Infrahyoid Anterior Neck Triangles, Levels of Cervical Lymph Nodes and Root of Neck Flashcards

Don't overburden yourself with the levels of cervical lymph nodes.

1
Q

Outline the boundaries of the anterior triangle of the neck. (anterior, posterior, base, apex, roof)

A

Anterior: anterior midline of the neck
Posterior: anterior border of sternocleidomastoid
Base: lower border of body of the mandible and a line extending from the angle of mandible to the mastoid process
Apex: suprasternal notch at the meeting point between the anterior border of the sternocleidomastoid and anterior median line
Roof: investing layer of deep cervical fascia
[Diagram 1] [Diagram 2]

Further notes:
The superficial fascia over the fascial roof contains platysma in the upper and anterior parts. The cervical branch of facial nerve and ascending and descending branches of transverse cervical cutaneous nerve traverse the plane between the platysma and the fascial roof of the triangle.

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2
Q

digastric muscle
(a) origin
(b) insertion
(c) action
(d) innervation

A

(a) origin
✔ It has two bellies: anterior and posterior.
✔ Origin of posterior belly: mastoid notch on medial surface of mastoid process of temporal bone.
✔ Origin of anterior belly: digastric fossa of lower border of mandible, close to symphysis menti

(b) insertion
Attachment of intermediate tendon between two bellies to body of hyoid bone.

[Diagram]

(c) action
Anterior belly: opens mouth by lowering mandible, raises hyoid bone
Posterior belly: pulls hyoid bone upward and back
[Alternatively, the actions of digastric can be stated as: (1) depression of the mandible when the hyoid bone is fixed, (2) elevation of the hyoid bone and larynx when the mandible is fixed.]

(d) innervation
✔ anterior belly is innervated by the nerve to mylohyoid muscle [a branch of the inferior alveolar nerve that arises from the mandibular nerve. The anterior belly is a derivative of the 1st pharyngeal arch.]
✔ the posterior belly is innervated by the digastric branch of the facial nerve [The posterior belly is a derivative of the second pharyngeal arch.]

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3
Q

omohyoid muscle
(a) origin
(b) insertion
(c) action
(d) innervation

A

(a) origin, (b) insertion
✔ It has two bellies: inferior and superior.
✔ The inferior belly originates from the inferior border of the scapula, medial to the suprascapular notch.
✔ From there, the muscle inclines anteriorly and superiorly towards the lower part of the neck, inserting into the omohyoid’s intermediate tendon.
✔ The superior belly begins at the intermediate tendon and runs superiorly to be attached to the lower border of the hyoid bone.
✔ [The intermediate tendon lies at the level of arch of cricoid cartilage and is anchored to the clavicle by fascial sling derived from investing layer of deep cervical fascia.]

(c) action
✔ it depresses the hyoid bone following its elevation during the act of swallowing [This action reopens the laryngeal inlet, which is normally closed of during swallowing to prevent inhalation of the food bolus. Thus, the act of opening the laryngeal inlet reestablishes breathing after swallowing. All the infrahyoid muscles share this function.]

(d) innervation
✔ superior belly is innervated by the superior root of ansa cervicalis (C1)
✔ inferior belly receives fibers from spinal nerves C1, C2 and C3 (via ansa cervicalis)

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4
Q

Click on Answer to view important landmarks in the neck.

A
  1. Hyoid bone between the floor and the superior end of the neck.
  2. Thyroid cartilage
  3. Cricoid cartilage
  4. Cricothyroid membrane
  5. Tracheal rings [particularly the 1st, 2nd and 3rd rings]
  6. Thyrohyoid membrane
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5
Q

The infrahyoid muscles of the neck/strap muscles of the neck are ribbon-like and comprise 4 paired muscles. List these muscles.

A

(a) Sternohyoid
(b) Sternothyroid
(c) Thyrohyoid
(d) Omohyoid

Omohyoid and sternohyoid are superficial to thyrohyoid and sternothyroid.

