Gill cleft

Gill Arch

A gill arch is a bony structure found in fish and some other aquatic creatures. It supports the gill and aids in respiration by allowing water to flow over the gill, facilitating the exchange of oxygen and carbon dioxide.

Structure and Function

The gill arch is a curved, bony structure that supports the gill. It is typically covered in gill rakers, which are comb-like structures that filter out food particles from the water. The gill arch also supports the gill filaments, which are the primary site of gas exchange in fish.

Water enters the mouth of the fish and flows over the gill arch and through the gill filaments. Oxygen in the water diffuses into the blood in the gill filaments, while carbon dioxide diffuses out of the blood and into the water. This process is known as respiration.

Variations

While all fish have gill arches, the number and structure of these arches can vary between species. For example, sharks and rays have five to seven gill arches, while most bony fish have four. Some species of fish, such as eels, have reduced gill arches.

Evolution

The gill arch is believed to have evolved from the pharyngeal arches of early fish-like creatures. Over time, these arches became specialized for respiration, eventually developing into the gill arches seen in modern fish.

In some amphibians and reptiles, the gill arches have further evolved into other structures, such as the hyoid bone and the bones of the inner ear.

See Also

• Fish anatomy
• Respiration (physiology)
• Gill raker
• Gill filament