Anatomy of the Thyroid Gland Flashcards
The thyroid gland is closely related to which anatomical structures in the anterior neck?
- Larynx
- Trachea
Usually, the thyroid gland consists of which three parts?
- Right lateral lobe
- Left lateral lobe
- Isthmus
What is the isthmus of the thyroid gland?
The connection between the right and left lateral lobes
The lateral lobes of the thyroid gland attach to what?
Lateral aspects of thyroid and cricoid cartilages
The isthmus lies anterior to the ____ and ____ cartilages of the trachea
The isthmus lies anterior to the 2nd and 3rd cartilages of the trachea
Where are the four parathyroid glands located?
Posterior surfaces of the thyroid gland’s lateral lobes
What is one of the most common anatomical variations of the thyroid gland?
Pyramidal lobe
Usually the pyramidal lobe originates from the _______ lateral lobe
Usually the pyramidal lobe originates from the left lateral lobe
How does the thyroid gland begin its development?
A midline epithelial proliferation at the junction between the anaterior and posterior aspects of the tongue
The thyroid gland will migrate inferiorly whist still being attached to the tongue via what?
Thyroglossal duct
In which week of development will the thyroid gland reach its final postition?
7th
What are the platysma?
Broad sheet-like superficial muscles that overlap the sternocleidomastoid and sit in the subcutaneous tissue in the neck
What is the nerve supply of the platysma muscles?
Facial nerve (CN VII)
How many fascial compartments are there in the neck?
4
What are the fascial compartments in the neck?
- Prevertebral deep fascia
- Investing deep fascia
- Carotid sheaths
- Pretracheal deep fascia
What is the location of the prevertebral deep fascia?
Deep to the investing fascia
Located most posteriorly in the neck
What is contained within the investing fascia?
- All other neck fascial compartments
- Trapezius
- Sternocleidomastoid
What is carried within the carotid sheaths in the neck?
- Vagus nerves
- Carotid arteries (common then internal)
- Internal jugular veins
- Deep cervical lymph nodes
Where is the pretracheal fascia located and what does it enclose?
Most anteriorly within the enclosure of the investing fascia
Encloses:
- Oesophagus
- Trachea
- Thyroid gland
- Strap muscles
- Recurrent laryngeal nerves
Which nerve supplies the sternocleidomastoid and trapezius?
Spinal accessory nerve (CN XI)
The external jugular vein runs within the __________ _______ and drains into the _____________ _____
The external jugular vein runs within the superficial fascia and drains into the subclavian vein
Where does the anterior jugular vein run and where does it drain?
Superficial fascia
External jugular vein
The sternocleidomastoid is enclosed within what?
Investing fascia
The sternocleidomastoid has two heads, what are they and where do they both insert?
- Sternal head - manubrium of the sternum
- Clavicular head - medial end of the clavicle
What is the origin of the sternocleidomastoid?
Mastoid process of the temporal bone
The carotid sheaths are located _____________ either side of the __________ ________
The carotid sheaths are located anterolaterally either side of the thyroid gland
Where do the carotid sheaths attach to the skull?
Base of skull
(around jugular foramen and entrance to carotid canal)
Where does the carotid sheath attach inferiorly?
Blends with mediastinal fascia
Where is the vagus nerve located in the neck?
Carotid sheath
(between the common carotid artery and the internal jugular vein)
What is the arterial supply of the thyroid gland?
- Superior thyroid arteries
- Inferior thyroid arteries
The inferior thyroid arteries are branches of which arteries?
Subclavian arteries
The superior thyroid arteries are branches of which arteries?
External carotid arteries
Which artery is an anatomical variant that may supply blood to the thyroid gland and where does it originate?
Thyroid ima artery
Usually brachiocephalic
What is the venous drainage of the thyroid gland?
Superior, middle and inferior thyroid veins
Where do the superior and middle thyroid veins drain?
Internal jugular veins
Where does the inferior thyroid vein drain?
Left brachiocephalic vein
Where do the internal jugular veins drain?
Right and left brachiocepalic veins
What is the lymphatic drainage of the thyroid gland
a) Superiorly
b) Inferiorly
a) Superior deep cervical lymph nodes
b) Inferior deep cervical lymph nodes
What are the types of lymph nodes surrounding the trachea?
- Pretracheal
- Paratracheal
How is lymph returned to the circulation
a) On the right side
b) On the left side
a) Via right lymphatic duct to right venous angle
b) Via thoracic duct to left venous angle
The vagus nerves branch from the ________ _________ and exit the skull via the _________ __________ then descend within the ___________ _________
The vagus nerves branch from the medulla oblongata and exit the skull via the jugular foramen then descend within the carotid sheaths
Within the chest the right vagus nerve will be found _______ to the trachea
Within the chest the right vagus nerve will be found lateral to the trachea
Within the chest, the left vagus nerve will be found to which side of the aortic arch?
Left
Both vagus nerve travel ________ to the lung hila
Both vagus nerve travel posterior to the lung hila
Both vagus nerves pass into the abdomen with the ___________
Both vagus nerves pass into the abdomen with the oesophagus
The right recurrent larngeal nerve recurs under what?
Right subclavian artery
The left recurrent laryngeal nerve recurs under what?
Arch of aorta
What are the four strap muscles?
- Sternohyoid
- Sternothyroid
- Thyrohyoid
- Omohyoid
How can the omohyoid muscle be distinguished?
- Tendinous section within the middle segment
- Fascial sling attaches it to clavcle preventing bowstringing
If structures are damaged iatrogenically, what does this mean?
They are damaged by a clinician
Recurent larngeal nerve injury results in what?
Paralysis of the vocal cords
- Unilaterally - weakvoice and cough, hoarse voice
- Bilaterally - aphonia (cannot make sound), inability to close rima glottidis, cannot produce good cough
With bilateral recurrent laryngeal nerve injury, what is the risk of being unable to close the rima glottidis?
Cannot prevent aspiration
