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Thymus (thymus) diseases

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 adolescence, and then undergoes a gradual involution with the replacement of the parenchyma with fatty tissue. The thymus has a pyramidal shape, is 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 external cortical layer surrounding the medulla located in the center. The main cells of the thymus are thymic epithelial cells and T-lymphocytes. Immediately under the capsule, the epithelial cells are densely packed, but deeper in the cortical and medulla they form a network containing lymphocytes. In the cortical substance, epithelial cells contain an abundant cytoplasm and pale chromatin-poor vesicle nuclei with one small nucleolus; cytoplasmic protrusions are in contact with neighboring cells. In the brain, epithelial cells, on the contrary, are poor in cytoplasm and lack processes, they have an oval or fusiform shape with oval dark-colored nuclei. Curls of these cells form the Gassal bodies with a keratinized center.

Thymus is the most important organ of the immune system. Bone marrow stem cells migrate to the thymus and give rise to T cells. On the periphery of the lobule is a layer of protimocytic lymphoblasts, which give rise to more mature thymocytes (T cells) located in the cortical and brain substance. Most cortical thymocytes are small, compact lymphocytes containing CDh markers CD2 and CDh as well as CD4 and C08. There are fewer lymphocytes in the gates of the brain, however, they are similar to those found in the peripheral bloodstream, and 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 gravis is associated with the thymus, and musculoskeletal diseases are diseases of an immune origin.

Morphological changes in the thymus are found in various systemic diseases - from immunological to hematological and oncological. Thymic diseases are relatively rare and are divided into: 1) congenital; 2) thymus hyperplasia; and 3) thymomas.

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

Thymus cysts. They are rare, usually they are discovered by chance during surgery or during pathological examination. Cysts rarely reach 4 cm in diameter, can be spherical or branching, and are lined with stratified or prismatic epithelium. The liquid contents may be serous or mucous, with hemorrhages often occurring.

Hyperplasia of the thymus. The disease is accompanied by the appearance of lymphoid follicles (follicular hyperplasia of the thymus). 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 amounts can be found in the normal thymus. Although follicular hyperplasia is noted both in chronic inflammation and in immunological diseases, it is more often observed in myasthenia gravis (65–75% of cases). In this neuromuscular disease, autoantibodies to acetylcholine receptors disrupt the transmission of impulses through myoneural compounds. Follicular hyperplasia involving B cells reflects their role in the formation of autoantibodies. Similar changes in the thymus are sometimes found in Graves disease, systemic lupus erythematosus, multiple sclerosis and rheumatoid arthritis, as well as other autoimmune diseases.

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Different tumors can form in the thymus - from germ cells (germ cells), lymphomas, carcinoids. However, the term "thymomas" is used exclusively for tumors from thymic epithelial cells.

The following varieties of thym are distinguished: 1) benign - cytologically and biologically benign; 2) malignant - type I - cytologically benign, but biologically aggressive and capable of local invasion and less distant metastases, type II - so-called thymic carcinoma - cytologically malignant with all the characteristics of cancer and comparable behavior.

All types of thymomas, benign and malignant, occur in adults (usually over 40 years old) people, rarely in children. Men and women get sick equally often. Thymomas usually appear in the anterior or superior mediastinum, but sometimes in the neck, thyroid, or gate of the lung, less commonly 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, a clear penetration of the capsule and infiltration of the surrounding tissues by the tumor cells are observed. 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 shape (medullary thymoma). Tumors containing significant amounts of medullary type epithelial cells are almost all benign. Often an admixture of rounded cortical epithelial cells is detected. Some tumors are made up entirely of such cells. Thymomas of this type often contain few lymphocytes. Gassal's bodies are rare, and when they are, they resemble poorly formed additional curls. Gassal's bodies have no diagnostic value, since they are residual normal tissue of the thymus. Medullary and mixed variants make up about 50% of all thymomas.

Malignant tymoma of type I is a cytologically benign tumor with local invasive growth and sometimes giving distant metastases. These tumors make up 20-25% of all thymomas. The ratio of epithelial cells and lymphocytes may be different. Epithelial cells are mainly of the cortical type with abundant cytoplasm and rounded vesicle nuclei. Sometimes a palisade forms along these vessels from these cells. Fusiform cells are also found. In the cytoarchitectonics 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 insignificant, which allows you to completely remove the tumor, then a 5-year period is experienced by 90% of patients. Massive invasion is often accompanied by metastasis, then less than 50% of patients experience a 5-year period.

