Firm proteinaceous rods also may support the branchial apparatus.
Discussed in this article as part of the axial skeleton is a third subdivision, the visceral, comprising the lower jaw, some elements of the upper jaw, and the branchial arches, including the hyoid bone.
The individual gill septa are lost, and there is a great modification of the posterior branchial muscles, with many of the elements found in sharks (e.g., levators and adductors) becoming reduced or absent.
The restructuring of the posterior jaw in mammals leads to the further replacement of this new muscle by the digastric, which is a compound muscle made up of parts of the constrictors of the first and second branchial arches.
As the water is driven from the branchial sac into the atrial cavity, a sheet of mucus, secreted by the endostyle, traps a variety of very small organisms suspended in the water current, especially small plantlike protists (phytoplankton).
A solitary tunicate has two major openings, or siphons, on the surface away from the area of attachment: a branchial aperture, through which water enters the body, and an atrial aperture, through which water, wastes, and gametes leave.
Rhipidistians probably had two respiratory apparatuses, a branchial (gill) system for aquatic respiration and a pulmonary (lung) system for air breathing.
There is a series of small valves near the exit from the heart, and several small contractile organs attached to the branchial arteries apparently fulfill the necessary function of assisting the propulsion of blood.
It then passes through a series of branchial arteries in the gills, where gas exchange takes place, and the oxygenated blood flows to the body, much of it returning to its origin via a dorsal aorta.
Land crabs have larger and more vascularized branchial chambers than do aquatic crabs.
Several zooids may share a single, common cloacal aperture through which water exits, but each zooid has its own branchial aperture through which water enters.
