Anatomy C9 Flashcards
Where is the thyroid gland located and at what vertebral level
Anterior aspect of the neck C5 - T1
What unites the right and left lobes and where?
a thin isthmus over the trachea, anterior to second and third tracheal rings
What cervical fascia is the capsule made from?
Pre tracheal
Describe the lateral lobe
The apex extends up to the oblique of the thyroid cartilage and the base to the level of 4th/5th ring
Describe the Isthmus
Crosses anterior to the 2nd - 4th tracheal ring
Describe the pyramidal lobe
Projects upwards from isthmus to left of the midline
What are the anterolateral relations of the lobes?
- Sternothyroid
- superior belly of omohyoid
- sternohyoid
- anterior border of the sternocleidomastoid
What are the posterolateral relations of the thyroid lobes?
- carotid sheath with common carotid
- internal jugular vein
- vagus nerve
What are the medial relations of the thyroid gland?
- Larynx
- trachea
- pharynx
- oesophagus
- cricothyroid muscle and nerve supply
- external laryngeal
- between oesophagus and trachea is a recurrent laryngeal nerve
What are the anterior relations of the isthmus?
- sternothyroid
- sternohyoid
- anterior jugular veins
- fascia
- skin
What are the posterior relations of the isthmus?
- 2nd - 4th rings of the trachea
- What artery supples the upper pole of each lobe?
superior thyroid artery
Where does the superior thyroid artery arise from?
External carotid
What nerve accoompanies the superior thyroid artery?
External laryngeal
What does the inferior thyroid artery supply?
posteroinferior aspect of the thyroid gland
Where does the inferior thyroid artery arise from?
Thyrocervical trunk a branch of subclavian, it ascends behind the gland to the level of cricoid cartilage
What nerve accompanies the inferior thyroid artery?
Reccurent laryngeal nerve crosses behind/in front/ in between the vessels
Where does the thyroid ima arise from?
- brachiocephalic
- arch of aorta
- right common carotid
- subclavian
- internal thoracic arteries
What nodes do the lymphatic vessels of thyroid gland drain to?
- Pretracheal
- paratracheal
- efferent vessels from these nodes go to deep cervical nodes
Where is the lymphatic network of the thyroid gland located
Connective tissue septa of the thyroid gland
Describe the innervation to the thyroid glland
- SNS innervation
- post ganglionic SNS fibres arise in the superior, middle and inferior cervical ganglia and pass through the cardiac, superior and inferior thyroid plexus to reach the gland
- vasomotor information
What is a thyroid goitre
An enlargement of the thyroid gland which may occur due to over activity or underactivity of the gland
Which direction does a thyroid goitre enlarge in?
- anterior
- infeiror
- lateral
- posterior
What structures may be compressed by a thyroid goitre?
- Oesophagus
- Recurrent laryngeal nervers
- Trachea
What prevents the thyroid gland from enlarging superiorly
The superior attachments of sternothyroid and sternohyoid muscles
Describes the development of the thyroid gland?
- The thyroid gland develops from a thickening on the floor of the embryonic pharynx in the developing tongue
- A diverticulum develops from this thickening forming the thyroglossal duct
- The thyroglossal duct elongates and its distal end becomes bi-lobed and proliferates into the thyroid gland
- The thyroid gland descends through the neck anterior to the hyoid bone.
- At 7 weeks the gland reaches its adult position
- The thyroglossal duct degenerates but a pit remains on the dorsum of the tongue marking its site of origin (foramen caceum)
What do the parathyroid glands secrete?
parathyroid hormone
Describe the structure of parathyroid glands?
- ovoid bodies
- 6mm long
- posterior border of the thyroid gland lying within its fascial capsule
- there are four glands: x2 superior and x2 inferior
Describe the two superior parathyroid glands?
- Where do they lie?
The more constant in position and lie at the level of the middle of the posterior border of the thyroid gland, lie below the point where the superior thyroid vessels enter the thyroid gland
Wherer do the inferior parathyroid glands lie?
Close to the inferior poles of the thyroid gland, may be located in the superior mediastinum, they may lie within or outside the facial sheath
What is the arterial supply to the parathyroid glands
- Superior thyroid arteries
- inferior thyroid arteries
Describe the innervation of the parathyroid glands?
Postganglionic sympathetic fibres from the superior or middle cervical ganglia, SNS provides secretomotor fibres to the parathyroid glands
