Early embryonic development 3 Flashcards
What does the notochord do to immediately overlying ectoderm?
Signals for it to convert to neuroectoderm
The edges then thicken and roll towards one another to form the neural tube
What are the somites?
segments of the paraxial (either side of axis) mesoderm
Appear in craniocaudal sequence at 3 pairs/day until there are 42-44
Some regress to leave 31
What does the organisation into somites give rise to?
Repeating strucutres and guides innervation
What does the Paraxial Mesoderm become?
Axial skeleton (vertebral column & ribs)
Dermis
Muscles of the axial body wall
Some limb muscles
What does the somatic mesoderm become?
Connective Tissue of limbs
Contributes to the axial body wall
What does the splanchnic mesoderm become?
Smooth musculature
Connective tissue and vasculature of gut
What does the immediate mesoderm become?
Urogenital system e.g. kidneys, Ureters, gonads
How can a somite differentiate into a myotome?
Somites appear as regular blocks of mesoderm
There is organised degeneration (ventral wall breaks down) leading to sclerotome
Dorsal wall breaks down forming the dermomyotome
Myotome proliferates and dermatome regresses
What is a dermotome?
A section of somite that can proliferate into a skin section
What is a myotome?
A section of somite which can proliferate into a muscle section
What is sclerotome?
A section of somite which can proliferate into a bone section
Clincially, what is a dermatome?
Strip of skin supplied by a single spinal nerve
Clincially, what is a myotome?
Muscle/group of muscles supplied by a single spinal nerve
What does the neural tube produce?
Nerves that innervate the dermomyotome
What does folding achieve?
3D structure
Creates the ventral body wall
Pulls the amniotic membrane around the disk so that the embryo becomes suspended in the amniotic sac.
Pulls the connective stalk ventrally
Creation of a new cavity within the embryo (the coelom)
