Neuromuscular embryology Flashcards
What is the mesoderm cell fate determined by
Where in the primitive streak the cells migrate through
What is somitogenesis
The formation of somites
What are somites derived from
Paraxial mesoderm- separating
what direction do somites form
Cranial to caudal
What do somites lie lateral to
Neural tube and notochord
What do somites differentiate into
Dermatome
Myotome
Sclerotome
What does the dermatome form
dermis
muscle stem cells
brown fat cells
What does the sclerotome form
Vertebrae and ribs
tendons
blood vessels
meninges
which 3 lineages generate the skeleton
- Somites= axial skeleton
- Lateral plate mesoderm= limb skeleton
- Neural crest and head mesoderm= skull and face
How do sclerotome cells join to form the vertebrae
Vertebral body develops from caudal part of one sclerotome and cranial part of the next
What is vertebrae formed by
Chondrification of sclerotomal mesenchyme
What does early fetal cartilaginous vertebrae undergo
Endochondral ossification
What are the 3 axes of limb development
- Proximo-distal (shoulder- fingertip )
- Antero-posterior (thumb- little finger)
- Dorso-ventral (knuckle-palm)
What are limb buds
Early structures of limbs
What causes the formation of limb buds
Activation of mesenchymal cells in the lateral plate mesoderm and cell accumulate under the ectoderm creating a bulge
What is the apical ectodermal ridge (AER)
A thickened area of ectoderm at the tip of a limb bud that promotes outgrowth of the limb bud
Which structures appear first in the limb bud
Proximal structures
What does the proximal-distal development require
Interaction between the AER and progress zone
Anterior-posterior axis- What specifies individual digits
Zone of polarising activity and sonic hedgehogs (signally molecule)
What is polydactyly caused by
Mutations affecting the zone of polarising activity
How do mutations affect the dorso-ventral axis
Dorsal features replaced by ventral features
What is the dorso-ventral axis specified by
ectoderm
How are digits formed
Initially form as plate, apoptosis needs to occur to seperate digits
What does expansion of lateral parts of the neural tube lead to
Formation of thick lateral walks- thin roof/floors
What are alar and basal plates
Are where the neural plate differentiates into ventral and dorsal halves
What are the alar and basal plates seperated by
Sulcus limitans
What do the cells in the alar plate develop into
Sensory neurons
What do cells in the basal plate develop into
Motor neurons
