15.1 Mesodermal development in frog and chick embryos (Part 1)

15.1 Mesodermal development in frog and chick embryos (Part 2)

15.2 Heart-forming cells of the chick embryo (Part 1) The presumptive heart cells originate in the early primitive streak, just posterior to Hensen’s node and extending about halfway down its length.

15.2 Heart-forming cells of the chick embryo (Part 2) To inhibit Wnt

15.2 Heart-forming cells of the chick embryo (Part 3)

15.3 Formation of the chick heart from the splanchnic lateral plate mesoderm (Part 1)

15.3 Formation of the chick heart from the splanchnic lateral plate mesoderm (Part 2)

15.4 Migration of heart primordial (Part 1)

15.4 Migration of heart primordial (Part 2) E12.5 WT E12.5 Foxp4 mutant

15.5 Double in situ hybridization for the expression of RADH2 and Tbx5 (Part 1) Orange: RADH2 (enconding the RA-synthesizing enzyme retinaldehyde dehydrogenase-2) Blue/Purple: Tbx5 (a marker for the early heart fields)

15.6 Cascade of heart development

-As cells migrate toward each other, the ventral mesoderm cells of the primordia begin to express N-cadherin and join together to form an epithelium. -This joining will lead to the formation of the pericardium. -A small population of these cells downregulate N-cadherin and delaminate from the epithelium to form the endocardium (lining of the heart that is continuous with the blood vessels). -The endocardial cells produce many of the heart valves, secrete the proteins that regulate myocardial growth, and regulate the placement of nervous tissue in the heart. -The epithelial cells form the myocardium that gives rise to the heart muscles.

15.7 Cardiac looping and chamber formation (Part 1)

15.7 Cardiac looping and chamber formation (Part 2) B and C: Xin expression (essential for heart looping) in chicken embryos. D and E: Specification of atria and ventricles occurs before heart looping (different types of myosins)

15.8 Formation of the chambers and valves of the heart

15.12 The aortic arches of the human embryo (Part 1)

15.12 The aortic arches of the human embryo (Part 2)

15.13 Vasculogenesis and angiogenesis (Part 1)

15.14 Vasculogenesis (Part 1) The inner cells of the blood islands (aggregates of cells from the splanchnic region) become blood progenitors, while the outer cells become angioblasts (progenitor of blood vessels). The angioblasts multiply and differentiate into endothelial cells which will form the lining of the blood vessels. The endothelial cells form tubes and connect to form the primary capillary plexus.

15.14 Vasculogenesis (Part 2)

15.15 Yolk sacs of a wild-type mouse and a littermate heterozygous for a loss-of- function mutation of VEGF

15.13 Vasculogenesis and angiogenesis (Part 2)

15.16 Model of the roles of ephrin and Eph receptors during angiogenesis (Part 1)

15.16 Model of the roles of ephrin and Eph receptors during angiogenesis (Part 2)

15.17 Blood vessel specification in the zebrafish embryo (Part 1)

15.18 Model for blood vessel formation in the chick blastoderm VEFG gradient (green) induce endothelial cells to become arteries (red), and these arteries induce veins (blue) to form.

15.19 Arteries are specifically aligned with peripheral nerves in mouse limb skin