3- Thyroid HW - Answered.docx

I- Answer the following questions on A&P of the thyroid and parathyroid glands: 1. What hormones does the thyroid gland secrete? It secretes: triiodothyronine (T3), thyroxine (T4), and calcitonin 2. What are the functions of the thyroid gland’s hormones? T3 and T4 both stimulate cellular metabol...

I- Answer the following questions on A&P of the thyroid and parathyroid glands: 1. What hormones does the thyroid gland secrete? It secretes: triiodothyronine (T3), thyroxine (T4), and calcitonin 2. What are the functions of the thyroid gland’s hormones? T3 and T4 both stimulate cellular metabolism Calcitonin inhibits the osteoclasts, thus increasing calcium storage in the bone and decreasing blood calcium level 3. How is the thyroid hormone secretion regulated? Thyroid gland is controlled by the pituitary gland which secretes TSH When the pituitary gland secretes TSH, it stimulates the thyroid gland to secrete T3 and T4 Calcitonin secretion is regulated directly by the blood calcium level, not by the pituitary gland. 4. What are the lobes of the thyroid gland? Right and left lobes, which are connected by the isthmus. Some people have pyramidal lobe extending from the isthmus 5. What structures border the thyroid gland anteriorly, posteriorly, and laterally? Strap muscles are located anterior to thyroid Longus colli muscle is located posterior to each thyroid lobe Trachea is located medial to each lobe and posterior to the isthmus Common carotid artery is located lateral to each lobe (you may mention the neurovascular bundle as the lateral border) 6. What is the measurements of the thyroid gland and the isthmus in adults? Each lobe of the thyroid: measures 40-60 mm in length x 15-20 mm in width x 13-18 mm thickness (AP) Isthmus: 2 to 6 mm AP diameter 7. How is the echogenicity and vascularity of the thyroid gland described? Thyroid gland is uniformly echogenic, with medium- to high-level echoes (similar to the liver) It appears hyperechoic to surrounding muscles, and it has a thin, hyperechoic capsule 8. What is the mathematical method used to calculate the volume of the thyroid gland? To calculate the volume of each lobe, use ellipsoid formula with a correction factor (length x width x thickness x 0.52 for each lobe) 9. Describe the appearance and location of the esophagus compared with the thyroid gland! The transverse section of the esophagus has a hypoechoic walls and the hyperechoic mucosa (target sign) and located posteromedial to the left lobe of the thyroid 10. What is the material that fills the thyroid follicles called? Colloid 11. Which arteries supply the thyroid gland with blood, and where do they originate from? Superior thyroid artery that originates from the ECA, and inferior thyroid artery that originates from the thyrocervical trunk (a branch of the subclavian artery) 12. Describe the location and the common shape of the parathyroid gland. Two superior parathyroid glands lie posterior to superior poles of thyroid; two inferior lie posterior to the inferior poles of the thyroid gland 13. What are the measurements of the parathyroid gland? 5.0-7.0 mm in length 1.0-2.0 mm in height 3.0-4.0 mm in width 14. What is the echogenicity of the parathyroid glands compared with the thyroid gland? Similar in echogenicity to thyroid, and are not generally identified with ultrasound unless they are abnormal 15. What hormone is secreted by the parathyroid gland? Explain the function of the hormone! Parathormone (PTH) It increases blood calcium level by three mechanisms: increasing the breakdown of bone matrix to release the calcium to the blood increasing the reabsorption of calcium from the renal tubules to the blood increasing the absorption of calcium from the intestines to the blood via vitamin D 16. Which arteries supply the parathyroid glands? Superior and inferior parathyroid arteries that originate form superior and inferior thyroid arteries, respectively. 17. What medical term refers to an enlarged thyroid gland? What is the most common cause of enlargement? Goiter Iodine deficiency 18. What is the most common indication for scanning the parathyroid gland? What is the most common cause of the problem? And how does it appear in sonography? Hypercalcemia Parathyroid adenoma Parathyroid adenoma appears as an oval hypoechoic mass in the triangle formed by thyroid, longus colli muscle and CCA 19. What is the percentage of ectopic parathyroid glands, and where does it occur? 15 to 20 % of population has ectopic parathyroid glands, and they are located in: thymus or peri-thymic tissues intrathyroidal tissue carotid bulb (at the bifurcation) retroesophageal space 20. What is the neurovascular bundle located posterolateral to the thyroid gland? Common carotid artery, internal jugular vein, and vagus nerve 21. Which is the correct patient’s position to obtain an ultrasound study for thyroid and parathyroids? Supine position with mild hyperextension of the neck by using a pillow under the shoulders. 22. Which is the preferred transducer to obtain an ultrasound study for thyroid and parathyroids? Linear, high frequency transducer 7.5 MHz to 15 MHz 23. Draw a diagram that shows a transverse section of the thyroid gland with its surroundings!