Anatomy - The Anterior Neck and Thyroid Gland Flashcards
What is the midline connection called of the two lateral thyroid gland lobes?
Isthmus.
What tracheal rings does the isthmus of the thyroid gland lie in front of?
2nd, 3rd and 4th.
Where do the thyroid arteries arise from?
- Superior thyroid artery - External carotid artery. 2. Inferior thyroid artery - Thyrocervical trunk, a branch of the Subclavian artery.
What vessels are contained within the carotid sheath?
- Carotid artery. 2. Jugular vein. 3. Vagus nerve.
What is the origin of sternocleidomastoid?
The manubrium of the sternum and the clavicle.
What is the insertion of sternocleidomastoid?
Mastoid process.
What nerve(s) are related to the superior thyroid arteries?
The external laryngeal nerves.
What nerve(s) are related to the inferior thyroid arteries?
The recurrent laryngeal nerve crosses the inferior thyroid artery.
Describe the location of the thyroid gland in relation to the vertebrae?
C5-T1
Why is it described as butterfly shaped?
- consists of two lobes, left and right
- Connected by central isthmus anteriorly
What compartment is the thyroid gland found in? what surrounds it?
- Visceral compartment of the neck (Along with the trachea and oesophagus and pharynx)
- this compartment is bound by the pretracheal fascia
What is associated on the anterior of the thyroid gland?
- infrahyoid muscles
- Sternothyroid
- Superior value of the omohyoid and sternohyoid
What is associated on the lateral side of the thyroid gland?
- carotid sheath
- Contains the common carotid artery internal jugular vein and vagus nerve
What is associated on the medial side of the thyroid gland?
- organs - larynx and pharynx trachea and oesophagus
- nerves - external laryngeal and recurrent laryngeal nerves
Why does the thyroid gland have to be highly vasculated?
Because it secretes hormones directly into the circulation
Describe the 2 main arteries supplying the thyroid gland?
- Superior thyroid artery -
- arises from the first branch of the external carotid artery
- in close proximity to the external branch the superior laryngeal nerve
- Inferior thyroid artery
- arises from the thyrocervical trunk (Subclaavian artery)
- lies in close proximity to the recurrent laryngeal nerve
Describe the venous drainage from the thyroid gland?
- venous plexus
- made up from the superior middle and inferior thyroid veins
- superior and middle veins drain into the internal jugular vein
- inferior Vein drains into the brachiocephalic vein
What is the innovation of the thyroid gland?
- branches derived from the sympathetic trunk
- no control of excretory functions gland ( regulated by the pituitary gland)
Describe the lymphatic drainage of the thyroid gland?
drains into the paratracheal and deep cervical nodes
What are the boundaries of the anterior triangle?
- superiorly - inferior border of the mandible
- Laterally - anterior border of the sternocleidomastoid
- medially - sagittal line down the midline of the neck
What fascia covers the roof and the floor of the triangle?
- investing fracture covers the roof
- visceral covers the floor
However muscles divided in relation to the hyoid bone?
- suprahyoid muscles are located superiorly to the hyoid bone
- Infrahyoid muscles are located inferiorly to the hyoid bone
Describe the vasculation of the anterior triangle?
- Common carotid artery bifurcates into the external and internal carotid branches
- The internal jugular vein is responsible for venous drainage of the head and neck
Name the cranial nerves found within the anterior triangle?
- facial VII
- loss of pharyngeal IX
- Vagus X
- accessory XI
- hypoglossal XII
Describe the 4 infra-hyoid muscles?
- omohyoid
- scapula to hyoid
- 2 muscle bellies
- Intermediate tendon, anchored to the clavicle
- depresses the Hyoid bone
- sternohyoid
- sternum/sternoclavical joint to hyoid
- depresses the hyoid bone
- sternothyroid
- manubrium of the sternum attaching to the thyroid cartilage
- depresses the thyroid cartilage
- thyrohyoid
- thyroid cartilage to to the hyoid bone
- depresses the hyoid, if higher bone is fixed it can elevate the larynx
What is the plastysma?
- thin ‘paper’ like muscle
- originates from the fascia of the pectorails major and deltoid
- inserts into the inferior border of the mandible
Describe the sternocleidomastoid muscle?
- Originates at the sternum and clavicle
- inserts into the mastoid process just behind the ear
What are the parathyroid responsible for?
- production of the parathyroid hormone
- acts to increase the levels of serum calcium
Describe the Anatomical location of the parathyroid glands?
- Located in the posterior aspect of the thyroid gland
- flattened oval shaped
- situated externally to the thyroid gland itself
- 2 Superior parathyroid glands - middle of the posterior border of each thyroid lobe
- 2 inferior parathyroid glands - usually found near the inferior pause of thyroid gland
Describe the vasculation of the thyroid gland?
- Supplied by the inferior thyroid artery
- Venous drainage us into the superior middle and inferior thyroid veins
Describes the innovation of the parathyroid glands?
extensive supply of sympathetic nerves to rifle the thyroid branches of the cervical ganglia
Describe the Anatomical location of the laryngeal nerves?
- in the groove between the trachea and oesophagus is the recurrent laryngeal nerve
- on the right is the recurrent laryngeal nerve wracking behind the subclavian artery
- follows the groove between the oesophagus and the trickiest passes to the larynx
What is found within the carotid sheath?
- tuber fascia
- carotid arteries
- Jugular vein
- vagus nerve X
What occurs at the bifurcation of the common carotid artery?
- Bifurcates into the internal and external carotid arteries
- At the bifurcation there are chemoreceptors
- Measures the blood pH
- feeds the control of breathing
- Swelling in the internal carotid artery
- carotid sinus
- contains barren receptors which feeds into the blood pressure control system
Describe how the vagus nerve gives rise to the recurrent laryngeal branch?
- on the right the vagus nerve runs anterior to the subclavian artery
- the inferior border of the subclavian artery branches to give rise to the recurrent laryngeal branch
- which passes under and behind the subclavian artery before ascending into the larynx
- in the groove between the oesophagus and trachea
What is the clinical relevance of a diseased thyroid gland?
- overproduce thyroxine results in low TRH and TSH
- lumps in the thyroid will elevate with swallowing ( lumps in the lymph nodes will not)
- As the virus around the trachea on three sides, lodgement can compress the trachea
- the inferior pole of the thyroid is very close to the recurrent laryngeal nerve, therefore making the nerve at risk from thyroid pathology and surgery
What are the functions of the extrinsic laryngeal muscles?
depress the larynx
Where do you create an emergency airway?
an incision made through the skin and cricothyroid membrane
What is the only complete real cartilage around the airway?
the cricoid cartilage - hyaline cartilage
Why has a patient developed hypocalaemia after thyroid surgery?
- Low calcium levels in blood
- The parathyroid glands are responsible for the release of parathyroid hormone
- which controls the levels of serum calcium
