Animal anatomy, histology, pathological anatomy

BIBLIOGRAPHY
1. Zharov A.V. Pathological anatomy of animals. – St. Petersburg; M.; Krasnodar: Lan, 2013. – 620 p. – Access mode: EBS “Lan” (http://e.lanbook.com), ISBN: 978-5-8114-1450-5 2. Zharov A.V. Forensic veterinary medicine. Textbook. – St. Petersburg; M.; Krasnodar: Lan, 2014. – 464 p. – Access mode: EBS “Lan” (http://e.lanbook.com),


Topic 2: Pathomorphology of necrosis and atrophy.

Plan:

1. Necrosis about understanding the etiology (cause) and pathogenesis (suspension

2. Types, causes and morphology of gangrene.

3. Atrophy and its types, etiology and pathogenesis.

Keywords: necrosis, coagulation, colliquation, wet, lysis, gangrene, atrophy.

1). Necrosis - local death (Greek: Necros - dead) is characterized by the destruction of certain organs or tissues of a living organism, the essence of necrosis is the complete and irreversible cessation of tissue activity. Usually, before necrosis, a process of gradual degradation occurs, which often lasts a long time, and this process is called necrobiosis. Etiology and pathogenesis of necrosis. Necrosis is of two types: physiological and pathological. Necrosis can be caused by mechanical, physical, chemical and biological factors. Types of necrosis. Direct necrosis is observed at the site of exposure of an organ or tissue to mechanical, physical, chemical and biological factors. Indirect (incorrect) necrosis is said to be caused by factors affecting the location, but not the location of necrosis. Coagulative (dry) necrosis quickly removes moisture from dead tissue, and foci of necrosis dry out. This is mainly observed on the skin and in tuberculosis. In liquefaction (wet) necrosis, dead tissue retains moisture, causing the necrotic lesions to become moist. Such necrosis is observed in the uterus, brain and tissues rich in water. Morphology of necrosis: The size of necrosis varies from visible to organ size. The shape is oval, round, cylindrical, they can be in spotted forms. When microscopically presenting necrosis, three different processes can be seen. Then the pyknosis shrinks to the size of the cells and hardens. Rexis, in which the cell disintegrates and divides into particles. Lysis is when the cells completely dissolve. The resulting dead tissue is surrounded by a membrane. In other cases, salts accumulate in decomposed sands, a process known as petrification or calcification. The torn tissue is limited to normal tissue. Necrosis in the heart muscle and brain leads to the death of the body.