[Diagram: Infrahyoid muscles of the neck]

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6
Q

Sternohyoid muscle
1. Origin
2. Insertion
3. Innervation
4. Action

A
  1. Origin: Posterior aspect of sternoclavicular joint and adjacent manubrium of sternum
  2. Insertion: Body of hyoid bone medial to attachment of omohyoid muscle
  3. Innervation: Anterior rami of C1 to C3 through the ansa cervicalis
  4. Action: Depresses hyoid bone after swallowing. Note that omohyoid does this during swallowing.
  5. [Diagram]
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7
Q

Sternothyroid muscle
(a) Origin
(b) Insertion
(c) Innervation
(d) Action

A

(a) Origin: Posterior surface of manubrium of sternum
(b) Insertion: Oblique line on lamina of thyroid cartilage
(c) Innervation: Anterior rami of C1 to C3 through the ansa cervicalis
(d) Action: depresses the larynx, aiding in functions such as swallowing, speaking, and chewing

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8
Q

Thyrohyoid muscle
a) Origin:
b) Insertion:
c) Innervation:
d) Action:

A

a) Origin: Oblique line of thyroid cartilage
b) Insertion: Greater horn and adjacent aspect of body of hyoid bone
c) Innervation: Fibers from anterior ramus of C1 carried along hypoglossal nerve [XII]
d) Action: Depresses hyoid bone, but when hyoid bone is fixed raises larynx
[Diagram]

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9
Q

For convenience of description, the anterior triangle has been subdivided, by the digastric muscle and superior belly of omohyoid muscle, into the following 31⁄2 triangles. List those triangles.

A
  1. Submental triangle (half only)
  2. Digastric (submandibular) triangle
  3. Carotid triangle
  4. Muscular triangle
  5. [Diagram]
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10
Q

State the boundaries and contents of the muscular triangle.

A

Boundaries:
Anterior: Anterior median line of the neck, extending from hyoid bone to the suprasternal notch.
Anterosuperior: Superior belly of the omohyoid.
Posteroinferior: Anterior border of sternocleidomastoid.
Roof: It is formed by investing layer of deep cervical fascia. The superficial fascia over the roof contains anterior jugular vein and associated lymph nodes. [Anterior jugular vein was covered in posterior neck triangles flashcards.]

Contents:
✔ Infrahyoid muscles, viz. sternothyroid, sternohyoid, and thyrohyoid. (One would argue that they form the floor of the muscular triangle.)
✔ The important deeper structures in the region of muscular triangle are thyroid gland, trachea, and esophagus.

[Diagram: Muscular Triangle]

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11
Q

State the clinical relevance of the muscular triangle.

A

boundaries of this triangle are used as landmarks during surgeries

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12
Q

State the location and gross morphology of the thyroid gland.

A

Location:
- anterior lower neck, in front of the trachea and below the thyroid cartilage
- enclosed by pretracheal layer of deep cervical fascia

Gross morphology:
- has two lobes-right and left lateral lobes, which are somewhat conical
- the two lobes are connected together by a narrow, median isthmus
- a pyramidal lobe may be present, attached to the isthmus and projecting towards the hyoid bone

[Diagram: Thyroid Gland] [Diagram 2: Thyroid Gland]

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13
Q

Describe the extents of the thyroid gland.

A

✔ The lobes extend from the level of C5-T1 vertebrae
✔ Upper extent: oblique line of thyroid cartilage
✔ Lower extent: 4th or 5th tracheal ring
✔ The isthmus lies at the level of the 2nd to 3rd or 4th tracheal ring, and measures less than 1.5 cm in thickness

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14
Q

Relations of the lobes of the thyroid gland are best described with its surfaces. State the relations of the anterolateral (superficial) surface of the thyroid lobe. [Hint: 4 muscular, 1 vascular]

A
  1. Sternothyroid
  2. Sternohyoid
  3. Superior belly of omohyoid
  4. Sternocleidomastoid muscle (more of the anterior border)
  5. Anterior jugular vein

[Diagram 1: Relational Anatomy of the Thyroid Gland]
[Diagram 2: Relational Anatomy of the Thyroid Gland]
[Diagram 3: Relational Anatomy of the Thyroid Gland]
[Diagram 4: Relational Anatomy of the Thyroid Gland]

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15
Q

State the relations of the posteromedial surface of the thyroid lobe.

