Week 3 - B - Week 3 - physiology and anatomy of the thyroid gland Flashcards
What is the function of the pineal gland?
The pineal gland produces melatonin, which helps maintain circadian rhythm (sleep is a circadian rhythm) and regulate reproductive hormones.
What are the three parts of the thyroid gland?
Righ and left lobe
And an isthmus connecting the two
What are the glands that lie posterior to the thyroid gland? (there are 4) What does this gland secrete?
Parathyroid glands
Secrete parathyroid hormone
Where does the thyroid gland lie?(between which vertebra/tracheal rings
The thryoid gland is normally lies from the 5th cervical to 1st thoracic vertebra
The 2nd - 4th tracheal rings
What is the approximate weight of a normal thyroid gland in adults? When can the gland physiologically increase in size?
25-30g
During pregnancy / menstruation
What is the arterial supply to the thyroid gland? What are the artieries branches off? What is the third artery to supply the thyroid that is not always present?
Superior thyroid artery - branch of external carotid artery
Inferior thyroid artery - branch of thyrocervical trunk from the subclavian artery
The third artery is the thyroid ima artery
What is the venous drainage of the thyroid gland? Where do the veins drain?
Superior thyroid vein and middle thyroid vein drain to the internal jugular veins
Inferior thyroid vein - drains to the brachiocephalic veins
What is the ligament that attaches the posterior aspect of the thyroid gland to the cricoid cartilage of the trachea?
The berry ligament
What is the berry ligament also known as?
The posterior suspensory ligament
What nerve travels very close to and can sometimes pierce the berry ligament? It is at risk of damage during a tracheostomy
The recurrent laryngeal nerve
How do the right and left recurrent laryngeal nerves arise? What do they arch round? What provides the thyroid gland with parasympathetic innervation?
The recurrent laryngeal nerves are branches of the vagus nerve
The right arches around the right subclavian artery
The left arches around the arch of the aorta
The recurrent laryngeal nerves provide the thyroid gland w/ parasympathetic innervation
What are the colloid containing sacs in the thyroid known as? What forms the outer circle of the follicle?
The colloid containing sacs are follicles
Follicular cells form the outer circle
What does the colloid contain? What are the cells that secrete calcitonin known as in the thyroid gland?
Colloid contains - tyrosine-containing thyroglobulin
The cells that secrete calcitonin are known as parafolicular cells (C cells)
What is the main fuel for the thyroid gland? Where is this fuel taken up in the thyroid gland?
Iodine
Iodine is taken up by the follicular cells from the blood and transported to the colloid
When the iodine is taken into the colloid, what does it combine with to form what?
Comines with tyrosine residues on the thyrglobulin molecule to form moniodotyroisne (MIT) or di-iodotyroisne(DIT) molecules
How many MITs and DITs are in T3 and T4? Where are T3 and T4 stored and how are they released?
T3 is formed by the coupling of a MIT + DIT
T4 is formed by the coupling of a DIT + DIT
Both T3 and T4 are stored in the colloid thyroglobulin until released via pinocytosis when required
What are the three thyroid hormones?
T3 - tri-iodothyronine
T4 - thyroxine
Calcitonin