World fauna is diverse and varied.All life on Earth is divided into types.One is the type of arthropods.It has about 2 million species and is represented by three classes: arachnids, insects and crustaceans.
structure
all arthropods, regardless of class, are similar to each other.Thus, they have a symmetrical body, which is divided into several sections - segments.Most often they are three.Among them distinguish the abdomen, head and chest.Sometimes the last two segments merge.They form a cephalothorax.The body is covered with arthropod cuticle epidermis and chitin, which represent something like exoskeleton.Also, there are several pairs of legs, which extend from the segments apart.Type of arthropods differ from other invertebrates that its representatives legs consist of several parts, among which contains resilin (elastic protein).Thanks to him, the creature can jump.
circulatory system
body cavity of animals, representing the type of arthropods - miksotsel.It is formed due to the mix of coelomic bags blastocoel.Fluid in the body cavity is called hemolymph.It mixes with the circulating blood and organs in between them, as well as in poorly developed vessels.With regard to the circulatory system, it is not closed.In arthropods have a heart.It is represented by spinal blood vessel, which acquired a definite shape.Through the side openings, so-called ostia, which have valves hemolymph enters the heart.
digestive system
digestive system represented arthropods rear, front and middle parts.A special tube is divided into sectors.Among them are the pharynx, stomach, esophagus.In addition, there hepatic outgrowth by which there is an allocation of enzymes.Mouthparts of arthropods is very complicated.
Respiratory
Depending on where the living creature entering into a type of arthropod, his respiratory system may be in the form of light, gills and trachea.But they are in their infancy.The lung bags (light) in this case are the appendages of the body wall having a leaf-shaped and directed into the body cavity.They are connected with respiratory slit.Tracheal formed by numerous branching tubes that have chitin in the ring.Gas exchange in these animals is due to the hemolymph, which delivers oxygen to all tissues.
nervous system
central nervous system of arthropods formed brain and nerve cord.It is located in the peritoneum.The chain has a connection in the abdominal ganglia, the brain and thoracic, allowing the animals of this type are well-developed senses.
Other system
With regard to the excretory system, it is represented by the Malpighian vessels and metanephridia.Pets such as arthropods heterosexual, and with a strong dimorphism.The muscular system is also present in these animals and shows striated tissue.
