Maintenance Functions
The gastrodermis line the gastrovascular cavity. The gastrovascular cavity functions in digestion, circulation, and sometimes it serves as a hydro-static skeleton. It is able to create a transfer of respiratory gasses and metabolic wastes, also it can discharge gametes. The gastrovascular cavity has a mouth that opens to the external environment.
Some cnidarians are able to feed on small fish. These fish can be captured and paralyzed by the cnidarian's nematocysts. There are contractile cells in the cnidarian's tentacles that cause the tentacles to be drawn back. The small fish is passed through the mouth and into the gastrovascular cavity, then gastrodermal cells release mucus and enzymes that turn the food into a "soupy broth". Nutritive-muscular cells, type of gastrodermal cell, are able to phagocytize partially digested food, which are then given to vacuoles, completing digestion. Nutritive-muscular cells have circularly oriented contractile fibers that aid in moving materials in and out the gastrovascular cavity.
Besides functioning in digestion and circulation the gastrovascular cavity can be a hydro-static skeleton. A hydro-static skeleton is water or body fluids confined in a cavity of the body and against which contractile elements of the body wall act. Epitheliomuscular cells are contractile and help in movement. These cells help when a polyp is closing it's mouth to prevent water from escaping. The polyp contract longitudinal epitheliomuscular cells on one side of the polyp, this causes the polyp to bend toward that side. But, if the epitheliomuscular cells were to contract while the mouth was open the polyp would collapse and water escapes. Circular epitheliomuscular cells also constrict a part of the polyp, the mouth being closed causes water in the gastrovascular cavity to become compressed, which elongates the polyp.
Polyp are able to move through somersaulting from their base to their tentacles and then from tentacles to base. Also, the are able to move through an inchworm manner, by using their base and tentacles for attachment. Polyps are also able to slide along their substrate. Medusae are able to swim and float, and water currents and wind help them move horizontally. Circular epitheliomuscular cells create pulsations underneath the medusa, allowing it to move through water.
Large surface-area-to-volume ratios in cnidarians cause all cells to be a short distance from the body surface, and oxygen, carbon dioxide, and nitrogenous wastes exchange through diffusion.
Some cnidarians are able to feed on small fish. These fish can be captured and paralyzed by the cnidarian's nematocysts. There are contractile cells in the cnidarian's tentacles that cause the tentacles to be drawn back. The small fish is passed through the mouth and into the gastrovascular cavity, then gastrodermal cells release mucus and enzymes that turn the food into a "soupy broth". Nutritive-muscular cells, type of gastrodermal cell, are able to phagocytize partially digested food, which are then given to vacuoles, completing digestion. Nutritive-muscular cells have circularly oriented contractile fibers that aid in moving materials in and out the gastrovascular cavity.
Besides functioning in digestion and circulation the gastrovascular cavity can be a hydro-static skeleton. A hydro-static skeleton is water or body fluids confined in a cavity of the body and against which contractile elements of the body wall act. Epitheliomuscular cells are contractile and help in movement. These cells help when a polyp is closing it's mouth to prevent water from escaping. The polyp contract longitudinal epitheliomuscular cells on one side of the polyp, this causes the polyp to bend toward that side. But, if the epitheliomuscular cells were to contract while the mouth was open the polyp would collapse and water escapes. Circular epitheliomuscular cells also constrict a part of the polyp, the mouth being closed causes water in the gastrovascular cavity to become compressed, which elongates the polyp.
Polyp are able to move through somersaulting from their base to their tentacles and then from tentacles to base. Also, the are able to move through an inchworm manner, by using their base and tentacles for attachment. Polyps are also able to slide along their substrate. Medusae are able to swim and float, and water currents and wind help them move horizontally. Circular epitheliomuscular cells create pulsations underneath the medusa, allowing it to move through water.
Large surface-area-to-volume ratios in cnidarians cause all cells to be a short distance from the body surface, and oxygen, carbon dioxide, and nitrogenous wastes exchange through diffusion.