The type of protozoa (protozoa) includes over 15,000 species of animals that live in seas, fresh water and soil.In addition to free-living forms, many parasitic forms are known, which sometimes cause serious diseases - protozoonoses.
The body of a protozoan consists of only one cell.The body shape of protozoa is diverse.It can be permanent, have radial, bilateral symmetry (flagellates, ciliates), or have no permanent shape at all (amoeba).The body sizes of protozoa are usually small - from 2-4 micrometers to 1.5 mm, although some large individuals reach 5 mm in length, and fossil shell rhizomes were 3 cm or more in diameter.
The body of protozoa consists of cytoplasm and nucleus.The cytoplasm is bounded 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.This results in the formation of a zygote.
Movement organelles of protozoa are flagella, cilia, pseudopodia;or there are none at all.Most protozoa, like all other representatives of the animal kingdom, are heterotrophic.However, among them there are also autotrophs.
The peculiarity of protozoa to tolerate unfavorable environmental conditions is their ability to encapsulate themselves, i.e. to form a cyst.When a cyst forms, the organelles of movement disappear, the volume of the animal decreases, it acquires a rounded shape, and the cell becomes covered with a dense membrane.The animal enters a resting state and returns to active life when conditions are favorable.
Encystment is a device that not only protects but also prevents the spread of parasites.Some protozoa (sporophytes) form an ovocyst and, during reproduction, a sporocyst.
The reproduction of protozoa is very diverse, ranging from simple division (asexual reproduction - biofile.ru) to a fairly complex sexual process - conjugation and copulation.
The habitat of protozoa is diverse - sea, freshwater, moist soil.Parasitism spread.Many species of parasitic protozoa cause serious illness in humans, domestic and farm animals, and plants.
Protozoa can move with the help of pseudopodia, flagella or cilia and react to various stimuli (phototaxis, chemotaxis, thermotaxis, etc.).Protozoa feed on tiny animals, plant organisms, and decaying organic material;Parasitic forms live on the body surface, in body cavities or in the tissue of their hosts.
The way food enters the cell body is also different: pinocytosis, phagocytosis, osmotic route, active transport of substances through the membrane.They digest the food they eat in digestive vacuoles, which are filled with digestive enzymes.Some of them have photosynthetic intracellular symbionts - Chlorella or chloroplasts (e.g. Euglena) - and are able to synthesize organic material from inorganic substances using photosynthesis.
Toxoplasma
Toxoplasmosis (Greek toxon - bow, bow) are diseases that are caused by single-celled protozoa in a wide variety of places in the human body, where they are introduced and reproduced.The causative agent of toxoplasmosis, Toxoplasma gondii, belongs to the genus Protozoa, to the class of flagellates.
Toxoplasma has a crescent shape and resembles an orange slice: one end of the parasite is usually pointed, the other is rounded and up to 7 micrometers long.Toxoplasma moves by gliding.They penetrate into the interior of the cells and rotate around the longitudinal axis.
Toxoplasma reproduces asexually, it occurs by longitudinal division into two parts.Repeated longitudinal division in the protoplasm of the host cell creates a collection of daughter parasites, which is called a “pseudocyst”.Pseudocysts occur in large numbers in various organs of the infected organism during the acute stage of infection.They are surrounded by a very vague membrane, apparently formed by the host cell, and have no shell of their own.Cells filled with such parasites are destroyed.The released parasites invade new cells, divide again and form new pseudocysts.
If the infection becomes chronic, toxoplasma remains in the form of true cysts (they surround themselves with a special shell).Such cysts can remain in the body of animals and humans for a long time (up to 5 years).Cysts also occur in the tissues of the eye, heart, lungs, and some other organs.The number of toxoplasmas in a cyst ranges from a few copies to several thousand.
Giardia
Giardia is the simplest parasitic animal of the flagellate class.It has a pear shape and a length of 10 to 20 micrometers.The dorsal side is convex, the ventral side is concave, forming a suction cup for temporary attachment to the epithelial cells of the host's 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 parasite transmission is common.Infection with cysts occurs when protozoa enter the lower intestine through the mouth through ingestion of contaminated food or water or through dirty hands, etc.The incidence occurs sporadically.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 cooked.In the United States, giardiasis is the most common gastrointestinal disease of parasitic origin.According to INTERNET, up to 20% of the entire world population suffers from giardiasis.Infection can occur by drinking unboiled tap water or ice made from it while washing vegetables and fruits with unboiled water.There is a high risk of illness when swimming in open water and pools contaminated with Giardia cysts.A newborn can become infected during childbirth during eruption and birth of the head.The contact route of infection is less common, but with a high prevalence of the disease it becomes quite real, especially among population groups with low general hygiene knowledge.
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.Non-sexual infections (from toiletries, bed, etc. shared with the patient) are less common.It can be transmitted from a sick mother to a newborn girl.The disease can become chronic.If it spreads to the limbs, it is difficult to treat.The vagina is most commonly affected in trichomoniasis;profuse 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 mild mucous discharge.
amoeba
Amoebas live in fresh water.The body shape is not constant.Makes very slow movements (13 mm/hour).It moves with the help of pseudopodia, the body flows from one part to another: either it shrinks into a round lump, or spreads its “hyoid legs” to the sides.
The pseudopodia are also used to absorb food.During the feeding process, food particles flow around the amoeba's body from all sides and these enter the cytoplasm.A digestive vacuole is created.This diet is called fabititosis.The diet consists of bacteria, unicellular algae and small protozoa.Dissolved substances from the environment are absorbed by pinocytosis.
The body of the amoeba has a contractile or pulsatile vacuole.Its function is to regulate the osmotic pressure in the body of the protozoan.Reproduction occurs asexually through mitosis and subsequent division of the amoeba body into two parts.Amoebas of the genus Entamoeba, which live in the human digestive tract, are of paramount importance in medicine.These include dysenteric or histolytic amoebas.
Malaria plasmodium
Malaria plasmodium causes malaria, which is accompanied by fever attacks, blood changes and enlargement of the liver and spleen.There are four forms of malaria: three-day malaria, four-day malaria, tropical malaria and oval malaria.The source of the disease is a person suffering from malaria and the carrier is a female malaria mosquito.A female mosquito that becomes infected by sucking a patient's blood is capable of transmitting Plasmodium.A healthy person becomes infected through the bite of 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 (tissue) development cycle, then enter the blood and penetrate the red blood cells.Here they complete the second (erythrocyte) development cycle, which ends with the breakdown of erythrocytes and the release of pathogens into the patient's blood, which is accompanied by a fever attack.