open access

Vol 82, No 2 (2023)
Original article
Submitted: 2022-01-05
Accepted: 2022-02-28
Published online: 2022-03-08
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Cavitation processes in a space filled with loose mesenchymal tissues: a comparison between the retrosternal space and the middle ear tympanic cavity in human fetuses

S. Hayashi1, J. H. Kim2, Z.-W. Jin3, G. Murakami4, J. F. Rodríguez-Vázquez5, S. Abe6
·
Pubmed: 35285509
·
Folia Morphol 2023;82(2):332-338.
Affiliations
  1. Department of Anatomy, Division of Basic Medicine, Tokai University School of Medicine, Isehara, Japan
  2. Department of Anatomy, Jeonbuk National University Medical School, Jeonju, Korea
  3. Department of Anatomy, Wuxi School of Medicine, Jiangnan University, Wuxi, Jiangsu, China
  4. Division of Internal Medicine, Cupid Clinic, Iwamizawa, Japan
  5. Department of Anatomy and Embryology, School of Medicine, Complutense University, Madrid, Spain
  6. Department of Anatomy, Tokyo Dental College, Tokyo, Japan

open access

Vol 82, No 2 (2023)
ORIGINAL ARTICLES
Submitted: 2022-01-05
Accepted: 2022-02-28
Published online: 2022-03-08

Abstract

Background: During the expansion of the pleural cavity in early fetuses, a thick
sheet of loose mesenchymal tissue (SLMT) appears between the lung bud and
body wall. Subsequently, the growing lung bud invades into the SLMT and the
latter becomes fragmented to disappear. To compare this with the tympanic cavity
filled with loose mesenchymal tissues, the present study aimed to demonstrate the
development, establishment, and breaking of the SLMT in the retrosternal space.
Materials and methods: Although the retrosternal tissue was almost absent
or very thin at 7 weeks, the SLMT appeared behind the manubrium sterni at
8 weeks. Accordingly, at 9–10 weeks, cavitation occurred in the SLMT to expand
the pleural cavity. Therefore, the volume of SLMT was not determined by the
adjacent structures such as the pericardium and sternum. Likewise, mesenchymal
tissues filling the middle ear disappeared after 26 weeks.
Results: There were considerable individual variations in the timing of beginning
and location of the tympanic cavitation. However, in contrast to the retrosternal
SLMT, the volume of the future tympanic cavity is determined by the adjacent
hard tissue and tympanic membrane much earlier than the cavitation. The mesenchymal
tissue carried abundant vessels in the middle ear but none or few veins
in the retrosternal SLMT.
Conclusions: The concept that the lung bud invades into the splanchnic mesoderm
to expand the pleural cavity seems oversimplified. Mechanical stresses from the
pleural cavity might induce retrosternal cavitation, while a loss in blood supply
might cause tympanic cavitation.

Abstract

Background: During the expansion of the pleural cavity in early fetuses, a thick
sheet of loose mesenchymal tissue (SLMT) appears between the lung bud and
body wall. Subsequently, the growing lung bud invades into the SLMT and the
latter becomes fragmented to disappear. To compare this with the tympanic cavity
filled with loose mesenchymal tissues, the present study aimed to demonstrate the
development, establishment, and breaking of the SLMT in the retrosternal space.
Materials and methods: Although the retrosternal tissue was almost absent
or very thin at 7 weeks, the SLMT appeared behind the manubrium sterni at
8 weeks. Accordingly, at 9–10 weeks, cavitation occurred in the SLMT to expand
the pleural cavity. Therefore, the volume of SLMT was not determined by the
adjacent structures such as the pericardium and sternum. Likewise, mesenchymal
tissues filling the middle ear disappeared after 26 weeks.
Results: There were considerable individual variations in the timing of beginning
and location of the tympanic cavitation. However, in contrast to the retrosternal
SLMT, the volume of the future tympanic cavity is determined by the adjacent
hard tissue and tympanic membrane much earlier than the cavitation. The mesenchymal
tissue carried abundant vessels in the middle ear but none or few veins
in the retrosternal SLMT.
Conclusions: The concept that the lung bud invades into the splanchnic mesoderm
to expand the pleural cavity seems oversimplified. Mechanical stresses from the
pleural cavity might induce retrosternal cavitation, while a loss in blood supply
might cause tympanic cavitation.

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Keywords

cavitation, retrosternal space, pleural cavity, middle ear, tympanic cavity, human fetuses

About this article
Title

Cavitation processes in a space filled with loose mesenchymal tissues: a comparison between the retrosternal space and the middle ear tympanic cavity in human fetuses

Journal

Folia Morphologica

Issue

Vol 82, No 2 (2023)

Article type

Original article

Pages

332-338

Published online

2022-03-08

Page views

2429

Article views/downloads

737

DOI

10.5603/FM.a2022.0026

Pubmed

35285509

Bibliographic record

Folia Morphol 2023;82(2):332-338.

Keywords

cavitation
retrosternal space
pleural cavity
middle ear
tympanic cavity
human fetuses

Authors

S. Hayashi
J. H. Kim
Z.-W. Jin
G. Murakami
J. F. Rodríguez-Vázquez
S. Abe

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