Thyroid gland and its main properties

Thyroid gland (Latin glandula thyr (e) oidea) is an endocrine gland in vertebrates that stores iodine and produces iodine-containing hormones (iodothyronines) involved in the regulation of metabolism and the growth of individual cells, as well as the body as a whole - thyroxine (tetriodothyronine, T4) and triiodothyronine (T3). The synthesis of these hormones occurs in epithelial follicular cells, called thyrocytes.

Calcitonin, a peptide hormone, is also synthesized in the thyroid gland: in parafollicular or C-cells. It compensates for bone deterioration by embedding calcium and phosphate in bone tissue, and also prevents the formation of osteoclasts, which in the activated state can lead to the destruction of bone tissue, and stimulates the functional activity and reproduction of osteoblasts. Thus, it participates in the regulation of the activity of these two types of formations, thanks to the hormone, new bone tissue is formed faster. The thyroid gland is located in the neck under the larynx in front of the trachea. In humans, it has the shape of a butterfly and is located on the surface of the thyroid cartilage. Diseases of the thyroid gland can occur against the background of unchanged, low (hypothyroidism) or increased (hyperthyroidism, thyrotoxicosis) endocrine function. Iodine deficiency found in certain areas can lead to the development of endemic goiter and even cretinism.

The thyroid gland consists of two lobes (lat. Lobus dexter and lobus sinister) connected by a narrow isthmus. This isthmus is located at the level of the second-third ring of the trachea. The lateral lobes enclose the trachea and are attached to it by connective tissue. The shape of the thyroid gland can be compared with the letter "H", with the lower horns short and wide, and the upper - tall, narrow and slightly divergent. Sometimes an additional (Pyramidal) thyroid lobe is determined.

On average, an adult human thyroid gland weighs 12–25 g and 2–3 g in a newborn. The dimensions of each lobe are 2.5–4 cm long, 1.5–2 cm wide, and 1–1.5 cm thick. A volume of up to 18 ml in women and up to 25 ml in men is considered normal. The weight and size of the thyroid gland is individual; so, women may have small variations in volume due to the menstrual cycle. [1]The thyroid gland is an endocrine gland, in the cells of which - thyrocytes - two hormones are produced (thyroxin, triiodothyronine) that control metabolism and energy, growth processes, maturation of tissues and organs. C-cells (parafollicular) related to the diffuse endocrine system, secrete calcitonin - one of the factors that regulate calcium metabolism in cells, a participant in the growth and development of the bone apparatus (along with other hormones). Both excessive (hyperthyroidism, thyrotoxicosis) and insufficient (hypothyroidism) functional activity of the thyroid gland cause various diseases, some of which can cause side effects in the form of systemic degeneration or obesity.

For the diagnosis of thyroid dysfunction, indicators T3, T4, TSH and the autoimmune process are examined.The blood supply to the gland is very abundant, carried out by the two upper (lat. Arteria thyroidea superior), extending from the external carotid artery (lat. Arteria carotis externa), and the two lower thyroid arteries (lat. Arteria thyroidea inferior), extending from the thyroid-neck (lat . truncus thyrocervicalis) of the subclavian artery (lat. arteria subclavia). In animals, the upper thyroid arteries are called cranial thyroid arteries (arteria thyroidea cranialis), and the lower ones are called caudal thyroid arteries (lat. Arteria thyroidea caudalis).

Approximately 5% of people have an unpaired artery (lat. Arteria thyroidea ima), extending directly from the aortic arch (may also depart from the brachiocephalic trunk (lat. Truncus brachiocephalicus), subclavian artery (lat. A. subclavia), as well as from the lower thyroid arteries (lat. A. thyroidea inferior). It enters the thyroid gland in the region of the isthmus or the lower pole of the gland. The thyroid tissue is also supplied by the small arterial branches of the anterior and lateral surface of the trachea. Inside the organ all small branches of the thyroid arteries are woven. After the arterial to Ov will give food and oxygen to the tissues of the thyroid gland, she, taking carbon dioxide, hormones and other metabolites, collects in small veins that are woven under the capsule of the thyroid gland. Thus, the venous outflow occurs through the unpaired thyroid plexus (Latin plexus thyroidus impar), which opens in brachiocephalic veins (lat. vena brachiocephalica) through the inferior thyroid veins (lat. vena thyroidea inferior).

The interstitial fluid (lymph) located between the cells of the thyroid gland flows through the lymphatic vessels to the lymph nodes. This lymphatic outflow of the thyroid gland is provided with a well-organized system of lymphatic vessels. There are many branches between individual lymphatic vessels and nodes.