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

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

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Thymus (thymus) diseases

  1. Thymus (goiter) gland (thymus).
    This gland in embryogenesis is a derivative of gill pockets. The gland has a relatively large mass in newborns and young children, consists of epithelial cells and a significant number of lymphocytes forming 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
    Thymus - thymus, or thymus gland (Fig. 304), is developed quite significantly in the fetal and at the beginning of the postfetal period of life and almost disappears in adult animals. In calf (A), the thymus is very developed. It consists of paired parts that extend along the neck, and a small unpaired part located in the chest cavity. The pig also has unpaired thoracic thymus and very
  3. Fork gland (thymus)
    Located in 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 sections of the aorta and pulmonary trunk, the left brachiocephalic and superior vena cava. The thymus gland consists of two asymmetric lobes: right and left. The lower part of each lobe is dilated, and the upper one is narrowed.
  4. Thymus gland (problems)
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  5. Thyroid and parathyroid glands. THYMUS
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  6. Diseases of the female genital organs and mammary glands. Cervical Diseases. UTERINE BODY DISEASES. Diseases of the fallopian tubes. DISEASES OF THE OVARIES. BREAST DISEASES
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  7. Diseases of the endocrine glands. Diseases of the endocrine pancreas. Diabetes. Thyroid disease. Thyroid tumors
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  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 sternum handle and sometimes reaching the thyroid gland. Expanding downward, the thymus gland lies in front of large vessels, the heart and part of the pericardium. Gland size
  9. Diseases of the kidneys and urinary system. Prostate diseases
    1. Microscopic characteristics of acute pyelonephritis 1. interstitial edema 2. leukocyte infiltration 3. lymphocytic infiltration 4. tubule atrophy 5. necrosis of the epithelium of the pelvis and tubules 2. Acute post-streptococcal glomerulonephritis is accompanied by 1. doubling of GBM 2. formation of half moon 3. development of hypercellularity. Chronic glomerulonephritis in post-streptococcal
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  11. Parathyroid diseases
    The parathyroid glands develop from the 3rd and 4th gill arches in close connection with the thymus; 4 small glands are located on the upper and lower poles of the thyroid gland. During surgical intervention on the thyroid gland, it should be remembered that agenesis of one or two glands or their atypical location is relatively often observed. The parathyroid glands are made up of main cells, the cytoplasm
  12. Thyroid disease
    Thyroid diseases are of particular importance, as they are very widespread. The thyroid gland controls many metabolic processes due to 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. The control
  13. Prostate diseases
    The prostate gland of a healthy adult male weighs about 20 g. This muscular-glandular organ, lying 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. However
  14. Salivary Gland Disease
    There are 3 pairs of large salivary glands - parotid, submandibular and sublingual, lying outside the mucous membrane of the oral cavity, but opening their excretory ducts into this cavity. In addition, in the thickness of the mucous membrane of the oral cavity are numerous small salivary glands - labial, lingual, buccal and palatine. All these glands, especially the large ones, undergo various inflammatory and
  15. Pancreatic disease
    The pancreas is located between the leaves of the mesentery of the duodenum and stomach, has a right and left lobe. Its 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 part of the gland is only 3% and is formed by the cells of the islets of Langerhans. Alpha cells secrete the hormone glucagon,
  16. Breast disease.
    The mammary gland consists of lobules, separated by layers of connective tissue. The lobule consists of a terminal duct that forms numerous tubular branches ending in end sections called alveoli. Terminal ducts flow into subsegmental ducts, which, in turn, form a segmental duct. Collective, dairy are formed from segmental ducts
  17. Thyroid disease.
    The thyroid gland consists of follicles, interfollicular islets and parafollicular cells. Follicles are constructed mainly from A cells, sometimes they contain B cells (eosinophilic thyrocytes, oncocytes, Ashkenazi-Gürtle cells). A-cells are involved in the formation of thyroglobulin (colloid), the synthesis and secretion of thyroid hormones - iodothyronines (primarily triiodothyronine and thyroxine). B cells in
    The factors most often leading to disruption of the activity of endocrine glands include dysfunction of the central nervous system, malnutrition, impaired blood circulation in the glands, damage to the tissue elements of the glands by infectious, mechanical, toxic factors, a tumor, perverse reactivity of peripheral tissues, and congenital developmental anomaly. Endocrine Dysfunction
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