68 Questions
Which formula is used to calculate the volume of each lobe of the thyroid gland?
Ellipsoid formula
What is the appearance of the esophagus compared to the thyroid gland in a transverse section?
Hypoechoic walls and hyperechoic mucosa
What is the material that fills the thyroid follicles called?
Colloid
Which arteries supply the thyroid gland with blood?
Superior thyroid artery and inferior thyroid artery
Describe the location of the parathyroid gland.
Posterior to the thyroid gland
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
What is the echogenicity of the parathyroid glands compared with the thyroid gland?
Isoechoic
What hormone is secreted by the parathyroid gland?
Parathormone (PTH)
Which arteries supply the parathyroid glands?
Superior and inferior thyroid arteries
What is the most common cause of thyroid gland enlargement?
Iodine deficiency
Which hormones does the thyroid gland secrete?
Triiodothyronine (T3), thyroxine (T4), and calcitonin
How is the thyroid hormone secretion regulated?
Controlled by the pituitary gland which secretes TSH
What are the lobes of the thyroid gland?
Right and left lobes, connected by the isthmus
What structures border the thyroid gland anteriorly, posteriorly, and laterally?
Strap muscles, Longus colli muscle, Trachea, Common carotid artery
What are the measurements of the thyroid gland and the isthmus in adults?
Each lobe: 40-60 mm length x 15-20 mm width x 13-18 mm thickness (AP), Isthmus: 2-6 mm AP diameter
How is the echogenicity and vascularity of the thyroid gland described?
Uniformly echogenic, with medium- to high-level echoes
What hormones does the parathyroid gland secrete?
Parathyroid hormone (PTH)
What is the function of parathyroid hormone (PTH)?
Increase blood calcium level
How many lobes does the parathyroid gland have?
Four
Which hormones does the parathyroid gland secrete?
Parathyroid hormone (PTH)
Describe the location of the parathyroid gland.
Posterior to the thyroid gland
What is the appearance of the esophagus compared to the thyroid gland in a transverse section?
Hypoechoic
What are the measurements of the parathyroid gland?
2 to 6 mm AP diameter
How is the echogenicity and vascularity of the thyroid gland described?
Uniformly echogenic, with medium- to high-level echoes
What are the functions of the thyroid gland's hormones?
Stimulates cellular metabolism
What are the lobes of the thyroid gland?
Right lobe and left lobe
What structures border the thyroid gland anteriorly, posteriorly, and laterally?
Strap muscles anteriorly, Longus colli muscle posteriorly, Trachea laterally
Which formula is used to calculate the volume of each lobe of the thyroid gland?
Ellipsoid formula with a correction factor
What is the appearance of the esophagus compared to the thyroid gland in a transverse section?
Hypoechoic walls and hyperechoic mucosa
What is the material that fills the thyroid follicles called?
Colloid
Which arteries supply the thyroid gland with blood, and where do they originate from?
Superior thyroid artery from the ECA, and inferior thyroid artery from the thyrocervical trunk
Describe the location of the parathyroid gland.
Two superior parathyroid glands lie posterior to superior poles of thyroid; two inferior lie posterior to inferior poles of the thyroid gland
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
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
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, and increasing the absorption of calcium from the intestines to the blood via vitamin D
Which muscles are located anterior and lateral to the thyroid gland?
Strap muscles
Which muscle is seen posterior to the thyroid gland?
Longus colli muscle
What forms the lateral border of the thyroid gland?
Trachea
Which structures are posterolateral to the thyroid gland?
CCA and IJV
How are nodules classified?
Hot or cold nodules
What is a hot nodule?
A nodule that traps an excessive amount of isotope and is hyperfunctioning
What is a cold nodule?
A nodule that does not absorb isotope and demonstrates an area of decreased or absent activity
Which veins drain into the IJV?
Superior & Middle thyroid vein
What is the function of the IJV?
B. Drains blood from the head and neck region
Which veins drain into the brachiocephalic veins?
Inferior thyroid veins
What is the function of the thyroid gland's hormones?
Metabolism regulation
What is the appearance of the thyroid gland compared to the esophagus in a transverse section?
Hypoechoic compared to the esophagus
Where is the parotid gland located?
In the retromandibular fossa
What is the function of the parotid gland?
Production of saliva
Which is the largest salivary gland?
Parotid gland
Which hormone stimulates the kidneys to convert vitamin D into its active form?
A. PTH
How does PTH regulate calcium levels in the extracellular fluid?
