The internal structure of insects.

Digestive system

The digestive system consists of the oral cavity (the ducts of the salivary glands flow here), pharynx, esophagus, goiter, stomach, midgut (where food is digested and absorbed), the hindgut and anus.
Between the stomach and the midgut there are special blind outgrowths in which food is absorbed.

Respiratory system

The respiratory system of most insects is represented by many highly branching tracheas that penetrate the entire body and open outward with the help of spiracles (stigmas) located on the sides of the abdomen. The spiracles regulate the flow of air to the internal organs (cells). Carbon dioxide is removed through the trachea.

Circulatory system

The circulatory system is not closed.
On the dorsal side, insects have a heart that looks like a long, muscular tube with holes on the sides. Hemolymph (“blood”) enters the heart through these holes and flows through it from the posterior to the anterior end. From the heart, hemolymph enters the body cavity (the circulatory system is not closed).

Hemolymph flows not only through the vessels, but also in the body cavities, washing various organs and transferring nutrients to them, while being saturated with waste products.
Hemolymph does not participate in gas exchange – the transfer of oxygen and carbon dioxide, since this function is performed by the trachea.

Excretory system

The excretory system, like in arachnids, is represented by malpighian vessels – bundles of tubules blindly closed from the side of the body cavity, which open into the intestine. Metabolic products are filtered by the walls of the malpighian vessels from the body cavity.

Nervous system

The nervous system is represented by a large supraopharyngeal ganglion (it is often called the brain), a subpharyngeal ganglion, and an abdominal nerve cord. Nerves extend from the head ganglion to the eyes and other sensory organs.
The senses are well developed.
The organs of vision are two large complex compound eyes and simple eyes.
On the antennae are the organs of touch and smell and heat-sensitive organs (detecting temperature changes).
The organs of taste are located on the mouth organs.

Reproduction

Insects are dioecious. Fertilization is internal.
The female reproductive system (♀) consists of the ovaries (where eggs are formed) and the oviduct.
The male (♂) has two testes, two vas deferens and an ejaculatory duct.

Among insects, there are groups that develop with incomplete transformation (the larva that emerged from the egg looks like an adult insect) and with complete transformation (the worm-like larva turns into a pupa, from which the adult insect emerges).

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