A

(1) Esophagus and trachea
(2) Pharynx and larynx
(3) Inferior pharyngeal constrictor and cricothyroid muscle
(4) The external laryngeal and recurrent laryngeal nerves

[Diagram 1]: Relational Anatomy of the Thyroid Gland
[Diagram 2]: Relational Anatomy of the Thyroid Gland
[Diagram 3]: Relational Anatomy of the Thyroid Gland
[Diagram 4]: Relational Anatomy of the Thyroid Gland

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16
Q

State the extents of the carotid sheath.

A

It extends from the arch of the aorta to the skull base.

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17
Q

State the relations of the posterolateral surface of the thyroid lobe.

A

Related to carotid sheath and its contents i.e.
1. Common carotid artery
2. Internal jugular vein
3. Vagus nerve

Further notes:
The ansa-cervicalis is embedded in the anterior wall of the sheath while cervical sympathetic chain lies posterior to sheath in front of prevertebral fascia.

[Diagram 1]: Relational Anatomy of the Thyroid Gland
[Diagram 2]: Relational Anatomy of the Thyroid Gland
[Diagram 3]: Relational Anatomy of the Thyroid Gland
[Diagram 4]: Relational Anatomy of the Thyroid Gland

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18
Q

relations of the posterior border of the thyroid gland

A
  • parathyroid glands
  • inferior thyroid artery

[Diagram 1: Posterior Surface of the Thyroid Gland]; The anterior surface is shown also shown.
[Diagram 2: Posterior Surface of the Thyroid Gland]; Here it clearly captures the two relations of the posterior border of the gland. The anterior surface is also shown.

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19
Q

State the relations of the thyroid isthmus.

A

Anteriorly: anterior jugular veins, sternothyroid, sternohyoid
Posteriorly: cervical trachea, with its intervening 2-4 rings
Superiorly: anastomosis between the anterior branches of two superior thyroid arteries.
Inferiorly: Along this border inferior thyroid vein emerge and thyroidea ima artery (when present) enters

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20
Q

Describe the arterial supply to the thyroid gland. Here, describe superior thyroid artery.

A

Superior thyroid artery
✓ the 1st anterior branch of the external carotid artery [Diagram]
✓ runs downwards and forwards in company with the external laryngeal nerve, which it leaves near the upper pole of the thyroid lobe
✓ divides into the anterior and posterior glandular branches at the apex of the lobe
✓ anterior branch eventually anastomoses with its fellow on the contralateral side at the upper superior border of the thyroid
✓ posterior branch descends along the posterior border of the lobe to anastomose with the ascending branch of the inferior thyroid artery ipsilaterally
Area of supply of superior thyroid artery: upper one-third of the lobe and upper half of the isthmus.

[Diagram: Arterial supply to the thyroid gland] [Cadaveric image]

Further notes:
The external laryngeal nerve is a branch of the superior laryngeal nerve, which is a branch of the vagus nerve. [Diagram]

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21
Q

Discuss the inferior thyroid and thyroidea ima arteries. [Hint: origin, area of supply, anastomoses, important neurovascular relations … where applicable]

A

(1) Inferior thyroid artery:
✓ terminal branch of thyrocervical trunk
✓ runs with recurrent laryngeal nerve
✓ the artery gives 4 or 5 branches. One ascending branch anastomoses with the posterior branch of the superior thyroid artery.
Area of supply of inferior thyroid artery: lower two-third of the lobe and lower half of the isthmus.

(2) Thyroidea ima artery:
✓ in 30% cases
✓ a branch of the brachiocephalic trunk or may arise directly from the arch of aorta. It enters the isthmus from below.

[Diagram]: Arterial supply to the thyroid gland
[Diagram]: Variable relationship of recurrent laryngeal nerve with the inferior thyroid artery

Further notes:
The recurrent laryngeal nerve presents a variable relationship with the inferior thyroid artery. It may pass behind or in front of the loop of the artery or between the branches of the artery.

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22
Q

The superior thyroid artery is a branch of ____(a)____, whereas the inferior thyroid artery is a branch of ____(b)____.

A

(a) the external carotid artery
(b) the thyrocervical trunk

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23
Q

Describe the venous drainage of the thyroid gland.