A. By increasing the release of calcium from bones
What is the main function of parathyroid hormone (PTH)?
A. Regulating calcium and phosphorous levels in extracellular fluid
Which of the following is NOT a function of the parotid glands?
Produce PTH
What is the role of the parotid glands in the digestion process?
Produce saliva that moistens the food
How do the parotid glands facilitate swallowing?
By producing saliva that helps in lubricating the food
Where is TSH (Thyroid Stimulating Hormone) produced?
Anterior pituitary gland
What is the role of TSH in the body?
Regulates metabolism, growth, and development
Which endocrine gland does TSH primarily target?
Thyroid gland
Which cells are the primary source for the production of parathyroid hormone (PTH)?
Chief cells
Where are the chief cells located?
Parathyroid glands
What is the role of parathyroid hormone (PTH) in the body?
Regulating calcium and phosphate levels
Which thyroid condition is associated with a deficiency in iodine?
Goiter
What is the function of parathyroid hormone (PTH) in the body?
Regulating blood calcium levels
Which arteries supply the thyroid gland with blood?
Carotid arteries
Which hormone is responsible for increasing blood calcium levels and decreasing blood phosphorus levels?
B. PTH
Which gland secretes parathyroid hormone (PTH)?
D. Parathyroid gland
What is the role of parathyroid hormone (PTH) in the body?
B. Regulating blood calcium and phosphorus levels
Study Notes
Thyroid Gland Anatomy
- The volume of each lobe of the thyroid gland is calculated using the formula: Volume = Length × Width × Thickness × 0.479.
- In a transverse section, the esophagus appears posterior to the thyroid gland.
- Thyroid follicles are filled with colloid material, which is essential for hormone production.
Blood Supply
- The thyroid gland receives blood supply primarily from the superior thyroid artery (branch of the external carotid artery) and the inferior thyroid artery (branch of the subclavian artery).
- The parathyroid glands are typically supplied by the inferior thyroid arteries.
Parathyroid Gland Characteristics
- Parathyroid glands are usually located on the posterior surface of the thyroid gland.
- Average measurements of the parathyroid gland are approximately 4-6 mm in length and 2-4 mm in width.
- Echogenicity of the parathyroid gland is typically lower compared to the thyroid gland, making them less visible on ultrasound.
Hormonal Functions
- The primary hormone secreted by the parathyroid gland is parathyroid hormone (PTH).
- PTH plays a critical role in regulating calcium levels in the blood and promotes bone resorption.
- The thyroid gland secretes hormones such as T3 (triiodothyronine) and T4 (thyroxine), which regulate metabolism.
Structural Relationships
- Anteriorly, the thyroid gland is bordered by the strap muscles; laterally by the common carotid artery, and posteriorly by the trachea and esophagus.
- Typical measurements of the thyroid gland in adults are approximately 4-6 cm in length and 1-2 cm in width for each lobe, with the isthmus measuring 4-6 mm.
Echogenicity and Vascularity
- The thyroid gland generally exhibits a homogeneous echogenicity with increased vascularity, visible on Doppler ultrasound.
Nodules and Conditions
- Thyroid nodules are classified based on their functionality; "hot nodules" take up more radioactive iodine and are usually benign, while "cold nodules" do not and may require further evaluation for malignancy.
- The most common cause of thyroid enlargement (goiter) is iodine deficiency.
Other Endocrine Functions
- Thyroid Stimulating Hormone (TSH) is produced by the pituitary gland and primarily targets the thyroid gland to stimulate the production of T3 and T4.
- The parotid gland, the largest salivary gland, is responsible for producing saliva to aid in digestion and facilitate swallowing.
Calcium Regulation
- TSH regulates thyroid hormone secretion, which is crucial for metabolic processes.
- PTH raises blood calcium levels and decreases blood phosphorus levels by increasing intestinal absorption of calcium and promoting renal reabsorption of calcium.
- Chief cells in the parathyroid gland are responsible for the production of parathyroid hormone (PTH).
Iodine Deficiency
- Iodine deficiency can lead to hypothyroidism and is associated with conditions like goiter.
Anatomy and Functions of Salivary Glands
- Parotid glands are located near the ear and play a significant role in the oral phase of digestion. They facilitate swallowing by moistening food.
Test your knowledge on the anatomy and physiology of the thyroid and parathyroid glands. Answer questions about the hormones secreted by the thyroid gland and their functions, including the role of calcitonin in regulating calcium levels.
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