Anterior triangle of the Neck

Question 1

There are 4 subdivisions of the anterior triangle- name these and what each contains

Answer 1

submandibular - submandibular glands, lymph nodes, CN XII, facial artery and veins
submental - submental lymph nodes, small veins forming anterior jugular
carotid - thyroid gland, larynx, pharynx, carotid sheath, cervical plexus, ansa cervicalis, parts of CN XI and XII
muscular - supra and infrahyoid muscles, hyoid bone

Question 2

Outline the borders of the anterior triangle

Answer 2

inferior border of mandible, anterior border of SCM and midline of neck

Question 3

Describe each of the 4 suprahyoid muscles and their function

Answer 3

Mylohyoid - from mylohyoid ridge on mandible to hyoid, mylohyoid raphe joins muscles in midline, reinforces floor of mouth, lifts hyoid

Digastric - 2 bellys - anterior belly originates at digastric fossa on lower medial aspect of mandible and posterior belly originates from mastoid notch on medial side of mastoid process, attached to hyoid by fascial sling, elevates hyoid, lowers mandible

Stylohyoid - originates at styloid process, elevates hyoid

Geniohyoid - originates from mandible (mental spine), elevates and pulls hyoid forward

Question 4

Outline the innervation of each of the suprahyoid muscles

Answer 4

Mylohyoid - CN V3 (nerve to mylohyoid)
Digastric - anterior= nerve to mylohyoid, posterior= digastric branch of CN VII
Stylohyoid- CN VII
Geniohyoid - anterior ramus of C1 (travels with CN XII)

Question 5

Describe each of the 4 infrahyoid muscles and their function

Answer 5

Sternohyoid (superficial) - sternum to hyoid, depression of hyoid

Omohyoid (superficial) - 2 bellies - superior originates at intermediate tendon, inferior originates at superior border of scapula to intermediate tendon - tendon attaches to clavicle via fascial sling. depresses and fixes hyoid

Thyrohyoid (deep) - originates at oblique line on thyroid cartilage, depresses hyoid

Sternothyroid (deep) - originates at posterior surface of manubrium and inserts into oblique line on thyroid cartilage, draws larynx downward

Question 6

Outline the innervation of the infrahyoid muscles

Answer 6

Sternohyoid - anterior rami C1 to C3 (through ansa cervicalis)
Omohyoid - anterior rami C1 to C3 (through ansa cervicalis)
Thyrohyoid - anterior rami C1 (fibres run with CN XII)
Sternothyroid - anterior rami C1 to C3 (through ansa cervicalis)

Question 7

The supra and infrahyoid muscles sit in the muscular compartment of the neck.

Which compartment of the neck does the thyroid gland sit in?

Answer 7

Visceral

Question 8

Outline the form and location of the thyroid gland

Answer 8

Made up of left and right lateral lobes- joined in the middle by isthmus (where a pyramidal lobe may be present- 50%)

Sits in the neck from the thyroid cartilage to the 5th tracheal ring

Question 9

Outline the blood supply and drainage of the thyroid gland

Answer 9

ECA branches to give superior thyroid artery
Subclavian artery branches to give inferior thyroid artery

Superior and middle thyroid veins drain into IJV
Inferior thyroid vein drains into brachiocephalic vein

10% people have small thyroid ima artery over midline arising from brachiocephalic trunk

Question 10

Describe the form of parathyroid gland and its location in the neck

Answer 10

2 pairs (superior and inferior) of small glands on posterior surface of thyroid gland

Question 11

Which blood vessels supply the parathyroid

Answer 11

Inferior thyroid artery
drainage the same as thyroid gland

Question 12

Describe the neurovascular control of the thyroid and parathyroid glands

Answer 12

Innervated by the thyroid branches from the cervical ganglia (sympathetic)

Question 13

Which procedure would be carried out in an emergency airway blockage?

Answer 13

Cricothyrotomy
A large bore needle is passed through cricothyroid ligament which is later replaced by small tracheostomy tube

Question 14

In a hospital setting, which procedure is often carried out in the case of airway obstruction?

Answer 14

Retraction of infrahyoid muscles and incision of thyroid isthmus to insert tube between 1-2 / 2-4 tracheal rings

Question 15

In terms of neck surgery, which vascular, neurovascular and other structures should be considered?

Answer 15

Possible presence of thyroid ima artery
Recurrent and external laryngeal nerves
Possible age variations - soft trachea in children and neonates etc)

Question 16

What is the recurrent laryngeal nerve?

Answer 16

Branch of the Vagus nerve (CN X)
Supplies intrinsic muscles and sensation of larynx and vocal cords
left loops around arch of aorta and right loops around subclavian artery

Question 17

Where does the carotid sheath being and end?

Answer 17

Runs from foramen of carotid canal to arotic arch

Question 18

Which structures are contained in carotid sheath?

Answer 18

CCA, IJV, CN X

Question 19

Where is the carotid sinus located?

Answer 19

level of C3/4 (at superior border of thyroid cartilage)
dilation at the bifurcation of CCA, in wall of ICA

Question 20

What is the function of the carotid sinus?

Answer 20

The function of the carotid sinus is to react to changes in blood pressure (contains baroreceptors which are sensitive to stretch)

Question 21

Which nerves innervate the carotid sinus and body?

Answer 21

The carotid sinus and body are innervated by the carotid sinus nerve (branch of CN IX) and CN X

Question 22

Where is the carotid body located?

Answer 22

The carotid body is located at the bifurcation of CCA, near the carotid sinus

Question 23

What is the function of the carotid body?

