Abstract
Myofibrous organization of the human inferior constrictor of the pharynx was analyzed in order to elucidate the relation between the deglutitive action of the pharyngeal muscles and the aging. The muscles were obtained from 19 adult humans (male 13, female 6) aged 30 to 87 years (average 68 years) . These materials were embedded in celloidin and stained with hematoxylin and eosin. The following results were obtained. 1) On the thickness of the muscular layer, the majority were thicker in the thyreopharyngeal part than in the cricopharyngeal part in males. This tendency was remarkable in aged muscle in males and in all ages in females. 2) On the number of the muscle fibers per sq. mm., the thyreopharyngeal part had more muscle fibers and the cricopharyngeal part had a little difference than the suprahyoid muscles. In the thyreopharyngeal part, the number tended to increase in aged muscles in both sexes. 3) On the muscle fiber size, the thyreopharyngeal part was smaller than the stylohyoid muscle which was the smallest in the suprahyoid muscles and the cricopharyngeal part was almost equal. The fiber size decreased over 70 years old and this tendency was remarkable in the thyreopharyngeal part. 4) On the distribution pattern of the muscle fiber size, the left shifted pattern which had high peak and the normal distribution pattern in the thyreopharyngeal part and the double peak pattern which had the low peak in the cricopharyngeal part were more predominant, respectively. 5) In both parts, the positive correlations between the fiber size and the number per sq. mm. were recognized. These muscles were differentiated into three groups with aging ; namely, the muscles which had the large fiber size comparatively contained a few fibers per sq. mm. and the muscles which had the small size contained many or a few fibers. 6) The density of the muscle fibers was equal to the most low muscle in the hyoid muscles in both sexes. In the cricopharyngeal part, the density was predominant to the thyreopharyngeal part and tended to decrease with aging. The density in some aged muscles was predominant in the thyreopharyngeal part. 7) On the pathological observation, the grouping muscular atrophy of the muscle fibers was found in half case in the thyreopharyngeal part and the scattered muscular atrophy and the appearance of the fatty cells were found in the greater number of muscles in the cricopharyngeal part. The increase of the connective tissue was found in majority of muscles in both parts and was more or stronger in the cricopharyngeal part. In the thyreopharyngeal part, the perivascular cell infiltration was observed in a third.