Necrosis Necrosis is the death of individual cells, tissue areas and organs. The essence of necrosis is the complete and irreversible cessation of vital activity, but not in the entire body, but only in some limited area (local death). The causes of necrosis are very diverse: the action of chemical and physical factors, viruses and microbes; damage to the nervous system; disturbance of blood supply. With slow death, dystrophic changes occur, which increase and reach a state of irreversibility. This process is called necrobiosis. Necrosis that occurs directly at the site of application of harmful agents is called direct. If they occur at a distance from the place of exposure to a harmful factor, they are called indirect. These include: 1. Angiogenic necrosis, which is formed as a result of cessation of blood flow. 2. Neurogenic necrosis, caused by damage to the central and 6 peripheral nervous systems. 3. Allergic necrosis: skin necrosis in chronic erysipelas of pigs. Morphological characteristics of necrosis. The sizes of dead areas vary: from microscopic to entire organs. The following types of necrosis are distinguished: A. Dry (coagulation) necrosis. Necrotic areas have a dense consistency, whitish-gray or grayish-yellow color. An example of dry necrosis can be anemic infarctions. Sometimes it resembles wax in appearance; This is where waxy or Zenker necrosis occurs. The cut surface is dry, the tissue pattern is erased; this includes the so-called caseous (cheesy) necrosis, in which the dead tissue is a dry crumbling mass of yellowish-gray color. B. Wet (colliquation) necrosis occurs in tissues rich in moisture (for example, the brain), and also provided that the area of ​​necrosis does not dry out. Sometimes foci of dry necrosis may undergo liquefaction (secondary colliquation). B. Gangrene is classified as necrosis, but is characterized by the fact that it may not occur throughout the entire body, but only in areas in contact with the external environment. Dry gangrene (mummification) is observed in the skin. Dead areas are dry and dense, brown or black in color. Wet gangrene (putrefactive or septic) is caused by the action of putrefactive microorganisms on dead tissue. Microscopic changes in the cell during necrosis. Changes in the nucleus have three types: karyopyknosis - wrinkling; karyorrhexis - decay or rupture; karyolysis - dissolution. With karyopyknosis, a decrease in nuclear volume occurs due to chromatin compaction; it wrinkles and therefore becomes more intensely colored. Karyorrhexis is characterized by the accumulation of chromatin clumps of varying sizes. During karyolysis, voids (vacuoles) are formed in the nucleus at the sites of chromatin dissolution. These voids merge into one large cavity, the chromatin disappears completely, the nucleus does not stain, but dies. Coagulation (folding) of proteins occurs in the cytoplasm. The cytoplasm becomes more dense. This is referred to as plasmopyknosis or hyalinization. Later, the cytoplasm breaks up into separate clumps and grains (plasmorhexis) and then the cytoplasm dissolves (plasmolysis). Collagen, elastic and reticular fibers lose their outlines, become basophilically stained and fragmented, and later liquefy. Sometimes the dead interstitial substance becomes similar to fibrin fibers (fibrinoid transformation). When the epithelium becomes necrosis, the soldering (cementing) substance liquefies - cell discomplexation and desquamation or desquamation. Outcomes of necrosis. In foci of necrosis, tissue decay products (detritus) accumulate, which irritate the surrounding living tissues and inflammation develops in them. A red stripe (demarcation line) forms at the border between living and dead tissues. At the site of necrosis, granulation tissue forms, from which a scar is formed. The replacement of necrosis by connective tissue is called organization. Calcium salts are easily deposited in dead material, which is called calcification or petrification. If dead tissue is not liquefied and replaced, a connective tissue capsule is formed around it - encapsulation occurs. When a capsule forms around the area of ​​wet necrosis, a cyst is formed - a cavity with liquid contents. If, during demarcation inflammation, increased emigration of leukocytes occurs, purulent softening occurs, leading to the delimitation of the necrotic focus from the surrounding tissues. This is called sequestration, and the isolated dead area is called sequestration. Granulation tissue develops around the sequester, from which a capsule is formed. When there is necrosis in the outer parts of the body, they can be completely rejected from the body - mutilation. The significance of necrosis is that the dead areas cease to function. Necrosis in the heart and brain often leads to death. Absorption of tissue decay products causes poisoning of the body (autointoxication). Questions for self-control 1. Clinical signs of death, determination of causes of death? 2. What are hypostases and the time of their occurrence? 3. What is the mechanism of the appearance of corpse green? 4. What is fibrinoid necrosis? 5. What is an organization? which have an irritating effect on surrounding living tissues and inflammation develops in them. A red stripe (demarcation line) forms at the border between living and dead tissues. At the site of necrosis, granulation tissue forms, from which a scar is formed. The replacement of necrosis by connective tissue is called organization. Calcium salts are easily deposited in dead material, which is called calcification or petrification. If dead tissue is not liquefied and replaced, a connective tissue capsule is formed around it - encapsulation occurs. When a capsule forms around the area of ​​wet necrosis, a cyst is formed - a cavity with liquid contents. If, during demarcation inflammation, increased emigration of leukocytes occurs, purulent softening occurs, leading to the delimitation of the necrotic focus from the surrounding tissues. This is called sequestration, and the isolated dead area is called sequestration. Granulation tissue develops around the sequester, from which a capsule is formed. When there is necrosis in the outer parts of the body, they can be completely rejected from the body - mutilation. The significance of necrosis is that the dead areas cease to function. Necrosis in the heart and brain often leads to death. Absorption of tissue decay products causes poisoning of the body (autointoxication). Questions for self-control 1. Clinical signs of death, determination of causes of death? 2. What are hypostases and the time of their occurrence? 3. What is the mechanism of the appearance of corpse green? 4. What is fibrinoid necrosis? 5. What is an organization? which have an irritating effect on surrounding living tissues and inflammation develops in them. A red stripe (demarcation line) forms at the border between living and dead tissues. At the site of necrosis, granulation tissue forms, from which a scar is formed. The replacement of necrosis by connective tissue is called organization. Calcium salts are easily deposited in dead material, which is called calcification or petrification. If dead tissue is not liquefied and replaced, a connective tissue capsule is formed around it - encapsulation occurs. When a capsule forms around the area of ​​wet necrosis, a cyst is formed - a cavity with liquid contents. If, during demarcation inflammation, increased emigration of leukocytes occurs, purulent softening occurs, leading to the delimitation of the necrotic focus from the surrounding tissues. This is called sequestration, and the isolated dead area is called sequestration. Granulation tissue develops around the sequester, from which a capsule is formed. When there is necrosis in the outer parts of the body, they can be completely rejected from the body - mutilation. The significance of necrosis is that the dead areas cease to function. Necrosis in the heart and brain often leads to death. Absorption of tissue decay products causes poisoning of the body (autointoxication). Questions for self-control 1. Clinical signs of death, determination of causes of death? 2. What are hypostases and the time of their occurrence? 3. What is the mechanism of the appearance of corpse green? 4. What is fibrinoid necrosis? 5. What is an organization? What are hypostases and when do they occur? 3. What is the mechanism of the appearance of corpse green? 4. What is fibrinoid necrosis? 5. What is an organization? What are hypostases and when do they occur? 3. What is the mechanism of the appearance of corpse green? 4. What is fibrinoid necrosis? 5. What is an organization?