Answer 23

The carotid body houses chemoreceptors - monitors oxygen, carbon dioxide, pH and temperature

Question 24

When is the carotid body stimulated?

Answer 24

The carotid body is stimulated in emergency situations to return the body back to homestatic conditions eg. increase respiration.

Question 25

What structures does the external carotid artery supply?

Answer 25

the ECA supplies the majority of the face and scalp

Question 26

In what region of the neck does the ECA split into branches?

Answer 26

The ECA splits into branches in the carotid triangle in the anterior neck (exception- the 2 terminal branches)

Question 27

The ECA has 1 medial, 2 posterior and 3 anterior branches and 2 terminal branches, name these.

Answer 27

Superior thyroid - anterior
Ascending pharyngeal - medial
Occipital - posterior
Lingual - anterior
Facial - anterior
Posterior auricular - posterior

Terminal branches - superficial temporal, maxillary

Question 28

The ECA supplies the internal capsule via the middle meningeal artery, which branch is this part of?

Answer 28

The middle meningeal artery is a branch of the maxillary artery.

Question 29

How does the middle meningeal artery enter the cranium?

Answer 29

the middle meningeal artery enters the cranium via the foramen spinosum (pterion)

Question 30

Which muscles does the ECA run deep to?

Answer 30

The ECA runs deep to the stylohyoid and mylohyoid

Question 31

Which structures does the IJV drain?

Answer 31

The IJV drains blood from the brain, skull, face and parts of the neck

Question 32

Which structures does the IJV run deep to?

Answer 32

The IJV runs deep to omohyoid and SCM and lateral to CCA

Question 33

Describe the journey of the IJV from the skull to the brachiocephalic vein

Answer 33

The IJV is a continuation of the sigmoid sinus in posterior cranial fossa and exits the skull via the jugular foramen, enters the carotid sheath and joins subclavian vein to become brachiocephalic vein.

Question 34

What is the inferior bulb of IJV?

Answer 34

This is a bicuspid valve that permits blood flow to the heart while preventing backflow

Question 35

What is the superior bulb of IJV?

Answer 35

This is a dilation at the origin of IJV where the inferior petrsoal sinus enters after it has left the cranium, via jugular foramen

Question 36

Which structures does the EJV drain?

Answer 36

The scalp, face and superficial neck

Question 37

Describe the course of EJV

Answer 37

The EJV begins at the angle of the mandible (just below parotid gland), joining the retromandibular and posterior auricular veins.
Crosses over SCM and pierces into investing fascia where it joins the subclavian vein at mid clavicle

Question 38

Which veins drain into EJV?

Answer 38

the posterior external jugular, transverse cervical, suprascapular, anterior jugular

Question 39

What is the location and function of the anterior jugular vein?

Answer 39

The anterior jugular vein arises superior to hyoid bone and descends between the midline and anterior border of SCM.
The anterior jugular vein communicates across the midline via jugular venous arch.
It drains into EJV or sometimes directly into subclavian.

Question 40

Briefly describe the course of the facial nerve (CN VII)?

Answer 40

The facial nerve (CN VII) exits the skull via internal acoustic meatus and forms a parotid plexus where it is engulfed by the parotid gland.
This gives rise to 5 branches - temporal, zygomatic, buccal, marginal mandibular and cervical.
The facial nerve also has a digastric branch which supplies the posterior belly of digastric and stylohyoid muscles.

Question 41

Briefly describe the course of the glossopharyngeal nerve (CN IX)?

Answer 41

CN IX emerges through the jugular foramen and travels downwards between IJV and ICA, innervates the tongue, pharynx and (together with vagus nerve) the carotid body and sinus via carotid sinus nerve

Question 42

Briefly describe the course of the vagus nerve (CN X)

Answer 42

CN X emerges through jugular foramen and travels within carotid sheath- gives rise to pharyngeal and laryngeal nerves (recurrent laryngeal nerves) and innervates the carotid body and sinus with CN IX

Question 43

Briefly describe the course of the accessory nerve (CN XI)

Answer 43

CN XI emerges through the jugular foramen and travels downwards between IJV and ICA, crosses lateral surface of IJV to descend to posterior triangle of the neck. Innervates SCM and trapezius

Question 44

Briefly describe the course of the hypoglossal nerve (CN XII)

Answer 44

CN XII exits the hypoglossal canal between IJV and ICA and crosses these arteries to enter the oral cavity.
this nerve has no branches in the anterior triangle of the neck.

Question 45

Which nerve supplies cutaneous innervation over SCM and anterior triangle of the neck?
From where does this nerve arise?

Answer 45

The transverse cervical nerve supplies cutaneous innervation over the SCM and anterior triangle of the neck - this nerve arises from the anterior rami of C2 and C3

Question 46

Which nerve innervates the infrahyoid muscles and where does this arise from?

Answer 46

Ansa cervicalis innervates the infrahyoid muscles- this is formed of the anterior rai of C1-C3 and loops around the carotid sheath at the second level loop of the cervical plexus

Question 47

What is the cervical plexus?

Answer 47

The cervical plexus is formed by the anterior rami of C1, C2-4 and innervates the infrahyoid muscles, diaphragm (via phrenic nerve) and the skin of anterior / lateral neck and inferior head.

Question 48

What is the brachial plexus?

Answer 48

The brachial plexus is a network of nerves which starts at C5-T1 and innervates the upper limbs.

Question 49

Describe the course of the phrenic nerve

Answer 49

The phrenic nerve arises from the cervical plexus at C3-5 and travels down the anterior scalene and towards the thorax to provide motor innervation of the diaphragm.