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Diseases of the thymus (thymus gland)



The thymus (thymus gland) is located in the mediastinum and plays a key role in cellular immunity. It is formed from the 3rd and 4th gill arches in close connection with the parathyroid glands. The thymus is relatively large in a newborn, weighs 10–25 g, continues to increase until puberty, and then undergoes a gradual involution with the replacement of the parenchyma with fatty tissue. The thymus is pyramidal, surrounded by a capsule and consists of two lobes. The fibrous processes of the capsule divide each lobe into numerous lobules, each of which has an outer cortical layer surrounding the medulla located in the center. The main cells of the thymus are thymic epithelial cells and T-lymphocytes. Directly beneath the capsule, epithelial cells are tightly packed, but deeper in the cortex and medulla they form a network containing lymphocytes. In the cortex, epithelial cells contain abundant cytoplasm and pale chromatin-poor vesicular nuclei with one small nucleolus; cytoplasmic protrusions contact with neighboring cells. In the medulla, epithelial cells, on the contrary, are poor in cytoplasm and lack processes, they are oval or spindle-shaped with oval dark-colored nuclei. Curls of these cells form Gassal's little bodies with keratinized center.

Thymus is the most important organ of the immune system. The bone marrow stem cells migrate into the thymus and give rise to T-cells here. At the periphery of the lobules there is a layer of protocytic lymphoblasts, which give rise to more mature thymocytes (T cells) located in the cortex and medulla. Most cortical thymocytes are small compact lymphocytes containing CDh markers CD2 and CDh as well as CD4 and C08. The lymphocytes are smaller in the gates of the medulla, but they are similar to those found in the peripheral bloodstream, and are slightly larger than cortical lymphocytes; depending on the presence of surface markers, they can be divided into CD / (TA) and CD8 + (T &) - lymphocytes. In addition, macrophages, dendritic cells, single neutrophils and eosinophils, B-lymphocytes and myoid (muscle-like) cells can be found in the thymus. Myoid cells are of particular interest, since the development of myasthenia (myasthenia gravis) is associated with thymus, and musculoskeletal diseases are diseases of immune origin.

Morphological changes in the thymus occur in various systemic diseases - from immunological to hematological, as well as oncological. Thymus diseases are relatively rare and are divided into: 1) congenital; 2) thymic hyperplasia and 3) thymoma.

Congenital diseases. Congenital thymus aplasia (Di Georgie syndrome; A.Di George). The syndrome develops in violation of the formation of the 3rd and 4th gill arches in the embryonic period, characterized by the following symptoms: 1) thymus aplasia, resulting in the absence of T-cell differentiation and deficiency of the cellular immunity; 2) congenital hypoparathyroidism caused by the genesis of the parathyroid glands; 3) heart defects and large vessels. Death can occur at an early age from tetany; older children develop recurrent and persistent infections.

Thymus cysts. They are rare, they are usually found by chance during an operation or during an autopsy. Cysts rarely reach 4 cm in diameter, can be spherical or branching and are lined with multi-layered or prismatic epithelium. Liquid contents can be serous or mucous, and often hemorrhages.

Thymus hyperplasia. The disease is accompanied by the appearance of lymphoid follicles (follicular thymic hyperplasia). Iron may not be increased. Lymphoid follicles do not differ from those found in the lymph nodes, have germinal centers and contain both dendritic reticular cells and B-lymphocytes, which in small quantities also occur in the normal thymus. Although follicular hyperplasia is observed both in chronic inflammation and in immunological diseases, it is more often observed in myasthenia gravis (65–75% of cases). In this case, the neuromuscular disease autoantibodies to acetylcholine receptors disrupt the transmission of impulses through myonevral compounds. B-cell follicular hyperplasia reflects their role in the formation of autoantibodies. Similar changes to the thymus are sometimes found in Graves' disease, systemic lupus erythematosus, multiple sclerosis and rheumatoid arthritis, as well as other autoimmune diseases.

T o m o m s.
In the thymus, various tumors can form - from germ cells (germ cells), lymphomas, carcinoids. However, the term "thymoma" is used exclusively for tumors of thymic epithelial cells.

There are the following types of tim: 1) Benign - cytologically and biologically benign; 2) malignant - I type - cytologically benign, but biologically aggressive and capable of local invasion and less often distant metastases, II type - the so-called thymic carcinoma - cytologically malignant with all the features of cancer and comparable behavior.

All types of thymomas, benign and malignant, occur in adults (usually over 40) of people, rarely in children. Men and women get sick equally often. Thymomas usually appear in the anterior or upper mediastinum, but sometimes in the neck, thyroid gland, lung gate, less often in the posterior mediastinum.

