thyroid anatomy

Question 1

where is the thyroid located

Answer 1

5th cervical to 1st thoracic vertebrae

2-4th tracheal rings

Question 2

how big is the thyroid in adults

Answer 2

12-15mm

25-30g

Question 3

when would the thyroid increase in size

Answer 3

pregnancy

menstruation

Question 4

what is the parasympathetic nerve supply

Answer 4

vagus nerve

Question 5

what is the sympathetic nerve supply

Answer 5

superior, middle, and inferior ganglia of sympathetic trunk

Question 6

what is the arterial blood supply of the thyroid

Answer 6

superior and inferior thyroid arteries

Question 7

where do the superior and inferior thyroid arteries originate

Answer 7

superior = branch of external carotid
inferior = subclavian

Question 8

what is the venous blood supply of the thyroid

Answer 8

superior, middle, and inferior thyroid veins

Question 9

where do the superior, middle, and inferior thyroid veins originate

Answer 9

superior & middle = internal jugular

inferior = brachiocephalic veins

Question 10

how is the thyroid gland attached

Answer 10

posterior suspensory ligament (aka berry ligament)

Question 11

what does the thyroid consist of

Answer 11

2 lateral lobes (L & R) and an isthmus

Question 12

what is the isthmus

Answer 12

narrow connecting band within the thyroid

Question 13

where do the lobes attach

Answer 13

cricoid cartilages and to the trachea

Question 14

where is the isthmus located

Answer 14

the 2nd & 3rd cartilages of the trachea

Question 15

a lump within the gland will do what on swallowing

Answer 15

move superiorly then inferiorly with the larynx

Question 16

how many parathyroid glands are there

Answer 16

4

Question 17

where are the parathyroid glands located

Answer 17

the posterior surfaces of the thyroid gland’s lateral lobes

Question 18

what is a pyramidal lobe

Answer 18

anatomical variant

Question 19

where does a pyramidal lobe commonly originate from

Answer 19

left lateral lobe, may extend as far superiorly as the hyoid bone

Question 20

where do most pyramidal lobes attach

Answer 20

superiorly to thyroid cartilage

Question 21

where does the thyroid gland begin its development

Answer 21

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

Question 22

how does the thyroid migrate during development

Answer 22

migrates inferiorly whilst remaining attached to the tongue via the thyroglossal duct

Question 23

when does the thyroid reach its final position during development

Answer 23

7th week of development

Question 24

where can Thyroglossal duct cysts or ectopic thyroid tissue be found

Answer 24

any position in the thyroid migratory path

Question 25

what is a platysma

Answer 25

A skeletal muscle in the superficial fascia, extending from the collar bone to the angle of the jaw.

Question 26

whats the innervation of the platysma muscles

Answer 26

CN VII (fascial nerve)

Question 27

what group of muscles does the platysma muscles belong to

Answer 27

muscles of facial expression

Question 28

how many fascial compartments are located within the neck

Answer 28

4

Question 29

what are the 4 neck fascial compartments

Answer 29

prevertebral (deep) fascia investing fascia carotid sheaths x2 pretracheal fascia

Question 30

where is the prevertebral (deep) fascia located

Answer 30

posteriorly within the neck (behind vertebra)

Question 31

what is located within the prevertebral (deep) fascia

Answer 31

postural neck muscles | cervical vertebrae

Question 32

what is the investing fascia

Answer 32

encloses ALL neck fascia

Question 33

what muscles are located within the investing fascia

Answer 33

trapezius | sternocleidomastoid

Question 34

where is the carotid sheaths located

Answer 34

anterolaterally (either side of the thyroid)

Question 35

what is located within each carotid sheaths

Answer 35

vagus nerve deep cervical lymph nodes carotid arteries (common then internal) internal jugular vein

Question 36

where is pretracheal fascia located

Answer 36

anteriorly (around the thyroid)

Question 37

what is located within pretracheal fascia

Answer 37

``` oesophagus trachea thyroid strap muscles recurrent laryngeal nerves ```

Question 38

what are the carotid sheaths

Answer 38

bilateral "tubes"of deep fascia

Question 39

where do the carotid sheaths attach (superiorly and anteriorly)

Answer 39

superiorly = base of the skull (around the jugular foramen & the entrance to carotid canal) inferiorly = blend with the mediastinal fascia

Question 40

what is the thyroid IMA artery

Answer 40

anatomical variant which lies centrally and supplies thyroid with material blood

Question 41

what is the lymphatic drainage of the thyroid

Answer 41

superior & inferior deep cervical lymph nodes tracheal lymph nodes

Question 42

what are the tracheal lymph nodes that supply the thyroid

Answer 42

Pretracheal node | Paratracheal nodes

Question 43

where does the RIGHT lymph nodes of the thyroid originate

Answer 43

Right lymphatic duct to the Right venous angle

Question 44

where does the LEFT lymph nodes of the thyroid originate

Answer 44

Thoracic duct to the Left venous angle

Question 45

how many strap muscles are there

Answer 45

4

Question 46

name the 4 strap muscles

Answer 46

thyrohyoid omohyoid sternohyoid sternothyroid

Question 47

what are the 4 surgical approaches to the thyroid gland

Answer 47

Classical thyroidectomy = open surgery Endoscopically assisted thyroidectomy Endoscopic trans-axillary approach Endoscopic trans-breast approach

Question 48

describe a classical thyroidectomy incision

Answer 48

a "collar" incision just superior to the clavicles and jugular notch is made in a natural crease though skin and platysma

Question 49

what nerve may be damaged during thyroid surgery

Answer 49

recurrent laryngeal

Question 50

what does damage to the recurrent laryngeal result in

Answer 50

paralysis of vocal cords

Question 51

what symptoms would you expect from recurrent laryngeal damage (unilateral and bilateral)

Answer 51

unilateral = “hoarseness” or weakness of the voice and a weak cough bilateral = aphonia and inability to close the rima glottidis resulting in an inability to to prevent aspiration or to produce a good cough

Question 52

what is aphonia

Answer 52

inability to produce sound