What Is the Thyroid?

The thyroid gland is a very important gland in vertebrates and is an endocrine organ. In mammals it is located below the neck thyroid cartilage, on both sides of the trachea. The human thyroid gland resembles a butterfly and is named after a shield.

The thyroid gland is a very important gland in vertebrates and is an endocrine organ. In mammals it is located below the neck thyroid cartilage, on both sides of the trachea. The human thyroid gland resembles a butterfly and is named after a shield.

Chinese name

thyroid

Foreign name

Glandula thyr (e) oidea

Nature

Endocrine organs

Features

Regulate calcium balance in the body

Secreted hormone

Thyroid hormone

Thyroid gland overview

The thyroid gland controls how fast it uses energy, makes protein, and regulates the body's sensitivity to other hormones. The thyroid gland relies on the production of thyroxine to regulate these reactions. There are triiodothyronine (T3) and thyroxine, also known as tetraiodothyronine (T4). Both regulate metabolism, growth rate, and mediate other body systems. T3 and T4 are synthesized from iodine and tyrosine. The thyroid gland also produces calcitonin, which regulates the calcium balance in the body.

Anatomy of the thyroid gland:

The thyroid is the largest endocrine gland in the adult. It is located in the front of the neck. It is brownish red and has an "H" shape. It weighs about 25g. The left and right lobes of the thyroid are cone-shaped (the right lobe is slightly larger), and are attached to the sides of the larynx and trachea. It is attached to the ring cartilage, so the thyroid can move up and down with the throat when swallowed. The thyroid gorge is connected to the left and right lobes and is located in front of the tracheal cartilage ring of 2-4. A few people may lack the thyroid gorge. More than 60% of people stick out a cone-shaped leaf from the isthmus. The cone-shaped leaves vary in length and some reach the hyoid bone, which is a remnant of the thyroid development process. Near the left and right lobes of the thyroid gland, there is an independent thyroid tissue block called the parathyroid gland. The thyroid gland has two layers of capsules. The outer layer is the thyroid sac, which is composed of the deep cervical fascia (frontal fascia). The surface of the glandular tissue and penetrates into the parenchyma of the gland, separating the glandular tissue into several leaflets. The loose connection between the thyroid sac and the fibrous sac is easy to separate, so it can be used clinically for intrathyroid cystectomy. From the hyoid bone to the thyroid isthmus or cone-shaped lobe, a small muscle bundle sometimes appears, called the levator thyroid muscle, which has the effect of raising the thyroid.

The thyroid parenchyma is mainly composed of many thyroid follicles. Follicular epithelial cells can synthesize, store, and secrete thyroid hormones. The main role of thyroid hormone is to promote the body's metabolism and maintain the normal growth and development of the body, which has a greater impact on the development of the bones and nervous system. When the thyroid secretion function is low, the body's basal metabolic rate is low, and myxedema can occur. If the thyroid secretion function is lost during the fetus or infancy, the development of the bones and the brain is retarded, manifested as a stunt with short bodies and mental retardation. When hyperthyroidism occurs, rapid heartbeat, insomnia, irritability, and hand tremor can occur, which are related to increased excitability of the sympathetic and central nervous systems.

Another type of endocrine cell in the thyroid, called parafollicular cells or bright cells, produces calcitonin. When blood calcium rises, it can promote calcium reduction.

Blood supply to the thyroid gland: The thyroid is supplied with blood from the upper thyroid artery and the lower thyroid artery. The superior thyroid artery originates from the external carotid artery or common carotid artery, with the lateral branch of the superior laryngeal nerve descending to the upper thyroid 1 to 2 cm into 2 to 3 glandular branches distributed in the glands. The inferior thyroid artery originates from the thyroid neck trunk, passes through the common carotid artery to the back of the left and right lobes of the thyroid, and branches into the glands. The inferior thyroid artery is closely related to the recurrent laryngeal nerve. Most of the arteries on the left are located in front of the left recurrent laryngeal nerve, and the arteries on the right pass through the back of the right recurrent laryngeal nerve; In addition to the above two arteries, the lower thyroid arteries (or thyroid arteries) originating from the trunk of the head, common carotid artery, or internal thoracic arteries, or directly from the autonomic arch, can be found in the lower part of the glands. The veins of the thyroid gland gather on the surface of the gland and are drained from the three pairs of veins of the upper, middle, and lower thyroid glands, which flow into the internal jugular vein and head and arm veins, respectively. The thyroid is an extremely rich blood vessel. In the anterior cervical region of patients with diffuse toxic goiter, murmurs or tremors are often heard. The thyroid gland is dominated by sympathetic and parasympathetic nerves. The former is mainly from the postganglionic fibers of the cervical sympathetic ganglia, and the latter is from the vagus nerve.