Anatomy of the Thyroid Gland Flashcards
At what vertebral level does the larynx become the trachea
C6
What 2 structures is the thyroid gland closely related to in the anterior neck
The larynx and the trachea
What does the thyroid gland usually consist of
2 lateral lobes (right and left) and an isthmus
What is the isthmus
A narrow connecting band
What do the lobes of the thyroid gland attach to
The lateral aspects of the thyroid and cricoid cartilages and to the trachea
What direction will the thyroid gland move when we swallow
Same as the larynx and the trachea
It will move superiorly then inferiorly
Where are the 4 parathyroid glands located
Not the posterior surfaces of the thyroid gland’s lateral lobes
What cartilage is located superiorly to the cricoid cartilage
The arytenoid cartilage
Where does the pyramidal lobe most commonly originate from
The left lateral lobe of the thyroid gland
Where doe most pyramidal lobes superiorly attach to
the thyroid cartilage
Some pyramidal lobes may extend as far superiorly as where?
The hyoid bone
Where does the thyroid gland begin its development
As a midline epithelial proliferation at the junction between the anterior 2/3rd and the posterior 1/3 of the tongue
Where does the gland migrate to
Migrates inferiorly whilst remaining attached to the tongue to the thryoglossbal duct
When does the thyroid gland reach its final position
7th week of development
Where might the pyramidal bone be found
Anywhere along the migratory path of the thyroid gland
It is an ectopic thyroid gland tissue
What encapsulates the trachea, the oesophagus and the thyroid gland
A layer of deep neck fascia - pre tracheal fascia
What muscle can be found in the superficial fascia
The platysma muscle - muscle of facial expression
Where nerve supplies the platysma muscles
cranial nerve VII (facial nerve)
Where does the platysma muscle lie
It extends for the lower border of the mandible to the lower border of the neck
Name the 4 fascial compartments of the neck
Prevertebral (deep) fascia
Investing (deep) fascia
The 2 carotid sheaths
Pretracheal (deep) fascia
What deep fascia layer is the most superficial
Investing
What is contained within the investing fascia
All other neck fascial compartments
encloses 2 pairs of muscles: trapezius and the sternocleidomastoid
What fascia is deep to the investing fascia
Prevertebral fascia, the pre tracheal fascia and the 2 carotid sheaths
What is contained within the prevertebral fascia
Encloses the cervical vertebrae and the postural neck muscles
What is enclosed by the carotid sheaths
Internal jugular veins
carotid arteries
the vagus nerves
the deep cervical lymph nodes
What are the strap muscles responsible for
Depressing the laryngeal cartilage when speaking and swallowing
What is the space between the prevertebral and the pre tracheal fascia called and why is this important
Retropharyngeal space - if infection develops, it will spread rapidly through this space
where does the sternocleidomastoid attach
Sternal head - manubrium of the sternum
clavicular head - medial end of the clavicle
Both heads pass superiorly to attach to the mastoid process of the temporal bone
Describe the anterior jugular vein
It is superficial vein in the superficial fascia which drains into he external jugular vein
Describe the external jugular vein
A superficial vein in the superficial fascia which drains in to the subclavian vein
what cranial nerve supplies the sternocleidomastoid and the trapezius
Cranial nerve XI - spinal accessory nerve
Where does the carotid sheaths lie
Deep to the investing fascia and located anterolaterally in the neck either side of the thyroid gland
Describe the structure of the carotid sheaths
Bilatera tubes of deep fascia which attach superiorly to the base of the skull. They run down the neck into the superior part of the thorax and the fascia will blend in with the mediastinal fascia
What is enclosed within each carotid sheath
The internal jugular vein
The common, then the internal carotid arteries
The vagus nerve
the deep cervical lymph nodes
Where do both the left and right inferior thyroid arteries branch from
The subclavian artery
Describe the venous drainage of the thyroid and parathyroid glands
Superior, middle and inferior
What drains into the internal jugular vein
The superior and middle thyroid veins
What drains into the left brachiocephalic vein
Both the right and left inferior veins
Where is the location of the venous angle
Between the internal jugular vein and the subclavian vein
Where do the paratracheal nodes sit
Either side of the trachea
What 2 somatic branches does the vagus nerve give rise to in the larynx
Superior laryngeal nerve and the right recurrent laryngeal nerve
Describe the route of the right recurrent laryngeal nerve
It is a branch of the vagus nerve that hooks up underrate the right subclavian artery to then ascend back up towards the larynx
Describe the route of the right vagus nerve
Lateral aspect of the trachea - it then passes posteriorly to the root of the lung and follow onto the surface of the oesophagus
Where does the phrenic nerve lie
Anteriorly to the root of the lung
Describe the route of the vagus nerve on the left hand side
It follows the arch of the aorta and it gives off the left recurrent laryngeal nerve - it hooks underneath the arch of the aorta to ascend back up towards the larynx
What are the names of the 4 strap muscles
Sternohyoid
Thyrohyoid
Omohyoid
Sternothyroid
What 1 of the 4 strap muscles has 2 bellies
The omohyoid - superior and inferior bellies
What causes the omohyoid muscle to change direction
A small tendon that grips the mid portion of the muscle
Where does the thyrohyoid muscle lie
The thyroid to the hyoid bone
Where does the sternohyoid muscle lie
Sternum to the hyoid bone
Where does the sternothroid muscle like
the sternum to the thyroid bone
Where does the omohyoid muscle lie
Extends out towards the shoulder and attaches to the scapula to the hyoid bone
What is the superior border of the manubrium
The jugular notch
The external jugular vein cross what
The muscle belly of the sternocleidomastoid
What forms the borders of anterior triangle of the neck
The laryngeal prominence of the thyroid cartilage,
The jugular notch
The sternal head border
The angle of the mandible and the inferior border of the mandible
What forms the borders of the posterior triangle of the neck
Trapezius
The clavicular head border of the sternocleidomastoid and the clavicle
How is a classical thyroidectomy performed
An incision through the skin and platysma just above the jugular notch and superior to the clavicle along langers lines
What 2 structures does the recurrent laryngeal nerve lie between
In a groove between the trachea and the oesophagus
What happens if a recurrent laryngeal nerve is damaged
Results in hoarse voice or losing the voice altogether
What happens if both recurrent laryngeals are damaged bilaterally
Aphonia (inability to produce sound and also the inability to close the rim glottidis to prevent aspiration or produce a good cough - very dangerous situation
What does the right recurrent laryngeal nerve provide
Somatic motor supply to most of the skeletal muscles that move the right vocal cord
