Gill membrane

The gill membrane is a hard cartilaginous or bony plate that connects the head and neck regions. The presence and size of this plate depends on the type of fish, the degree of their development and lifestyle. Sometimes it is absent in a number of underwater inhabitants as a result of phylogenetic changes in embryonic evolutionary processes. On the gill membrane of higher vertebrates there is a gill opening through which gas exchange with the environment occurs. The size of the gill opening depends on the density of the substance that is extracted