Thyroid Gland Flashcards
What are the components of the thyroid gland?
Two lateral lobes
Connecting isthmus
Where do the lobes of the thyroid attach?
Lateral aspects of the thyroid and cricoid cartilages and trachea
Where does the isthmus lie?
Anterior to the 2nd and 3rd cartilages of the trachea
In what direction would a lump on the thyroid move when swallowing?
Superiorly then inferiorly
Where are the parathyroid glands located?
Posterior surface of the thyroid’s lateral lobes
What is a pyramidal lobe of the thyroid gland?
Extra thyroid tissue (due to embryological migration)
Most commonly originates from left lateral lobe
Most attach superiorly to thyroid cartilage but ca extend to the hyoid bone
What is the developmental path of the thyroid gland?
Foramen caecum
Migrates inferiorly via thyroglossal duct
Final position by week 7
What are the platysma muscles?
Muscles of facial expression
located immediately deep to the skin within superficial fascia of the neck
Supplied by CN VII
What are the fascial compartments of the neck?
Prevertebral fascia
Investing fascia
Carotid sheaths
Pretracheal fascia
Where is the prevertebral fascia and what is contained within it?
Deep to investing fascia
Posteriorly
Cervical vertebrae and postural neck muscles
Where is the investing fascia and what is contained within it?
Deep to supeficial fascia
Encloses all other neck fascial compartments
Trapezius and sternocleidomastoid
Where are the carotid sheaths and what is contained within them?
Deep to investing fascia
Anetrolaterally
IJVs, carotid arteries, vagus nerves, deep cervical lymph nodes
Where is the pretracheal fascia and what is contained within it?
Deep to investing fascia
Anteriorly
Strap muscles, thyroid gland trachea, oesophagus, recurrent laryngeal nerves
Where does the retropharyngeal space lie and why is it clinically significant?
Between pre tracheal and prevertebral fascia
Site for infection spread
What are the attachments of the sternocleidomastoid?
Sternal head = manubrium of sternum
Clavicular head = medial end of the clavicle
Both heads = Mastoid process of temporal bone
What is the innervation of trapezius and sternocleidomastoid?
CN XI (Spinal Accessory)
What are the inferior attachments of trapezius?
Spine of the scapula and lateral end of clavicle
Where does the anterior jugular vein drain to?
External jugular vein
Where does the external jugular vein drain to?
Subclavian vein
What are the attachments of the carotid sheaths?
Superiorly = base of the skull (around jugular foramen and entrance to carotid canal) Inferiorly = blend with mediastinal fascia
What is the arterial supply to the thyroid gland?
Inferior and superior thyroid arteries
Where does the inferior thyroid artery branch from?
Subclavian artery
Where does the superior thyroid artery branch from?
External carotid artery
What is the venous drainage of the thyroid gland?
Superior, middle and inferior thyroid veins
Where do the superior and middle thyroid veins drain to?
Internal jugular vein on right and left sides
Where does the inferior thyroid vein drain to?
Brachiocephalic vein, usually on left side
Where does the right lymphatic duct drain to?
Right venous angle
Where does the thoracic duct drain to?
Left venous angle
What is the course of CN X within the cranial cavity?
Connects with medulla oblongata
Passes through jugular foramen
What is the course of CN X in the neck?
Descends in carotid sheath
Gives somatic branches to the larynx - superior laryngeal nerve and right recurrent laryngeal nerve
What is the course of CN X in the chest?
Right vagus
Right lateral aspect of trachea
Posterior to right lung root
Onto oesophagus
Left vagus Left side of arch of aorta Gives left recurrent laryngeal nerve Posterior to left lung root Onto oesophagus
What is the course of CN X in the abdomen?
L and R pass through diaphragm with oesophagus
Divide into terminal branches on stomach surface
Supply abdominal organs with parasympathetic axons to distal midgut
Where does the left recurrent laryngeal nerve recur?
Under arch of aorta
Where does the right recurrent laryngeal nerve recur?
Under the subclavian artery
What are the strap muscles?
Sternohyoid
Omohyoid
Thyrohyoid
Sternothyroid
What is the function of the strap muscles?
Movement of larynx during speech and swallowing
What is the purpose of the fascial sling?
Attaches intermediate tendon of omohyoid to the clavicle
What are the surgical approaches to the thyroid gland?
Classical thyroidectomy
Endoscopically assisted thyroidectomy
Endoscopic trans-axillary approach
Endoscopic trans-breast approach
What are the surface markers for the anterior triangle of the neck?
Inferior border of mandible/angle of mandible
Sternal head of sternocleidomastoid
Midline
What are the surface markers of the posterior triangle of the neck?
Clavicular head of sternocleidomastoid
Trapezius
Clavicle
Where should the classical thyroidectomy incision be made?
Within a natural skin crease or in the direction of Langer’s lines
Just superior to the clavicles and jugular notch
Through skin and platysma
What is the function of the right recurrent laryngeal nerve?
Somatic motor supply to most of the skeletal muscles that move the right vocal cord
What is the result of unilateral recurrent nerve injury?
Hoarseness or weakness of the voice and cough
What is the result of bilateral recurrent nerve injury?
Aphonia
Inability to close the rima glottidis to prevent aspiration or to produce a good cough
