E1 - thyroid/parathyroid

Question 1

what are the borders of the anterior triangle of the neck?

Answer 1

anterior = midline neck
posterior = sternal head of sternocleidomastoid
superior = inferior border of mandible

Question 2

what are borders of posterior triangle of the neck?

Answer 2

anterior = clavicular head of sternocleidomastoid
posterior = trapezius
inferior = clavicle

Question 3

what is the platysma muscle?

Answer 3

• muscles in neck immediately deep to skin within superficial fascia
• belongs to muscles of facial expression and supplied by CN VII

Question 4

where does external and anterior jugular vein drain to?

Answer 4

anterior jugular vein drains to external jugular vein which drains to subclavian vein which drains to SVC

Question 5

what is carotid sheath? and where?

Answer 5

connective tissue layer, deep to investing fascia that’s located anterolaterally in neck and posterolateral to thyroid gland

• tube like bilateral compartments. attach superiorly at base of skull and around jugular foramen
• travels through neck and blends with mediastinal fascia

Question 6

what are the contents of carotid sheath?

Answer 6

1. internal jugular vein
2. common carotid artery (that carries up as internal carotid)
3. vagus nerve
4. deep cervical lymph nodes

Question 7

what are strap muscles?

Answer 7

= infrahyoid muscles. 4 paired muscles.important for speech & swallowing
1. omohyoid (shoulder)
2. sternohyoid
3. thyrohyoid
4. sternothyroid

Question 8

what is structure of thyroid gland?

Answer 8

2 lobes (R&L) connected by isthmus
= lobes are attached to thyroid, cricothyroid & trachea. isthmus lies anterior to 2nd&3rd cartilage of trachea

Question 9

where are parathyroid glands?

Answer 9

4 parathyroid glands on posterior surface of thyroid gland lateral lobes (small pea-sized glands located in the neck just behind the butterfly-shaped thyroid gland)

Question 10

what is the pyramidal lobe?

Answer 10

additional lobe that is in some people (not connected to thyroid)

Question 11

what are the 4 fascial compartments of neck?

Answer 11

1. investing fascia = encloses all neck compartments (1 big circle)
2. prevertebral deep fascia = posteriorly
3. carotid sheath = anterolaterally
4. pretracheal fascia = anteriorly (encloses oesophagus, trachea, thyroid gland, strap muscles, recurrent laryngeal nerves)

Question 12

what is arterial blood supply to thyroid gland?

Answer 12

supplied by superior thyroid artery (branch of external carotid) and inferior thyroid artery (branch of subclavian)

Question 13

what is venous drainage of thyroid?

Answer 13

superior thyroid & middle thyroid drain into internal jugular vein and inferior thyroid drains into brachiocephalic = these meet to make superior vena cava

→veins highly variable

Question 14

what are lymphatics of thyroid?

Answer 14

there are superior & inferior deep cervical lymph nodes (on each side)
- these drain to right lymphatic duct or left thoracic duct that then drain to L&R venous angles

Question 15

what is route of vagus nerve?

Answer 15

emerges from medulla oblongata exiting via jugular foramen then descends through carotid sheath
- in thorax RHS runs next to trachea and LHS next to aortic arch. both posterior to hilum
- they form plexus on oesophagus then perforate diaphragm to supply organs

Question 16

what are the recurrent laryngeal nerves?

Answer 16

branches off vagus
- left hooks around arch of aorta
- right hooks around subclavian

Question 17

what is main surgical approach to thyroid gland removal?

Answer 17

classic thyroidectomy
= collar incision made within natural skin crease (langer line) just superior to clavicle & jugular notch

• strap muscles lateralized (not cut)
• then view under carotid sheath and make sure to identify to protect recurrent laryngeal nerves to protect them
• also section berry’s ligament = thickened area of pretracheal fascia

Question 18

what happens if recurrent laryngeal nerve injury?

Answer 18

unilateral = hoarse or weak voice, weak cough
bilateral = aphonia (no sound) and inability to close rima glottidis (needed to prevent aspiration or make good cough)

Question 19

what lobe of brain lies within middle cranial fossa?

Answer 19

temporal lobe

Question 20

what are 3 foramen for CN V divisions?

Answer 20

• 3 foramen for CN V (trigeminal)
  • superior orbital fissure = CN V1 (ophthalmic division)
  • foramen rotundum = CN V2 (maxillary division)
  • foramen ovale = CN V3 (mandibular division)

Question 21

what nerve supplies the strap muscles? (except thyrohyoid)

Answer 21

innervated by ansa cervicalis = neural necklace around internal jugular vein.

ansa cervicalis = anterior rami C1-3

Question 22

what is adrenal cortex and adrenal medulla function?

Answer 22

• adrenal cortex = outer part of adrenal gland →secretes glucocorticoids, mineralocorticoids & androgens
• adrenal medulla = inner part of adrenaline & noradrenaline

Question 23

what is adrenal gland vasculature? what is the difference between left & right vein?

Answer 23

= superior, middle & inferior suprarenal artery.

left suprarenal vein drains to left renal vein but right suprarenal veins drains to IVC