چکیده
A rare muscle named Levator Submandibuli (LS) or Banjo muscle (after the author) is present in few persons. It is situated in the submandibular region superficial to the mylohyoid muscle. It consists of two triangular right and left halves whose fibres originate by interdigitating with each other from a median intermuscular septum attached above to the mandible, below to the
hyoid bone, parallel and continuous with the intermuscular septum of the mylohyoid muscle. Levator Submandibuli muscle fibres of each side insert into a tendon which is continuous at each side with the central tendon of the digastric muscles. Contraction of the muscle would elevate and support the submandibular region particularly during swallowing and during any activity which increasesthe oro-pharyngeal pressure such as blowing a trumpet. The muscle is not an accessory/anomaly of the digastric nor of mylohyoid muscle. Its anatomy indicated that, it is a separate muscle innervated by a branch from the mylohyoid nerve. It is suggested that, there is predilection for the appearance of a separate muscle in the submandiblar region distinct from mylohyoid and digastric muscles. It is further suggested that during myogenesis when the migrating myogenic (myoblasts) cells destined to form levator submandibuli are halted at the proximity of the site of formation of anterior belly of the digastric muscle, an anomalous/accessory muscle of the digastric is formed. But when the myoblasts reach their predestined position in the submandibular region, an independent muscle, levator submandibuli (Banjo muscle) is formed. The muscle has an incidence of about 0.3% in Caucasian and 0.4% in black Africans.
Keywords: Levator Submandibuli, Banjo muscle, submandibular region, digastric, mylohyoid, intermuscular septum
Résumé
Un muscle rare nomme Levator Submandibu1i ou bien 1e muscle Banjo (apres le nom de l’auteur) se trouve chez peu de gens. Il se situe dans triangle sous-mental, a la surface du muscle mylohyiod. Il consiste en 2 moitiestriangulaires droite et gauche dont les fibres prennent sources par interdigiter l’un avec l’autre a partir d’un septum median intermusculaire attaché par 1e dessus au mandible et par le dessous a l’os hyoid, parallel et continu avec le septum intermusculaire du muscle mylohyoid. Les fibers du muscle de chaque cote s’inserrent dans le tendon qui est f. continu avec le tendon central du muscle digastric du leur cote. La contractiondu muscle leverait et soutiendrait la region submandibulaire surtout lors d’un avalement. et pendant toute activite susceptible d’augmenter la pression oro-pharyngeale. Le muscle n’est pas un accessoire/anomalie du digastric anterieur. Il est ennerve par un petit. nerf provenant du nerf mylohyoid. Notre hypothese a suggere qu’il y a une predilection pour l’apparition d’un muscle distinct dans le triangle sous-mental, different du digastric anterieur. Il est en plus suggere que pendant la morphogenese lorsque les myoblastes migrants destines a former le levator submandibuli sont arretes aux environs du site de formation du ventral anterieur du muscle digastric, un muscle anomaleux/accessoire du digastric est forme. Mais quand les myoblastes atteignent leur position predestinee dans le triangle sous-mental, un nouveau muscle independant, le muscle Banjo ou bien le levator submandibuli est forme. L’incidence de ce muscle est inconnue. II est. probablement moins de 0.3 % chez les Caucassiens aussi 0.4% que chez les noir Africains.
Correspondence: Dr. Adesegun O. Banjo, 21, Talbot Road, Ijebu Ode, Ogun State, Nigeria.
مراجع
Alberts B., Bray D., Lewis J., Raff M., Roberts K. and Watson J.D . Molecular Biology of the Cell. 2nd and 4th Edn.Garland Publishing Inc. N.Y.1989 and 2002, Pg 1209 and 1219.
Bergman R, Thompson S, Afifi A. and SaadehF. Compendium of Human Anatomic Variation. Text, Atlas and World literature. Urban and Schwarzenberg. Baltimore - Munich 1988.
Blau, HM. et al. Plasticity of the differentiated state. Science. 1985. 230 : 758 - 766.
Bloom, D. and Fawcett, DW. A Textbook of Histology, 11th ed., Philadelphia. Saunders. 1986; 136- 187.
Bronner-Fraser, M. An antibody to a receptor for fibronectin and laminin perturbs cranial neural crest development in vivo. Dev. BioI. 1986; 117: 528 - 536.
Bryant S.V., Gardiner D.M. and Muneoka K., Limb development and regeneration. Am. Zool. 1987; 27: 675 - 696.
Cahn RD and Cahn MB. Heritability of Cellular differentiation; clonal growth and expression of differentiation in retinal pigment cell in vitro. Proc. Natl. Acad. Sci. USA.1966; 55: 106 - 114.
Chabot B., Stephenson DA., Chapman VM., Besmer P. and Bernstein A. The proto-oncogene c-kit encoding a transmembrane tyrosine kinase receptor maps to the mouse W locus. Nature 1988; 335: 88- 89.