A

(a) Superior thyroid vein: emerges at the upper pole of the thyroid lobe, travels alongside the superior thyroid artery; terminates in the internal jugular vein.
(b) Middle thyroid vein: emerges from the lateral part of the gland; also drains into the internal jugular vein.
(c) Inferior thyroid vein/veins: emerge at the lower border of the isthmus, form plexus in front of the trachea and then run downwards to drain into the brachiocephalic veins. These veins receive other veins e.g. esophageal, tracheal and inferior laryngeal veins.
[Diagram]: venous drainage of the thyroid gland

Further notes:
☑ Sometimes a fourth vein, the thyroid vein (of Kocher) emerges between the middle and inferior thyroid veins to drain into the internal jugular vein.
☑ The brachiocephalic veins drain into the superior vena cava.

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24
Q

State the nerve supply to the thyroid gland.

A

The thyroid gland is supplied by both sympathetic and parasympathetic nerve fibres:
1. The parasympathetic supply is derived from the vagus and recurrent laryngeal nerves. [recurrent laryngeal nerve is a branch of the vagus nerve]
2. The sympathetic supply is derived from the superior, middle, and inferior cervical sympathetic ganglia, but mainly from the middle one.

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25
Q

Describe the location and gross morphology of the parathyroid glands.

A

☑ small, ovoid or lentiform glands that lie in the posterior borders of the thyroid lobes
☑ usually 4 in number, each measuring 6mm by 3-4 mm by 1-2 mm
☑ the superior glands are more constant in their location than the inferior ones

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26
Q

Mention 2 ectopic sites of parathyroid glands.

A
  • Inferior parathyroid glands may be found within the thymus.
  • Superior parathyroid glands may be found within the tracheoesophageal groove and retroesophageal region.
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27
Q

State the origin, course, and distribution of the recurrent laryngeal nerve.

A

The recurrent laryngeal nerve (RLN), a branch of the vagus nerve (cranial nerve X), plays a crucial role in innervating the larynx.
Origin:
✔ The RLN emerges from the vagus nerve.
✔ There are two recurrent laryngeal nerves: one on the right and another on the left.
✔ These nerves are not symmetrical: [Diagram]
The left RLN loops under the aortic arch.
The right RLN loops under the right subclavian artery before ascending.
✔ Both nerves travel alongside the trachea.

Course:
✔ The right RLN has a shorter course, passing under the subclavian artery.
✔ The left RLN takes a more circuitous route:
It passes under the aortic arch and the ligamentum arteriosum.
✔ After branching, it ascends in a groove at the junction of the trachea and esophagus. [tracheoesophageal groove]
It then passes behind the posterior, middle part of the outer lobes of the thyroid gland.
✔ Finally, it enters the larynx underneath the inferior constrictor muscle, just posterior to the cricothyroid joint.

Distribution:
✔ The RLN supplies all the intrinsic muscles of the larynx, except for the cricothyroid muscles.
It provides sensation to the larynx below the vocal cords.
✔ Additionally, the RLN gives cardiac branches to the deep cardiac plexus and branches to the trachea, esophagus, and the inferior constrictor muscles.
✔ Notably, the posterior cricoarytenoid muscles, responsible for opening the vocal folds, are innervated by this nerve.

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28
Q

What is thyroidectomy?

A

A thyroidectomy is a common surgical procedure. In most cases it involves excision of part or most of the thyroid gland. This surgical procedure is usually carried out for benign diseases, such as multinodular goiter and thyroid cancer.

Further notes:
~ Given the location of the thyroid gland, there is a possibility of damaging other structures when carrying out a thyroidectomy, namely the parathyroid glands and the recurrent laryngeal nerve. Assessment of the vocal folds is necessary before and after thyroid surgery because the recurrent laryngeal nerves are closely related to ligaments that bind the gland to the larynx and can be easily traumatized during surgical procedures.
~ Since colossal sizes of goitre may damage the recurrent laryngeal nerve, it is good habit to do laryngoscopy before thyroidectomy, so that pre-operative damage can be distinguished from post-operative damage.

29
Q

State the anatomical basis for the following complications of thyroidectomy:
a) Hoarseness of voice
b) Reduced pitch of voice
c) Hypocalcemia

A

a) Hoarseness of voice: The recurrent laryngeal nerve, which innervates the muscles controlling vocal cord movement, may be injured due to its close proximity with the thyroid gland.
b) Reduced pitch of voice: The superior laryngeal nerve supplies the cricothyroid muscle responsible for pitch modulation. Again, its close proximity with the thyroid gland makes it prone to injury if thyroidectomy goes wrong.
c) Hypocalcemia: Parathyroid glands secrete parathyroid hormone which regulates serum calcium levels by raising the calcium levels. If the glands are injured during thyroidectomy, they’ll be reduced serum calcium levels, leading to hypocalcemia.

