tailieunhanh - Embryology of medical (Twelfth edition): Part 2

(BQ) Continued part 1, part 2 of the document Embryology of medical (Twelfth edition) has contents: Respiratory system, digestive system, urogenital system, head and neck, integumentary system, central nervous system,. and other contents. Invite you to refer. | Chapter 13 Cardiovascular System ESTABLISHMENT AND PATTERNING OF THE PRIMARY HEART FIELD The vascular system appears in the middle of the third week when the embryo is no longer able to satisfy its nutritional requirements by diffusion alone. Progenitor heart cells lie in the epiblast immediately adjacent to the cranial end of the primitive streak. From there they migrate through the streak and into the splanchnic layer of lateral plate mesoderm where they form a horseshoe-shaped cluster of cells called the primary heart field PHF cranial to the neural folds Fig. . As the progenitor heart cells migrate and form the PHF during days 16 to 18 they are specified on both sides from lateral to medial to become the atria left ventricle and most of the right ventricle Patterning of these cells occurs at the same time that laterality left-right sidedness is being established for the entire embryo and this process and the signaling pathway it is dependent upon Fig. is essential for normal heart development. The remainder of the heart including part of the right ventricle and outflow tract conus cordis and truncus arteriosus is derived from the secondary heart field SHF . This field of cells appears slightly later days 20 to 21 than Primary heart field Primary heart field Endoderm Primitive node Primitive streak A Splanchnic mesoderm layer Intraembryonic cavity Primary heart field C Cranial r neural folds Pericardial cavity Connecting stalk I Ectoderm Allantois Notochord Figure A. Dorsal view of a late presomite embryo approximately 18 days after removal of the amnion. Progenitor heart cells have migrated and formed the horseshoe-shaped primary heart field PHF located in the splanchnic layer of lateral plate mesoderm. As they migrated PHF cells were specified to form left and right sides of the heart and to form the atria left ventricle and part of the right ventricle. The remainder of the right ventricle and the outflow tract consisting of conus .