Chevallier A. Role of the somitic mesoderm in the development of the thorax in bird embryos. II Origin of thorax and appendicular musculature J. Embryol. Exp. Morphol. 1979; 49: 73 - 88.
Clegg CH., Linkhart TA., Olwin BB. and Hauschka SD. Growth factor control of skeletal muscle differentiation: commitment to terminal differentiation occurs in G1 phase and is repressed by fibroblast growth factor. J. Cell BioI. 1987; 105: 949 - 956.
Coon HG. Clonal stability and phenotypic expression of chick cartilage cells in vitro. Proc. Natl. Acad. Sci. USA. 1966; 55: 66 - 73.
Davis RL, Weintraub H. and Lassar AB. Expression of a single transfectedc (DNA converts fibroblasts to myoblasts. Cell 1987; 51: 987 - 1000.
Delvin RB and Emerson CP. Coordinate regulation of contractile protein synthesis during myoblast differentiation. Cell 1978; 13: 599 - 611.
Dufour S, Duband JL and Konblihtt AR, Thiery JP. The role of fibronectins in embryonic cell migrations. Trends Genet.1988; 4: 198 - 203.
Gabbiani G, Rungger-Brandle E. The fibroblast. In Tissue repair and regeneration (L.E. Glynn, ed),. Handbook of inflamation, Vol.3. Amsterdam: Elsevier. 1981; pp 1-50.
Itoh Y. and Eguchi G. In vitro analysis of cellular metaplasia from pigmented epithelial cells to lens phenotypes: a unique model for studying cellular and molecular mechanisms of “trans- differentiation” Dev. BioI. 1986; 115: 353 – 362
Kieny M. and Chevalier A. Autonomy of tendon development in the embryonic chick wing.J. Embryol. Exp. Morphol. 1979; 49: 153 - 165.
Konigsberg IR. Diffusion-mediated control of myoblast fusion. Dev. BioI.1971; 26: 133 - 152.
Larsson, SG and Lufkin, RB. Anomalies of digastric muscles: Computer tomography and magnetic resonance imaging demonstration. Journal of Computer Assisted Tomography 1987; 11(3): 422-425.
Le Douarin N. The Neural Crest cambridge, UK: Cambridge University Press. 1982.
MacAlister, J. Cited in: Quain’s Elements of Anatomy Vol. 1, 9th edn. Longmans, Green and Co. London. 1882.
Mackie EJ. et al. The distribution of tenascin coincides with pathways of neural crest cell migration. Development 1988; 102: 237 - 250.
Martin P. and Lewis J. Normal development of the skeleton in the chick limb buds devoid of dorsal ectoderm. Dev. BioI. 1986; 118: 233 - 246.
Menko AS and Boettieger D. Occupation of the extracellular matrix receptor, intergrin, is a control point for myogenic differentiation: Cell 1987; 51: 51 - 57.
Michna H. Anatomical Anomaly of human Digastric muscles. Acta Anatomica. 1989; 134: 263 - 264.
Newgreen DF and Erickson CA. The Migration of Neural Crest Cells. Int. Rev. Cytol. 1989; 103: 89 -145.
Pinney, DF., Pearson-white, S.H.; Konieczny, S.F.; Lantham, K.E. and Emerson, C.P. Myogenic lineage determination and differentiation: evidence for a regulatory gene pathway. Cell 1988; 53:781-793.
Spemann H. New Haven: Yale University Press 1938; 260 - 296. Reprinted, New York: Garland, Embryonic. 1988.
Testut L. Les anomalies musculaire chez l’homme expliquees par l’anatomie comparee: leur importance en anthropogie. Masson Paris.1884.
Traini M. Bilateral accessory digastric muscles. Anatomica Clinica. 1983; 5: 199 - 200.
Waern A. Contribution a la connaissance des muscles interposes entre les ventres anterieurs des digastriques chez l’homme et presentation d’un project de denomination pour ceux-ci. Archives D’ Anatomie D’Histologie & embrryologie. 1935; 20: 325 - 327.
Wessells NK. Tissue Interactions and development. Menlo Park, CA. Benjamin-Cummings. 1977.
Weston J. Phenotypic diversification in neural crest-derived cells: the time and stability of commitment during early development. Curro Top. BioI. 1986; 20: 195 - 210.
Wylie CC, Stott D, Donovan PJ. Primordial germ cell migration. In Developmental Biology: A Comprehensive Synthesis, Vol. 2: The Cellular Basis of Morphogenesis. (L. W.Browder, ed.) New York, Plenum. 1986; 433 – 448.
Yaffe D. Retention of differentiation potentialities during prolonged cultivation of myogenic cells. Proc. Natl. Acad. Sci. U.S.A. 1968; 61: 477 - 483.
Research Grant: From James Henry Memorial Hospital and Research Centre. Ilesa, Nigeria.