GENERAL HISTOLOGY

Detailed explanation-1: -Pharyngeal slits are in the pharynx, the region of the digestive tract just behind the mouth (Fig. 3.98). In some chordates, such as tunicates, these slits filter food from the water.

Detailed explanation-2: -Like most tunicates, lancelets are filter feeders with the pharynx situated in an atrial cavity where it functions to filter food particles from the water currents that flow through the cavity. Water is taken in through the mouth and expelled through an opening called the atriopore.

Detailed explanation-3: -Cephalochordata-Lancelets They are filter feeders and use cilia to filter food out of the water. They anchor their tails in the sand and let the water wash over their mouths. They have a nerve cord, but no brain or vertebrae.

Detailed explanation-4: -Lancelets are suspension feeders that extract small particles suspended in the water. The mouth is covered by an oral hood, the edges of which form the buccal cirri. The cephalochordate commonly is buried in the substrate and positions its mouth above the surface of the sand.

Detailed explanation-5: -Tunicates are filter feeders, feeding by drawing often hundreds of litres of water each day through the inhalant siphon. This water passes through the pharynx where small particles are filtered out before the water is expelled through the exhalent siphon. The water current is caused by beating cilia.