Thyroid Gland Histo &Anatomy
Where does the post synthesis processing of T3 and T4 occur and what organelles are involved?
False. T3 and T4 are endocytosed and undergo modification inside the follicular cell via lysosomal fusion prior to transcytosis.
What is the most abundant type of endocrine cell in the thyroid gland, what does it produce, and where is it found?
Follicular cells are the most abundant and can be seen surrounding the colloid filled follicles. Follicular cells produce and secrete T3 and T4 thyroid hormones.
What is the foramen cecum and where can this structure be found in the adult?
Foramen Cecum is the location where the Thyroid Gland Primordium buds off from the pharyngeal endoderm. In the adult, the Foramen Cecum is located on the posterior aspect of the tongue.
What blood vessel supplies the parathyroid glands?
Inferior thyroid artery.
What portions of the thyroid gland are supplied by inferior thyroid artery?
Inferior thyroid supplies the posterior and inferior portions of the thyroid gland.
Which thyroid vein drains into the brachiocephalic veins?
Inferior thyroid vein
About what percentage of the population has a Thyroid Ima Artery?
About 10%
Through what plexii do nerve fibers that innervate the thyroid gland distribute through?
Cardiac Periarterial Plexus. Superior and Inferior Thyroid Plexii.
What do parafollicular cells secrete and what is another name for these cells?
Parafolliculcar cells, also called C cells, secrete calcitonin.
What nerve can be found ascending along the backside of the thyroid gland near the inferior thyroid artery?
Recurrent Laryngeal Nerve.
What portions of the thyroid gland are supplied by the Superior Thyroid Artery?
Superior thyroid gives off an anterior and posterior branch that supply the superior and anterior portions of thyroid.
From which ganglia do sympathetic fibers that innervate the thyroid gland originate from?
Superior, middle, and inferrior (or stellate if fused with T1 ganglia).
How do C-cells appear in histological resection when compared to follicular cells?
C cells are larger with paler staining cytoplasm and a larger nucleus.
What difference in appearance would you expect to find knowing that follicular cells use the colloid follicle to synthesize and store T3 and T4 and C-cells store calcitonin within the cytoplasm?
C-cells will have numerous secretory vessicles where as Follicular cells will not.
What types of cells are found in the parathyroid gland and which one carries out the endocrine function of this gland?
Chief Cells, oxyphil cells, and adipocytes are found in the parathyroid glands. Chief cells, also called principal cells, carry out the the endocrine function by secreting Parathyroid Hormone
True or False. Sympathetic as well has hormonal stimulation can cause thyroid to release hormones into the blood.
False. Nervous innervations only carry vasomotor efferents. Endocrine functions are under hormonal control.
Which thyroid veins drain into the internal jugular?
Superior and middle thryroid veins.
What veins drain the thyroid gland and what vessels do they empty into?
Superior & Middle Thyroid Veins drain into Internal Jugular. Inferior thyroid vein drains into the left and right brachiocephalic veins.
What nerve can be found paralleling the course of the superior thyroid artery?
Superior Laryngeal Nerve.
Understanding that there is significant variation with parathyroid gland locations in adults, where would you start your search for the superior and inferior PT glands?
Superior PT glands usually can be found 1 cm above the inferior thyroid artery. Inferior PT glands can usually be found 1 cm below the inferior thyroid artery.
What arteries supply the thyroid gland and from what parent arteries do they arise?
Superior Thyroid Artery arises from the External Carotid. Inferrior Thyroid Artery arises from the Thyrocervical Trunk.
Which lymph nodes should be checked if a patient is suspected of having metastatic thyroid cancer?
Superior and inferior deep cervical nodes
What cell types in the thyroid gland will express TSH receptors and what type of signaling pathway does these receptors initiate once ligated?
TSH receptors are found on follicular cells as they are responsible for producing and secreting T3 and T4. TSH receptor will initiate a Gs signal cascade.
Where is thyroid ima artery found, what parent artery does it arise from, and from why is this vascular variation significant?
Thryroid ima artery is found midline at the inferior aspect of the thyroid isthmus. It arises from the common carotid artery and is significant during surgical procedures as a potential source of bleeding.
What is thyroglobulin, where is it produced, and where is it converted into T3 and T4?
Thyroglobulin is the protein precurser for T3 and T4. It is produced by follicular cells and secreted into the colloid filled follicle where it will combine with iodide to become T3 and T4.
What enzyme catalyzes the addition of iodide to thyroglobulin?
Thyroid Peroxidase
What is the function of Thyroid Peroxidase?
Thyroid Peroxidase catalyzes the addition of iodide to thyroglobulin to produce T3 and T4.
What is unique about the appearance of thyroid tissue with regards to cellular arrangement when viewed histologically?
Thyroid gland has distinct follicles surrounded by follicular and parafollicular cells.
The thyroid gland is invested in which layer of cervical fascia?
Visceral layer of pretracheal fascia.
