thyroid gland Flashcards
what forms the thyroid gland?
it is formed by 2 lobes
right and left lobes
what connects the lobes of the thyroid gland?
they are connective via isthmus
when is thyroid visible?
it is not visible under normal conditions
but visible during swallowing
what is the extension of thyroid gland in respective of the vertebrae?
C5-T1
HYOID BONE - C3
THYROID CARTILAGE - C4/C5
Cricoid cartilage C6
what does the isthmus overlie ?
the connection between the right and left lobe
what the extension of the isthmus in respective to cartilage rings?
2nd 3rd and 4th
what forms the lateral side that extend from the thyroid cartilage to the 6th tracheal cartilage?
lateral lobes of the thyroid gland
so at the 6th tracheal cartilage it is T1
where does the thyroid gland develop from ?
it is from the oral pharynx as well js like the rathke pouche
from the nasopharyngeal tonsils
since both rathke pouch and thyroid gland come from the oropharynx what is the difference?
the rathke pouch ascends upwards to the brain area
the thyroid gland descends down to the neck area
what is the thyroglossal duct?
short time connection that still connects to the thyroid from the neck to the pharynx
epithelial tube /fibrous cord
what happens to the thyroglossal duct in adults?
it disintegrates and disappear
when does the gland starts functioning ?
4 months of intra uterine life
what is thyroglossal duct cyst?
a condition where part of the thyroglossal duct has not disappeared and its remnants will form cyst
where is the cyst usually seen ?
near or within the body of hyoid bone
they form swellings in the anterior part of the neck
where the possible locations where the thyroid gland/cyst might form along its way going down?
if it is in the tongue –lingual thyroid
if it is below the tongue –> sublingual thyroid
in front of the trachea/larynx —> prelaryngeal / pretracheal thyroid
what is it called when the thyroid gland gets stuck in the trachea before the rings are even formed?
it will get stuck inside the trachea itself —> Intrathoracic thyroid
Retrosternal thyroid
is the thyroid gland same in everyone?
no it has variations
Sometimes Isthmus is absent and sometimes there are projections
what is pyramidal lobe?
inconstant upward projection from the isthmus or the lateral lobe and it attaches to the hyoid bone
represent embryological descent of the thyroid
from which side does the pyramidal lobe usually project from?
the left side
how does the pyramidal lobe connect to the hyoid bone?
Levator glandulae thyrideae
fibromuscular extension from hyoid bone to the isthmus / pyramidal lobe
what is a true capsule?
fibrous capsule
it is peripheral condensation of connective tissue of the GLAND ITSELF
so its a capsule surrounding the gland itself
what is false capsule ?
fascial capsule that surrounds the true fibrous capsule
describe the thickness of the false fascial capsule?
it is thick anteriorly
but posteriorly it is weak and thin
what happens when a tumor starts to grow inside the capsule ?
it will stop pushing forward because it is hard and thick anteriorly and it will push posteriorly since it is weaker
what are the structures found posteriorly to the thyroid lobe?
Trachea
treacheoesophageal groove
esophagus
if tumor grows it will cause dysphagia and difficulty breathing
what runs in the tracheoesophageal groove?
recurrent laryngeal nerve
if it is stretched it will cause hoarseness of the voice
what does the false fascial capsule thickens to form?
it thickens to form the suspensory ligament of berry
what is the function of suspensory ligament of berry ?
it attaches the thyroid lobe to the cricoid cartilage
then it will make it so that the thyroid moves with the cricoid cartilage
what is present in the space between true fibrous capsule and false fascial capsule?
parathyroid gland
what is the difference between the thyroid gland and prostate in respective of venus plexus ?
Thyroid gland has the venus plexus deep to the true capsule –> it is within the true capsule, SO during surgery we have to remove the gland itself with the true fibrous capsule to avoid bleeding
Prostate –> venous plexus it is between the true fibrous and false fascial capsule –> in surgery we can take the prostate alone and leave the capsule behind
what is the shape of the lobes of thyroid gland?
cone shaped
where is the apex located?
apex extends to oblique line of thyroid cartilage
sandwiched between inferior constrictor and sternothyroid
which muscles lies medially to the apex of thyroid lobe?
inferior constrictor
which muscles lies LATERALLY to the apex of thyroid lobe?
sternothyroid
where is the base of the thyroid lobe located?
located between 5-6 tracheal cartilage
what are the 3 surfaces of thyroid lobe?
anterolateral
posterolateral
medial
what are the borders of thyroid lobe?
anterior border
posterior border
what are the branches of vagus nerve?
superior laryngeal nerve
Recurrent laryngeal nerve
what are the divisions of the superior laryngeal nerve?
external laryngeal nerve
internal laryngeal nerve
what does the internal laryngeal nerve supply?
mucosa of larynx ABOVE the level of the vocal fold
what is cricothyroid muscle?
muscle extending from cricoid to thyroid
what is the function of cricothyroid muscle?
stretch the vocal cords to make the voice higher in pitch
what is the nerve supplying the cricothyroid muscle?
external laryngeal nerve
what is the muscle posterior/deep to the thyroid gland?
inferior constrictor
what is the muscles anterior/superficial to the thyroid gland ?
sternothyroid
what are the structures related to the medial surface of the thyroid gland ?
