The type of protozoa (Protozoa) includes more than 15,000 species of animals that live in the seas, fresh waters and soil.In addition to free-living forms, many parasitic forms are known that sometimes cause serious diseases: protozoonosis.
The body of a protozoan consists of a single cell.The body shape of protozoa is varied.It can be permanent, have radial symmetry, bilateral (flagellates, ciliates) or have no permanent shape (amoeba).The body size of the simplest ones is usually small: from 2 to 4 microns to 1.5 mm, although some large individuals reach 5 mm in length, and the rhizomes of fossil shells had a diameter of 3 cm or more.
The body of protozoa is made up of cytoplasm and nucleus.The cytoplasm is limited by the outer cytoplasmic membrane;It contains organelles: mitochondria, ribosomes, endoplasmic reticulum and Golgi apparatus.Protozoa have one or more nuclei.The form of nuclear division is mitosis.There is also the sexual process.It involves the formation of a zygote.
The simplest movement organelles are flagella, cilia and pseudopodia;or there are none at all.Most protozoa, like all other representatives of the animal kingdom, are heterotrophs.However, among them there are also autotrophs.
The peculiarity of protozoa to tolerate unfavorable environmental conditions is their ability to encyst, that is, form a cyst.When a cyst forms, the movement organelles disappear, the volume of the animal decreases, it acquires a rounded shape, and the cell is covered with a dense membrane.The animal enters a state of rest and, when favorable conditions arise, returns to active life.
Encystment is a device that serves not only for protection, but also for the spread of parasites.Some protozoa (sporophytes) form an oocyst and, during the reproduction process, a sporocyst.
The reproduction of the simplest is very diverse, from simple division (asexual reproduction - biofile.ru) to a rather complex sexual process - conjugation and copulation.
The habitat of the simplest ones is varied: the sea, fresh water and humid soil.Parasitism became widespread.Many species of parasitic protozoa cause severe forms of disease in humans, domestic and commercial animals, and plants.
Protozoa are able to move with the help of pseudopodia, flagella or cilia and respond to various stimuli (phototaxis, chemotaxis, thermotaxis, etc.).Protozoa feed on smaller animals, plant organisms and decaying organic matter;Parasitic forms live on the body surface, in body cavities or in the tissues of their hosts.
The ways in which food enters the cell body are also different: pinocytosis, phagocytosis, osmotic pathway, active transport of substances across the membrane.They digest incoming food in digestive vacuoles filled with digestive enzymes.Some of them, having photosynthetic intracellular symbionts - chlorella or chloroplasts (for example, euglena), are capable of synthesizing organic matter from inorganic substances through photosynthesis.
toxoplasma
Toxoplasmosis (from the Greek toxon - bow, arch) are diseases caused by protozoan unicellular organisms in a wide variety of places in the human body, where their introduction and reproduction occurred.The causative agent of toxoplasmosis, Toxoplasma gondii, belongs to the genus of protozoa, to the class of flagellates.
Toxoplasma is crescent-shaped and resembles an orange slice: one end of the parasite is usually pointed and the other rounded, with a length of up to 7 microns.Toxoplasma moves by sliding.They penetrate the interior of the cells, rotating around the longitudinal axis.
Toxoplasma reproduction is asexual, it occurs by longitudinal division in 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 loose membrane, apparently formed by the host cell, and have no shell of their own.Cells filled with these parasites are destroyed.The released parasites penetrate new cells, where they divide again and form new pseudocysts.
When the infection becomes chronic, the Toxoplasma remains in the form of true cysts (they are surrounded by a special layer).These cysts have the ability to persist 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 a cyst varies from a few copies to several thousand.
giardiana
Giardia is the simplest parasitic animal of the flagellate class.It is pear-shaped, length 10 to 20 microns;the dorsal side is convex, the ventral side is concave and forms a suction cup for temporary attachment to the epithelial cells of the host intestine.2 oval nuclei, 4 pairs of flagella.It lives in the human intestine (mainly in children), mainly in the duodenum, less often in the bile duct and gallbladder, causing giardiasis.Asymptomatic carriage of parasites is common.Cyst infection occurs when protozoa enter the small intestine through the mouth by ingesting contaminated food or water, or through dirty hands, etc.The incidence is sporadic.Giardiasis is common in all parts of the world.
The causative agent of the disease is lamblia (Lamblia intestinalis).Giardia are single-celled microscopic parasites.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 entire world population suffers from giardiasis.Infection can occur from drinking unboiled tap water or ice made from tap water from washing vegetables and fruits with unboiled water.There is a high risk of getting sick from swimming in open water and in pools contaminated with Giardia cysts.A newborn baby can become infected during childbirth during the rash and birth of the head.The contact route of infection is rarer, 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 the disease is transmitted sexually.Extrasexual infection (through toiletries, bed, etc. shared with the patient) is less common.It can be transmitted to a newborn girl from a sick mother.The disease can become chronic.If it spreads to the appendages, it is difficult to treat.With trichomoniasis, the vagina is most affected;abundant purulent discharge appears with an unpleasant odor;there is itching and burning in the vagina.In men, the symptom is inflammation of the urethra (urethritis), accompanied by a slight mucous discharge.
Amoeba
The amoeba lives in fresh waters.The shape of the body is not constant.Make very slow movements (13 mm/hour).It moves with the help of pseudopods, the body flows from one part to another: either shrinking into a round lump or spreading its "tongues-legs" to the sides.
The pseudopods also serve to capture food.During the feeding process, the body of the amoeba flows around food particles from all sides and ends up inside the cytoplasm.A digestive vacuole appears.This way of eating is called fabititosis.The food is made up of bacteria, single-celled algae and small protozoa.Solutes from the environment are absorbed by pinocytosis.
The body of the amoeba has a contractile or pulsating vacuole.Its function is to regulate the osmotic pressure within the body of the protozoan.Reproduction is asexual, through mitosis followed by the division of the amoeba's body in two.Amoebas of the genus Entamoeba, which live in the human digestive tract, are of great importance in medicine.These include the dysenteric or histolytic amoeba.
malaria plasmodium
Malaria plasmodium causes malaria, which presents with attacks of fever, blood changes, and enlargement of the liver and spleen.There are four forms of malaria: three-day, four-day, tropical and ovalemalaria.The source of the disease is a person with malaria and the carrier is a female malaria mosquito.A female mosquito, which becomes infected by sucking the blood of a patient, becomes capable of transmitting plasmodia.A healthy person becomes infected when bitten by a mosquito infected with Plasmodium, through whose saliva the pathogens enter the body.With the bloodstream, plasmodia enter the liver, where they go through the first cycle of development (tissue), then pass into the blood and penetrate red blood cells.Here they complete the second cycle of development (erythrocytes), which ends with the breakdown of erythrocytes and the release of pathogens into the patient's blood, which is accompanied by an attack of fever.