Archs oral Bid.
Vol. 12, pp.1203-1204,
PergamonPress Ltd. Printedin Cit. Britain.
MUSCLE SPINDLES IN THE LATERAL PTERYGOID MUSCLE OF MINIATURE SWINE Department
L. V. CHRISTENSEN Dentistry, The Royal Dental Denmark
the negative results of various recent investigators (COOPER,1960; FREIMANN, 1954; KARLSEN,1965) to demonstrate muscle spindles in the lateral pterygoid muscle of different mammals, spindles were demonstrated in the rabbit seventy years ago (CIPOLLONE,1897) and in human material only recently (HoNBE, 1966). CIPOLLONE (1897) found nineteen spindles in the lateral pterygoid muscle of one adult rabbit, and in a study on six human lateral pterygoid muscles HONBE(1966) found, in all cases, from one to fifteen spindles localized in the mid-portions of the specimens. In an investigation of the temporomandibular disc of miniature swine the present author found spindles located at the area of insertion of the lateral pterygoid muscle to the disc. In three miniature swine, serial sections of six temporomandibular discs, together with their attached muscle fibres, were examined. After fixation with Lillie’s neutral buffered formalin and double embedding, the specimens were stained with haematoxylin and eosin. The examined muscle areas comprised approximately l-15 mm2. Only the area in close proximity to the anterior margin of the disc was studied as the remaining muscle fibres had been lost. In the first animal the specimen of the left muscle contained four spindles, and the right none. In the second animal no spindles were seen in the right and left specimens of the lateral pterygoid muscle. The third animal showed one spindle in the right muscle specimen, and no spindles in the left. Thus, five spindles were demonstrated. The structure of the muscle spindles complied with the usual description (COOPER, 1960) i.e. a laminated connective tissue capsule surrounding the intrafusal muscle fibres (Figs. 1 and 2). The five spindles contained from four to nine intrafusal fibres, as well as bag and chain fibres. The small muscular areas examined may account for the demonstration of only five spindles. However, the finding of muscle spindles in the lateral pterygoid muscle of miniature swine, together with similar demonstrations in rabbit (CIPOLLONE, 1897), and man (HoNBE, 1966), may indicate the existence of muscle spindles in the lateral pterygoid muscle of other mammals. REFERENCES CIPOLLONE,L. T. 1897. Ricerche sull’anatomia
normale e patologica delle terminazioni
muscoli striati. Bertero, Roma. 1203
L. V. C~R~STEIWEN
COOPER,S. 1960. Muscle spindles and other muscle receptors. In: Structure and Function of Muscle (Edited by BOURNE,G. H.), pp. 381420. Academic Press, New York. FREIMANN, R. 1954. Untersuchungen iiber Zahl und Anordnung der Muskelspindeln in den Kaumuskeln des Menschen. Anat. Am. 100, 258-264.
HONI?E,G. L. J. M. 1966. Voorlopig verslag in de m. pterygoideus lateralis van de KARLSEN,K. 1965. The location of motor of muscle spindles in the jaw muscles
van een onderzoek naar de aanweizigheid van spierspoelen mens. Ned. T. Tandheelk. 73, 509-515. end piates and the distribution and histological structure of the rat. Acta odont. stand. 23, 521-547.
MUSCLE SPINDLES IN THE LATERAL
FIG. I. Muscle spindle from left lateral pterygoid muscle of miniature swine, Haematoxylin and containing seven, and possibly eight, intrafusal muscle fibres. eosin. :.: 800. FIG. 2. Muscle spindle from same muscle as Fig. I, containing four intrafusal ?’ 800. Haematoxylin and eosin. muscle fibres. Two bag fibres and two chain fibres.
A.O.B. f.p. 1204