Anatomy of the Thyroid

Question 1

what are the components of the thyroid?

Answer 1

2 lateral lobes (right and left) and an isthmus (narrow connecting band between lobes)

Question 2

where do the lobes of the thyroid attach?

Answer 2

lateral aspects of the thyroid and cricoid cartilage

Question 3

what is the isthmus and where is it found?

Answer 3

band connecting 2 lobes of thyroid

sits in front of 2nd and 3rd cartilages of trachea

Question 4

how would an enlarged or lump in the thyroid move during swallowing and why?

Answer 4

will move superiorly then inferiorly with the larynx during swallowing
due to close relationship with larynx and trachea

Question 5

what is a goitre?

Answer 5

enlarged gland

Question 6

where are the 4 parathyroid glands located?

Answer 6

posterior surfaces of lateral lobes of thyroid

Question 7

what is the pyramidal lobe?

Answer 7

a third lobe of the thyroid which is present in some people
originates from one lobe (usually left) and attaches superiorly to the thyroid cartilage but can extend up to hyoid bone in some

Question 8

where does the thyroid gland originate?

Answer 8

midline epithelial proliferation at the junction between the anterior 2/3rds and posterior 1/3rd of the tongue (foramen caecum)

Question 9

where does the thyroid move to during development?

Answer 9

migrates inferiorly form the foramen caecum to the area of the larynx/trachea while remaining attached to the tongue via the thyroglossal duct

Question 10

when does the thyroid reach its final position?

Answer 10

week 7 of deveopment

Question 11

what forms compartments in the neck?

Answer 11

invaginations of deep fascia

Question 12

what is the platysma and what nerve innervates it?

Answer 12

thin muscle in superficial fascia of the neck which controls facial expression and supplied by facial nerve (cringe muscle)

Question 13

what are the fascial compartments of the neck?

Answer 13

prevertebral (deep) fascia
investing fascia
2 carotid sheaths
pretracheal fascia

Question 14

what is contained within the prevertebral fascia?

Answer 14

posterior compartment
postural neck muscles
cervical vertebrae

Question 15

what is contained within the investing fascia?

Answer 15

encloses all the other neck fascial compartment and 2 pairs of muscles

• trapezius
• sternocleidomastoid

Question 16

what is contained within the carotid sheaths?

Answer 16

located anterolaterally
vagus nerves
deep cervical lymph nodes
carotid arteries
internal jugular vein

Question 17

what is contained within the pretracheal fascia?

Answer 17

anterior and central
oesophagus
trachea
thyroid gland
strap muscles
recurrent laryngeal nerves

Question 18

what are the 2 main muscles in the neck and where do they attach?

Answer 18

trapezius - attaches to spine of scapula and lateral end of clavicle
sternocleidomastoid - sternal head attachment = manubrium of sternum, clavicular head attachment = medial end of clavicle
- both pass superiorly to attach to the mastoid process of temporal bone

Question 19

where are the carotid sheaths?

Answer 19

deep to investing fascia and located anterolaterally in the neck either side of thyroid

Question 20

where do the carotid sheaths attach?

Answer 20

superiorly = base of skull around jugular foramen and entrance to carotid canal

Question 21

what is the function of the carotid sheaths?

Answer 21

blend with mediastinal fascia

enclose internal jugular vein, common and internal carotids, vagus nerve and deep cervical lymph nodes

Question 22

blood supply to the thyroid?

Answer 22

inferior thyroid artery (branch off subclavian)
superior thyroid (branch off external carotid)
thyroid ima sometimes present (can come off brachiocephalic trunk or common carotid)

Question 23

venous drainage of thyroid?

Answer 23

superior thyroid and middle thyroid veins (drain into internal jugular veins)
inferior thyroid (drain into brachiocephalic viens)
then into IVC etc

Question 24

lymphatic drainage of thyroid?

Answer 24

deep cervical lymph nodes (superior and inferior)
pretracheal and paratracheal nodes (on trachea)
right = deep cervical nodes drain into right lymphatic duct and then to right venous angle
left = deep cervical nodes drain into thoracic duct then into left venous angle

Question 25

describe course of the vagus in the neck

Answer 25

branch from medulla oblongata exits skull via jugular foramen descends through carotid sheath

Question 26

course of vagus in thorax?

Answer 26

descends through chest - right = lateral to trachea - left = left side of aortic arch both travel posterior to lung hilum and attached to the oesopahgus

Question 27

right/left recurrent laryngeal nerves?

Answer 27

``` right = loops around right subclavian left = loops around arch of aorta ```

Question 28

connection between right subclavian and arch of aorta?

Answer 28

same embryological origin - 4th aortic arch artery

Question 29

what are strap muscles?

Answer 29

thin long muscles in the neck

Question 30

what are the superficial strap msucles?

Answer 30

sternohyoid | omohyoid

Question 31

what are the deep strap muscles?

Answer 31

thyrohyoid | sternothyroid

Question 32

surgical approaches to thyroid gland?

Answer 32

thyroidectomy endoscopy assisted thyroidectomy endoscopic trans-axillary approach endoscopic trans-breast approach

Question 33

regions of the neck

Answer 33

anterior triangle - between mandible, jugular notch and SCM | posterior triangle - between trapezius, clavicle and SCM

Question 34

what separates the anterior and posterior triangle of the neck?

Answer 34

sternocleidomastoid

Question 35

what are langers lines?

Answer 35

lines of tension/cleavage lines

Question 36

where is a classical thyroidectomy incision made?

Answer 36

collar incision made through skin and platysma within langer line incision just superior to clavicles and jugular notch

Question 37

what can injury to the recurrent nerve cause?

Answer 37

paralysis of the vocal cord unilateral injury = hoarseness/weak voice, cough bilateral = aphonia, inability to close rima glottidis to prevent aspiration or to produce a cough

Question 38

what nerve innervates the trapezius and sternocleidomastoid?

Answer 38

spinal accessory nerve (CN 11)

Question 39

venous drainage in the neck?

Answer 39

external jugular vein runs within superficial fascia and drains into subclavian anterior jugular vein runs in superficial fascia and drains into external jugular

Question 40

course of vagus in the abdomen?

Answer 40

both vagus nerves pass through the diaphragm with the oesophagus then divide into terminal branches on surface of stomach supply abdominal organs with parasympathetic axons to the distal midgut

Question 41

where do the inferior thyroid veins lie?

Answer 41

on the anterior surface of the trachea and thyroid

Question 42

what is ectopic thyroid tissue?

Answer 42

thyroid tissue outside the gland | can be located anywhere in the migratory path

Question 43

what does the right recurrent laryngeal nerve do?

Answer 43

provides somatic motor supply to most of the skeletal muscles that move the right vocal cord (same with left)