pac Flashcards
What is the “false capsule” that covers the thyroid gland formed by?
pretracheal fascia
What are the right and left lobes of the thyroid connected by and how does this structure extend?
They are connected by a narrow isthmus.
The isthmus continues upwards crossing the second and third tracheal cartilages.
What is the structure that extends from the isthmus that is found in some people called?
Pyrimdal lobe that ascends towards the hyoid bone
What are the posterior relations of the thyroid gland?
Trachea, esophagus, larynx, pharynx
What are the two muscles that lie infront of the thyroid gland?
sternothyroid and sternohyoid muscles
What are the vessels that lie postero-lateral to the thyroid gland?
Common carotid artery and internal jugular vein
What arch is the trachea attached to and what unique feature does this give it?
Attached to the arch of the cricoid cartlige and moves up down while swallowing and osillatces while speaking
What is the main arterial supply of the thyroid gland and where do those arteries lie and anastmose?
Main: Superior and inferior thyroid arteries
Lie Between the capsule and the pretracheal fascia
Anastmose inside the matter of the thyroid
What is the superior thyroid a branch of and where does it descend?
It is a branch of the External carotid artery and it descends towards the superior lobe of the thyroid
What is the inferior thyroid artery a branch of and how does it run?
It is a branch of thyro-cervical trunk
It runs superomedially posterior to carotid sheath reaches posterior aspect of the gland and supplies the inferior pole of the gland
What nerve does the inferior thyroid artery have a relationship with?
Recurrent larygeal nerve
What type of artery is found 10% of people that supplies the thyroid and what exactly does it supply?
Artery: Thyroid Ima Artery
Arises: From Aorta, brachiocephalic trunk, or internal carotid artery.
Supplies: Isthmus
What are the nerves, arteries, and veins that are located posterior to the thyroid?
Common carotid artery
Internal jugular vein
Recurrent laryngeal nerve
Trachea
Thyroid cartlige
Superior laryngeal nerve
Vagus nerve
What is the venous drainage of the thyroid?
Usually 3 veins on anterior surface
Superior thyroid veins Drain superior poles of thyroid
Middle thyroid veins Drain lateral poles
Inferior thyroid veins Drain inferior poles
Where do the superior and middle thyroid veins drain?
Drain into the Internal jugular veins
Where does the inferior thyroid vein drain?
Brachiocephalic vein
What is the lymphatic drainage of the thyroid?
- prelaryngeal lymph nodes
- pretracheal and paratracheal lymph nodes.
Lateral lymph nodes: Drain into deep cervical lymph nodes
Finally: Into either brachiocephalic or thoracic duct
What do the lateral lymph nodes that drain the thyroid run along?
Superior thyroid veins
Where are the parathyroid glands embeded?
In the fibrous capsule
How is the thyroid gland subdivided and what do these divisions contain
The thyroid gland is subdivided by
capsular septa into lobules
containing follicles.
Label
What do thyroid follicles contain?
colloid, a viscous gel consisting mostly of iodinated
thyroglobulin.
What are the thyroid follicles surrounded by?
Thyroid follicles are enveloped by a layer of epithelial
cells, called follicular cells, which in turn are
surrounded by parafollicular cells.
What is the function of follicular cells?
Synthesize and store thyroid hormones
Label
What type of epithelium do the follicular cells have?
Simple Cuboidal epithelium that becomes columnar when active and squamos when inactive
What are the two major hormones that the thyroid secretes?
Thyroxine (T4) an Triiodothyronine (T3).
What role does the pituitary gland have in regulating the thyroid?
It releases thyroid stimulating hormone that regulates Thyroid secretion.
What else does the thyroid secrete?
Calcitonin which plays a role in regulating calcium metabolism
What is the structural difference between T3 and T4?
