The Evolution of the Suspensory System of the Liver: A Narrative Review
Bibliographic record
Abstract
Introduction & Objective It is known that the viscera in the body of vertebrates participate in the major vital functions of the body, however the role of visceral mobility in the proper functioning of the musculoskeletal system remains insufficiently investigated. In order to understand the potential influence of viscera on the musculoskeletal system, we need to clarify how the suspensory system of viscera has evolved within the outer body of species at different evolutionary timepoints. More importantly, we need to determine how the suspensory system of high‐density organs, which are more prone to influencing the outer body due to their mass, adapted to different types of locomotion. This narrative review was undertaken to reconstruct the theoretical evolution of the liver and related peritoneal ligaments, to investigate its adaptation to bipedal locomotion. Materials & Methods The primary focus of this review was the evolution of the peritoneal suspensory ligaments of the liver through documented species at specific evolutionary timepoints: annelid, agnathans, gnathostomes and tetrapods (amphibians to quadrupedal and bipedal mammals). Keyword searches in SCOPUS, PubMed, Google Scholar, and McGill Library databases were conducted in addition to manual searches of other relevant journals, textbooks and dissection manuals. Results Qualitative studies on the gross anatomy of the liver and the suspensory peritoneal ligaments of species at different evolutionary time points were identified. A theoretical timeline of the evolution of the suspensory system of the liver was assembled. Marine species, which rely on lateral undulation, and terrestrial quadrupeds both possess a highly mobile liver and few reliably seen ligaments of suspension. This is concluded to be due to environmental demands and consequent locomotive requirements, such as running, hopping, and leaping. The human liver, in contrast, is securely attached to the diaphragm and the body walls in the upper right quadrant of the abdominal cavity via consistently present ligaments. Conclusion This study suggests that locomotive methods led to the adaptation of ligaments that suspend high‐density organs within the body, such as the liver. Compared to other mammals, the human liver has been securely suspended to the diaphragm via peritoneal ligaments and attached to the body walls in response to two‐legged locomotion. Significance/Implication This study provides a theoretical timeline of the evolution of the suspensory system of the liver related to locomotion types. Like the musculoskeletal system, it appears that the visceral suspensory ligaments adapted to the different locomotion types found over the evolutionary timeline. Over time, as species adapted, more numerous ligaments provided further attachment. This adaptation is suggestive of potential mechanical influence between the musculoskeletal system and viscera, or vice‐versa. This raises questions regarding the implication of high‐density organs on some musculoskeletal disorders. To better understand the potential mechanical influence of the human liver on the musculoskeletal system, the suspensory system of the liver and anatomical variations needs to be clearly described.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.004 | 0.004 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".