gill slit

anatomy

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June 29, 2026

Quick Summary

A gill slit is an opening or cleft between the gill arches in vertebrates that breathe with gills. Water passes through these slits to bathe the gills, allowing for gas exchange between the water and the blood. In fish, water enters the mouth and flows over gill filaments supported by gill arches. Oxygen diffuses into the blood, and carbon dioxide is released into the water. This process is made more efficient by countercurrent exchange, where blood and water flow in opposite directions, maximizing oxygen absorption. Rudimentary gill slits are also found in the neck region of air-breathing vertebrate embryos.12

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chordate
General features
…through the mouth, using the gill slits as a kind of filter. The feeding apparatus in cephalochordates is similar. They have a well-developed musculature and can swim rapidly by undulating the body. Cephalochordates usually live partially buried in marine sand and gravel.
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…through the mouth, using the gill slits as a kind of filter. The feeding apparatus in cephalochordates is similar. They have a well-developed musculature and can swim rapidly by undulating the body. Cephalochordates usually live partially buried in marine sand and gravel.
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evolution
Embryonic development and vestiges
…and other nonaquatic vertebrates exhibit gill slits even though they never breathe through gills. These slits are found in the embryos of all vertebrates because they share as common ancestors the fish in which these structures first evolved. Human embryos also exhibit by the fourth week of development a well-defined…
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…and other nonaquatic vertebrates exhibit gill slits even though they never breathe through gills. These slits are found in the embryos of all vertebrates because they share as common ancestors the fish in which these structures first evolved. Human embryos also exhibit by the fourth week of development a well-defined…
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