2 tubes
2 muscles
2 nerves
what are the 2 tubes related to the thyroid gland ?
larynx / trachea
Pharynx / esophagus
what are the 2 nerves related to the medial surface of the thyroid gland ?
external laryngeal nerve –> supply cricothyroid
recurrent laryngeal nerve
what are the 2 muscles related to the medial surface?
inferior constrictor
cricothyroid
what lies on the posterolateral surface ?
carotid sheath and its contents
what lies in the anterolateral surface?
all the muscles
Strap muscles
where is the location of the recurrent laryngeal nerve?
it is not specific and very variable
what is the artery running in the anterior border?
anterior descending branch of superior thyroid artery
what is found in the posterior border of the thyroid gland?
anastomosis of the superior and inferior thyroid artery
parathyroid gland
lower part of thoracic duct
what is anterior to the isthmus?
sternothyroid and sternohyoid muscle
what is posterior to the isthmus?
2nd 3rd 4th tracheal rings
what is superior to the ishmus?
pyramidal lobe
levator glanduli thyroidae
what is inferior to the isthmus ?
inferior thyroid veins
what are the veins of the thyroid gland?
superior
middle
inferior –> inferior border of the isthmus
where do the veins of the thyroid gland empty to?
brachiocephalic vein
what is the blood supply of the thyroid gland? ( arteries )
superior thyroid artery
inferior thyroid
thyroidea ima artery
where does the superior thyroid artery come from?
external carotid artery
what does the superior thyroid artery divide into to?
anterior and posterior branches
what does it supply?
upper 1/3 of the lobes
upper half of isthmus
where does the inferior thyroid artery come from?
branch of thyrocervical trunk
15% of ppl it is from subclavian
what does the inferior thyroid artery supply?
lower 2/3 of lobes
lower half of isthmus
where does the thyroidea ima artery come from?
in 3% individuals from the brachiocephalic trunk
what are the veins of thyroid gland?
superior thyroid
middle thyroid
inferior thyroid vein
4th thyroid vein of kocher
where does the superior thyroid vein drain into?
upper part of thyroid gland
ends in internal jugular vein
where does the middle thyroid vein drain from?
middle thyroid gland
empty in internal jugular vein
where does the inferior thyroid vein drain from?
drain inferior part of the gland
plexus infront of trachea
empty to the left brachiocephalic
where does the 4th thyroid vein of kocher empty to?
form betweeen middle and inferior vein
drain into Internal jugular vein
where is the lymphatic drainage of the upper part of the gland?
upper deep cervical
via prelaryngeal , pretracheal , paratracheal nodes
where is the lymphatic drainage of the lower part thyroid gland?
lower deep cervical nodes
what is the nerve supply of the gland?
superior cervical sympathatic ganglia
middle cervical sympathetic ganglia
inferior cervical sympathetic ganglia
how do the nerves reach the gland?
cardiac , superior and inferior thyroid , peri arteriolar plexuses accompanying the thyroid arteries
what type of fibers are the nerves supplying the gland?
vasomotor
not secreto motor
what is horners syndrome?
when the sympathetic ganglia get removed cuz it appeared like a lymph node
what are the complications that could happen due to thyroidectomy?
injury to the external laryngeal nerve –> paralysis of cricothyroid muscle
injury of the recurrent laryngeal nerve –> hoarsensess of the voice or stridor
injury to the cerivcal sympathetic trunk or sympathetic ganglion—> due to confusion with lymph nodes –> horners syndrome
what are the possible variations of the recurrent laryngeal nerve?
4% intrathyroid
42% paratracheal
48% tracheosoph groove
6% parasophageal
what happens in cases of atrophy of one lobe due to tumor?
the other lobe will hypertrophy to compensate
what are the changes that happens to the colloid in regard to the activity?
inactive gland –> large colloid filled with thyroid and flat cells due to compression
moderately active glands —> cuboid cells and moderate colloid
hyperactive gland –> small colloid and COLUMNAR CELLS
what is the blood , lymphatic and nerve supply of the parathyroid gland?
same as thyroid
what is the embyro origin of the parathyroid gland?
3rd and 4th brachial pouches
which pouch give raise to the SUPERIOR GLAND?
4th pouch
which pouch give raise to INFERIOR GLAND?
3rd pouch
what happens to the inferior gland ?
descend with the thymus
