Human Development – Lecture 18 – The Skeleton and muscle
system
Epiblast migrate to form intraembryonic mesoderm (FGF-8 controls this cell
specification) and endoderm.
Ectoderm – mesoderm – endoderm
Ectoderm give rise to neural tube (brain and spinal cord), epidermis, hair, nails, lens
of eye, skin glands.
Mesoderm give rise to axial, paraxial, intermediate, lateral mesoderm and
cardiovascular systems, dermis
Endoderm give rise to digestive, respiratory, bladder and thyroid liver and pancrease
Lateral mesoderm; splanchnic, somatic and extra-embryonic. Limbs, lining body
wall
o Somatic/pariental mesoderm + ectoderm; lateral & ventral body wall; boven
o Splanic/visceral mesoderm + endoderm; gut wall; onder
Intermediate mesoderm; kidney, urogenital tract
Paraxial mesoderm; forms only in medial-cranial part
o Head
o Somite;
o Sclerotome
o Myotome (muscle)
▪ Dicht bij neural tube; epimere (epaxial myotome) (dorsal side)
▪ Ver weg neural tube; hypomere (hypaxial myotome) (lateral &
ventral body wall)
o Syndotome (spinal vertebrae, skull basis)
o Dermatome (skin)
▪ Dicht bij neural tube; pars epaxialis
▪ Ver weg neural tube; pars hypaxialis
o Endothelial cells
First the mesoderm is epithelial, forming a lumen.
Ventral and medial become mesenchymal, they migrate
around neural tube & notochord = sclerotome
Dermomyotome is formed first. Dorsomedial (epimere) and
ventrolateral (hypomere) become muscle cells.
Responsible for this?
o Dorsomedial; medium BMP4 and high Wnt (MYF5)
o Ventrolateral; high BMP4 and medium Wnt → become
sclerotome (MYOD)
Upregulation FGF and Shh lead to upregulation Chorin &
noggin which leads to decrease BMP4
With BMP4; NOT all tissues become neural plate
Without BMP4; all tissues become neural plate
BMP4 and SHH induces (veroorzaken) expression of other factors → PAX genes
that determine fate (lot) of neural cells. PAX genes also important in dermatome
development
system
Epiblast migrate to form intraembryonic mesoderm (FGF-8 controls this cell
specification) and endoderm.
Ectoderm – mesoderm – endoderm
Ectoderm give rise to neural tube (brain and spinal cord), epidermis, hair, nails, lens
of eye, skin glands.
Mesoderm give rise to axial, paraxial, intermediate, lateral mesoderm and
cardiovascular systems, dermis
Endoderm give rise to digestive, respiratory, bladder and thyroid liver and pancrease
Lateral mesoderm; splanchnic, somatic and extra-embryonic. Limbs, lining body
wall
o Somatic/pariental mesoderm + ectoderm; lateral & ventral body wall; boven
o Splanic/visceral mesoderm + endoderm; gut wall; onder
Intermediate mesoderm; kidney, urogenital tract
Paraxial mesoderm; forms only in medial-cranial part
o Head
o Somite;
o Sclerotome
o Myotome (muscle)
▪ Dicht bij neural tube; epimere (epaxial myotome) (dorsal side)
▪ Ver weg neural tube; hypomere (hypaxial myotome) (lateral &
ventral body wall)
o Syndotome (spinal vertebrae, skull basis)
o Dermatome (skin)
▪ Dicht bij neural tube; pars epaxialis
▪ Ver weg neural tube; pars hypaxialis
o Endothelial cells
First the mesoderm is epithelial, forming a lumen.
Ventral and medial become mesenchymal, they migrate
around neural tube & notochord = sclerotome
Dermomyotome is formed first. Dorsomedial (epimere) and
ventrolateral (hypomere) become muscle cells.
Responsible for this?
o Dorsomedial; medium BMP4 and high Wnt (MYF5)
o Ventrolateral; high BMP4 and medium Wnt → become
sclerotome (MYOD)
Upregulation FGF and Shh lead to upregulation Chorin &
noggin which leads to decrease BMP4
With BMP4; NOT all tissues become neural plate
Without BMP4; all tissues become neural plate
BMP4 and SHH induces (veroorzaken) expression of other factors → PAX genes
that determine fate (lot) of neural cells. PAX genes also important in dermatome
development