2) Gangrene is a type of necrosis in which dying tissue is formed under the influence of external factors such as air, temperature, bacteria. The decay is called gangrene. The word gangrene comes from the Greek word meaning fire. There are two types of gangrene: dry and wet. Dry gangrene is most common on the skin and feet. Wet gangrene is more common in internal organs.

3). Atrophy (Greek Α-negation, trophe - nutrition) is a decrease in the size of an organ, tissue or similar cell and a corresponding decrease or loss of function. Atrophy should not be confused with congenital pathological conditions (disability), hypoplasia (organ failure), aplasia (absence of an organ). There are physiological and pathological atrophies. Atrophic changes in physiological conditions develop throughout the life of the organism. Physiological atrophy is usually divided into evolutionary and involutional (I.V. Davidovsky). Evolutionary atrophy is the reduction of an organ or cell during the growth and development of the organism. In animals and humans, the thyroid gland completely atrophies during growth retardation, while in birds the sac begins to disappear during puberty. In female mammals, the uterus and mammary glands sometimes experience atrophy and hypertrophy. Involution throughout the body during aging and slows down protein synthesis in cells due to their characterized by a gradual decrease in size. Pathological atrophy is divided into general and local, respectively. General atrophy is characterized by the sudden entry into the pathological process of several organs at once. This is associated with starvation, chronic diseases, malignant tumors, as well as disorders of the blood, nerves and digestive organs. Local atrophy is divided into six types for reasons: 1. Neurotic atrophy occurs as a result of damage to the nervous system.2. Angiogenic atrophy occurs due to local circulatory disorders, narrowing of blood vessels or thickening of the vascular wall (sclerosis).3. Hormonal atrophy is caused by dysfunction of the endocrine glands.4. Inactivity occurs as a result of atrophy resulting from weakening or complete loss of the functional activity of organs and tissues.5. Compression atrophy. In mechanically suppressed organs, the blood vessels narrow, the organ’s nutritional process is disrupted, and they undergo atrophy. 6. Physico-chemical atrophy. Physical atrophy is caused by exposure to radiation. Chemicals are formed by exposure to chemicals. Pathogenesis of atrophy. Microscopic changes in atrophied organs and tissues are characterized by drying out due to thickening of the cytoplasm of the cells, but their structure does not change. The shape of the organ does not change, the size decreases, the color is darker or darker due to the lack of blood, the surface is smooth or granular. With atrophy caused by lipofuscin, the organ becomes gray, which is called gray atrophy. Atrophy of internal organs (heart, intestines, etc.) occurs in a concentric and eccentric state. If the middle wall becomes thinner and the cavity widens, it is called eccentric (seen in emphysema). Simultaneous thinning of the organ wall and reduction of the cavity is called concentric atrophy. Consequences of atrophy. Atrophy is a reversible process, when the cause is identified and eliminated, the tissue and organ are restored.