So what exactly are gills?


Sharks (and their relatives, the skates and rays) have 5-7 pairs of gill slits located on the sides of their heads. They breathe through these gill slits.

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There are usually between five and seven gill arches, each having one opening (the gill slit). In other fish species (and in chimaeras) the gills are covered by the operculum, a hardened protective lid over the gill. Sharks do not have an operculum.

how do gills work?

Water will pass over the gill's membranes where tiny blood vessels extract oxygen from the salty water. Carbon dioxide waste also passes from the shark's blood and out of the body through the gills!

two different ways sharks breathe...

ram ventilation

Most "modern sharks" will use this method to breathe. Whys is it called... well, what it is? Ram ventilation is called such because of these animals are "ramming" the water into their mouths by swimming fast, letting it flow out through and over the gills slits. This demand for constant oxygenated water means these sharks need to continuously swim! Most sharks can alternate between buccal pumping and ram ventilation, depending their activity!

buccal pumping

Named for the buccal (cheek) muscles that help pull the water into the mouth and through their gills. Sharks aren't the only ones who breathe this way-- skates and rays do too! This sort of breathing has been retained by those species that spend most of their time lying on the bottom of the ocean floor. As you may imagine, yes, they have strong facial muscles to help them gulp in water! 
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The tiger shark is one species that cannot switch between buccal pumping and ram ventilation.

However, some shark species cannot alternate between the two and have lost the ability to do buccal pumping.

These species (and there aren't that many of them) will die if they stop continuously swimming. The species that must continuously swim in order to breathe include the whale shark, the mako shark, the salmon shark and the famous great white shark.

​These sharks are known as obligate ram ventilators (or obligate ram breathers).