Resumen por el autor, E. J. Carey.Observaciones directas sobre la transformacion del mesenquima en el muslo del embri6n de cerdo (Sus scrofa), con especial mencihn de la genesis de 10s mfisculos del muslo, de las articulaciones de la rodilla y csdera y del hueso primario del femur.El autor ha estudiado intensamente mediante una serie de
1. The region of most active mitosis per mm. of cross-section in the intestine is the entodermal epithelial tube. The mitotic figures primarily follow the path of a right-handed helix. In one of the twenty embryos the mitotic figures describe the path of a right-handed helix. 2. The region of least active or relatively passive growth per mm. of cross-section is the mesenchyme, derived from the splanchnic mesoderm surrounding the epithelial tube. 3. The rapid expansion, due to epithelial growth in a rotating spiral manner, of the intestinal lumen is greater than the activity manifest in the surrounding mesenchyme. This causes a pressure in the latter resulting in a flattening and elongation of the mesenchymal cells. The successive changes in shape of these cells through the spherical, ellipsoidal, and spindle cellular phases are seen. The mesenchymal wall decreases in thickness, due to tension caused by epithelial tubular dilation. 4. The rotating spiral growth of the epithelial cells causes the formation of a series of mesenchymal cellular and fibrillar concentric rings due to the centripetal force of the former. 5. The circular, smooth muscle cells are differentiated in the outer, more condensed margins of the ring. At these points the developing tensional stresses are greater than within the ring. 6. The inner circular smooth muscle coat is the first one differentiated and is incident to the rapid growth of the epithelial tube in diameter. The former soon tends to restrict the growth of the epithelial tube in diameter. The tube, pursuing the lines of least resistance, grows in length. During the period of rapid growth in length the outer longitudinal muscle coat is in the process of formation. 7. The tensional stresses to which the elongated strained mesenchymal cells are subjected appear to be a dynamic stimulus to smooth muscle differentiation. 8. From this study of a closely graded and progressive series of sections of intestinal development, the conclusion is drawn that muscle tissue is not self-differentiating, in the strict sense of the term, but that the tension of differential growth acts as the stimulus to smooth muscle differentiation.
Resumen por el autor, Eben J. Carey.Estudios sobre la estructura y funci6n del intestino delgado.I. La arquitectura helicoidal del intestino delgado. 11. La acci6n espiral del intestino delgado.La capa muscular interna del intestino delgado es una litmina continua arrollada en espiral apretada. Una vuelta completa de espiral tiene lugar en cada 0.5 a 1 mm. de longitud, o menos. La capa muscular externa forma una espiral alargada, que termina una vuelta completa en una extensi6n de unos 200 a 500 111111. o mAs. La submucosa est& compuesta de fibrillas de tejido conjuntivo que forman una espiral interna apretada y otra externa m6s laxa. La interna efecttia una vuelta completa en 0.5 a 1 mm. o menos, la externa en cada 4 a 10 mm. La capa muscular interna, por consiguiente, esth arrollada en espiral apretada, la externa en espiral laxa.La diferencia en la velocidad de la progresi6n translatoria de las dos ondas de contraccibn depende de esta disposici6n en espiral. La onda que marcha a lo largo del grupo interno de fibras toma un curso rotatorio, mientras que la que camina a lo largo de las fibras externas sigue una direcci6n m&s translatoria hasta alcanzar su punto de destino. Por consiguiente, la contraccibn de la capa muscular interna, mits fuerte, seguirh inevitablemente a la de la capa externa. La disposici6n de las capas musculares intestinales explica claramente el fen6meno de la contrisci6n cefAlica y la dilataci6n caudal durante la diastalsis, sin necesitar invocar la ayuda de vias nerviosas hipotbticas. La peristalsis, por consiguiente, es un fen6meno de doble contracci6n producido por la velocidad diferencial del avance translatorio de las dos ondas de contracci6n en las capas musculares externa e interna, respectivamente. Estas conclusiones se basan en experimentos en 10s cuales el autor separ6 del intestino vivo las capas externa e interna.
