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Of the One-Humped Camel

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Of the One-Humped Camel J. Anat. (1970), 106, 2, pp. 341-348 341 With 3 figures Printed in Great Britain The course and branches of the facial nerve of the one-humped camel I. ARNAUTOVIC, M. E. ABU SINEINA AND M. STANIC Faculty of Veterinary Science, University of Khartoum (Received 14 February 1969) The course and ramification of the facial nerve of the camel have not previously been clearly established, and the brief references that occur in the literature are of a rather general kind. Thus Lesbre (1906) stated that the cranial nerves of the camel were similar to those of ruminants, and Leese (1927) concluded that there were no significant differences between the course of the facial nerve of the camel and that of other ruminants. Droandi (1936) gave a more detailed account of the facial nerve which he described as ramifying on the external surface of the head. Tayeb (1958), who studied the cranial nerves of the camel, did not give the full account of the facial nerve. MATERIAL AND METHODS During the period July 1966 to December 1967 the heads of fifteen camels slaugh- tered at Tamboul Slaughterhouse, south-east of Khartoum, were collected for dis- section at the Faculty of Veterinary Science, Shambat. The heads belonged to normal healthy animals, seven males and eight females, varying in age from 4 to 10 years. Both sides of each head were used in the study. The heads were removed, with their skin intact, from the carcasses at the level of the third cervical vertebra. Some of the specimens were dissected immediately after collection, others were injected with 10 % formalin and studied later. OBSERVATIONS The facial nerve, which originates from the lateral part of the trapezoid body immediately behind the pons, enters the facial canal through the porus acusticus internus. After it emerges through the stylomastoid foramen it assumes a ventral and somewhat oral direction for about 2 cm (Fig. 2 [1]), after which it divides into two main branches; a large dorsal branch (n. buccalis dorsalis, Fig. 2 [2]) and a smaller ventral branch (n. buccalis ventralis, Fig. 2 [3]). After it emerges through the stylomastoid foramen the facial nerve gives off four branches before if bifurcates. These are as follows: (1) At the level of the stylomastoid foramen the facial nerve gives off a very small branch, the posterior auricular nerve (Fig. 2 [4]). This originates from its caudal border and for 2-3 cm assumes a caudo-dorsal direction, 3-5 mm posterior to and parallel with the caudal margin of the auricle. Then it ramifies posteriorly and dorsally in the muscles and skin of the ear. This branch sometimes separates from the facial nerve before it emerges through the stylomastoid foramen. 342 I. ARNAUTOVIC, M. E. ABU SINEINA AND M. STANI_6 (2) From the dorsal border and approximately 1 cm after emerging through the stylomastoid foramen, it gives off an internal auricular nerve which, after a short while, enters the interior ofthe auricle where it ramifies (Fig. 2 [5]). Before reaching the interior of the auricle the internal auricular nerve often gives off a very small branch which supplies the oro-dorsal part of the parotid gland. Occasionally the internal auricular nerve leaves the facial nerve before the latter emerges from the stylo- mastoid foramen. In three cases both the internal auricular and the posterior auri- cular nerves left the facial nerve through a common trunk. Fig. 1. Muscles and superficial nerves of head of camel (lateral view). a, masseter; b, buccinator; c, zygomaticus; d, depressor palpebralis inferioris; e, lacrimalis; f, levator communis naso- labialis superioris; g, risorius. 1, ventral branch of facial nerve; 2 & 3, dorsal branch of facial nerve; the auriculo-palpebral nerve lies immediately in front of the auricle. (3) From its ventral border about 1 5 cm after it leaves the stylomastoid foramen, the facial nerve gives a branch which runs ventrally to, and ramifies in, the deep layers of the middle part of the parotid gland (Fig. 2 [6]). (4) From its ventral margin, the facial nerve gives off a small branch, which more or less corresponds to the digastric branch in the horse, about 17 cm after emerging through the stylomastoid foramen (Fig. 2 [7]). The branch runs in a caudo-ventral direction under the dorsal part of the parotid gland; it then pierces the parotid gland about a third of the distance from its lower border and lies on its surface. Here it is covered by the caudal part of the risorius muscle. * It continues in the same direction for about 2-3 cm after which it ramifies in the risorius muscle. * Terminology after Tayeb (1951) and Droandi (1936). r, ' 1 nerve of camel 343 The facial nerve divides into two main branches about 2 cm ventral to the lower margin of the external acoustic process. The smaller of these, the ventral buccal nerve, runs ventrally and passes under the parotid gland. The nerve then pierces the medial surface of the parotid gland at its centre and continues in the same direction within the parenchymatous tissue. Finally, it leaves the gland at the level of the angle of the mandible close to the caudal margin of the vertical part of the ramus. From this point, the nerve takes an oro-ventral direction, passes over the lateral surface of the masseter muscle and is covered by the caudal part of the risorius muscle and the Fig. 2. Nerves and muscles of head of camel (lateral view). 