Branchial Sources of Auditory Ossicles in Man: I. Literature

Hox-A2 protein expression in avian jaws cartilages and muscle primordia development

“…However, it has been demonstrated that Hox-A2 is expressed in the mouse palatal primordia, independently from the second pharyngeal arch, and that this gene could play a role in the muscular connections in the Xenopus [24] Concerning the mammalian middle ear ossicles, Louryan et al [1] showed that, if Hox-A2 expressed strongly in the stapes, Reichert's cartilage, and the short process of the malleus, a diffuse immunoreactivity was observed in the whole ossicular primordia, while the Meckel's cartilage of the first arch displayed no staining. This confirms the close association of stapes end short process of the malleus with the second arch but suggests a wider contribution of the second arch to the ossicular chain, already supported by morphologic and experimental previous studies [5][6][7][8][9][10][11][12][13][14]. Using in situ hybridization, Santagati et al [22] published interesting pictures in which HOXA was present in the malleus and the incus, without comment on this unexpected observation.…”

“…However, the precise contribution of the first (mandibular) and second (hyoid) arch is still discussed [1] The classical and more accepted theory implies that malleus and incus arise from the first pharyngeal arch cartilage (Meckel's cartilage), and the stapes from the second one (Reichert's cartilage). This hypothesis is validated by some morphologic evidence [2] and is consistent with several experimental data relative to Hox genes knock-out and overexpression [3,4] However, another model could be proposed, based upon morphologic features and in vitro experiments, in which the ventral parts of the malleus (including the handle) and incus derive from the second arch cartilage, with the stapes and the laterohyale [5][6][7][8][9][10][11][12][13][14] To decide between these two hypotheses, Louryan et al [1] studied the expression of Hox-A2 protein using immunohistochemistry during mouse ossicle development. HOXA2 gene is known to express in second-arch derivatives, but not in the first-arch elements.…”

Anatomical and functional aspects of ligaments between the malleus and the temporomandibular joint

“…The remaining ones extend from the posterior discal region to the tympanosquamosal fissure. The authors agree that the DML attaches to the disc or fibers of the posterosuperior part of the capsule after passing through the PTF 7,11,12,24,27,28,37,40 ; histopathology has revealed the attachment site of the ligament 42 .…”

Early development of the malleus and incus in humans

“…; Strickland et al. ), the first‐ and second‐arch components of the malleus and incus are distinguishable only at the mesenchymal stage. Hanson et al.…”