gill septum

anatomy

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Last updated

June 11, 2026

Quick Summary

The gill septum is a structure found in jawed fishes, specifically within the gill arches. It is a thin sheet of muscle that covers each gill slit. These muscles help to constrict the pharynx, which is part of the pumping action required for gill breathing.1

Gills, in general, are respiratory organs for aquatic animals. They are made of tissue rich in blood vessels that facilitate the exchange of oxygen and carbon dioxide between the water and the animal's blood. In fish, water flows over gill filaments, allowing oxygen to enter the blood and carbon dioxide to exit. This process is made more efficient by a countercurrent exchange mechanism, where blood and water flow in opposite directions.23

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muscle
Jawed fishes
In bony fishes the gill septum of the hyoid arch is greatly modified to become a single, movable, bony covering for the whole gill chamber—the operculum. The individual gill septa are lost, and there is a great modification of the posterior branchial muscles, with many of the elements found…
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In bony fishes the gill septum of the hyoid arch is greatly modified to become a single, movable, bony covering for the whole gill chamber—the operculum. The individual gill septa are lost, and there is a great modification of the posterior branchial muscles, with many of the elements found…
Read More