The development of the thoracic vertebræ in man

Abstract

WITH 7 PLATES.There is a somewhat extensive literature dealing with the development of the spinal column in various vertebrates. The chief stages in its differentiation are fairly well determined. Special attention has been given to the early development in the lower vertebrates. The recent literature on this subject up to 1897 h q been reviewed by Gaupp, 97.l Somewhat less attention hm been devoted to the mammals. To Proriep, 86, is due a valuable account of the development of the cervical vertebm in the cow, and to Weiss, 01, an important description of the development of the thoracic and cervical vertebrs in the white rat.We shall not attempt to enter here into a description of the early stages of differentiation in the spinal axis; that is of the period covering the formation of the chorda dorsalis and of axial and peripheral mesotlast, the differentiation of primitive segments, and the origin of the axial mesenchyme. This period in the human embryo has been well treated by Kollmann, 91, and some account of it has previously been given in this JOURNAL (Bardeen and Lewis, 01). We shall therefore proceed at once to a consideration of vertebral differentiation in the axial mesenchyme.Vertebral development in the embryo may be divided into three overlapping periods: a membranous or blastem~al, a chondrogenous, and an osseogenous.'

Significance of Resegmentation in the Pathogenesis of Vertebral Body Malformation

“…Thus, he concluded that the vertebral column had changed its scgmentation during the early development and he called it 'hew segmentation (Neue Gliederung)". Many papers on the development o f the vertebral column were produced thereafter (Bardeen & Lewis 1901, Bardeen 1905, Keyes & Compere 1932, Wyburn 1944, Sensenig 1949, and Peacock 1951. Sensenig (1949) carried out the last extensive study on which the current concepts of the vertebral development seem to be based.…”

“…Firstly, Junghanns' basic concept that the cartilaginous anlage of the vertebral body consists of two lateral halves was not observed in our study ( Figure 8). Although Bardeen (1901Bardeen ( , 1905 described two chondrification centres of the vertebral body divided by the perichordal septum, no descriptions of it can be found in the later literature (Keyes & Compere 1932, Wyburn 1944, Sensenig 1949. Secondly, failure of formation is already present in the very early stage of chondrification in our embryo of 13 mm C-R length (6 weeks).…”

“…Embryology of the human vertebral column has been described repeatedly (Bardeen & Lewis 1901, Bardeen 1905, Keyes & Compere 1932, Wyburn 1944, Sensenig 1949, and Peacock 1951. The study of Sensenig (1949) is the most extensive and best documented, and confirms the resegmentation theory which was proposed by Remak (1855) for the chick embryo.…”

IV. The development of the vertebral column in mammals, as illustrated by its development inMus musculus

“…In the trunk region of Bos, the primordia of the vertebral bodies are derived from the caudal half of one sclerotome and the cranial half of the next posterior sclerotome. Weiss (1901) identified the fissure in the rat, Schauinsland (1906) and Piiper (1928) found it in birds, and Bardeen (1905) observed it in the human embryo, noting that it appeared after the disappearance of the myoccele, at the end of the 3rd week.…”

“…R obin (1864) rejected this idea and maintained that the circular appearance of the rudiment of the body of a vertebra is specific for the mammalian embryo. Froriep (1886) and Bardeen (1905) found suggestions of this bilateral origin, the centrum rudiment at first consisting of a pair of lateral masses subchordally united by means of a strand of pro-cartilage, the whole appearing as a U-shaped structure. In Mus this U-shape is characteristic, and in the case of the axis, the earliest rudiment of the centrum shows no subchordal connection and is therefore truly bilateral.…”