Mesoderm Differentiation

Question 1

by the end of the first week of embryogenesis, the ____ forms with these 2 populations of cells:

Answer 1

week 1 of embryogenesis: blastocyst made of trophoblasts (fetal part of placenta) and embryoblast (embryonic body proper)

Question 2

by the end of week 2 of embryogenesis, the ____ forms with these 2 layers:

Answer 2

week 2 of embryogenesis: bilaminar disc with hypoblast (ventral), epiblast (dorsal, form all precursor cells of embryonic body)

Question 3

during 3rd week of embryogenesis, ______ occurs, forming the ____

Answer 3

week 3 of embryogenesis: gastrulation, forming trilaminar disc (ecto/meso/endoderm)

via epiblast cell migration

Question 4

the neural tube (future CNS) and neural crest cells are derived from which embryonic layer?

Answer 4

ectoderm

*note that neural tube undergoes neurulation during week 4

Question 5

describe neurulation in week 4 of embryogenesis

Answer 5

neural tube formation occurs with induction of ectoderm by underlying notochord mesoderm —> developing neuroectoderm cells organizing in midline as a thickening called neural plate

proliferation of neural plate cells causes “buckling” to form depression called neural groove with bilateral neural folds

neural folds fuse in dorsal midline to form neural tube, which detaches from epidermis-forming surface ectoderm (future brain and spinal cord)

neural crest cells detach from neural tube and migrate throughout body (PNS)

Question 6

what forms from each of the following mesoderms?
a. notochord mesoderm
b. lateral plate mesoderm
c. intermediate mesoderm
d. paraxial mesoderm

Answer 6

a. notochord mesoderm: induces overlying ectoderm to form nervous system
b. lateral plate mesoderm: CV system
c. intermediate mesoderm: UG system
d. paraxial mesoderm: axial skeleton, skeletal muscles, connective tissue

Question 7

in the lateral plate mesoderm (LPM), vacuoles form and coalesce to form the body cavity, which separates the LPM into 2 separate layers:

Answer 7

1. parietal/somatic mesoderm layer: deep to ectoderm, forms CT of body wall and parietal serosa lining body cavity
2. visceral/splanchnic mesoderm layer: superficial to endoderm, forms muscles and CT of internal viscera/organs and visceral serosa covering viscera/organs

Question 8

what are the 2 types of embryonic folding and when do they occur?

Answer 8

embryonic folding occurs in week 4 of embryogenesis

1. cranial-caudal folding: achieves C-shaped (shrimp) embryo
2. lateral folding: achieves tube-shaped embryo

each occur simultaneously