Roundworms, or as they are called Nematodes are organisms with the primary body cavity.They live in the most diverse places on the planet - in the seas, fresh water and soil.Some representatives are parasites - they exist at the expense of plant and animal organisms.The most famous are human parasites and roundworm Trichinella.
type Roundworms: structural features .Title indicates quite a few members of this type of structure - in cross section they have circular shape.Their body is fusiform and narrowed at the ends, you can clearly see the head on the front end.Type of body symmetry - bilateral.
regard to the size of these organisms, they vary greatly - from the microscopic (80 microns) to about giant (more than 8 meters from the whale parasites).
Their body is their skin-muscular sac, which is separated from the internal cavity of the primary or psevdotselem.The skin is covered with a dense layer on top of the cuticle, which is produced by the epithelium of the outer covers.
Roundworms: the structure of the digestive system .Digestion of this group of organisms through.Mouth disposed at the front end of the body and surrounded by lips and muscle tissue.It leads to muscular pharynx, which is used for active food ingestion.Food further falls in the middle, and then in the hindgut.Food exchanges are ejected through the anus of females and males in the cloaca.
wonder that some parasitic organisms of this type of digestive tube and transformed into a small bag with no holes.
Roundworms: respiration and excretion .The excretory system is quite roundworms.These include a large single-cell cervical glands.The metabolic products accumulate in the cavity fluid, after which the two longitudinal lateral channels are moved in the iron and discharged to the outside.The neck has a separate iron excretory opening, which opens into the ventral part of the body.Some metabolites, such as ammonia, are ejected directly through the body wall.
As for breathing, then a specially designated bodies in organisms not.Oxygen is absorbed by the intestinal tissue.In that case, if you have to live in conditions of oxygen starvation, roundworms can pass to an anaerobic type of respiration.
Roundworms and nervous system .The nervous system in these organisms is quite primitive, especially in parasitic forms.The main associative center presented peripharyngeal nerve ganglia, which runs two of the nerve trunk.
As for the senses, they are presented with papillae, bristles amphids drugiemi and formations.All this - the bodies of mechanical, chemical and light sensitivity.In this type of parasites senses developed worse than free-form.
Roundworms: reproduction .Representatives of this type of animal is a dioecious organisms.At the same time, and there is quite a marked sexual dimorphism - the male rear end is bent to the ventral part of the body.
female sexual organs are represented by the ovaries, uterus and oviducts.The male has testicles, vas efferens and ejaculatory duct.Male sperm introduced into the vagina of the female through the copulatory organ.Interestingly, the sperm do not have flagella, they have limited mobility and amoeboid shape.
The Roundworms are different from the flat ?In fact, the differences between these two types of animals is quite noticeable.First, let's mention the shape of the body - a cross-sectional Flatworms have a flattened body.Another major difference - it is the primary body cavity, which is absent from representatives of flatworms.In addition, the nematode is already there-through the digestive system.It should be noted that the flat worms - hermaphrodites.
