This amazing animal lives exclusively in fresh water, leads a predatory or parasitic lifestyle, is widely used in medicine. It's about a leech. The structure of the body, the features of life and the beneficial properties of this organism will be discussed in our article.
Systematic position
It is rather difficult to classify this organism by morphological features. The external structure of a leech (the photo below shows it) resembles that of slugs, which are representatives of molluscs. Leeches are actually annelid worms.
External structure of a leech
The maximum length of this worm reaches 15 cm. The body structure of the leech is characterized by the presence of suckers, which are located at both ends of the body. The ventral side is always flat, and the dorsal side is convex.
Leeches are attached to the substrate with one or the other suction cup. Thus, they carry out "stepping" movements. Leeches are excellent swimmers. Thanks to the wave-like bending of the body, they can travel considerable distances.
Where the leeches live
Features of the structure of leeches and the way of feeding determine the habitat of this species of worms. They prefer fresh water: swamps, lakes, small rivers and even puddles. One of the necessary conditions for leeches is cleanliness. They breathe oxygen dissolved in water. Inside the body, it penetrates through the integument of the animal. And this process is most productive in clean water.
Some species live on land. They burrow into moist soil, clay, moss. But without water, their life is impossible, because they are not adapted to breathing atmospheric air.
Variety
Currently 400 species of leeches are known to taxonomists. The most common of them are ground, fish, lozhnokonskaya. But of all the diversity, only one species has medicinal properties. This is a medicinal leech.
By feeding method, these worms are predators and parasites. There are three jaws in the leech's mouth. On each of them are numerous chitinous teeth. Their leeches are used to cut through the integument of the victim. After that, the leech sucks blood with a maximum volume of 15 ml.
Features of difference
The structure of the medical leech has its own characteristics. Due to this, this type is easy to distinguish from "non-medical". Her body is dark green. On the dorsal side, which is darker, narrow orange stripes are clearly visible. In their extensions there are black spots of irregular shape,the number of which varies widely.
The integument of the medicinal leech is smooth. They do not have hairs, bristles or other outgrowths. The body is flattened in the dorso-abdominal region, almost flat. It consists of 33 segments. The number of rings is small - up to five. The front suction cup is used for feeding. The back is much larger. It is used to attach to the substrate and move.
Integuments are represented by the cuticle. This substance is inextensible. Therefore, the growth process is accompanied by periodic molts.
Internal structure of a leech
The active movement of these annelids is possible due to the developed muscular system. It is represented by four layers of fibers. Thanks to the outside, blood is swallowed. Movement in space is provided by diagonal and deep longitudinal layers. The contraction of the body is the result of the work of the dorsal-abdominal muscles. Outside, the fibers are covered with a dense layer of connective tissue.
The structure of the leech is characterized by increased sensitivity of the integument. She is able to perceive a whole range of sensations: changes in temperature and pressure, the influence of chemicals. There are five pairs of eyes on the head. They are composed of pigmented photosensitive cells. Thanks to such a variety of receptors, leeches can easily navigate in space, find food for themselves and respond to changes in the environment.
The nervous system of annelids is of the ganglionic type. It consists of an abdominal chain, which forms a knot in each ring of the body. From here to everyonenerve fibers leave the organ.
Digestive system of the through type. It begins with a mouth opening with jaws, passes into a muscular stomach and intestines, which opens outward with an anus. Excretory organs include numerous nephridia. Urine is excreted through the nephropores. Symbiotic bacteria constantly live in the stomach of leeches. They have bactericidal properties, keep the sucked blood liquid, digest it.
All leeches are hermaphrodites. This means that male and female gametes are formed in each individual. Despite this feature, these animals are incapable of self-fertilization. A new organism develops as a result of mating of two individuals.
Useful properties
In medicine, the structure of a leech and its practical application is studied by a separate science - hirudology. The beneficial properties of this organism have been known since ancient times. As early as the 5th century BC, the ancient Greek scientist Hippocrates described them in his writings.
The theory of "bad blood" contributed to the widespread use of leeches for medical purposes. She dominated in the 17-18 centuries in Europe. In this regard, the method of bloodletting was widely used. Doctors used tens of millions of leeches a year for this purpose.
Over time, this theory was recognized as erroneous. The use of leeches has practically ceased. And only in the 19th century, their beneficial properties were scientifically substantiated.
What is hirudin
Officially, the healing effect of leeches was confirmed by Englishscientist John Haycraft. In the blood of these rings, he found a chemical compound that has an anticoagulant effect. It is to prevent blood clotting and the formation of blood clots.
The substance hirudin has such properties. It is secreted in the salivary glands of leeches and is a natural heparin. In nature, it is also found in bee venom and some snakes. Currently, artificially synthesized hirudin has been created. However, compared to natural, its effectiveness is several times lower.
By chemical nature, this substance is a polypeptide chain, which consists of amino acid residues. It stops the activity of the enzyme thrombin, thereby stopping blood clotting.
The action of hirudin also extends to the blood that is in the digestive system of leeches. It can be stored for a long time in special expansions of the intestines. If necessary, this can continue up to six months. Therefore, the leech can feed again after a long period of time.
Mechanism of action
Leech bites stimulate the human immune system. How is this possible? Hirudin causes the secretion of blood lymph. As a result, the lymph nodes are irritated, and lymphocytes begin to stand out. These are blood cells that have a protective effect - they increase local and general immunity.
The body perceives such a situation as a threat. Therefore, there is a mobilization of its protective functions. Abilityphagocytic cells to digest foreign microorganisms increases dramatically.
Hirudotherapy is used to lower and normalize blood pressure. Moreover, the result is stored for several days.
The ability of leeches to break down lipids is also widely used, which significantly reduces the manifestation of signs of atherosclerosis. Such activity is used as a means to combat cellulite.
But the importance of leeches in the fight against blood clots is especially great. This is due to the fact that hirudin interrupts some of the links in the process of their formation. But if blood clots have already formed, this substance contributes to their gradual dissolution. As a result, vascular patency is normalized.
As a result
The leech, the structure of which we examined in our article, is a representative of the type Annelids. The habitat of these animals is fresh water and wet soils. Leeches have long been used for medicinal purposes. Their salivary glands contain a special substance - hirudin. Its main property is to prevent blood clotting and the formation of blood clots inside the vessels.
Leech class animals have the following traits:
- the body is flattened in the dorsal-abdominal direction;
- the presence of oral and posterior suckers;
- lack of bristles on the integument of the body, which are represented by an inextensible cuticle;
- all representatives are hermaphrodites with a direct type of development;
- according to the type of food they are predators, parasites or bloodsuckersviews.
