Background Many studies have been published on the development of the human wrist joint, but scant attention has been given to the development of the wrist joint ligaments. Moreover, traditional description of wrist anatomy usually depict only the superficial capsular fibers of the wrist joint. The only ligamentous structure to receive much attention is the articular disc of the wrist joint, which has been described as a fibro‐cartilaginous structure extending from the medial edge of the lower end of the radius to the ulnar styloid process. Methods In the present report, we synthesize our observations in the wrist joint ligaments in 35 serially sectioned human embryonic and fetal hands (16 embryos and 19 fetuses). Results The interosseous intercarpal ligaments are organized from the mesenchyme, which, until O'Rahilly's stage 23, fills the intercarpal spaces. These ligaments are not individually distinguishable until the 9th week of development. The collateral ligaments begin to form in O'Rahilly's stage 22 and are completely formed by the end of week 10. The palmar radiocarpal and ulnocarpal ligaments (beginning with the palmar radiocarpal ligament) begin to form in O'Rahilly's stage 23 and are fully developed by the end of week 10. At this time, development of the dorsal radiocarpal ligament begins; this process is completed by the end of week 13. The articular disc which is initially formed of a single element, first appears in O'Rahilly's stage 23 and its organization is completed at week 10 of development. Conclusions We establish the morphogenetic time‐table of the wrist joint ligaments. Our descriptive findings may help explain carpal motion and the origin of wrist injuries. © 1996 Wiley‐Liss, Inc.

The development and morphogenetic timetable of the submandibular gland was studied in 37 human embryos and human fetuses. The medial paralingual groove constituted the anlage of the submandibular gland: Its anterior three-quarters gave rise to Wharton's duct, and its posterior quarter to the submandibular gland proper. The sublingual process of the submandibular gland originated from a lateral ectodermal bud of the anlage of the submandibular gland, in the posterior quarter of the medial paralingual groove.

The early development of the ultimobranchial body and its colonizing cells was studied in human embryos (O’Rahilly’s stages 14 and 15). In our studies we have obtained evidence that permits us to propose a new hypothesis on the origin of both the ultimobranchial body and its colonizing cells. Based on our interpretation of the morphogenetic features in human development, we think that the ultimobranchial body derives from the fifth endodermal pharyngeal pouch, which is colonized, from O’Rahilly’s stage 14 on, by cellular material of ectodermal placodial nature that originates in the most caudal portion of the epicardiac branchial placode.

A correlation was sought between the organization of the dental crest and the ossification of the corpus mandibulae in 14 human embryos and 13 human fetuses. The different types of ossification between the corpus and the ramus mandibulae suggest that the cartilago mandibularis (meckeliensis) guides the formation of the mandibula, while the dental crest acts as a coorganizer. In the area of the foramen mentale, the lamina dentalis begins to invaginate (to give rise to the dental crest), and at this level intramembranous ossification of the corpus mandibulae commences. These findings, together with the presence of the cartilago mandibularis before the appearance of the dental crest, and the fact that the former is seen along the entire length of the mandibula (from the symphysis mandibulae to the capsula otica), support the hypothesis that the dental crest, rather than the cartilago mandibularis, acts as the coorganizer in the corpus mandibulae.

A correlation was sought between the organization of the parotid gland and the formation of the large vessels and nerves that passed through the glands of 12 human embryos and 12 human fetuses. There was no evidence that the gland became a bilobate structure as a result of the course of the facial nerve, whose interglandular branches were surrounded during development by the multidirectional ramifications of the expanding parotid anlage.