Details
Thyroid gland and levator glandulae thyroidae
This specimen shows the thyroid gland along with a fibrous structure known as the levator glandulae thyroideae.
The thyroid gland is a brownish-red and highly vascular endocrine gland, placed in the lower part of the neck. It is made up of the right lobe and the left lobe, connected with each other by the isthmus. A conical pyramidal lobe often ascends towards the hyoid bone from the isthmus or the adjacent part of either lobe. A fibrous or fibromuscular band, the levator glandulae thyroideae, sometimes descends from the body of the hyoid bone to the isthmus or the pyramidal lobe. The thymus, the left brachiocephalic vein, the right brachiocephalic vein, the arch of aorta and the superior vena cava can also be identified in this specimen.
Thymus:
The thymus is a lymphoid structure situated in the lower part of the neck. It produces the T-lymphocytes which are required for the immune functions. It is highly active in children. It regresses after puberty and persist as a fibrofatty tissue.
Left brachiocephalic vein:
The left brachiocephalic vein is formed in the lower part of the neck, by the union of the left internal jugular vein and the left subclavian vein. It enters the superior mediastinum, crosses the midline and joins with the right brachiocephalic vein to form the superior vena cava. Therefore, the left brachiocephalic vein in longer compared to the right brachiocephalic vein. It receives veins from the upper intercostal space and the thyroid gland.
Right brachiocephalic vein:
The right brachiocephalic vein is formed in the lower part of the neck, by the union of the right internal jugular vein and the right subclavian vein. It descends downwards into the superior mediastinum, where it is joined by the left brachiocephalic vein to form the superior vena cava.
Arch of aorta:
The arch of aorta is a large artery seen in the superior mediastinum. It begins as a continuation of the ascending aorta, at the level of the sternal angle and continues as the descending thoracic aorta at the level of the sternal angle. Usually three branches arise from the arch of aorta, namely, the brachiocephalic trunk, the left common carotid artery and the left subclavian artery.
Superior vena cava:
The superior vena cava is a large vein, which drains the venous blood from the head and neck region and the upper limbs. It is formed by the union of the right and the left brachiocephalic veins in the superior mediastinum. It pierces the pericardium to open into the right atrium. Before piercing the pericardium, it receives the arch of azygos vein. It is devoid of valves.
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