Dental diseases ( thymus ) gland
Endocrinology / / August 12, 2017
name "thymus" many authors, not without reason considered a failure, as the term "goiter" is associated with the word "goiter."Name iron "thymus" is more appropriate, because it contains a reference to the external form of cancer, the top of the arc which have the form of a fork.
thymus gland (glandula thymus) has long attracted the attention of researchers.Issues embryogenesis, histology, age gland morphology and physiology and pathology of the subject of numerous studies of domestic and foreign authors.However, until now there remain many unclear not only to the physiological role of cancer and its clinical manifestations of disease, and the histological structure of the body.Many researchers are skeptical accessories thymus endocrine organs.
embryogenesis, anatomy and histology
thymic epithelium tab comes from the third pair of pharyngeal pouches in the form of a pair of blind outgrowths on the 4th week of intrauterine life.Both outgrowth further otshnurovyvayutsya and placed under the thyroid
thymus gland is located behind the arm and body of the sternum in the upper part of the anterior mediastinum, in a space that is free of the pleura.The front and sides on the edge of the iron enter the lungs and the back of it are the upper section of the pericardium and the initial part of the large vessels of the heart.Both the proportion of cancer in close contact along the median line, making the body think unpaired.At the bottom and up the share of expenditures.The upper arc (fork ends), gradually narrowing, sometimes close to the isthmus of the thyroid gland.The front side of the gland is slightly convex, the rear - concave surface of the gland hummocky.body color of grayish-pink children, in adults (due to the development of fat) - yellow.Sometimes there are additional share of the thymus gland.In extremely rare cases, the iron does not.The shape and size of the thymus gland is highly variable: the newborn weighs an average of 10-15 g;its weight reaches a maximum of 11-15 years (25-35 g), and with the onset of puberty, the thymus gland begins to regress.Slices
thymus have a diameter of from 1 to 10 mm.In each lobe distinguishes its peripheral part (cortex) and the center (medulla).A clear boundary between the cortex and medulla there.Free cellular elements are arranged in loops formed by Process reticular stromal cells lobules.In the peripheral zone generally found small, round cells limfotsitopodobnye.Most researchers identify with their blood lymphocytes.However, some authors consider the marginal zone cells less differentiated epithelial cells, thus having a greater capacity to proliferate and actively involved in regeneration.
In the central area distinguish large cells with pale cytoplasm of epithelial origin and Hassall's corpuscles.The latter are concentrically layered on each other in one or more rows of flat epithelial cell clusters with granular decay phenomena in the heart.Furthermore, especially in the central and peripheral lobes area detected in a more or less significant amount of eosinophils, neutrophils, plasma cells.
The thymus gland is richly provided with blood vessels.Arterial branches that feed the gland, often come from a.thoracica interna, truncus brachio-cephalicus, a.thyreoidea caudalis, a.thyreoidea ima.
In children, according to the riches thymus vessels only slightly inferior to the typical endocrine organs, as is the thyroid gland.
total number of vessels included in the thymus, it is quite different.In iron distinguish more permanent and powerful main artery and additional arterial vessels.Capillary arterial network is particularly well developed in the cortex.Vienna, departing from the thymus gland, go into outer brachial vein, and larger - to the nameless and the jugular vein.Blood vessels are accompanied by lymphatic vessels.Recent on leaving the pouring prostate to the lymph nodes located behind the sternum and around the upper pole of the thymus.
gland innervation carried branches of the sympathetic and vagus nerves.The first originated from the lower cervical and first thoracic sympathetic ganglia, the second - from the vagal cardiac plexus.Nerves form a grid in the capsule gland and follow vessels.In addition to vascular nerves in the thymus found bellied nerve endings in the parenchyma.
Age changes apply not only to the prostate parenchyma and connective its core, but also vascular organ supply.
Histological study of the age dynamics of human thymus allowed to allocate 4 basic structural types:
1. Fetal type (on average up to a year) is characterized by a predominance of the cortex of the brain, small gassalevymi calves, very little development of connective tissue skeleton, abundant small vessel power.
2. Infantile type (1 to 3 years).The structural features of its disappearance is a predominance of the cortical layer of the brain, enlargement of Hassall corpuscles and the emergence of some large vascular branches.
3. Children Type (3 to 8 years) is characterized by a distinct development of connective tissue skeleton with the advent of the interlobular septa, rich gland parenchyma with an equal development of the cortex and medulla, a decrease in the number of vessels, but increasing their diameter.
4. Teenage ranneinvolyutivny or type (from 9 to 13-15 years).In this period there is a gradual decrease in parenchymal organ, the appearance of an amorphous mass in the center of large gassalevyh cells.The nature of the vascular supply is the same as in the children's class, but the diameter of the lumen of blood vessels decreases somewhat.
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process of involution of the body, which began with the onset of puberty, later gradually progresses.Thus there is a substitution of parenchymal organ connective tissue and fat, zapustevanie vascular bed.However, in extreme old age in the thymus ( "sternum fat body") on histological examination revealed separate clusters of epithelial cells and gassalevyh cells.
long been known that, in addition to age involution, thymus quickly undergoes changes at various harmful effects of external and internal environment of the body: starvation, burns, infection, vaccination, poisoning by different poisons, ionizing radiation, etc. Under these influences iron..drastically reduced in size.In contrast to the age-related changes involution of the thymus gland under the influence of various factors on the body called random (aktsidentalnoy).Histological changes during accidental involution expressed in lobular breast reduction due to lymphoid cells of the marginal zone.With regard to the epithelial cells of the central zone and gassalevyh cells, they, by contrast, hypertrophy and increase in the number of (false involution).
in the thymus rabbits and rats poisoned with formalin and other poisons, biopsy revealed signs of secretory activity gassalevyh cells and epithelial cells, ie. E. Iron, despite the reduction of its weight at the expense of lymphoid cells, is under these conditions in a state of secretory excitation.When intense and long-acting damaging factors (starvation, toxicity, etc. X-ray irradiation. D.), Along with the destruction of lymphocytes and epithelial gland tissue loses the ability to proliferate, which ultimately leads to the true organ involution.