ULTR-3016 Thyroid Anatomy & Physiology Part 1

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Questions and Answers

What is the location of the thyroid isthmus?

Inferior to cricoid cartilage and superior to the sternal notch

From where does the thyroid gland develop embryologically?

Base of the tongue

The thyroid gland has a good vascular supply with the veins located posteriorly.

False

Which of the following hormones are produced by the thyroid gland using iodine?

T3 Signup and view all the answers

The functional unit of the thyroid gland is the ______.

follicle Signup and view all the answers

What cells in the thyroid make calcitonin?

Parafollicular cells Signup and view all the answers

What part of the body regulates the thyroid through a feedback mechanism?

Hypothalamus Signup and view all the answers

Which imaging technique can be used to scan the function of the thyroid?

NM radioactive iodine Signup and view all the answers

What is the primary function of the infrahyoid muscles in relation to the thyroid?

To stabilize the thyroid gland and maintain its position Signup and view all the answers

Which statement accurately describes the vascular supply to the thyroid gland?

The thyroid gland receives blood from both the superior and inferior thyroid arteries. Signup and view all the answers

What role does the sternocleidomastoid (SCM) muscle play in relation to the thyroid gland?

It contributes to the elevation of the thyroid gland during swallowing. Signup and view all the answers

Which statement is true regarding the innervation of the thyroid gland?

The thyroid receives sympathetic innervation from the cervical sympathetic ganglia. Signup and view all the answers

How does the structure of the thyroid gland contribute to its function?

Its colloid storage allows for a rapid release of hormones as needed. Signup and view all the answers

What anatomical structure lies posterior to the thyroid gland?

Longus colli muscle Signup and view all the answers

Which artery is primarily responsible for vascular supply to the thyroid gland?

Inferior thyroid artery Signup and view all the answers

Which nerve is closely associated with the thyroid gland and is critical for the function of the vocal cords?

Recurrent laryngeal nerve Signup and view all the answers

What is one function of the sternocleidomastoid muscle?

Flexion of the neck Signup and view all the answers

Which muscle lies anterior to the longus colli muscle relative to the thyroid gland?

Sternocleidomastoid muscle Signup and view all the answers

What is the relationship between the inferior thyroid artery and the recurrent laryngeal nerve?

The artery lies posterior to the nerve Signup and view all the answers

Which of the following describes the positioning of the minor neurovascular bundle?

Posterior to the thyroid Signup and view all the answers

Which structure listed below is NOT typically associated with the vascular supply to the thyroid gland?

Jugular vein Signup and view all the answers

What important vascular structure is situated within the minor neurovascular bundle?

Inferior thyroid artery Signup and view all the answers

Which muscle assists in rotating the head and flexing the neck?

Sternocleidomastoid muscle Signup and view all the answers

Study Notes

Thyroid Anatomy & Physiology Overview

Thyroid gland is positioned inferior to the cricoid cartilage and superior to the sternal notch.
Development occurs at the base of the tongue, descending along the midline via the thyroglossal duct.

Key Variants and Ectopics

Pyramidal lobe can be a normal anatomical variant.
Ectopic thyroid tissue and thyroglossal duct cysts may be present.

Vascularization

Thyroid has a robust vascular supply; veins located anteriorly and arteries posteriorly.

Thyroid Physiology

The functional unit of the thyroid is the follicle, which uses iodine to synthesize hormones T3 and T4.
Parafollicular cells in the thyroid produce calcitonin, which helps to lower blood calcium levels.
The hypothalamus-pituitary-thyroid axis acts as a feedback mechanism regulating thyroid function.

Metabolic Regulation

Thyroid gland plays a critical role in metabolism, categorized under euthyroid, hypothyroid, and hyperthyroid states.

Imaging and Ultrasound

Cross-sectional anatomy knowledge is essential for effective ultrasound imaging.
Important structures to identify on ultrasound include:
- Trachea
- Common carotid artery (CCA) and internal jugular vein (IJV)
- Esophagus
- Neck muscles: sternocleidomastoid (SCM), strap muscles, anterior scalene, longus colli, and platysma.

Patient Positioning

For optimal imaging, patient should have the neck extended during ultrasound procedures.

Scanning Techniques

NM radioactive iodine scans are beneficial for assessing thyroid function and morphology.

Thyroid Gland Overview

Utilizes iodine for synthesis of hormones T3 (triiodothyronine) and T4 (thyroxine), stored in colloid.
Controlled by a feedback mechanism involving the hypothalamus, pituitary gland, and thyroid.
Regulates metabolism, influencing energy levels and general body function.

Hormonal Functions

Parafollicular cells produce calcitonin which reduces blood calcium levels.
Conditions based on thyroid function include euthyroid (normal), hypothyroid (underactive), and hyperthyroid (overactive).
Scanning and assessing thyroid function can involve the use of NM radioactive iodine.

Anatomical Position

Located in the anterior neck, inferior to the larynx and superior to the trachea.
Normally positioned in the inferior third of the neck, surrounded by thyroid and cricoid cartilages.

Morphology and Embryology

Composed of two main lobes connected by an isthmus, with possible pyramidal lobe variations.
Development begins at the base of the tongue, migrating via the thyroglossal duct to its final position at the 2nd-4th tracheal rings by the 9th week of gestation.
Thyroglossal duct typically degenerates before birth but can persist in some individuals.

Variants and Anomalies

Common thyroid variants include the pyramidal lobe (present in ~50% of individuals) and Zuckerkandl tubercle, a normal projection of thyroid tissue often mistaken for pathology.
Ectopic or accessory thyroid tissues may also be present.
Thyroglossal duct cysts can develop from remnants of the embryological structure.

Thyroid Mobility and Function

The levator muscle of the thyroid attaches the isthmus or pyramidal lobe to the hyoid bone, assisting in elevation during swallowing.
Thyroid gland typically moves with swallowing due to its connection to pretracheal fascia.

Neurovascular Considerations

The minor neurovascular bundle includes the inferior thyroid artery and the recurrent laryngeal nerve, located posterior to the thyroid and anterior to the longus colli muscle.
Important for surgical procedures involving the thyroid, ensuring the protection of surrounding structures.

Clinical Considerations

In cases of life-threatening situations, a cricothyrotomy may be performed to secure an airway through an incision in the cricothyroid membrane.
Anatomical landmarks such as the sternocleidomastoid (SCM) and various neck muscles are critical for understanding thyroid positioning.

Imaging Techniques

Neck extension is essential for proper patient positioning during thyroid imaging and assessments.

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Description

This quiz focuses on the anatomy and physiology of the thyroid gland, as part of the Ultrasonography module A.24 on Superficial Structures and Vascular Sonography. Gain an understanding of thyroid functions, structures, and their relevance in ultrasound imaging.