Lecture 5 - Anterior triangle of neck

Question 1

Anterior triangle - why is it important

Answer 1

• goitre (thyroid enlarged)
• Central vien catherterisation - can put through 2 heads of sternocleidomastoid
• Penetrating trauma
• cricothyroidotomy

Question 2

Muscles in anterior triangle

Answer 2

Infrahyoid (strap muscles) - Sternohyoid, omohyoid, thyrohyoid, sternothyroid

Suprahyoid - stylohyoid, digastric, mylohyoid, geniohyoid

Question 3

Cervical plexus

Ansa cervicalis

Answer 3

C1-C4
Ansa cervicalis - loop fomred by C1- C3

Superior root - (C1) - innovates one muslce (infrahyoid - shorter)

Inferior root (c2-c3) - longer muscles of the neck - omohyoid, sternohyoid, sternothyroid

-rest of cervical plexus - sensory component of neck

Phrenic nerve - some contribution from this plexus

Question 4

Where does the thyroid sit?

Answer 4

isthmus sits at 2-3 tracheal cartilage
thyroid cartilage is above this
-if cut the thyroid need to know that cartilage is below

Question 5

Blood supply to thyroid

why important?

Answer 5

• Superior and inferior thyroid artery
• superior is the first branch off the external carotid
• Inferior thyroid - comes off from thyrocervical branch, a branch of subclavian artery

Ima artery - to isthmus - comes from subclavian - need to make sure this artery is not here

When do a thyroidectomy, need to ligate these arteries

Venous arteries - usually after operation the bleeding is coming from these arteries
Venous drainage - superior and middle- drains to IVC, and inferior drains to left brachiocephalic vien

Question 6

**

Subclavian artery branches (exam Q)

Answer 6

sdfjds

Question 7

**

Lymphatic drainage of thyroid

Answer 7

paratracehal and deep cervical lymph nodes

Question 8

Innervation of thyroid

Answer 8

sympathetic - middle cervical ganglion (runs with arteries)

parasympathetic - vagus (recurrent laryngeal nerve - runs in a groove between oesophagus and the trachea)

Question 9

Embryology of thyroid

Answer 9

starts as foreamen caecu at base of tongue as the thyroglossal duct, then it travels down past hyoid bone

• then reaches final destination which is anterior to trachea of neck
• tyroglossal duct usually disappears but if it doesn’t can get food here

Question 10

Suprahyoid muscles

Answer 10

Important - because they form the floor of the mouth

between hyoid bone and mandible

Superficial - anterior belly of digastric
myohyoid muscle
genohyoid (deepest)

Posterior belly of digastric and stylohyoid

Question 11

Styloid process - what attaches

Answer 11

stylohyoid attaches here

-innovated by facial nerve

Question 12

Mylohyoid and anterior belly of digastric - nerve supply

Answer 12

V3

Question 13

Geniohyoid muscle - nerve supply and what other muscle is stimulated by this?

Answer 13

C1, thyrohyoid

Question 14

** What forms the external jugular vien? (need to know for exam)

Answer 14

posterior auricular and retromandibular

Question 15

Pathways for different cranial nerves

Answer 15

MUST MEMORISE THESE!!!

Question 16

Path of glossopharyngeal nerve

Answer 16

Jugular foreamen
deep to styloid process
internal and external carotid arteries 
curves around lateral border of stylopharyngeus goes to 
base of tonuge

Question 17

Path of vagus nerve

Answer 17

jugular foreamen
between 9,11
runs in carotid sheath betewen internal carodi arter and internal jugular vien
root of neck - passes in front of subclavian artery and behind subclaian vien to enter the mediastinum

Question 18

**Path of accessory nerve

Answer 18

jugular foreamen posteiror to 9
runs poserolaterally either medial or lateral to inernal jugular vien in cartodi sheath
-crosses transverse prceoss of atlas and passes medial to styloid process and postteiror belly of digastric to perforate the sternocleidomastoid muscle and reach the posterior triangle of the neck

Question 19

Path of hypoglossal nerve

Answer 19

hypoglossal foreamen
between inernal cartoid artery and internal jugular vien and crosses 3 artiers (cocipital, external carotid and lingual arteries)
-deep to posteiror belly of digastric to reach the tongue
-branch from anterior rami of C1 hitchhikes with it
-this branch innervates some of the suprahyoid muscules thyrohyodi and genio hyoid

Question 20

** Surface anatomy of thyroid

Answer 20

The thyroid cartilage is found between vertebral levels C3-C4, the lower edge of this (C4) is also where the carotid bifurcation is found. The hyoid bone is found at level C3.
The internal jugular can be distinguished from the carotid on ultrasound by using the valsalva manoeuvre in which the patient is asked to blow on their thumb. The diameter of the carotid artery should remain the same, but the internal jugular will inflate.
The thyroid gland is found at vertebral levels C5-T1