The type of protozoa (Protozoa) includes more than 15,000 species of animals that live in the sea, freshwater and soil.In addition to free-living forms, many parasites are known, which sometimes cause serious diseases - protozoonosis.
The protozoan body consists of only one cell.The body shape of protozoa is diverse.They can be permanent, have radial, bilateral symmetry (flagellates, ciliates) or have no permanent shape at all (amoeba).The size of the protozoan body is usually small - from 2-4 microns to 1.5 mm, although some large individuals reach 5 mm in length, and the rhizome of the fossil skin has a diameter of 3 cm or more.
The protozoan body consists of cytoplasm and nucleus.The cytoplasm is bounded by an outer cytoplasmic membrane;it contains organelles - mitochondria, ribosomes, endoplasmic reticulum, and Golgi apparatus.Protozoa have one or more nuclei.A form of nuclear division is mitosis.There is also a sexual process.It involves the formation of a zygote.
Protozoan movement organelles are flagella, cilia, pseudopods;or none at all.Most protozoa, like all other representatives of the animal kingdom, are heterotrophic.However, among them there are also autotrophs.
The specialty of protozoa to tolerate adverse environmental conditions is their ability to extract, i.e. form cysts.When the cyst is formed, the movement organelles disappear, the number of animals decreases, it acquires a round shape, and the cells are covered with a dense membrane.The animal enters a state of rest and, when favorable conditions occur, returns to active life.
Encystment is a device that works not only for protection, but also for the spread of parasites.Some protozoa (sporophytes) form ovocysts and, during the reproductive process, sporocysts.
Protozoan reproduction is very diverse, from simple division (asexual reproduction - biofile.ru) to quite complex sexual processes - conjugation and copulation.
The habitat of protozoa is diverse - sea, fresh water, wetlands.Parasitism becomes widespread.Many species of parasitic protozoa cause severe forms of disease in humans, domestic and commercial animals, and plants.
Protozoa can move with the help of pseudopods, flagella or cilia, and respond to various stimuli (phototaxis, chemotaxis, thermotaxis, etc.).Protozoa feed on the smallest animals, plant organisms and decaying organic matter;Parasite forms live on the surface of the body, in the body cavity or host tissue.
The way food enters the cell body is also different: pinocytosis, phagocytosis, osmotic pathway, active transport of substances across the membrane.They digest food that enters in a digestive vacuole filled with digestive enzymes.Some of them, have photosynthetic intracellular symbionts - chlorella or chloroplasts (for example, euglena) capable of synthesizing organic matter from inorganic matter using photosynthesis.
Toxoplasma
Toxoplasmosis (Toxon Greek - arch, arch) is a disease caused by single-celled organisms of protozoa in various places in the human body, where their identification and reproduction takes place.The causative agent of toxoplasmosis, Toxoplasma gondii, belongs to the genus protozoa, in the class flagellata.
Toxoplasma has a crescent shape and resembles an orange slice: one end of the parasite is usually pointed, the other round, up to 7 microns long.Toxoplasma moves by sliding.They penetrate inside the cell, rotating around the longitudinal axis.
Toxoplasma reproduction is asexual, it occurs by longitudinal division into two.As a result of repeated longitudinal divisions in the protoplasm of the host cell, an accumulation of daughter parasites is formed, which is called a "pseudocyst".Pseudocysts are found in large numbers in various organs of the infected organism during the acute stage of infection.They are surrounded by a very fuzzy membrane, apparently formed by the host cell, and have no shell of their own.Cells filled with such parasites are destroyed.The released parasites penetrate into new cells, where they divide again and form new pseudocysts.
When the infection becomes chronic, Toxoplasma remains in the form of true cysts (they surround themselves with a special shell).Such cysts have the ability to survive in the body of animals and humans for a long time (up to 5 years).Cysts are also found in the tissues of the eyes, heart, lungs and some other organs.The number of Toxoplasma in the cyst ranges from a few copies to several thousand.
Giardia
Giardia is the simplest animal parasite of the flagellate class.It has a pear shape, 10-20 microns long;the dorsal part is convex, the ventral part is concave and forms a sucker to temporarily attach to the intestinal epithelial cells of the host.2 oval nuclei, 4 pairs of flagella.It lives in the human intestine (especially in children), mainly in the duodenum, less often in the bile ducts and gall bladder, causing giardiasis.Asymptomatic parasite carriage is common.Cystic infections occur when protozoa enter the lower intestine through the mouth through ingestion of contaminated food or water, or through dirty hands, etc.Its occurrence is sporadic.Giardiasis is common in all parts of the world.
The causative agent of this disease is lamblia (Lamblia intestinalis).Giardia is a single-celled microscopic parasite.Giardia can withstand freezing and heating up to 50 ° C, but dies when boiled.In the United States, giardiasis is the leading gastrointestinal disease of parasitic origin.According to the INTERNET, up to 20% of the world's population suffers from giardiasis.Infection can occur by drinking unboiled tap water or ice made from such water when washing vegetables and fruits with unboiled water.There is a high risk of getting sick when swimming in open water and in pools contaminated with Giardia cysts.Newborns can be infected during childbirth during eruption and head birth.The path of infection is less common, but with a high prevalence of the disease it becomes quite real, especially among segments of the population with poor general hygiene skills.
Trichomonas
Trichomonas vaginalis does not form cysts and feeds on bacteria and red blood cells.Causes inflammation of the genitourinary system - trichomoniasis.The causative agent of this disease is sexually transmitted.Extrasexual infection (through toilet articles, beds, etc. shared with the patient) is less common.It can be transmitted to a newborn baby girl from a sick mother.The disease may become chronic.If it spreads to the appendages, it is difficult to treat.With trichomoniasis, the vagina is most often affected;abundant purulent discharge with an unpleasant odor appears;There is itching and burning in the vagina.In men, the symptom is inflammation of the urethra (urethritis), accompanied by only a slight discharge of mucus.
Amoeba
Amoeba lives in fresh water.Body shape is not fixed.Makes very slow movements (13 mm/hour).It moves with the help of pseudopods, the body flows from one part to another: either it shrinks into a round lump, or spreads the "leg-tongue" to the sides.
Pseudopods also serve to capture food.During the feeding process, the amoeba body flows around the food particles from all sides, and they end up in the cytoplasm.Digestive vacuoles appear.This way of eating is called fabititosis.Its diet consists of bacteria, unicellular algae, and small protozoa.Solutes from the environment are absorbed by pinocytosis.
Amoeba bodies have contractile or pulsating vacuoles.Its function is to control the osmotic pressure in the protozoan body.Reproduction is asexual, through mitosis followed by the division of the amoeba body into two.Amoeba from the genus Entamoeba, which lives in the human digestive tract, is of great importance in medicine.These include dysentery or histolytic amoebas.
Plasmodium malaria
Plasmodium malaria causes malaria, which occurs with attacks of fever, changes in the blood, and enlargement of the liver and spleen.There are four forms of malaria: three-day, four-day, tropical, and ovalemalaria.The cause of the disease is a person with malaria, and the carrier is a female malaria mosquito.Female mosquitoes, infected by sucking the patient's blood, become capable of transmitting plasmodia.A healthy person becomes infected when bitten by a mosquito infected with Plasmodium, through whose saliva the pathogen enters the body.With the bloodstream, plasmodia enter the liver, where they undergo the first development cycle (tissue), then enter the blood and penetrate the red blood cells.Here they complete the second cycle of development (erythrocytes), ending with the breakdown of erythrocytes and the release of pathogens into the patient's blood, which is accompanied by an attack of fever.