THYROID AND PARATHYROID GLANDS Flashcards
location of the thyroid gland
a. The thyroid gland is located in the anterior neck and spans the C5-T1 vertebrae.
b. It consists of two lobes (left and right), which are connected by a central isthmus anteriorly – this produces a butterfly-shaped appearance.
The lobes of the thyroid gland are wrapped around by the;
cricoid cartilage and superior rings of the trachea.
c. The gland is located within the visceral compartment of the neck (along with the trachea, esophagus, and pharynx).
d. This compartment is bound by the pretracheal fascia.
anatomical relations
Anteriorly – infrahyoid muscles, namely the sternothyroid, superior belly of the omohyoid, and sternohyoid
Laterally – carotid sheath, containing the common carotid artery, internal jugular vein, and vagus nerve
Medially –Organs – larynx, pharynx, trachea, and esophagus
Nervea – external laryngeal and recurrent laryngeal
•The posterior surface of the isthmus is firmly adherent to the second to
fourth tracheal rings and the pretracheal fascia is here fixed between
them
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•This fixation and investment of the whole gland by pretracheal fascia
are responsible for the gland moving up and down with the larynx
during swallowing
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A small portion of the gland substance often projects superiorly from
the isthmus, generally to the left of the midline as the pyramidal lobe
and represents a development of glandular tissue from the caudal end
of the thyroglossal duct
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The thyroid gland secretes hormones directly into the circulation and is highly vascularised
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arterial supply of the thyroid gland
Superior thyroid artery – arises as to the first branch of the external carotid artery. It lies in close proximity to the external branch of the superior laryngeal nerve (innervates the larynx).
Inferior thyroid artery – arises from the thyrocervical trunk (a branch of the subclavian artery). It lies in close proximity to the recurrent laryngeal nerve (innervates the larynx).
branches of inferior thyroid artery
- Ascending cervical artery
- Pharyngeal branch
- Oesophageal branch
- Laryngeal branch
- Tracheal branch
- Inferior laryngeal artery
In a small proportion of people (around 10%) there is an additional artery present – the thyroid ima artery. It arises from the brachiocephalic trunk and supplies the anterior surface and isthmus of the thyroid gland
SUPERIOR THYROID VEIN
MIDDLE THYROID VEIN
INFERIOR THYROID VEIN
venous drainage of the thyroid gland
Venous drainage is carried by the superior, middle, and inferior thyroid veins, which form a venous plexus around the thyroid gland.
The superior and middle veins drain into the internal jugular vein and the inferior empties into the brachiocephalic vein.
innervation of the thyroid gland
The thyroid gland is innervated by branches derived from the sympathetic trunk.
These nerves do not control the secretory function of the gland – the release of thyroid hormones is regulated by the pituitary gland.
lymphatics
The lymphatic drainage of the thyroid is to the paratracheal and deep cervical nodes.
parathyroid glands
The parathyroid glands are endocrine glands located in the anterior neck.
they are responsible for
They are responsible for the production of parathyroid hormone (PTH), which acts to increase the level of serum calcium.
The parathyroid glands are usually located on the posterior aspect of the thyroid gland. They are flattened and oval in shape – situated external to the thyroid gland itself but within the pretracheal fascia.
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