Blood system of earthworm: description, structure and features

Ringworms are practically the largest species of higher animals, living freely in soil, sea and fresh water. This kind of worm has a more complex organization than round worms or flat worms .

Worms of the ringed type first appear secondary cavity, highly organized system of blood supply and nervous system.

Earthworm: structure

In the transverse section the body is practically round. The average length is about 30 cm. It is divided into 150-180 segments or segments. The belt located in the anterior third of the body performs its function during the period of sexual activity (earthworm - hermaphrodite). On the sides of the segments there are four rigid well developed small setae. They contribute to the movement of the body of the worm in the soil.

The color of the calf is reddish-brown, and on the abdomen it is slightly lighter than on the back.

Natural necessity

The circulatory system is present in all animals, beginning with the second- ribbed annelids. It was formed due to an increase in vital activity (compared, for example, with flatworms). Life in constant movement requires stable, energetic work of the muscles, which in turn calls for an increase in the cells of incoming oxygen and nutrients, which can only be delivered by blood.

What is the circulatory system in the earthworm? The two main arteries are dorsal and in the abdominal cavity. In each segment between the arteries, looped vessels pass. Some of them are slightly thickened and covered with muscle tissue. In these vessels, performing the work of the heart, the muscles, contracting, push blood into the abdominal artery. Ring "hearts" at the outlet to the dorsal artery have special valves that do not allow blood flow to go in the wrong direction. All the vessels are divided into a large network of the thinnest capillaries. Oxygen in them comes from the air, and nutrients are absorbed from the intestine. Capillaries, located in muscle tissues, give carbon dioxide and decomposition products.

The circulatory system of the earthworm is closed, since it does not mix with the cavity fluid during the entire movement. This makes it possible to significantly increase the rate of metabolism. In animals that do not have a pumping system, the heat exchange is two times lower.

Blood system of earthworm

Nutrients, which sucked the intestines during the movement of the worm, are distributed through a well-formed circulatory system.

Her scheme is quite complicated for this species of animals. Vessels pass over and under the intestine along the entire body. The vessel that passes in the back is muscled. She, squeezing and stretching, wavyly pushes blood from the back to the front of the body. In the anterior segments (in some species of worms it is 7-11, in others - 7-13) the vessel going along the back, communicates with several pairs of vessels passing transversely to the main (usually 5-7). The circulatory system of the earthworm with these vessels imitates the hearts. The musculature is developed much more strongly than the others, therefore they are the main ones in the whole system.

Functional features

Functions of the circulatory system of the earthworm are similar to the functions of vertebral hemodynamics. Blood, released from the hearts, falls into a vessel that is in the abdominal cavity. It moves to the posterior end of the worm body. On its way, this blood carries nutrients through smaller vessels that are in the walls of the calf. During puberty, blood enters the genitals.

The structure of the circulatory system of the earthworm is such that the vessels in each organ pass into the smallest capillaries. Blood from them flows into vessels located across the main ones, from which blood flows down into the dorsal artery. The musculature is present in all blood vessels, even the smallest. This allows the blood to not stagnate, especially in the peripheral part of the blood supply system of this type of ringed.

Intestines

In this part of the body of the worm is a particularly dense wreath of capillaries. They seem to entangle the intestines. Part of the capillaries brings nutrients, the other part carries them all over the body. The muscles of the vessels surrounding the intestine of this species are annular, not as strong as the spinal vessel or heart.

Composition of blood

The circulatory system of the earthworm on the lumen is red. This is because the blood contains substances that are close in chemical structure to hemoglobin, which is part of the blood composition of vertebrates. The difference lies in the fact that these substances are in the plasma (the liquid part of the blood composition) in a dissolved form, and not in the blood cells. The very blood of the earthworm is cells without color, of several types. They are similar in structure to colorless cells that make up the blood of vertebrates.

Transport of oxygen cells

Oxygen cells in vertebrates from the respiratory system transfer hemoglobin. In the blood of earthworms, a substance similar in composition also brings oxygen to all the cells of the body. The only difference is that the worms have no respiratory organs. They "breathe in" and "exhale" the surface of the body.

Thin protective film (cuticle) and epithelium of the skin of the worm together with a large capillary net of the skin ensure good absorption of oxygen from the air. The capillary spiderweb is so large that it is even in the epithelium. From here, the blood moves through the body wall vessels and transverse vessels into the main stem channels, so that the whole body is enriched with oxygen. A reddish shade of the body of this kind of annular is provided by a large capillary network of walls.

Here it is necessary to take into account that the finest film covering the body of the earthworm (cuticle) is very easily moistened. Therefore, first, oxygen dissolves in water droplets that are retained by the skin epithelium. It follows that the skin should always be moistened. Thus, it becomes clear that the humidity of the environment is one of the important conditions for the life of these animals.

Even the slightest drying of the skin stops breathing. For the circulatory system of the earthworm does not bring oxygen cells. Not very long, he can hold out in such conditions, using internal water supplies. The glands located in the skin. When the situation becomes really acute, the earthworm starts recycling the cavity fluid, sprinkling it in parts from the pores located on the back.

Digestive and nervous systems

The digestive system of earthworms consists of the anterior colon, the middle and the back. In connection with the need to live more actively, the digestive system of earthworms has gone through several stages of improvement. The digestive apparatus appeared departments, behind each of which a certain function was fixed.

The main organ of this system is the intestinal tube. It is divided into the oral cavity, pharynx, esophagus, stomach (muscular body), middle and posterior intestines, anus.

In the esophagus and pharynx, ducts of gland come out, which influence the pushing of food. In the mid-gut, the food is chemically processed, and the digestive products are absorbed into the blood. The remains leave through the anus.

Through the entire length of the body of the worm, on the side of the peritoneum, there passes a nervous chain. Thus, each segment has its own developed nerve lumps. In the anterior part of the neural chain is an annular jumper, consisting of two connected nodes. It is called the peripheral nerve ring. From it the network of nerve endings is dispersed all over the body.

The digestive, circulatory and nervous systems of the earthworm are considerably complicated, in connection with the progress of the entire species of the ringlets. Therefore, in comparison with other types of worms, they have a very high organization.