. A laboratory manual and text-book of embryology. Embryology. 52 THE STUDY OF CHICK EMBRYOS is differentiated into a thick walled pouch on each side lateral to the endothelial layer of the veins. Transverse Section through the Heart (Fig. 36).âAs we pass cephalad in the series of sections the vitelline veins open into the heart just in front of the fovea cardiaca. The entoderm in the head-fold now forms the crescentic pharynx or fore-gut separated by the heart and splanchnic mesothelium from the entoderm of the germinal disc. The descending aorta? are larger, forming conspicuous spaces betwee
. A laboratory manual and text-book of embryology. Embryology. 52 THE STUDY OF CHICK EMBRYOS is differentiated into a thick walled pouch on each side lateral to the endothelial layer of the veins. Transverse Section through the Heart (Fig. 36).âAs we pass cephalad in the series of sections the vitelline veins open into the heart just in front of the fovea cardiaca. The entoderm in the head-fold now forms the crescentic pharynx or fore-gut separated by the heart and splanchnic mesothelium from the entoderm of the germinal disc. The descending aorta? are larger, forming conspicuous spaces between the neural tube (hind-brain) and the pharynx. The heart, as will be seen, is formed by the union of two endothelial tubes, similar to those which form the walls of the vitelline veins in the preceding sections. The median walls of these tubes disappear at a slightly later stage to form a single tube. Thick- Ectoclerm Somatic mesoder g. Notochorcl Myocardium Entoderm. â Neural tube Descending aorta Pharynx- Endocardium Splanchnic mes. Fig. 36.âTransverse section through the heart of a twenty-five-hour chick embryo. X 90. ened layers of splanchnic mesoderm which, in the preceding section, invested the vitelline veins laterally, now form the mesothelial wall of the heart. In the median ventral line, the layers of splanchnic mesoderm of each side have fused, separated from the splanchnic mesothelium of the germinal disc and thus the two pleuro-pericardial cavities are in communication. The mesothelial wall of the heart forms the myocardium and epicardium of the adult. Dorsally, the splanch- nic mesoderm is continuous with the somatic mesoderm and forms the dorsal mesocardium. Origin of Primitive Heart.âFrom the two sections just described, it is seen that the heart arises as a pair of endothelial tubes lying in the pockets of the splanchnic mesoderm. Later, the endothelial tubes fuse to form a single tube. The heart then consists of an endo- thelial tube within a thick-walled
Size: 1777px × 1406px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectembryology, bookyear1
