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The presence of gill slits (in blue) in an acorn worm (left) and a tunicate (right). Pharyngeal slits are filter-feeding organs found among deuterostomes. Pharyngeal slits are repeated openings that appear along the pharynx caudal to the mouth. With this position, they allow for the movement of water in the mouth and out the pharyngeal slits.
The true gill slits in embryonic fish develop into fish gills. However, the slits in tetrapods do not, so a more general name for the vertebral structures is pharyngeal slits. Gill slits likely originated from pharyngeal slits (as found in tunicates) that were used for filter-feeding. The term "gill slits" has also been used to refer to the ...
Lampreys and hagfish do not have gill slits as such. Instead, the gills are contained in spherical pouches, with a circular opening to the outside. Like the gill slits of higher fish, each pouch contains two gills. In some cases, the openings may be fused together, effectively forming an operculum.
Some fish species have a second set of jaws in their throat, known as pharyngeal jaws, which develop using the same genetic pathways involved in oral jaw formation. [6] During embryonic development, a series of pharyngeal arch pairs form. These project forward from the back of the embryo toward the front of the face and neck.
Amniotes do not have gills. The gill arches form as pharyngeal arches during embryogenesis, and lay the basis of essential structures such as jaws, the thyroid gland, the larynx, the columella (corresponding to the stapes in mammals) and in mammals, the malleus and incus. [2]
Gill filaments are lateral to the gill arches and have a high surface area, where they form folds inside the gill slits. Lamellae in the gill slits are thin, membrane folds that have access to blood supplies via arteries and are the site of gas exchange. When oxygen-rich water enters the gills, the blood takes up the oxygen through diffusion at ...
The filtered water is then expelled through the gill slits, while the food and mucus are swept into the esophagus by movements of the cilia that coat the endostyle. [ 3 ] [ 4 ] The endostyle in larval lampreys ( ammocoetes ) metamorphoses into the thyroid gland in adults, and is regarded as being homologous to the thyroid in all other ...
Lampreys and hagfish do not have gill slits as such. Instead, the gills are contained in spherical pouches, with a circular opening to the outside. Like the gill slits of higher fish, each pouch contains two gills. In some cases, the openings may be fused together, effectively forming an operculum.