Comparative Anatomy of the Buccinator Muscle in Cat ( Felis domestica )

1. Comparative Anatomy of the Buccinator Muscle in Cat(Felis domestica) Tomo, Soichiro, Tomo, Ikuko, Nakajmia, Koh, Townsend, Grant C., & Hirata, Kazuaki, “Comparative Anatomy of the Buccinator Muscle in Cat (Felis domestica).” The Anatomical Record, Volume 267, Issue 1, Pages 78 – 86. Published Online: 25 April 2002

2. Taxonomy • Kingdom: Animalia • Phylum: Chordata • Class: Mammalia • Order: Carnivora • Family: Felidae • Genus: Felis • Species: domestica

3. Background Information • WHAT IS A BUCCINATOR MUSCLE? • It is a muscle located underneath the orbicularis oris muscle. It arises from the lower buccal membrane and from the molar region of the alveolar border of the mandible. This muscle may aid in mastication which includes suckling, and expelling air forcibly. • Cats have often been used for experimental research because their uniform shape make them more suitable for physiological experimentation. • There are only a few reported studies on the buccinator muscles of cats.

4. The buccal part of the buccinator muscle in the cat has been discovered by a Japanese/Australian research team at The University of Adelaide's Dental School. • These researchers found a technique in which they traced nerves into muscles and classified musculature according to the innervation (to supply with nerves).

5. *- Represents the Buccinator Muscle

6. Hypothesis • The goals of this study were: • (1) to identify the buccinator muscles in the cat and to report on its anatomical features in detail. • (2) to clarify the homology of the buccinator in mammals.

7. Methods and Materials • Dissections of the facial muscle were carried out in 12 specimens of adult cats (6 males and 6 females). • They were fixed with 10% formalin, and then transferred to 70% ethanol. • The upper parts of their cervical columns were removed and their heads were cut in half in a sagittal plane. • In each dissected specimen, the skin was removed following the underlying superficial layer of the facial muscles.

8. The species were immersed in water for further dissection, and the facial muscles were observed. • Their innervations, arteries, and veins were traced under a binocular microscope.

9. Figure: Superficial nerves of the face in cat: lateral view, left side. The platysma and orbicularis oris have been reflected. (a) The dorsal ramus of the facial nerve divided into a temporal branch and a zygomatic branch. The buccal nerve ran laterally to the buccinator muscle. (b)The auriculotemporal nerve of the mandibular nerve anastomosed with the ventral branch ramus of the facial nerve (c) under the eyelid. A branch from the ventral ramus of the facial nerve and the buccal nerve of the mandibular nerve anastomosed and innervated the buccinator muscle in most of the cases. BC, buccal nerve; OO, orbicularis oris; MG, molar gland; MS, masseter; PD, parotid grand; PL, platysma.

10. Results and Discussion • The buccinator was identified underneath the orbicularis oris muscle and it was located deeper than the other facial muscles. • The muscle was determined to be approximately 3mm wide at its origin and 4mm wide at its insertion. • It was 11mm in length from origin to insertion. • Males > Females (cats). • The muscle was determined to be smaller than the buccinator muscles of dogs and humans. • Classification of the buccinator muscle is not consistent in different mammals.

11. The buccinator muscle in cats is different from the buccinator muscle of humans because in humans the muscle arises from the mandible and the maxilla. • Similarities of the buccinator muscle of cats and humans were; • 1) innervated by facial nerve • 2) supports buccal muscle • 3) inserts into the modiolus (auditory nerve fiber) • 4) its bundles run antero-posteriorly • 5) posterior part of the muscle is located medially to the masseter muscle • 6) parotid duct, facial nerve, artery, and vein run lateral to the muscle. • 7) located deeper than other facial muscles • 8) buccal nerve runs on its surface.

12. The findings of the structural similarity of the buccinator muscle in cats and humans opens up new opportunities for future experimental work on aspects of masticatory function. • This anatomy has provided insights into the homology of the buccinator muscle but further studies of the facial musculature in other mammals are needed to confirm whether the findings are applicable.

13. Comparative classification of the buccinator and orbicularis oris muscles   a. Muscles run longitudinally like the buccinator muscle in humans.  b. Muscles originate medial to the masseter muscles.

14. Figure: Innervation of the buccinator muscle in cat: lateral view, left side. A branch of the facial nerve innervates the buccinator muscle (*). The buccal nerve (>) communicates with a branch of the facial nerve. The buccal nerve runs on the surface of the buccinator muscle. FN, facial nerve; OO, orbicularis oris; PD, parotid duct; MS, masseter muscle.

15. The Main Points of the Study • The buccinator muscle in cats contrasts with humans because in humans the muscle arises from the mandible and maxilla. • This muscles in the cats displays the following similarities to human. • 1) innervated by the facial nerve • 2) supports the buccal muscle • 3) inserts into the modiolus (auditory nerve fiber) • 4) its bundles run antero-posteriorly • 5) posterior part of the muscle is located medially to the masseter muscle • 6) parotid duct, facial nerve, artery, and vein run lateral to the muscle. • 7) located deeper than other facial muscles • 8) buccal nerve runs on its surface.

16. ANY QUESTIONS?