere and hypomere. Limb muscles are from hypomere.
*Paraxial mesoderm»_space;>Somites»>dermomyotome»>myotome»>Hypomere
What is the upper limb inneravatd by?
brachial plexus (C5 - T1)
What is the lower limb innervated by?
lumbosacral plexus (L4-S3)
During limb rotation in which direction do the limbs rotate?
Upper limb = 90’ laterally so the flexors lie anteriorly
Lower Limb = 90’ medially so flexors lie posteriorly
When does limb rotation occur?
between weeks 6-8
What dermatome supplies the thumb?
C6
What dermatome supplies the 3 digit?
C7
What dermatome supplies the 5th digit?
C8
What does the lateral plate mesoderm, forming the mesenchymal core of the limb bud secrete.???
(It enduces thickening of the overlying ectoderm along the tip of the limb bud)
Fibroblast growth factor (Fgf 10)
Fibroblast growth factor (Fgf 10) induces thickening of the overlying ectoderm along the tip of the limb bud. What is this thickening called?
Apical ectodermal ridge (AER)
The apical ectodermal ridge expresses fibroblastic growth factors that cause rapid proliferation of the mesenchymal cells underlying the AER, the progress zone. What are these growth factors?
Fgf 4 and 8
What growth factors causes proliferation of the progress zone. (are secreted by the apical ectodermal ridge)
Fgf 4 and Fgf 8
Control of dorsoventral patterning:
the dorsal ectoderm expresses Wnt7, what does the ventral ectoderm express?
Ventral ectoderm expresses engrailed-1 , this inhibits Wnt7
Sonic hedghog (Shh) controls craniocaudal patterning. A high conc of Shh induced formation of the little finger. Low conc induces formation of the thumb. Where is Shh expressed?
Shh is expressed in the caudal part of the limb bud called the zone of polarising activity (ZPA)
What is Amelia?
complete abscence of a limb
What is meromelia
partiall abscence of a limb
What is phocomelia?
- digits develop prematurely
- limbs get shorter
(can be caused by thalidomide)
What limb malformation is caused by thalidomide?
Phocomelia - premature development of limbs. (limbs are shorter)
What is syndactyly?
fused digits caused by failure of apoptosis
What is polydactyly?
extra digits
caused by inappropriate Shh expression
What is ectrodactyly?
Split hand / foot
caused by the apicle ectodermal ridge to form properly