Macroscopically thymomas are lobed, dense, gray-white formations. Sometimes there are areas of cystic necrosis and calcification, even in those tumors that later turn out to be biologically benign. Most tumors are encapsulated, but in 20-25% of cases there is a clear capsule penetration and infiltration of surrounding tissues by tumor cells. Microscopically, all thymomas are a mixture of epithelial cells and infiltrate from non-tumor lymphocytes in approximately equal proportions.

In benign thymomas, epithelial cells resemble those in the medulla and often have an elongated or fusiform form (medullary thymoma). Tumors containing significant quantities of epithelial cells of the medullary type are almost all benign. Often revealed an admixture of rounded epithelial cells of the cortical type. Some tumors are completely composed of such cells. Thymomas of this type often contain few lymphocytes. Gassal's calves are rare, and when they are, they resemble poorly formed additional curls. Gassal bodies do not have a diagnostic value, as they represent residual normal thymus tissue. Medullary and mixed variants account for about 50% of all tim.

Type I malignant tyoma is a cytologically benign tumor with local invasive growth and sometimes distant metastases. These tumors account for 20-25% of all tim. The ratio of epithelial cells and lymphocytes may be different. Epithelial cells are mainly cortical with abundant cytoplasm and rounded vesicular nuclei. Sometimes palisade is formed from these cells along the vessels. There are also fusiform cells. In the cytoarchitecture of the tumor, there are no signs of malignancy, which, however, is evidenced by the invasive nature of its growth and the younger age of the patients. The prognosis of these tumors is determined by the penetration of the capsule and the degree of invasion into the surrounding structures. If the invasion is minor, which allows you to completely remove the tumor, then 90% of patients experience a 5-year period. Massive invasion is often accompanied by metastasis, while less than 50% of patients experience a 5-year period.

Malignant thymoma type II is also called thymic carcinoma. It makes up about 5% of all tim. Unlike type I malignant thymoma type II has cytological signs of malignancy. The most frequent histological variant of the tumor is squamous cell carcinoma. Another common type of malignant thymoma is lymphoepithelioma, which consists of anaplastic cortical epithelial cells located among a large number of benign lymphocytes. Some of these tumors contain the Epstein — Barr virus genome. Other types of thymus carcinomas include sarcomatoid variants, basaloid carcinoma and clear cell carcinoma.

Thymomas can be asymptomatic, sometimes they are discovered by chance during heart and vascular operations. Among clinically significant tims, 40% of tumors are detected by X-ray examination or due to the appearance of symptoms of pressure on the surrounding tissues, and 50% due to their connection with myasthenia. About 10% of thymomas are associated with so-called systemic paraneoplastic syndromes, such as Graves disease, pernicious anemia, dermatomyositis-polymyositis, and Cushing's syndrome.

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Diseases of the thymus (thymus gland)

