Embryology - 26 Apr 2024 Expand to Translate
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Paper - The Development of the Human Mandibular Joint

The Development of the Human Mandibular Joint

By N. B. B. Symons

Dental School, University of St Andrews, Dundee

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Introduction

The mandibular joint has long been of interest in that phylogenetically it represents a new joint replacing the older one between the articulare (malleus) and the quadrate (incus). In this connexion considerable controversy has arisen over the formation of the articular disc and its relation to the lateral pterygoid muscle. Furthermore, the mode of formation of the mandibular joint is somewhat different from that of most other synovial joints.

In the literature, so far as I have found, the only previous workers who studied the development of the human mandibular joint by means of a series of specimens are Kjellberg (1904), Vinogradoff (1910) and Mundaca (194-8) The earliest stage described by any of these three workers is one of 35 mm. 0.1:. length.

A considerable period before there is any sign of a joint-cavity the chief elements of the mandibular joint have been mapped out. This is particularly true with regard to the condylar process of the mandible. Even as early as the 22 mm. stage in the human embryo there is some indication of its form.

Material and Methods

The materials used in this work were one embryo of 22 mm. C.R. length and a series of foetuses of 80, 84, 40, 48, 57 (two specimens), 60, 65, 70 (two specimens), 95, 150, 180 mm. (two specimens) C.R. length and one of full term. The material was fixed in formalin, dehydrated and cleared by routine methods and embedded in paraffin. One of the 57 mm. specimens, the 180 mm. and the full-term specimens, however, were treated by a double embedding method.

Observations

22 mm stage

A considerable amount of bone-formation has taken place and formed a plate on the lateral side of Meckel’s cartilage; this plate is in the substance of, and is surrounded by, that mesodermal condensation which outlines the mandible and precedes the formation of bone. The plate of bone is conﬁned to the region of what approximately corresponds to the future body of the mandible, but the mesodermal condensation can be traced further backwards, always, of course, on the lateral side of Meckel’s cartilage and the associated branches of the mandibular nerve. The condensation admittedly becomes gradually much less sharply deﬁned but is still

distinguishable from the surrounding tissue. Finally, some distance beyond the limit of bone-formation, the lateral pterygoid muscle can be seen running into and outlining the terminal part of the mesodermal condensation. This is the first indication

Cite this page: Hill, M.A. (2024, April 26) Embryology Paper - The Development of the Human Mandibular Joint. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_The_Development_of_the_Human_Mandibular_Joint

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