Thyroid and parathyroid glands

thyroid ima artery

In approximately 10% of people, a small, unpaired thyroid ima artery (L. arteria thyroidea ima) arises from the *brachiocephalic trunk (Fig. B8.5); however, it may arise from the *arch of the aorta or *from the right common carotid, *subclavian, or *internal thoracic arteries. -This small ima artery ascends on the anterior surface of the trachea to the isthmus of the thyroid gland, *supplying branches to both structures. -The possible presence of this artery must be considered when performing procedures in the midline of the neck inferior to the isthmus, because it is a potential source of bleeding (see the blue box "Tracheostomy," p. 1045).

Lymphatic vessels from the parathyroid glands drain

Lymphatic vessels from the parathyroid glands drain with those from the thyroid gland into *deep cervical lymph nodes and *paratracheal lymph nodes

Parathyroid veins drain ?

Parathyroid veins drain into the thyroid plexus of veins of the thyroid gland and trachea

Nerves of Parathyroid Glands

-The nerve supply of the parathyroid glands is abundant; it is derived from *thyroid branches of the cervical (sympathetic) ganglia -Like the nerves to the thyroid, they are vasomotor rather than secretomotor because these glands are ***hormonally regulated.

Thyroid gland cover 😅

-The thyroid gland is surrounded by a thin fibrous capsule, which sends septa deeply into the gland. -Dense connective tissue attaches the capsule to the cricoid cartilage and superior tracheal rings. -External to the capsule is a loose sheath formed by the visceral portion of the pretracheal layer of deep cervical fascia.

Arteries of Parathyroid Glands.

Because the *inferior thyroid arteries provide the primary blood supply to the posterior aspect of the thyroid gland where the parathyroid glands are located, branches of these arteries usually supply these glands (Figs. 8.26B and 8.30A). However, they may also be supplied by branches from the *superior thyroid arteries; *thyroid ima artery; *or laryngeal, *tracheal, and *esophageal arteries.

Arteries of Thyroid Gland.

The highly vascular thyroid gland is supplied by the superior and inferior thyroid arteries (Figs. 8.26B and 8.27). -These vessels lie between the fi brous capsule and the loose fascial sheath.

Parathyroid secretions

The hormone produced by the parathyroid glands, *parathormone (PTH), controls the metabolism of phosphorus and calcium in the blood.

inferior thyroid arteries

The largest branches of the thyro cervical trunks arising from the subclavian arteries, run superomedially **posterior to the carotid sheaths to reach the posterior aspect of the thyroid gland. -They divide into several branches that pierce the *pretracheal layer of the deep cervical fascia and supply the *posteroinferior aspect, including the inferior poles of the gland.

Lymphatic Drainage of Thyroid Gland

The lymphatic vessels of this gland run in the interlobular connective tissue, usually near the arteries; they communicate with a capsular network of lymphatic vessels. -From here, the vessels pass initially to prelaryngeal, pretracheal, and paratracheal lymph nodes. The prelaryngeal nodes drain in turn to the superior deep cervical lymph nodes, and the pretracheal and paratracheal lymph nodes drain to the inferior deep cervical nodes -Laterally, lymphatic vessels located along the superior thyroid veins pass directly to the inferior deep cervical lymph nodes. Some lymphatic vessels may drain into the brachiocephalic lymph nodes or the thoracic duct

Nerves of Thyroid Gland

The nerves of the thyroid gland are derived from the *superior, *middle, and *inferior cervical (*sympathetic) ganglia -they reach the gland through the *cardiac and *superior and *inferior thyroid periarterial plexuses that accompany the thyroid arteries -these fibers are vasomotor, not secretomotor ,they cause constriction of blood vessels -Endocrine secretion from the thyroid gland is hormonally regulated by the pituitary gland.

Parathyroid location

The small fl attened, oval parathyroid glands usually lie external to the thyroid capsule on the medial half of the poste- rior surface of each lobe of the thyroid gland, inside its sheath -superior parathyroid glands usually lie slightly more than 1 cm superior to the point of entry of the inferior thyroid arteries into the thyroid gland. The inferior parathyroid glands usually lie slightly more than 1 cm inferior to the arterial entry point -The superior parathyroid glands, more constant in position than the inferior ones, are usually *at the level of the inferior border of the cricoid cartilage. -The inferior parathyroid glands are usually near the *inferior poles of the thyroid gland, but they may lie in various positions (Fig. 8.30B). In 1-5% of people, an inferior parathyroid gland is deep in the superior mediastinum

Thyroid gland affects ?

The thyroid gland affects all areas of the body except itself and the spleen, testes, and uterus.

Thyroid gland secretion

The thyroid gland is the body's largest endocrine gland. It produces *thyroid hormone, which controls the rate of metabolism, and *calcitonin, a hormone controlling calcium metabolism. -Endocrine secretion from the thyroid gland is hormonally regulated by the pituitary gland.

thyroid gland location

The thyroid gland lies deep to the sternothyroid and ster- nohyoid muscles, located anteriorly in the neck at the level of the C5-T1 vertebrae (Fig. 8.26). -consists primarily of right and left lobes, anterolateral to the larynx and trachea. A rela- tively thin isthmus unites the lobes over the trachea, usually **anterior to the second and third tracheal rings

inferior thyroid veins

The usually independent inferior thyroid veins drain the *inferior poles.; the inferior thyroid veins drain into the *brachiocephalic veins posterior to the manubrium.

Veins of Thyroid Gland

Three pairs of thyroid veins usually form a thyroid plexus of veins on the anterior sur- face of the thyroid gland and anterior to the trachea (Figs. 8.27 and 8.28). *The superior thyroid veins * middle thyroid veins * inferior thyroid veins

superior thyroid arteries

Usually the first branches of the external carotid arteries, the superior thyroid arteries, descend to the *superior poles of the gland, pierce the *pretracheal layer of deep cervical fascia, and divide into *anterior and posterior branches supplying mainly the *anterosuperior aspect of the gland.

The right and left superior and inferior thyroid arteries anastomose extensively within the gland

ensuring its ( the thyroid ) supply while providing potential collateral circulation between the subclavian and external carotid arteries.

middle thyroid veins

middle thyroid veins do not accompany but run essentially parallel courses with the *inferior thyroid arteries; they drain the *middle of the loves -The superior and middle thyroid veins drain into the IJVs

parathyroid glands target ?

parathyroid glands target the *skeleton, *kidneys, and *intestine.

prelaryngeal nodes drain

prelaryngeal nodes drain in turn to the superior deep cervical lymph nodes

superior thyroid veins

superior thyroid veins accompany the *superior thyroid arteries; they drain the *superior poles of the thyroid gland; -The superior and middle thyroid veins drain into the IJVs

the pretracheal and paratracheal lymph nodes drain

the pretracheal and paratracheal lymph nodes drain to the inferior deep cervical nodes