  1. Thymus (thymus).
    This gland is a derivative of gill pockets in embryogenesis. The gland has a relatively large mass in newborns and young children, consists of epithelial cells and a significant number of lymphocytes that form follicles. Its maximum development occurs in utero and lasts up to 2 years. Then begins a gradual involution. It is believed that in the prenatal period
  2. Thymus, or forked iron
    The thymus, the thymus, or thymus gland (Fig. 304), is developed quite significantly in the fetal and early postfetal period of life and almost disappears in adult animals. The calf (A) thymus is developed very strongly. It consists of paired parts that stretch along the neck, and a small unpaired part located in the chest cavity. The piglet also has an unpaired thoracic thymus and a very
  3. FORK IRON (thymus)
    Located in the front of the upper mediastinum. The anterior surface of the thymus gland is adjacent to the posterior surface of the sternum, and the posterior surface to the upper part of the pericardium, the initial parts of the aorta and pulmonary trunk, the left brachial head and superior vena cava. The thymus gland consists of two asymmetric lobes: right and left. The lower part of each lobe is expanded, and the upper is narrowed.
  4. Thymus gland (problems)
    The thymus gland, or thymus, is located in the lower part of the neck and is the central organ of the immune system. See the article HEART (PROBLEMS) and the explanation below. The thymus gland binds the physical body of a person to its heart chakra (energy center). The violation of the functions of this gland speaks of a blocked energy, a stagnation in the heart. It is interesting to note that this iron
  5. Thyroid and parathyroid glands. THYMUS
    Thyroid and parathyroid glands. VILOCHKOVAYA
  6. Diseases of the female genital organs and the mammary glands. Diseases of the cervix uterus. DISEASES OF THE BODY OF THE UTERUS. Diseases of uterine tubes. Diseases of the ovaries. BREAST DISEASES
    Diseases of the female genital organs and the mammary glands. Diseases of the cervix uterus. DISEASES OF THE BODY OF THE UTERUS. Diseases of uterine tubes. Diseases of the ovaries. DAIRY DISEASES
  7. Diseases of the endocrine glands. Diseases of the endocrine pancreas. Diabetes. Diseases of the thyroid gland. Thyroid tumors
    1. Etiological factors of diabetes mellitus 1. intoxication 2. tobacco smoking 3. helminth infections 4. viral infections 5. genetic predisposition 2. Pathogenetic mechanisms of acute pancreatitis development 1. duct dyskinesia 4. fungi poisoning 2. biliary reflux 5. alcohol poisoning 3. gastroduodenal reflux 6. overeating 3. Establish compliance by functional
  8. The structure and role of the thymus in the activity of the immune system
    The thymus consists of two lobes: lobus dexter and lobus sinister, connected to each other through loose connective tissue. The upper, narrower ends of the lobes usually extend beyond the chest cavity, protruding above the upper edge of the handle of the sternum and sometimes reaching the thyroid gland. Expanding down, the thymus lies in front of large vessels, heart and part of the pericardium. Gland size
  9. Diseases of the kidneys and urinary system. Prostate diseases
    1. Microscopic characterization of acute pyelonephritis 1. interstitial edema 2. leukocyte infiltration 3. lymphocytic infiltration 4. tubular atrophy 5. necrosis of the pelvis and tubule epithelium 2. Acute post-streptococcal glomerulonephritis is accompanied by 1. doubling of GBM 2. the formation of hemi-lunitis 3. development of hypercellular lymphoma. Chronic glomerulonephritis with post-streptococcal
  10. Specific features of the structure and function of the mammary gland of females of different species of animals. sssn Breast Diseases and Abnormalities
    Mastitis in animals: causes, pathogenesis, signs, classification, treatment and
  11. Diseases of the parathyroid glands
    The parathyroid glands develop from the 3rd and 4th gill arches in close connection with the thymus gland; 4 small glands are located on the upper and lower poles of the thyroid gland. When surgery on the thyroid gland should be remembered that relatively often there is angenesis of one or two glands or their atypical location. The parathyroid glands are made up of the main cells, the cytoplasm
  12. Diseases of the thyroid gland
    Thyroid diseases are of particular importance as they are very widespread. The thyroid gland controls many metabolic processes through the hormones thyroxine (T4) and triiodothyronine (T3). The amount of thyroid hormones is an important indicator of the body's metabolic rate, including oxidative reactions. In the blood, T3 and T4 are in a protein-bound state. Control
  13. Prostate diseases
    The prostate gland of a healthy adult male weighs about 20 g. This muscle-glandular organ, which lies retroperitoneally, covers the upper part of the urethra (urethra). The prostate gland is covered with a rather thin connective tissue capsule. In classical evolutionary anatomy, it is customary to divide the gland into 5 lobes: the posterior, middle, anterior, and two lateral lobes. but
  14. Diseases of the salivary glands
    There are 3 pairs of large salivary glands - the parotid, submandibular and sublingual, lying outside the oral mucosa, but opening their excretory ducts into this cavity. In addition, in the thickness of the oral mucosa are numerous small salivary glands - labial, lingual, cheek and palatine. All of these glands, especially the large ones, are subject to various inflammatory and
  15. Pancreatic Diseases
    The pancreas is located between the sheets of the mesentery of the duodenum and stomach, has a right and left lobe. Her excretory ducts open into the duodenum. The mass of the gland is 10-100 g, which corresponds to 0.13-0.36% of the body weight of the dog. The endocrine portion of the gland is only 3% and is formed by cells of the islets of Langerhans. Alpha cells secrete the hormone glucagon,
  16. Diseases of the breast.
    The mammary gland consists of lobules separated by layers of connective tissue. The lobule consists of a terminal duct, forming numerous tubular ramifications, ending in terminal sections called alveoli. Terminal ducts flow into subsegmental ducts, which, in turn, form a segmental duct. Segmental ducts are formed collective, dairy
  17. Diseases of the thyroid gland.
    The thyroid gland consists of follicles, interfollicular islets and parafollicular cells. The follicles are constructed mainly of A-cells, sometimes contain B-cells (eosinophilic thyrocytes, oncocytes, Ashkenazy — Hurtle cells). A-cells are involved in the formation of thyroglobulin (colloid), the synthesis and secretion of thyroid hormones - iodothyronines (primarily triiodothyronine and thyroxin). B cells in
  18. DISEASES OF IRONS OF INTERNAL SECRETION
    The factors that most often lead to impaired activity of the endocrine glands include a disorder of the function of the CNS, malnutrition, poor circulation in the glands, damage to the tissue elements of the glands with infectious, mechanical, toxic factors, tumor, perverse peripheral tissue reactivity, congenital developmental anomaly. Endocrine dysfunction
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