J. Jimenez Collado

The relationships between the temporomandibular joint disc and related masticatory muscles in humans.

A study of the relationships of the temporomandibular joint disc and the lateral pterygoid, temporalis, and masseter muscles during the human fetal period and in the adult was conducted. The superior head of the lateral pterygoid muscle was seen to insert into the anteromedial two thirds of the temporomandibular joint disc. The fibers of the posterior one third of the temporalis muscle and fibers of the deep bundle of the masseter muscle were attached on the anterolateral one third of the disc. The attachment of these muscles to the disc was through the anterior extension of the disc, also known as the premeniscal or prediscal lamina. The possible functional role of these muscle attachments is discussed.

Relationships between the Temporomandibular Joint and the Middle Ear in Human Fetuses

A study was conducted, on 30 human fetuses, of the structures passing through the tympanosquamosal fissure. The tympanosquamosal fissure lies between the middle ear and the temporomandibular region. Meckels cartilage passes through the tympanosquamosal fissure and continues on into the middle ear with the cartilaginous anlage of the malleus. A tract of fibrous tissue arises from the mesenchyme, located cranial and lateral to Meckels cartilage, that enters from the posterior area of the temporomandibular joint disc to the middle ear through the tympanosquamosal fissure, and attaches onto the area of continuity of Meckels cartilage with the malleus. Transformation of Meckels cartilage into the sphenomandibular ligament and anterior ligament of the malleus determines their continuity through the tympanosquamosal fissure. The posterior fibers of the temporomandibular joint disc giving rise to the discomalleolar ligament insert into the anterior ligament of the malleus.

A study of the Os goniale in man

The anterior process of the malleus of the middle ear develops irrespective of Meckel’s cartilage through an intramembranous ossification center that appears in the human embryo of 26.5 mm crown-rump length at a caudo-medial position in relation to Meckel’s cartilage. The malleus has a double origin: the anterior process originates from the os goniale through intramembranous ossification, and the rest from MeckeΓs cartilage through endochondral ossification.

Anterior Tympanic Artery: Course, Ramification and Relationship with the Temporomandibular Joint

The anterior tympanic artery, a branch of the maxillary artery, ascends through the retroarticular region dividing into anterior branches that spread through the posterior part of the temporomandibular joint, and posterior branches that contribute to the vascularization of the external acoustic meatus and the tympanic cavity. The arrangement of the anterior tympanic artery was studied bilaterally in 18 adult cadavers. In some cases, the anterior tympanic artery branches off from the superficial temporal artery. The relationships of the anterior tympanic artery with the posterior part of the temporomandibular joint were analyzed.

Orbital Muscle of Müller: Observations on Human Fetuses Measuring 35–150 mm

The arrangement and relationships of the orbital muscle of Muller in human fetuses have been analyzed. This is a constant muscle made of smooth muscle fibers arranged over the longer axis of the inferior orbital fissure; some of its fibers reach the inferior wall of the cavernous sinus. The muscle layer is pierced by orbital rami of the medial maxillary artery and by thin veins communicating with the ophthalmic vein system and pterygoid plexus. The zygomatic nerve can be found in the midst of the muscle mass along most of its course. It is innervated by short rami from the sphenopalatine ganglion.

The development of heterologous grafts, labeled with thymidine-3H in the cardiac area of the chick blastoderm

Abstract Under certain experimental conditions, E + M of the noncardiac area (squares 15–18 of Fig. 1) in stages 5− to 5+, transplanted in the cardiac area of another embryo in the same stage, was incorporated within the host and had the capacity of differentiating into heart tissue (endocardium, epimyocardium) and coelomic mesothelium of the host (Figs. 2–4). The endoderm of the same squares gave rise to the endoderm of the foregut and intestinal canal. During the development there was a displacement between the mesoderm and endoderm, the first displacing in a cranial direction with relation to the second. This demonstrates that in these experimental circumstances grafts of these squares to the heart area can differentiate into structures different from those of their prospective fate and that therefore they are not determined or only partially determined at the time of grafting. In these cases, the heterologous graft continued the morphogenetic movements of the host region and became incorporated within it, resulting in a typical, or almost typical, embryo with a single heart, the same as occurs with a homologous graft, e.g., of a heart area. In the cases in which the graft did not become incorporated within the embryo, the endoderm of the graft formed extraembryonic endoderm of the host but could be recognized, even “in toto,” because of its different structure (Figs. 6 and 8). Even in these cases, isolated cells could pass on to the host and formed parts of some of its structures, but never as a cohesive sheet of cells as in the cases in which incorporation was complete. Even when the graft was divided into three or four portions, as in the case of embryo 2–68, these fused with themselves and with the host and developed as if they were only one piece, going on to form part of the coelomic mesothelium and of the endocardium and myoepicardium of the heart of the host.

Study of Pterygospinosus Muscle in Human Fetuses

The arrangement of the pterygospinosus muscle was analyzed in 5 human fetuses. The pterygospinosus muscle extends from the posterior border of the lateral lamina of the pterygoid process to Meckel’s c

Analyse expérimentale de la régulation cardiaque sur l’embryon de poulet

Homochronous homografts of prospective cardiac area labeled with 3H thymidine have been carried out in chicken embryos at stages 5 and 6 of Hamburger and Hamilton. It has been observed how