Medical: Glandula thyroidea
- Thyroid lobe
- Cold knot
- Warm knot
- Hot knot
- Cyst
- Thyroid tumor
- Graves’ disease
- Hashimoto’s thyroiditis
Definition
The thyroid gland (Glandula thyroidea) is an unpaired gland, which is located on the neck below the larynx. It consists of two lobes connected with each other over the so-called isthmus, which extend to both sides of the neck. Through this, it resembles a shield; therefore the name.
It is called a gland because it produces and secretes hormones. Its primary function is the regulation of energy metabolism and growth. At the back of the thyroid gland, the human being still has so-called parathyroid glands, which are to be distinguished from the thyroid gland.
Anatomy of the thyroid gland
The thyroid gland, which weighs 20 to 25g in adults, is one of the so-called endocrine organs of the body. Its (endocrine) main task is therefore the production of hormones which are released (secreted) into the blood. It consists of two lobes located on either side of the trachea and the cartilages of the larynx.
Accordingly, these laryngeal cartilages are called thyroid cartilages. In men, it shows as a bulge on the neck, the Adam’s apple. The connecting piece between the two lobes is the so-called isthmus.
- Throat
- Thyroid cartilage of the larynx
- Thyroid gland
- Trachea (windpipe)
Additionally there is the so-called parathyroid gland. The parathyroid glands are four lenticular-sized glands weighing about 40 mg. They are located behind the thyroid gland.
Sometimes an additional parathyroid gland can also be found. The parathyroid gland produces an important hormone (parathyroid hormone) that regulates the calcium balance. Thyroid gland anatomy
- Shield nozzle flaps
- Connecting piece (isthmus)
Function of the thyroid gland
The main task of the thyroid gland is the regulation of the energy metabolism. For this purpose it produces two hormones that regulate the basal metabolic rate, i.e. the energy produced under resting conditions: Thyroxine (T4 for short) and triiodothyronine (T3 for short). They are not only released into the blood in a hormone-dependent manner, but are also stored within the organ in so-called follicles.
The follicles are hollow spaces enclosed by flat surface cells (epithelial cells). However, these are not filled with biologically active hormone, but contain a precursor of the hormone that is easier to store, thyroglobulin. This is also called colloid, is produced by the thyroid cells and then released into the cavity.
From these large protein molecules (thyroglobulin), the required amount of hormone is then cut out by enzymes as required and released into the bloodstream. Structure of the thyroid gland under the microscope
- Epithelial cells (flat)
- Filled follicles (thyroid follicles with thyroglobulin)
The most important component of thyroid hormones is iodine, which is absorbed as a negatively charged ion, i.e. as iodide, into the epithelial cells of the thyroid gland and the amino acid tyrosine is coupled. Thyroxine requires 4 iodine atoms (therefore it is also called tetraiodothyronine or T4; Greek tetra = four), whereas triiodothyronine, T3- Hormone, requires only three iodine atoms.
T4 represents the hormone that is initially predominantly produced by the thyroid gland, but which is converted into the tenfold more effective T3 in the target tissues. This task is performed by an enzyme called deodase, which removes one iodine atom from tyrosine at a time. T3 itself is only produced in small amounts by the thyroid gland itself.
The size of the cells surrounding the thyroid follicles and the filling state of the follicles reflect the activity of the entire organ. In childhood, a lot of hormone is needed, accordingly the follicles are small, colloid poor and lined with large epithelial cells. This is due to the hormone that stimulates the thyroid gland to grow and release hormones (Thyroidea Stimulating Hormone, TSH for short), which is produced by the hypothalamus (a part of the brain) and reaches the thyroid gland via the bloodstream.
In contrast, large amounts of hormone are stored in old age and the thyroid follicles contain a lot of colloid. (Less hormone is needed; in older people the energy requirement decreases accordingly).Due to the increased energy requirement, both cold and pregnancy have an activating effect on the thyroid gland; heat tends to have an inactivating effect. A further function of the thyroid gland is the regulation of the calcium level in the blood.
Specialized cells, which are interspersed between the follicle cells, form the hormone calcitonin. This small hormone lowers the calcium level in the blood by promoting the incorporation of calcium into the bones. It thus counteracts osteoporosis. In addition, it inhibits the cells that are naturally responsible for the breakdown of bone tissue (and thus prevent excessive ossification in the body), since these too can contribute to an increased calcium level in the blood. Another mechanism of Calcitonin is to promote the excretion of calcium through the kidneys.
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