Thyroid Anatomy Flashcards
What tethers the thyroid to the trachea
pre-tacheal fascia
What is in the pre-tacheal fascia (5)
thyroid recurrent layngeal nerve oesophagus trachea pharynx
What vertebral level is the thyroid at?
C5-T1
Where are the parathyroid glands located on the thyroid?
posterior aspect
What is the function of parathyroid glands?
calcium homeostasis
How many parathyroid glands are there?
four
2 main sources of thyroid blood supply
superior thyroid artery
inferior thyroid artery
What is the superior thyroid artery a branch of?
external carotid artery
What is the inferior thyroid artery a branch of?
thyrocervical trunk
from the subclavian artery
Venous drainage of the thyroid occurs through..
superior
middle
inferior thyroid veins
Which veins drain to the internal jugular vein?
superior
middle thyroid vein
Which vein drains to the brachiocephalic vein
inferior thyroid vein
What innervates the thyroid?
sympathetic fibres
from superior, middle and inferior cervical ganglia
What travels behind the thyroid to supply laryngeal muscles?
recurrent laryngeal nerve
Perithyroid Pre-laryngeal Pre-tracheal Paratracheal Superior and inferior deep cervical
Lymph nodes draining the thyroid
What is the site of hormone production and storage in the thyroid?
colloid
Function of C cells/parafollicular cells?
secrete calcitonin
for calcium homeostasis
Thyroid hormones
Thyroxine (T4)
Triiodothyronine (T3)
Calcitonin
Most abundant thyroid hormone
T4
Most active thyroid hormone
T3
Thyroid transport proteins
thyroid binding globulin
albumin
transthyretin
In response to stimuli, what does the hypothalamus release?
thyrotropin-releasing hormone (TRH)
In response to TRH, what does the anterior pituitary release?
thyroid stimulating hormone (TSH)
What does TSH stimulate the production of?
T3 and T4
What is the negative feedback loop of the thyroid
Increase in T3 and T4 results in
reduction in TRH and TSH
What happens to T3 and T4 in Hypothyroidism
decreases
What happens to T3 and T4 in Hyperthyroidism
increases
What is most plasma T3 derived from?
peripheral metabolism of T4
What does conversion from T4 to T3 require?
removal of iodine by a deiodinase enzyme
What can T4 also be metabolised to?
reverse T3 (rT3)
Thyroid hormone receptors
TRa1
TRa2
TRb1
TRb2
Which hormone receptor does not bind T3?
TRa2
What happens when T3 binds to the thyroid hormone receptor
gene transcription activated
form mRNA
followed by a translation to a protein
Function of thyroid hormones in metabolism
increase in basal metabolic rate glycolysis O2 consumption thermogenesis protein turnover
Function of thyroid hormones in cardiovascular system
increase in systolic pressure
increase in B-adrenergic receptor
enhances catecholamine actions
