Roundworms have a simple digestive system composed of a mouth, a triangular shaped pharynx, intestines and an anus. Roundworms lack circulatory systems; instead, resources and wastes diffuse through their body cavities. Roundworms have two nerve cords, and one travels along their ventral side, while the other stretches along the dorsal side. These nerves work in conjunction with their longitudinal muscles to propel the worms through their environment. Like most animals, roundworms primarily engage in aerobic respiration, meaning that they use oxygen to convert food into energy.
However, roundworms do not use lungs to move the oxygen around their bodies. Roundworms absorb oxygen and release carbon dioxide directly through their cuticle, which is permeable to both gases. Once oxygen has crossed into their bodies, it diffuses throughout the tissues. Worms swallow pieces of dirt and decaying leaves, and the food passes through the pharynx , located in body segments , the esophagus segments , and into the crop, which stores food temporarily.
The worm's stomach is very muscular, so is called a gizzard. Like a bird's gizzard, it grinds up the food, which then moves into the intestine. The intestine extends over two-thirds of the worm's body length. In the intestine, food is broken down into usable chemicals which are absorbed into the bloodstream. Leftover soil particles and undigested organic matter pass out of the worm through the rectum and anus in the form of castings , or worm poop.
Worm poop is dark, moist, soil-colored, and very rich in nutrients. That's why farmers and gardeners like to have lots of worms in their soil. Cleaning out the blood : Worms don't have kidneys, but they have something serving the same purpose. Worms have nephridia to filter out the dead cells and other wastes that are sloughed into the blood. Wastes from the nephridia are eliminated through the same opening as the digestive wastes.
Worm urine is more dilute than ours, but has ammonia as well as urea. Heartbeats : Worms don't have just one heart. They have FIVE! Nematodes are one of the simplest animal groups to have a complete digestive system, with a separate orifice for food intake and waste excretion, a pattern followed by all subsequent, more complex animals.
The mouth is often surrounded by various flaps or projections used in feeding and sensation. The portion of the body past the anus or cloaca is called the "tail. Although this cuticle allows movement and shape changes via a hydrostatic skeletal system, it is very inelastic so does not allow the volume of the worm to increase.
Therefore, as the worm grows, it has to moult and form new cuticles. Most free-living nematodes are microscopic, though a few parasitic forms can grow to several meters in length. There are no circular muscles, so the body can only undulate from side to side. Contact with solid objects is necessary for locomotion; its thrashing motions vary from mostly to completely ineffective at swimming. Roundworms generally eat bacteria, algae, fungi and protozoans, although some are filter feeders.
However, the system is linear with food coming into the mouth and traveling in a straight line through the pharynx and intestines, then out through the anus. They also lack a circulatory system, and their nervous system consists only of two cords of nerve cells that send messages through the worm's body. Considering the simplicity of their anatomy, we should not be surprised that roundworms lack a respiratory system and rely on a more simplistic gas exchange process to take in oxygen.
In science, diffusion refers to the movement of molecules from an area where they are highly concentrated into an area where they are less concentrated. For example, the molecules in a lump of sugar added to water will spread apart in the water because they can be less concentrated in the water than they were in the sugar cube.
As a result, the sugar lump dissolves in the water. Diffusion occurs in the human body, too.
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