30
Q

A) During thyroidectomy, where should the superior thyroid artery be ligated. Explain why.
B) During thyroidectomy, where should the inferior thyroid artery be ligated. Explain why.

A

A) As close to the apex of the thyroid lobe as possible. This is to avoid injury to the external laryngeal nerve. The superior thyroid artery runs together with the external laryngeal nerve, but near the apex of the thyroid lobe, the two diverge from each other, the artery lies superficial and the nerve lies deep to the apex.
B) As away from the base of the thyroid lobe as possible to avoid injury to the recurrent laryngeal nerve. The recurrent laryngeal nerve lies very close to the inferior thyroid artery near the base of the thyroid lobe.

31
Q

State the boundaries of the carotid triangle.
[Hints: superiorly, anteroinferiorly, posteriorly, roof, floor]

A

Superiorly: Posterior belly of digastric supplemented by stylohyoid.
Anteroinferiorly: Superior belly of omohyoid.
Posteriorly: Anterior border of sternocleidomastoid.
Roof: It is formed by investing layer of deep cervical fascia. The superficial fascia over the roof contains platysma, cervical branch of facial nerve and transverse cervical nerve (a cutaneous branch of the cervical plexus).
Floor: Formed by,
1. Thyrohyoid membrane
2. Hyoglossus
3. Middle constrictor
4. Inferior constrictor

[Diagram 1] [Diagram 2] [Diagram: constrictor muscles] [Animated video: 3 mins]

32
Q

List the contents of the carotid triangle.

A
  1. Common carotid artery and its bifurcation into external carotid artery and internal carotid artery.
  2. The first five branches of the external carotid artery; ascending pharyngeal artery, superior thyroid artery, lingual artery, facial artery, occipital artery, and their corresponding veins.
  3. Internal jugular vein and its tributaries [notably, the common facial vein].
  4. Hypoglossal nerve and the superior root of ansa cervicalis.
  5. Internal laryngeal, external laryngeal and vagus nerves.
  6. Deep cervical lymph nodes.
  7. Cervical part of the sympathetic chain.
  8. [Diagram] [Animated video: 3 mins]
33
Q

origin of common carotid artery (CCA)

A

Right CCA arises from the innominate artery (brachiocephalic trunk); left CCA arises directly from the aortic arch.

34
Q

Why is the transverse process of C6 an important landmark for the common carotid artery?

A

The common carotid artery can be compressed against the prominent anterior tubercle of transverse process of the 6th cervical vertebra called carotid tubercle (of Chassaignac) by pressing medially and posteriorly with the thumb. The carotid tubercle of the 6th cervical vertebra is about 4 cm above the sternoclavicular joint.

[Diagram: Carotid Tubercle]

35
Q

The common carotid artery bifurcates at the level of the ________________.

A

thyroid cartilage (corresponds with C3/C4 level)
[Diagram]
[Cadaveric Image]
[Radiograph]

36
Q

Origin, course, branches of external carotid artery.

A

Origin and course: arise from CCA in the carotid triangle, anteromedial to the ICA, but later becomes anterior, then lateral to the ICA as it (ECA) ascends.

Branches:
Posterior branches: occipital and posterior auricular arteries
Anterior branches: superior thyroid, lingual and facial arteries
Medial branch: ascending pharyngeal artery
Terminal branches: maxillary and superficial temporal arteries

[Diagram: Branches of external carotid artery]
[Cadaveric image]

37
Q

origin and course of internal carotid artery (ICA)

A

✓ Arises from carotid bifurcation, and is surrounded by postganglionic autonomic nerve plexus from the superior cervical ganglion.
✓ It ascends in the neck within the carotid sheath and enters the cranial cavity through the carotid canal.
✓ ICA supplies the ipsilateral cerebral hemisphere, eye and its adnexa and the forehead.

