Book - Manual of Human Embryology 18-4
Embryology - 23 Apr 2024    Expand to Translate
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العربية | català | 中文 | 中國傳統的 | français | Deutsche | עִברִית | हिंदी | bahasa Indonesia | italiano | 日本語 | 한국어 | မြန်မာ | Pilipino | Polskie | português | ਪੰਜਾਬੀ ਦੇ | Română | русский | Español | Swahili | Svensk | ไทย | Türkçe | اردو | ייִדיש | Tiếng Việt These external translations are automated and may not be accurate. (More? About Translations) |
Keibel F. and Mall FP. Manual of Human Embryology II. (1912) J. B. Lippincott Company, Philadelphia.
- XVIII. Development of Blood, Vascular System and Spleen: Introduction | Origin of the Angioblast and Development of the Blood | Development of the Heart | The Development of the Vascular System | General | Special Development of the Blood-vessels | Origin of the Blood-vascular System | Blood-vascular System in Series of Human Embryos | Arteries | Veins | Development of the Lymphatic System | Development of the Spleen
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A. Origin of the Vascular System
By Herbert M. Evans. Johns Hopkins University, Baltimore.
The question of the source of the cells which form the vascular system still remains, as it has for a long time, one of the most disputed problems of mammalian and indeed of general vertebrate embryology. The question has met no undisputed solution for the case of any vertebrate, and here, in contrast to the dearth of human material, we can possess a wealth of all the necessary stages. When such fundamental questions as the genetic relation between extra-embryonic and embryonic vessels, and indeed even the method of origin of the former — the well-known vitelline vascular anlagen — are still unsettled, and when we consider the paucity of these earlier stages which should be necessary for the determination of this question in man, a speedy solution of the problem in human ontogeny is expected by no one.
u Such, for instance, as that of the upper thoracic aorta on the columna vertebralis. Whereas in enibryos of 20 mm. the upper aa. intercostales find their interstitia intercostalia at the same level, in the adult, as is well known, they must course upwards to reach their interspaces.
13 When completing the present account of the development of the human vascular system, I had access to six young embryos in the possession of Professors Kollman, Eternod, R. Meyer, Strahl and Felix. These were studied in the laboratory of Professor Wiedersheim in Freiburg i. B. To all of these gentlemen I wish to express my sincere thanks. Four very valuable ernbryos in the collection of Graf Spee were studied in his institute in Kiel, for which great privilege I am deeply indebted.
If, then, we posses no safe generalizations with which to interpret the few observations possible on human embryos, we are also still further retarded by certain peculiarities of the early history of the primate embryo which affect profoundly the vascular system. The presence of an early vascularized belly stalk and chorion distorts the entire sequence of tbe usual development of the vessels and furnishes us at once in embryos astonishingly young with highly specialized and characteristic phenomena. These latter facts are now beyond doubt and I shall present them briefly below. Here only it need be remarked that the early history of the human vascular sj-stem has not enabled us as yet to make any statement as to the exact cellular origin of the endothelium in man. The only facts in the human embryo's history which may be brought into relation with this important question seem to point clearly to a mesodermal source for the primary blood-vessels. These are: 1. The abundant vascularization of the early chorion, where apparently any role of the entoderm can be excluded. 14 2. The early vitelline vascular anlagen which cause a characteristic " hummocking " of the yolk-sac wall lie in the mesodermal coat of the latter and are sharply separated from the entoderm.
3. The earliest vascular cells within the body of the embryo (in the Graf Spee embryo " Glaevecke " ) are certainly in more intimate relation with the mesodermal than with the entodermal cell layer.
| Embryology - 23 Apr 2024 Expand to Translate
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العربية | català | 中文 | 中國傳統的 | français | Deutsche | עִברִית | हिंदी | bahasa Indonesia | italiano | 日本語 | 한국어 | မြန်မာ | Pilipino | Polskie | português | ਪੰਜਾਬੀ ਦੇ | Română | русский | Español | Swahili | Svensk | ไทย | Türkçe | اردو | ייִדיש | Tiếng Việt These external translations are automated and may not be accurate. (More? About Translations) |
Keibel F. and Mall FP. Manual of Human Embryology II. (1912) J. B. Lippincott Company, Philadelphia.
- XVIII. Development of Blood, Vascular System and Spleen: Introduction | Origin of the Angioblast and Development of the Blood | Development of the Heart | The Development of the Vascular System | General | Special Development of the Blood-vessels | Origin of the Blood-vascular System | Blood-vascular System in Series of Human Embryos | Arteries | Veins | Development of the Lymphatic System | Development of the Spleen
| Historic Disclaimer - information about historic embryology pages |
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