Thyroid gland - teachmeanatomy

Question 1

the thyroid gland is an

Answer 1

an endocrine structure located in the neck. It plays a key role in regulating the metabolic rate of the body.

Question 2

anatomical location of the thyroid gland

Answer 2

The thyroid gland is located in the anterior neck and spans the C5-T1 vertebrae.

Question 3

gross structure of the thyroid gland

Answer 3

It consists of two lobes (left and right), which are connected by a central isthmus anteriorly – this produces a butterfly-shape appearance.

Question 4

relation of the thyroid to other nearby structures

Answer 4

lobes of the thyroid gland are wrapped around the cricoid cartilage and superior rings of the trachea.

Question 5

where is the ghland loated withint he compartments of the neck

Answer 5

the gland is located within the visceralcompartment of the neck (along with the trachea, oesophagus and pharynx). This compartment is bound by the pretracheal fascia.

Question 9

Clinical Relevance: Thyroglossal Cyst

Answer 9

In the embryo, the thyroid gland begins development near the base of the tongue – in an area known as the foramen cecum. It descends during development and reaches its destination in the anterior neck by week 7.

The descent of the developing thyroid gland forms the thyroglossal duct – an epithelialised tract that connects the gland to its origin at the foramen cecum. It usually regresses by the 10th week of gestation, but can persist in some individuals. If it fails to regress, the duct can give rise to cysts or fistulae.

A thyroglossal cyst results from a build-up of secretions within the duct. It typically presents as a midline lump in the anterior neck which rises on tongue protrusion. If left untreated, this cyst can become infected, and form a cutaneous fistula – discharging out onto the skin of the anterior neck.

Thyroglossal cysts and fistulae are usually treated with complete excision. Recurrence is quoted at approximately 2.5%.

Question 10

anterior anatomical relation

Answer 10

infrahyoid muscles, namely the sternothyroid, superior belly of the omohyoid and sternohyoid

Question 11

lateral anatomical relation of the thyroid

Answer 11

carotid sheath, containing the common carotid artey, internal jugular vein and vagus nerve

Question 12

medial anatomical relations of the thyroid

Answer 12

Medially –

Organs – larynx, pharynx, trachea and oesophagus

Nervea – external laryngeal and recurrent laryngeal

Question 13

why is the thyroid highly vascularised

Answer 13

The thyroid gland secretes hormones directly into the circulation

Question 14

which 2 main arteries supply the thryoid

Answer 14

superior thyroid artery

inferior thyroid artery

Question 15

Superior thyroid artery –

Answer 15

arises as the first branch of the external carotid artery. It lies in close proximity to the external branch of the superior laryngeal nerve (innervates the larynx).

Question 16

Inferior thyroid artery –

Answer 16

arises from the thyrocervical trunk (a branch of the subclavian artery). It lies in close proximity to the recurrent laryngeal nerve (innervates the larynx).

Question 17

In a small proportion of people (around 10%) there is an additional artery present – the

Answer 17

thyroid ima arter

It arises from the brachiocephalic trunk and supplies the anterior surface and isthmus of the thyroid gland.

Question 18

Venous drainage is carried by the

Answer 18

superior, middle, and inferior thyroid veins, which form a venous plexus around the thyroid gland.

Question 19

superior and middle veins drain intot he

Answer 19

internal jugular vein

Question 20

inferior vein drains intot he

Answer 20

brachiocephalic vein

Question 21

Innervatio

Answer 21

The thyroid gland is innervated by branches derived from the sympathetic trunk.

These nerves do not control the secretory function of the gland – the release of thyroid hormones is regulated by the pituitary gland.

Question 22

Lymphatic Drainage

Answer 22

The lymphatic drainage of the thyroid is to the paratracheal and deep cervical nodes.

Question 23

Clinical Relevance: Recurrent Laryngeal Nerve

Answer 23

The left and right recurrent laryngeal nerves lie in close proximity to the thyroid gland and care must be taken not to damage them during thyroid surgery.

They branch from their respective vagus nerve within the chest and hook around the right subclavian artery (right RL nerve), or the arch of aorta (left RL nerve).

The recurrent laryngeal nerve then travels back up the neck, running between the trachea and oesophagus in the tracheoesophageal groove. It then passes underneath the thyroid gland to innervate the larynx.

Question 24

During a thyroidectomy, the inferior thyroid artery is identified and ligated. Which vessel directly gives rise to the inferior thyroid artery?

Answer 24

thyrocervical trunk