case 9 anatomy Flashcards
Which vertebral level is the suprasternal notch located?
T2/3
Which vertebral level is the thyroid notch located?
C4
Which vertebral level is the lower border of cricoid cartilage located?
C6
Which vertebral level is the hyoid bone located?
C3
lobes of thyroid gland
The thyroid gland is made up of an isthmus and two lateral lobes; in some cases a pyramidal lobe is also present.
lateral lobe
The apex extends up to the oblique line of the thyroid cartilage and the base to the level of the fourth or fifth tracheal ring.
isthmus
Crosses anterior to the 2nd, 3rd and 4th tracheal ring.
pyramidal lobe
Projects upwards from the isthmus to the left of the midline
sheath of thyroid gland
The thyroid gland is enclosed by a thin connective tissue capsule, from which, septa project into the gland. A loose connective tissue sheath surrounds the gland and the capsule. Its derived from the pretracheal fascia
relations to the lateral lobes
anterolateral: superior belly of omohyoid, sternohyoid, ant border SCM, sternothyroid,
posterolateral: common carotid artery, vagus, internal jugular vein, carotid sheath
Medial: oesophagus, recurrent laryngeal nerve, external laryngeal nerve, trachea, cricothyroid, pharynx, larynx
relations to the isthmus
anterior: ant jugular vein, sternohyoid, sternothyroid
posterior: 2nd, 3rd, 4th rings of tracheal cartilages
arterial supply of thyroid gland
As it is an endocrine organ the thyroid gland has to receive a rich blood supply. The blood vessels of lie between the capsule and the fascial sheath.
Arterial blood is supplied by the superior and inferior thyroid arteries; the superior thyroid artery supplies the upper pole of each lobe whilst the inferior thyroid artery supplies the posteroinferior aspect. There is considerable anastomosis between vessels.
The superior thyroid artery arises from the external carotid artery. the superior laryngeal nerve runs alongside the artery. ITA arises from thyrocervical trunk, which arises from subclavian artery. the recurrent laryngeal crosses the ITA. 4In 10% of the population a third artery also contributes. This vessel is termed the thyroid ima artery and it may arise from the brachiocephalic trunk or arch of aorta, less commonly it has been seen to arise from the right common carotid, subclavian or internal thoracic arteries.
venous drainage of the thyroid gland
Three pairs of veins, the superior, middle and inferior thyroid veins drain the superior, middle and inferior parts of the thyroid gland respectively. These vessels form a plexus of nerves on the anterior aspect of the gland. the superior and middle drain into the IJV. the inferior drains into the brachiocephalic vein.
lymphatic drainage
A rich lymphatic network is found within the connective tissue septa of the thyroid gland. These vessels drain into the prelaryngeal, pretracheal and paratracheal nodes. Efferent vessels from these nodes go to the deep cervical nodes.
innervation
The thyroid gland receives sympathetic innervation. Post ganglionic sympathetic fibres arise in the superior, middle and inferior cervical ganglia and pass through the cardiac, superior and inferior thyroid plexuses to reach the gland. it transmits vasomotor information.