Anat Cell Biol.  2021 Jun;54(2):202-211. 10.5115/acb.20.301.

Comparative study of the digastric and the stylohyoid muscles between wild boars (Sus scrofa scrofa) and domestic swine (Sus scrofa domesticus): revisiting the gross anatomy

• Magalhães HIR
• Barcelos JB
• Romão FB
• Borges TRJ
• Carvalho-Barros RAd
• Miglino MA
• e Silva FOC
• Ribeiro LdA

• KMID: 2516904
• DOI: http://doi.org/10.5115/acb.20.301

Abstract

Considering Suidae Familie as a perfect and viable experimental biomedical model for research applied to human medicine, it has been sought to describe the comparative anatomy of the digastric and the stylohyoid muscles between boars and domestic swine. Heads of Sus scrofa scrofa and Sus scrofa domesticus were dissected. The digastric muscle presented only one muscle belly as anatomical component of a tendinous origin in the jugular process of the occipital bone, and muscle insertion in the midventral edge of the caudal two thirds of the body of the mandible. Thus, its function is fundamentally associated with the lowering and the retracting of the mandible which, by the way, can deliver greater muscle power at lesser energy expense. For the stylohyoid muscle, the tendinous origin was in the laterocaudal edge of the dorsal third of the stylohyoid bone. The muscle insertion - primarily, was in the lateral and caudal edges from the mid third portion up to the ventral extremity of the thyrohyoid bone, and secondarily as a laterolateral aponeurotic blade which would unite, in a bilateral manner, an insertion that was common to the sternohyoid, the geniohyoid, and the mylohyoid muscles in a median ventral region. This morphology were similar to the two specimens studied expanding the information available, which were completely unknown for the suidae until the moment.

Keyword

Comparative anatomy; Deglutition; Hyoid bone; Mastication; Suidae

Figure

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  Fig. 1 (A) Medial view of right hemihead of boar, dm and the t of the digastric muscle. Other structures: j, a, b, and angular incisure of the mandible (white arrow). Animal direction: D, V, R, and C. (B) Medial view of right hemihead of domestic swine dm and the t of the digastric muscle. Other structures: j, a, and b. Animal direction: D, V, R, and C. (C) Medial view of left hemihead of domestic swine highlighting the rb and cb bellies, and the mt of the digastric muscle. Other structures: j, a, and b. Animal direction: D, V, R, and C. a, angle of the mandible; b, body of the mandible; C, caudal; cb, caudal belly; D, dorsal; dm, highlighting the single muscle belly; j, jugular process of the occipital bone; mt, middle tendon; R, rostral; rb, rostral belly; t, tendon of origin; V, ventral.

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  Fig. 2 (A) Left ventrolateral view of boar head highlighting the common insertion, and in the form of an aponeurotic blade (white circle), of sh, sth, and mh. There is also demonstration of the tendon of origin of the stylohyoid muscle (white arrow) as from the κ. Other structures: b, t, dm, sg, oh, and j. Animal direction: D, V, R, and C. (B) Right ventrolateral view of a domestic swine head highlighting the common insertion, and in the form of an aponeurotic blade (black circle), of sh, sth, and mh. Other structures: b, t, dm, hg, oh, and j. Animal direction: D, V, R, and C. b, body of the mandible; C, caudal; D, dorsal; dm, single belly of the digastric muscle; hg, hyoglossus muscle; j, jugular process of the occipital bone; mh, mylohyoid muscles; oh, omohyoid muscle; R, rostral; sg, styloglossus muscle; sh, stylohyoid; sth, sternohyoid; t, tendon of origin of the digastric muscle; V, ventral; κ, laterocaudal edge of the dorsal third of the stylohyoid bone.

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  Fig. 3 (A) Left ventrolateral view of boar head highlighting the insertion of the sh in the lateral and caudal edges from the mid third as far as the ventral extremity of the α. There is also demonstration of the tendon of origin of the stylohyoid muscle (white arrow) as from the κ. Other structures: common insertion, and in the form of an aponeurotic blade (white circle), of sh, sth, and the mh, b, dm, oh, and sg. Animal direction: D, V, R, and C. (B) Left lateroventral view of a domestic swine head highlighting the insertion of the sh in the lateral and caudal edges from the mid third as far as the ventral extremity of the α. There is also demonstration of the tendon of origin of the stylohyoid muscle (black arrow) as from the κ. Other structures: common insertion, and in the form of an aponeurotic blade (white circle), of sh, sth, and gh, b, dm, oh, sg, bhb, chb, and ehb. Animal direction: D, V, R, and C. b, body of the mandible; bhb, basihyoid bone; C, caudal; chb, ceratohyoid bone; D, dorsal; dm, digastric muscle open with caudodorsal orientation; ehb, epihyoid bone; hg, hyoglossus muscle; j, jugular process of the occipital bone; mh, mylohyoid muscles; oh, omohyoid muscle; R, rostral; sg, styloglossus muscle; sh, stylohyoid muscle; sth, sternohyoid; t, tendon of origin of the digastric muscle; V, ventral; α, thyrohyoid bone; κ, laterocaudal edge of the dorsal third of the stylohyoid bone.

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  Fig. 4 (A) Ventral view of a domestic swine head highlighting the common insertion with short and aponeurotic morphology, stretching with laterolateral orientation to be a point of common insertion to muscles positioned in a counterlateral manner, bilaterally uniting the same in a medioventral fashion (white arrow). Other structures: sh’, sh’’, mh, and gh. Animal direction: LL, RL, R, and C. (B) Ventral view of the hyoid bone of a domestic swine highlighting the common insertion with short and aponeurotic morphology of the stylohyoid, the sternohyoid, the geniohyoid, and the mylohyoid muscles (white arrow). Other structures: bhb, chb, and α. Animal direction: LL, RL, R, and C. (C) Ventral view of the hyoid bone of a domestic swine upon removal of the aponeurotic blade of insertion of the stylohyoid, the sternohyoid, the geniohyoid, and the mylohyoid muscles, highlighting the point of attachment of the same (*). Other structures: bhb, chb, and α. Animal direction: LL, RL, R, and C. bhb, basihyoid bone; C, caudal; chb, ceratohyoid bone; gh, geniohyoid muscle; LL, left lateral; mh, mylohyoid muscle open with laterodorsal orientation; R, rostral; RL, right lateral; sh’, left stylohyoid muscle; sh’’, ight stylohyoid muscle; α, thyrohyoid bone.

Reference

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