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Thyroid Gland and its blood supply
This specimen shows the blood supply of the thyroid gland.
The thyroid gland is a brownish-red and highly vascular endocrine gland, placed in the lower part of the neck. It is covered by a true capsule (made up of the condensation of the glandular connective) and a false capsule (made up of the pre-tracheal layer of deep fascia of the neck). It is made up of the right lobe and the left lobe, connected with each other by the isthmus. It receives arterial supply by the superior thyroid artery and the inferior thyroid artery. At times, it is also supplied by an additional artery known as the arteria thyroidea ima. A venous plexus is situated deep to the true capsule. The venous blood is drained by three veins: the superior thyroid vein, the middle thyroid vein and the inferior thyroid vein. The other structures such as the thyroid cartilage, the thyrohyoid muscle, the cricothyroid muscle, the common carotid artery, the internal carotid artery, the external carotid artery are also seen in this specimen.
Superior thyroid artery:
The superior thyroid artery is a branch of the External carotid artery. It accompanies the External laryngeal nerve towards, the apex of the lobe of the thyroid gland, pierces the thyroid fascia and then divides into anterior and posterior branches. During the thyroid surgeries, the artery is ligated close to the gland, in order to prevent the damage to the external laryngeal nerve.
Inferior thyroid artery:
The inferior thyroid artery is a branch of the thyrocervical trunk, which in turn is a branch of the first part of the subclavian artery. It is related to the base of the thyroid gland, where it is accompanied by the external laryngeal nerve. It accompanies the Recurrent laryngeal nerve. During the thyroid surgeries, the artery is ligated away from the gland, in order to prevent the damage to recurrent laryngeal nerve.
Superior thyroid vein:
The superior thyroid vein drains the venous blood of the thyroid gland into the Internal jugular vein.
Middle thyroid vein:
The middle thyroid vein drains the venous blood of the thyroid gland into the Internal jugular vein.
Inferior thyroid vein:
The inferior thyroid veins drain the venous blood of the thyroid gland into the left brachiocephalic vein.
Thyroid cartilage:
The thyroid cartilage is a shield-like, unpaired cartilage of the larynx. It is made up of two laminae, which unite to form the thyroid angle (Adam’s apple) in the midline of the neck.
Thyrohyoid muscle:
The thyrohyoid muscle is an infrahyoid muscle, situated in the midline of the neck. It extends from the thyroid cartilage to the hyoid bone. It is supplied by the first cervical spinal nerve.
Cricothyroid muscle:
The cricothyroid muscle, is the only intrinsic muscle of the larynx, that can be seen along the anterior aspect of the larynx. It extends from the cricoid cartilage to the thyroid cartilage. It is supplied by the External laryngeal nerve.
Common carotid artery:
The left common carotid artery, is a branch of the arch of aorta. The right common carotid artery is a branch of the brachiocephalic trunk. The common carotid artery along with the internal jugular vein is enclosed within the carotid sheath. The common carotid artery bifurcates into the internal carotid and the external carotid arteries at the upper border of the thyroid cartilage.
Internal carotid artery:
The internal carotid artery is one of the terminal branches of the common carotid artery. It enters the cranial cavity and supply the brain and the meninges.
External carotid artery:
The external carotid artery is one of the terminal branches of the common carotid artery. It supplies the structures in the neck, the face and the scalp.
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