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Ahead of Print
ORIGINAL ARTICLES
Published online: 2020-09-02
Submitted: 2020-07-09
Accepted: 2020-08-12
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Development and growth of the foot lumbricalis muscle: a histological study using human fetuses

Z.-W. Jin, S. Hayashi, K. H. Cho, G. Murakami, J. Wilting, J. F. Rodríguez-Vázquez
DOI: 10.5603/FM.a2020.0108
·
Pubmed: 32896871

open access

Ahead of Print
ORIGINAL ARTICLES
Published online: 2020-09-02
Submitted: 2020-07-09
Accepted: 2020-08-12

Abstract

Our group has shown early development of the hand lumbricalis and hypothesized that, at midterm, the lumbricalis (LU) bundles flexor tendons to provide a configuration of “one tendon per one finger” (Folia Morphologica 2012; 71:154). However, the study concentrated on the hand and contained no sections of near-term fetuses. The present examination of paraffin-embedded tangential sections along the planta from 25 embryos and fetuses at 6-40 weeks (15-320 mm crown-rump length or CRL) demonstrated that, at 8 weeks, the initial foot LU appeared in the proximal side of the common tendinous plate of all five deep tendons. After midterm, a drastic three phase change occurred at the muscle origin: 1) the LU originated from each of the flexor digitorum longus tendon (FDLT), but abundant tenocyte candidates separated the muscle fiber from the tendon collagen bundle; 2) the LU arose from the covering fascia depending on increased thickness of the muscle; and 3) the LU muscle fibers intermingled with tendon collagen bundles and partly surrounded the tendon. Simultaneously, a dividing site of the FDLT migrated distally to accelerate the changes at the LU origin. These phases did not always correspond to the size of fetus after 30 weeks. Consequently, in contrast to the hand LU, the delayed changes in the foot were characterized by involvement of the LU origin into a single common part of the FDLT. The quadratus plantae muscle fibers did not attach to the LU at any phase, and connected with the fourth and fifth toe tendons.

Abstract

Our group has shown early development of the hand lumbricalis and hypothesized that, at midterm, the lumbricalis (LU) bundles flexor tendons to provide a configuration of “one tendon per one finger” (Folia Morphologica 2012; 71:154). However, the study concentrated on the hand and contained no sections of near-term fetuses. The present examination of paraffin-embedded tangential sections along the planta from 25 embryos and fetuses at 6-40 weeks (15-320 mm crown-rump length or CRL) demonstrated that, at 8 weeks, the initial foot LU appeared in the proximal side of the common tendinous plate of all five deep tendons. After midterm, a drastic three phase change occurred at the muscle origin: 1) the LU originated from each of the flexor digitorum longus tendon (FDLT), but abundant tenocyte candidates separated the muscle fiber from the tendon collagen bundle; 2) the LU arose from the covering fascia depending on increased thickness of the muscle; and 3) the LU muscle fibers intermingled with tendon collagen bundles and partly surrounded the tendon. Simultaneously, a dividing site of the FDLT migrated distally to accelerate the changes at the LU origin. These phases did not always correspond to the size of fetus after 30 weeks. Consequently, in contrast to the hand LU, the delayed changes in the foot were characterized by involvement of the LU origin into a single common part of the FDLT. The quadratus plantae muscle fibers did not attach to the LU at any phase, and connected with the fourth and fifth toe tendons.

Get Citation

Keywords

flexor digitorum longus muscle, flexor halluces longus muscle, quadratus plantae muscle

About this article
Title

Development and growth of the foot lumbricalis muscle: a histological study using human fetuses

Journal

Folia Morphologica

Issue

Ahead of Print

Published online

2020-09-02

DOI

10.5603/FM.a2020.0108

Pubmed

32896871

Keywords

flexor digitorum longus muscle
flexor halluces longus muscle
quadratus plantae muscle

Authors

Z.-W. Jin
S. Hayashi
K. H. Cho
G. Murakami
J. Wilting
J. F. Rodríguez-Vázquez

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