The two active thyroid hormones are triiodothyronine
(T3) and tetraiodothyronine, or thyroxine (T4). The
structures of T3 and T4 differ only by a single atom of
iodine, as shown in Figure 9.16. Although T3 is more
active than T4, almost all hormonal output of the
thyroid gland is T4. This “problem” of secreting the less
active form is solved by the target tissues, which
convert T4 to T3. A third compound, reverse T3
What is the functional difference between T3 and T4?
T3 is more active than T4
But T4 has a longer half life and is synthsized in greater amounts
What are 2 causes of hyperthyroidism?
Autoimmune disease where antibodies (Thyroid-Stimulating Immunoglobulins: TSI) bind to the TSH receptor and induces continual activation (12 hours) of cAMP system. High levels of Thyroid hormone caused by TSI depress the pituitary gland secretion of TSH that drop to zero.
Thyroid adenoma: cancer within a region of thyroid gland that secrete large quantities of thyroid. The healthy part of the gland will show reduction in thyroid secretion due to the feedback mechanism exerted on the pituitary gland (less TSH secretion).
What are some symptoms of hyperthyroidism?
1- High state of excitability
2- Intolerance to heat
3- Increased sweating
4- Mild to extreme weight loss
5- Varying degrees of diarrhea
6- Muscle weakness
7- Nervousness
8- Extreme fatigue but inability to sleep
9- Tremor of the hands
What is exothalmos and what is it caused by?
Protrusion of the eyeballs caused by swelling of the retro-orbital tissue and degenerative changes in the extraocular muscles. IgGs reacting with eye muscle
What are diagnostic tests of hyperthyrodism?
Direct measurement of free thyroxine (sometimes
triiodothyronine) in the plasma.
Basal metabolic rate is increased +30 to +60.
Measuring plasma levels of TSH (close to zero)
or TSI
levels (high in thyrotoxicosis, low in thyroid adenoma).
What are the physiological treatments for hyperthyroidism?
Physiological treatment for hyperthyroidism primarily involves surgically removing most of the thyroid gland. Before surgery, patients typically receive propylthiouracil for 1 to 2 weeks to reduce metabolic activity. Alternatively, treatment can include administering 5 mCi of radioactive iodine, which is absorbed by the hyperplastic thyroid gland and destroys most of its cells. If the patient remains hyperthyroid after the initial dose, additional doses may be given.
What is hashimoto disease?
Hypothyroidism caused by immune cells attacking the thyroid
This will cause inflamation and fibrosis.
What is thyroid goiter?
Hypothyroidism caused by thyroid hypertrophy
What is endemic thyroid goiter caused by?
caused by dietary iodide deficiency:
Deficiency in iodide > deficiency in thyroxine and triiodothyronine > increased TSH by pituitary gland increased Thyroglobulin in the thyroid follicle > enlarged thyroid follicle (10 to 20 X).
What is Idiopathic Non-toxic Colloid Goiter?
Thyroiditis leading to decreased production of thyroid hormone which in turn leads to increased TSH which will lead to increased thyroglobulin which will lead to hypertrophy in non inflammed areas with nodular shape
What are some of the symptoms of hypothyroidism?
Regardless the cause or type of hypothyroidism the physiological characteristics are similar:
Fatigue and somnolence (12-14 hours of sleep)
Extreme muscular sluggishness
Slow heart rate
Decreased cardiac output
Decreased blood volume
Sometimes increased body weight
Constipation
Mental sluggishness
Depressed growth of hair and scaliness of the skin
Froglike husky voice
Edematous appearance throughout the body (myxedema)
What is myxedema
Develops in patients with total absence of thyroid hormone function:
1- Bagginess under the eye
2- Swelling of the face
Greatly increased quantities of Hyaluronic acid and chondroitin sulfate bound with protein from excessive tissue gel in the interstitial space leading to increased interstitial spaces. The nature of the excess fluid leads to nonpitting edema.
GO back to slides and study the tables from first aid
What is creatnism?
Severe hypothyroidsim in early childhood which causes mental retardation and failure of bodygrowth
