The document provides information about mesoderm development in human embryos, including: - The mesoderm arises from epiblast cells that migrate through the primitive streak during gastrulation. - The mesoderm is initially divided into paraxial, intermediate and lateral mesoderm. Lateral mesoderm further splits into splanchnic and somatic mesoderm. - The mesoderm gives rise to various tissues and organs, including muscle, bone, kidney and other parts of the urogenital system. It also forms the walls of body cavities.

1. Mesoderm I Embryos, Tissues, Cells August 25, 2008 Douglas L. Falls, M.D.

8. Epiblast cells that do migrate down (ventrally) through the primitive streak during later stages of gastrulation constitute the mesoderm layer ( dull red in 16 day image at lower right ) day 16 14-15 days 16 days 2 wks

9. Human embryo during gastrulation Carlson Fig. 5-4 (p86)+ 5-5 (p87) transverse section

10. Derivatives of the bilaminar embryo Carlson Fig. 5-1 (p84) Laminae of bilaminar embryo Extraembryonic mesoderm

11. Though early on you were a quite flat disk, now are a doughnut http://www.abdn.ac.uk/langling/resources/usflimgs.html [And what is in the middle?]

14. Major subdivisions of the mesoderm Sadler 3-4 (p19) “ parietal” (wall) layer “ visceral” (organ) layer

15. Postnatal derivatives of embryonic mesoderm From Carlson 6-25 (p125) Embryonic mesoderm Intermediate mesoderm Urogenital system (kidney, ureter, not bladder adrenal cortex gonads not gametes) Vagina, uterus, uterine tubes Dermis of skin Skeleton (axial, not limb ) Lateral mesoderm Paraxial mesoderm Muscles (axial & limb) Splanchnic mesoderm Somatic mesoderm Skeleton ( not axial , limb) Parietal pleura pericardium peritoneum Visceral pleura peritoneum Mesenteries Blood cells, blood vessel endothelium, endocardium Respiratory tract wall Gut wall Epicardium Myocardium somatic = “parietal” = wall layer. For gut and gut derivatives, the parietal layer lines body wall. splanchnic = visceral = organ layer epicardium= visceral pericardium

19. Mesodermal origin of muscle From Carlson 6-25 (p125) Embryonic mesoderm Intermediate mesoderm Urogenital system (kidney, ureter, not bladder adrenal cortex gonads not gametes) Vagina, uterus, uterine tubes Dermis of skin Skeleton (axial, not limb) Lateral mesoderm Paraxial mesoderm Muscles (axial & limb) Splanchnic mesoderm Somatic mesoderm Skeleton (not axial, limb) Parietal pleura pericardium peritoneum Visceral pleura peritoneum Mesenteries Blood cells, blood vessel endothelium, endocardium Respiratory tract wall Gut wall Epicardium Myocardium skeletal cardiac smooth

20. Lineage tracing studies demonstrate that limb muscles derive from somites

22. Muscle fibers exhibit different functional characteristics reflecting formation from different myoblast subpopulations Carlson 9-30 (p201) muscle stem cells?

23. In contrast to skeletal muscle, cardiac and smooth muscle myocytes do not undergo fusion, but remain as individual cells Carlson 9-34 (p205)

25. Mesodermal origin of bone From Carlson 6-25 (p125) Embryonic mesoderm Intermediate mesoderm Urogenital system (kidney, ureter, not bladder adrenal cortex gonads not gametes) Vagina, uterus, uterine tubes Dermis of skin Skeleton (axial, not limb) Lateral mesoderm Paraxial mesoderm Muscles (axial & limb) Splanchnic mesoderm Somatic mesoderm Skeleton (not axial, limb) Parietal pleura pericardium peritoneum Visceral pleura peritoneum Mesenteries Blood cells, blood vessel endothelium, endocardium Respiratory tract wall Gut wall Epicardium Myocardium

28. The End

30. Postnatal derivatives of embryonic mesoderm From Carlson 6-25 (p125) Embryonic mesoderm Intermediate mesoderm Urogenital system (kidney, ureter, not bladder adrenal cortex gonads not gametes) Vagina, uterus, uterine tubes Dermis of skin Skeleton (axial, not limb ) Lateral mesoderm Paraxial mesoderm Muscles (axial & limb) Splanchnic mesoderm Somatic mesoderm Skeleton ( not axial , limb) Parietal pleura pericardium peritoneum Visceral pleura peritoneum Mesenteries Blood cells, blood vessel endothelium, endocardium Respiratory tract wall Gut wall Epicardium Myocardium somatic = “parietal” = wall layer. For gut and gut derivatives, the parietal layer lines body wall. splanchnic = visceral = organ layer epicardium= visceral pericardium

31. Postnatal derivatives of embryonic mesoderm From Carlson 6-25 (p125) Embryonic mesoderm Intermediate mesoderm Lateral mesoderm Paraxial mesoderm Splanchnic mesoderm Somatic mesoderm Parietal parietal pleura parietal pericardium parietal peritoneum Visceral visceral pleura visceral pericardium visceral peritoneum Mesenteries somatic = “parietal” = wall layer. For example, gut and gut derivatives, the parietal layer lines body wall. splanchnic = visceral = organ layer epicardium= visceral pericardium