MSK Embryology Flashcards
Okay let me start by saying
This lecture went into a lot of detail and was a bit confusing in places.
Realistically, if any of this comes up, it’ll be at most two questions.
These flashcards cover basics I think, but should be enough for a general idea.
Maybe rewatch the lecture before exams if worried.
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What does the development of the limbs start?
End of week 4
Where do limb buds form from?
Form deep to a thick band of ectoderm
AER= apical ectodermal ridge
What is the AER?
Thickened ectoderm at the apex of a limb bud
What induces the AER?
Paracrine Growth Factor FGF-10
ZPA= zone of polarizing activity
What happens here?
Mesodermal cells aggravate the base of each limb bud
Which are larger- upper limb buds or lower limb buds?
UL buds
Where do UL buds appear?
Opposite the caudal and cervical segments (C4-T2)
Where do LL buds appear?
Opposite the lumbar and upper sacral segments (L2-S2)
In which week do the digits of the hands and feet become separated and how does this occur?
Week 8- do to apoptosis of the tissue between fingers and toes
->if this does not occur, there may be webbing of hands or feet
By which process do limb buds elongate?
By mesenchymal proliferation
All of the bones of the upper limb are formed from the lateral plate mesoderm except for which?
Clavicle
Where are the primary ossification centres in the upper limb>
Clavicle
Humerus
Radius
Ulna
What are all the bones of the lower limb formed from?
Lateral plate mesoderm
How are myocytes (muscle cell precursors) formed?
Mesoderm from the dermamytomone regions of somites migrate into the limb bud and condense and differentiate into the myocytes
Where are the primary ossification centres for the lower limbs during weeks 7-9?
Tibia and fibula
->more develop after birth e.g. ilium, ischium, pubis, talus, phalanges etc
Which types of muscle in the upper limb does posterior condensation of myoblasts form?
Extensors and supinator muscle
Which types of muscle in the upper limb does anterior condensation of myoblasts form?
Flexors and pronator muscles
Which types of muscle in the lower limb does posterior condensation of myoblasts form?
Extensors and abductors
Which types of muscle in the lower limb does anterior condensation of myoblasts form?
Flexors and abductors
What does the 4th aortic arch form in terms of vasculature?
Proximal right subclavian artery
Where does the distal part of the right subclavian artery and the entire left subclavian artery come from?
7th intersegmental artery
What provides the axis artery of the upper limb?
Subclavian artery
What provides the axis artery of the lower limb?
Umbilical artery
Rotation occurs of the limbs. What type of rotation occurs in the upper and lower limb at week 6?
Limbs rotate horizontally into a sagittal orientation
In week 7, the rotation of upper and lower limbs differs.
What happens in the upper limb?
Rotates laterally
->this is so elbows are dorsal with the extensors posterior of the UL
In week 7, the rotation of upper and lower limbs differs.
What happens in the lower limb?
Rotates medially
->this is so knees are ventral with the extensors anterior and flexors posterior
During which week do the peripheral nerves grow from the developing limb plexuses?
Week 5
Dermatome?
Area of skin supplied by a single spinal nerve and its ganglion
Cutaneous nerve area?
Area of skin supplied by a peripheral nerve
If there are problems during development, the congenital defects are more severe when…?
They occur earlier in the development process
What are some of the causes of congenital defects?
Genes
Environment e.g. drugs, alcohol
Which drug in particular is known to lead to congenital problems e.g. amelia (lacking one or more limbs)?
Thalidomide
->can still be used today in myeloma and leprosy treatment but must be avoided in all women of child bearing age
Amelia?
Loss of one or more limbs
Meromelia?
Partial absence of at least one limb
Brachydactyly?
Reduced number of digits
Polydactyly?
Additional digits