1, Facial nerve; 2, dorsal branch of facial nerve; 3, ventral branch of facial nerve; 4, posterior auricular nerve; 5, internal auricular nerve; 6, branch to parotid gland; 7, branch of risorius muscle, 8, branches to parotid gland; 9, communicating branches of the superficial temporal and dorsal buccal nerves; 10, auriculo- palpebral nerve; lOa, auricular branch; lOb, temporal branch; 10c, zygomatic branch; 11, branch to risorius muscle; 12, branches to risorius, buccinator and zygomatic muscles; 13, communicating branch from buccinator nerve; 14, branch to the angle of the mouth; 15, infraorbital nerve. skin. It continues in an oro-ventral direction parallel to, and at a distance of 3-4 cm above, the ventral margin of the horizontal part of the ramus. It is covered by the risorius muscle until the level of the oral margin of the masseter muscle is reached. Thereafter, it runs in the same direction along the ventral border of the buccinator and underneath the risorius, parallel to and at a distance of 2-3 cm above the ventral margin of the horizontal part of the ramus. Just in front of the mental foramen (Fig. 3 [3 a]), it joins the mental branch of the mandibular alveolar nerve and forms an extensive plexus which sends branches to the lower lip and the chin. 344 I. ARNAUTOVIC, M. E. ABU SINEINA AND M. STANIt From the point at which the ventral buccal nerve separates from the main trunk until its communication with the mental branches it gives off the following branches: (1) While passing underneath and within the parotid gland it supplies the latter with three to five small branches which leave the nerve at variable distances (Fig. 2 [8]). (2) It gives off small branches to the occipito-mandibularis, risorius and buccinator muscles, as well as to the buccal glands. (3) It receives two communicating branches, a larger one about 5-6 cm in front of the angle of the mandible (Fig. 2 [9]) and a smaller one just behind the oral border of the masseter muscle (Fig. 2 [9]). These branches originate from a communication between the~~~~~~~~~~~~~~~~~~~~~~~ventral branch of the superficial 3temporal and dorsal buccal nerves. Fig. 3. Diagram showing the nerves of head of camel. 1, Facial nerve; 2, dorsal branch of facial nerve; 3, ventral branch of facial nerve; 3a, mental branch; 4, posterior auricular nerve; 5, internal auricular nerve; 6, branch to parotid gland; 7, branch to risorius muscle; 8, branches to parotid gland; 9, communicating branches of the superficial temporal and dorsal buccal nerves; 9 a, communicating branch of the alveolar mandibular nerve; 10, auriculo-palpebral nerve; 10a, auricular branch; 0b, temporal branch; 10c, zygomatic branch; 11, branch to risorius muscle; 12, branches to risorius, buccinator and zygomaticus muscles; 13, communicating branch from buccinator nerve; 14, branch to the angle of the mouth; 15, infraorbital nerve. (4) About 5-6 cm from the midpoint between the angle of the mandible and the mental foramen, the ventral buccal nerve joins a nerve which is about 2-3 times larger than itself. This nerve emerges from a large foramen situated about 2-3 cm in front of the mid-point between the angle of the mandible and the mental foramen (Fig. 3 [2]). This foramen exists only in the camel. Droandi (1936) called it the anterior opening of the canalis dentalis inferioris. The nerve which emerges from this foramen was traced inside the horizontal part of the ramus and found to be a branch of the Facial nerve of camel 345 mandibular alveolar nerve. When it emerges through the foramen, it takes an oro- ventral direction 2-2 5 cm above and runs parallel to the ventral border of the hori- zontal part of the ramus until it joins the ventral buccal nerve. After joining this nerve, the ventral buccal nerve becomes more than twice the size of the trunk of the facial nerve after it emerges through the stylomastoid foramen. In its further course the ventral buccal nerve proceeds oro-ventrally and is partially covered by the ventral part of the buccinator muscle (Fig. 1 [1]). It gives off a number of branches to the buccinator muscle as well as communicating filaments to the buccinator nerve.
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