Pacinian corpuscle-like structure in the digital tendon sheath and nail bed: a study using late-stage human fetuses

Abstract

stage, characterized by lamellae or an outer bulb of perineural origin and observed in fetuses of CRL ≥120 mm; and (3) a vascular stage, characterized by the gradual incorporation of surrounding blood vessels into the lamellae and observed in fetuses of CRL ≥200 mm [1]. To verify these observations, we studied serial transverse sections of the distal and middle segments of the thumb and all fingers obtained from 12 hands of 12 late-stage fetuses of gestational age 20-34 weeks (CRL,. We found that the corpuscles in late-stage fetuses can be classified into two types: (1) thin, small, immature corpuscles with tightly packed lamellae, of thickness 30-70 µm and length 0.3-0.7 mm; and (2) thick, long, mature corpuscles with loosely packed lamellae, of thickness 80-150 µm and length 0.5-2.0 mm and morphology similar to that in IntroductionThree stages in the development of digital Pacinian corpuscles in the human fetus have been described: (1) a primordial stage, consisting of one type of cell distributed along "stag-horn-like" nerve twigs and observed in fetuses of crown-rump length (CRL) 70-90 mm; (2) Abstract: Pacinian corpuscle-like structures were identified in the digital tendon sheaths and nail beds of hands obtained from eight of 12 human fetuses of gestational age 20-34 weeks (crown-rump length, 150-290 mm). The aberrant corpuscles were present in tight fibrous tissue connecting the flexor tendon sheath to the dorsal aponeurosis (138 corpuscles in the thumbs and all fingers of eight fetuses); loose fibrous tissue inside the sheath on the dorsal side of the tendon (37 corpuscles in the thumbs and all fingers of four fetuses); and the nail bed (10 clusters in the thumbs and second fingers of four smaller fetuses). The aberrant corpuscles in the tendon sheath were classified into two types: thin and short, with tightly packed lamellae, of diameter 20-40 µm and length 20-200 µm; and thick and long, with loosely packed lamellae, of diameter 70-150 µm and length 0.5-1.5 mm. The small corpuscles tended to form clusters, each containing 5-10 structures. Their similarity indicated that the tight and loose lamellae in these two types of corpuscles corresponded to typical immature and mature corpuscles, respectively, usually distributed along the palmar digital nerve. However, mature, large corpuscles were absent from the nail bed, and most aberrant corpuscles were smaller than typical corpuscles along the nerve. The aberrant corpuscles were apparently incorporated into the tendon sheath or nail bed during fetal vascular development, but they appeared to degenerate after birth due to mechanical stress from the tendon or nail.