The early development of the pericardium, diaphragm, and great veins / by C.B. Lockwood.

  • Lockwood, Charles Barrett, 1856-1914.
Date:
1888
Catalogue details

Licence: Public Domain Mark

Credit: The early development of the pericardium, diaphragm, and great veins / by C.B. Lockwood. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    unites with both the uro-genital ridge and with the pericardium (figs. 59i and 60i), and, finally, with a triangular mass of mesoblast which covers the dorsal lobe of the liver (figs. 59i and 60i). As yet its hinder edge is crescentic, and the*lungs project beyond it into the peritoneum ; but this protrusion gradually becomes less apparent (fig. 64j, Lng. and D.D.). A gradual separation of the dorsal diaphragm and mesone- phros from the superior venae cavse accompanies the growth of the thorax. By the time the dorsal diaphragm is on the point of uniting with the mesentery it has both grown and been carried tailwards so far that its median part unites with the mesoblast which covers the dorsum of the liver some distance beyond its junction with the pericardium (fig. 63J, D.D.). And, in consequence, the hepatic mesoblast takes a share, as Cadiat claims, in forming the diaphragm.* The final closure of the aperture between the dorsal diaphragm and the mesentery has no particular feature. Before it is accomplished muscular fibres are abundant in the position of the crura and wherever the diaphragm springs from the body wall. All of these originate in situ, and those of the crura begin the earliest (12^ days) in the base of the mesentery (fig. 54h, Cr. D.). After a while (14th day) they become quite distinct, and consist of bands of muscular fibres situated in front of the cartilaginous bodies of the vertebrae and at the base of the mesentery. These fibres run ventralwards round the sides of the oesophagus to spread out in the dorsal part of the ventral diaphragm, and some of them almost surround the vena cava inferior. After the diaphragm has become a complete septum the history of its development would mainly relate to the gradual growth of the structures whose origin has been described and their gradual approximation to their permanent condition. These processes are unaccompanied by any remarkable circumstances. The main factor associated with them is the expansion of the lungs, which, in the higher types, spread ventralwards round the sides of the pericardium (fig. 62) and forwards between the superior vense cavee and the body wall; but, as none of these ever affect the principles of the processes which I have endeavoured to explain, I do not propose, at present, to pursue them further. However, the recess, apical recess, between the Cuvierian ducts, or superior venae cavse, and the body wall seems to commence at an early stage of development (figs. 37f and 39f, R). Finally, I may add that the following conclusions have been arrived at;— 1. The heart develops from splanchnopleure into the foremost end of the coelom, which afterwards becomes the pericardial sac. 2. The cardiac portion of the coelom is cut off by (a) the vitelline veins; (6) the Cuvierian ducts. 3. The mesocardium laterale is a point at which the mesoblast is uncleft, and at which on each side the somatic umbilical vein is transmitted into the splanchnic vitelline vein. Afterwards the mesocardium laterale transmits the Cuvierian ducts. * “Du Developpement de la Portion Cephalo-thoracique de I’Embrjon, &c,,” ‘Journal de I’Anatomie et de la Physiol.,’ vol. 14, 1878, p, 620