BIOL 303 Introductory Developmental Biology and Embryology lectures notes 16 Chapter 13 Limb Development
The Development of the Tetrapod Limb , ,
The 3D Vertebrate Limb Proximal-Distal axis: three segments, stylopod (proximal), zeugopod and autopod (distal) develop in sequence. Cartilage is replaced by bone sequentially in the above order. Anterior-Posterior axis: the small fingers ( p inky) are p osterior, our thumbs anterior. Dorsal-Ventral axis: palm is ventral the knuckles (and nails) dorsal. These three axes, plus the element of time create a four-dimensional coordinate system within the embryo. By interpreting their positional value within this coordinate system, cells are instructed how to differentiate.
Tickle C (2006) Making digit patterns in the vertebrate limb Nat. Rev. Mol. Cell Biol. 7: 1–9 doi:10.1038/nrm1830 The three main axes of the human hand.
Formation of the Limb Bud Limbs are formed at defined positions (they don’t show up just anywhere) Experiments with the “important” mesodermal cells: 1)Removing cells and noting that the limb doesn’t develop in their absence 2)Transplanting cells to a new location and seeing if they develop a limb at that site 3)Marking groups of cells and following the dye or radioactivity through limb formation
Prospective forelimb field of the Salamander Limb field: An area of the embryo containing all of the cells capable of forming a limb. In the salamander - the tissues that make up the limb and surrounding tissue, the shoulder girdle and flank can be removed and the limb will still develop with some delay Removing the area in gray in addition to the limb and surrounding progenitors will prevent limb development. limb field
Kidney and gonads (intermediate mesoderm) Gut lining (endoderm) • Parietal serosa • Limb bud Somatic mesoderm • Dermis • Visceral serosa Splanchnic mesoderm • Smooth muscle of gut Epidermis (ectoderm) Dermatome Myotome Sclerotome peritoneal cavity (coelom) Neural tube (ectoderm) Somite The first mesenchyme cells proliferate from the somatic layer of the limb field lateral plate mesoderm (
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