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The mesorectum: hypothesis on its evolution
M Nano1, M Prunotto, M Ferronato
1Department of Clinical Pathophysiology, University of Turin, Turin, Italy. mario.nano@unito.it
Techniques in Coloproctology
|November 23, 2006
Summary
The mesorectum and lateral ligaments are absent in quadrupedal mammals but present in primates. These structures likely evolved with the upright posture, aiding rectal support.
Area of Science:
- Anatomy
- Evolutionary Biology
- Comparative Anatomy
Background:
- The anatomical origin and existence of mesorectal and lateral ligaments are debated.
- Understanding these structures is crucial for rectal anatomy.
Purpose of the Study:
- To investigate the anatomical origin and presence of the mesorectum and lateral ligaments.
- To compare these structures across different species, including humans and various mammals.
Main Methods:
- Performed dissections on quadrupedal mammals (dogs, pigs) and primates (Macaca apes).
- Examined histological macroslices of Macaca ape and human fetuses (182) up to the fifth month of gestation.
Main Results:
- Quadrupedal mammals lacked structures comparable to the human mesorectum or lateral ligaments.
- Primates exhibited an adipose cuff surrounding the rectum and distinct connective bands (lateral ligaments).
- Mesorectum and lateral ligaments were identifiable in human fetuses after the fifth month of gestation.
Conclusions:
- Mesorectum and lateral ligaments are absent in quadrupedal mammals but present in primates.
- Hypothesize that these structures evolved with the upright posture in primates.
- Acknowledge that alternative hypotheses for their evolution exist.
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