Authors
Satoru Muro, Toshiro Tanioka, Niina Hirano, Tong Liu, Akimoto Nimura, Yusuke Kinugasa, Keiichi Akita
Published in
Anatomical science international. Jun 18, 2026. Epub Jun 18, 2026.
Abstract
The umbilicus is a distinct anatomical feature of the anterior abdominal wall, characterized by persistent postnatal depression. Despite its clinical and surgical relevance, the histological and spatial structures underlying the umbilical concavity remain unclear. Herein, we investigated the fibrous connective tissue underlying the umbilical concavity. Five formalin-fixed cadaveric specimens (mean age: 77.4 years) were used. Two were used for macroscopic dissection, two for histological examination, and one for quasi-continuous serial sectioning with three-dimensional reconstruction. Macroscopic dissection revealed a vertically cylindrical fibrous structure extending from the umbilical fossa to the anterior rectus sheath. Histological analysis confirmed that this structure enclosed a small fat compartment distinct from subcutaneous fat, representing an extraperitoneal fat protrusion in contact with the underside of the umbilical skin. Serial sections and three-dimensional reconstruction identified a tunnel-like fibrous structure, termed "umbilical sheath," enveloping the protruded fat and bridging the umbilical ring and dermis. This sheath connected the invaginated skin to the linea alba and rectus sheath. We identified a previously undescribed fibrous structure, the umbilical sheath, enclosing a localized protrusion of extraperitoneal fat, maintaining umbilical concavity. Recognition of this structure may guide optimal port placement and promote abdominal wall closure techniques that preserve anatomical support, potentially reducing incisional hernia risk.
PMID:
42313266
Bibliographic data and abstract were imported from PubMed on 18 Jun 2026.
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