Esophageal Development. 1. The region of most active mitosis per mm. of cross-section in the esophagus is the entodermal epithelial tube. The mitotic figures follow a spiral path in the manner of a left-handed helix from the cephalic to the caudal direction. 2. The region of least active growth per mm. of cross-section in the esophagus is the mesenchyme surrounding the epithelial tube. 3. The helicoidal activity of the epithelial tube causes a vortical reaction in the surrounding mesenchyme. The mesenchymal whirlpool represents a reaction to the spirally grooving epithelial tube. 4. In embryos 9.5 to 14 mm. in length the esophageal epithelial tube grows relatively more rapidly in width than in length. During this period the myoblasts which form the inner, close spiral, muscle coat of the esophagus are becoming rapidly differentiated in the outer condensed margin of the mesenchymal maelstrom. 5. The nuclei, first spherical then oval, and finally rod shaped with rounded ends, are drawn out in the direction of the circumference of the mesenchymal rim which is directed tangentially. 6. The cytoplasm is also drawn out in the direction of the mesenchymal rim of the vortex. The elongated rows of isolated granules appear which subsequently, by confluence, form the myofibrillæ. These cytoplasmic derivatives are elongated in the direction of the circumference of the vortex. 7. Between the epithelial tube and the myoblastic rim at the periphery of the mesenchymal whorl is found the embryonic connective tissue. From this direct observation the conclusion is made that an optimum tensional stress stimulus is necessary to elicit the formation of muscular tissue at the circumference of the mesenchymal vortex. Consequently, the formation of a specific derivative from a pluripotent mesenchymal cell is due to the fortuitous circumstance of position. 8. In embryos from 14 to 24 mm. in length, the esophagus grows relatively more rapidly in length than in width. This elongation is due to two factors; first, the descent of the stomach, and, second, the resistance to diametrical growth presented by the inner close spiral musculature. The epithelial tube, still the dominant zone of mitotic activity, pursues the lines of least resistance, and consequently growth in length takes place. This is due to the shifting of the planes of cell division on account of the compression of the inner, close spiral, muscle coat. 9. The undifferentiated mesenchyme peripherad to the inner, close spiral musculature is elongated and the histogenetic changes in muscular formation are gradually taking place between 14 and 24 mm. A very attenuated, outer, elongated, spiral, or longitudinal muscle coat is detected in the esophagus of a 24 mm. pig embryo. 10. The characteristic intestino-colic flexure is a torsional reaction of the mesenchyme. The mesenchymal cells are thrown into a left-handed helicoidal series, corresponding to the activity in the epithelial tube. The right-handed helicoidal reaction of the mesenchyme, therefore, is due to the left-handed helicoidal growth of the epithelial tube. 11. The normal asymmetry of the abdominal viscera as well as the position of the gut is dependent upon the clockwise reaction of the stretched mesenchymal cell. These cells are stretched by the left-handed helicoidal growth of the epithelial tube. One factor producing situs inversus viscerum could be the reversal of the spiral growth of the epithelial tube resulting in a reaction of the mesenchyme in a direction opposite, namely counterclockwise, to that which occurs normally.
NINE PLATES (FOURTEEN FIGURES) THE OBJECTThe object of paper is the presentation of evidence which supports the ,ollr)wiiig findings, namely :1. That, under the adequate mechanical conditions produced by an intact, normally mobile knee-joint and its related soft parts, patellar cartilage and bone will regenerate from young connective-tissue cells which had not been destined as specific formers of bone.2. That, where the adequate mechanical conditions are altered by means of immobilizing the knee-joint, with the patella left intact, patellar cartilage and bone will atrophy.3. That, mhere the patella is excised in toto and the adequate mechanical conditions are altered by means of kneejoint fixation, patellar cartilage and bone will not regenerate, even with the tendon of the quadriceps extensor femoris muscle and the patellar ligament united by suture.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.