19 MSK embryology Flashcards
What problem is presented by the blastocyst to the uterus?
It is technically foreign material, and could provoke an immune response
What will the connecting stalk ultimately form?
the umbilical chord
When do somites begin to form?
Week 3 - gastrulation
What is gastrulation?
epiblast cells are pushing into the primitive streak, pushing the original hypoblast out of the way, forming a new layer called mesoderm, and the top cells are the endoderm
What does gastrulation form?
the tri-laminar disc
On each side, what does the mesoderm divide into?
paraxial mesoderm
intermediate mesoderm
lateral plate mesoderm
Do humans use the left-over yolk sac?
nope, it’s an artefact of our ancestors who laid eggs
Once all the folding shit is complete, what two structures does the mesoderm form?
splanchnopleuric mesoderm
somatopleuric mesoderm
(intramembryonic coelom in between)
What does the dermamyotome split into?
the dermatome and the myotome
What is the sclerotome?
division which goes on the form the skeleton, they can often be seen to cluster around the notochord, for the vertebral bodies
How does the sclerotome form vertebrae?
The sclerotome at the top of one somite and the bottom of another form the vertebrae, this allows the spinal nerve to go out a bit
What types of genes control vertebral differentiation?
HOX (homeobox)
Why do limb muscles have a more complex development?
They are no segmental, and therefore originate from multiple somites
they are the somite of the spinal nerves supplying it
What is the position of the embryo?
NOT anatomical position
limbs grow straight anteriorly with palms and soles facing each other
Why do the limbs have to rotate outwards?
We have anterior and posterior divisions of nerves, so the antrior muscles originally started on the inner bit of the limbs (all flexors and abductors)
what part of the brachial plexus supplies the anterior flexors of the arm?
anterior divisions
Embryologically, which is more advanced, the upper or lower limb?
the upper limb is always about 2 days ahead
What is the difference between mesoderm and mesenchyme?
mesoderm - layer in tri-laminar germ disc
mesenchyme - loose connnective tissue, you don’t normally find it in an adult
What is phacomelia?
thalidomide poisoning - limb defects
What is Syndactyly?
fused fingers or toes
What is Polydactyly
extra digits
What is Clinodactyly?
What other diseases might it be a sign of?
bent digit (especially little finger)
Turner syndrome
Down syndrome
Klinefelter syndrome
What is club foot
inverted feet
What parts of the skull develops from cartilage?
base of the skull
viscerocranium
larynx
(rest from mesenchyme)
What are pharyngeal arches artefacts of?
ancestors with gills