38
Q

Branches of the internal carotid artery. Historically, the ICA has been described to have 4 segments based on its course. State the branches arising from the following segments/parts of the ICA.
a) Extracranial/cervical part
b) Petrous part
c) Cavernous part
d) Supraclinoid/cerebral part

A

a) Extracranial/cervical part: no branches
b) Petrous part: caroticotympanic and pterygoid arteries
c) Cavernous part: cavernous, meningeal and hypophyseal branches
d) Supraclinoid/cerebral part: ophthalmic, posterior communicating and anterior choroidal arteries, before it bifurcates into the anterior and middle cerebral arteries (its terminal branches).

[Diagram: Branches of Internal Carotid Artery]]; perfectly showing the four parts that we’ve just discussed and the branches.

39
Q

Bouthillier classification describes 7 segments of the ICA; from C1 to C7. State the name of each segment from C1 to C7.
(Don’t stress much with this one, just click on Answer to view the segments and a linked image.)

A

C1: cervical segment
C2: petrous segment
C3: lacerum segment
C4: cavernous segment
C5: clinoid segment
C6: ophthalmic segment
C7: communicating (terminal) segment

[Radiograph: Bouthillier classification of ICA segments.]

40
Q

Carotid sinus: location, function, innervation

A

Location: Appears as a dilation at the origin of the ICA.
Function: Houses baroreceptors - present within the walls of the ICA - and specialized in detecting pressure changes in the artery, especially increase in the arterial blood pressure.
Innervation: has rich innervation from glossopharyngeal, vagus, and sympathetic nerves, but mainly innervated by the carotid branch of glossopharyngeal nerve

[Cadaveric image: carotid sinus]

Further notes:
Get to know the differences between dilation and dilatation here.

41
Q

Carotid body/glomus caroticum: Location, function, innervation

A

Location and morphology:
~ Richly innervated and highly vascularised, ovoid structure in the adventitia of carotid bifurcation (at the medial aspect of the bifurcation)
~ The organ is encapsulated, with multiple lobules.
~ Each lobule has glomus (type I) cells, sustentacular (type II) cells & extensive network of sinusoidal capillaries.
Function: The glomus cells are chemoreceptors - sensitive to low oxygen or high H+, high carbon dioxide concentration in the blood
Innervation: has rich nerve supply from glossopharyngeal, vagus, and sympathetic nerves

[Diagram: Carotid body]

42
Q

State the following regarding internal jugular vein:
a) Formation
b) Course
c) Tributaries
d) Termination
e) Territory of drainage

A

a) Formation:
✔ continuation of the sigmoid sinus at the jugular foramen
alternatively:
✔ union of the sigmoid sinus and inferior petrosal sinus

b) Course:
runs within the carotid sheath

c) Tributaries:
✔ inferior petrosal sinus
✔ common facial vein
✔ lingual vein
✔ pharyngeal vein
✔ superior thyroid vein
✔ middle thyroid veins

d) Termination:
✔ unites with subclavian vein to form brachiocephalic vein
✔ receives the thoracic duct (left) and right lymphatic duct (Right)
[The thoracic duct drains lymph from the lower half of the body below the diaphragm, both right and left, and from the left side above the diaphragm. Right upper half of the body, drained by the right lymphatic duct]

e) Territory of drainage: Skull, brain, parts of superficial face and much of neck

[Diagram: Internal Jugular Vein]

43
Q

There are 2 jugular bulbs of the IJV. State their locations and contents.

A

Superior jugular bulb: At IJV origin and below the floor of the tympanic cavity; it houses the glomus jugulare (tympanic body)
Inferior jugular bulb: At IJV termination, above which is a pair of valves.
[Diagram]

44
Q

functional components and nuclei of glossopharyngeal nerve

A

Nucleus ambiguus: gives SVE to stylopharyngeus (3rd arch muscle)
Inferior salivatory nucleus: gives GVE fibers to the parotid gland
Nucleus of the solitary tract: receives GVA from carotid body and carotid sinus
Gustatory nucleus: receives SVA from the posterior 1/3 of tongue
Sensory nucleus of trigeminal: receives GSA fibers from the tympanic membrane, outer ear, Eustachian tube, posterior tongue and pharynx
[Diagram: Functional components and nuclei of glossopharyngeal nerve]

45
Q

intracranial course and branches of CN IX

A

✔ Exits the brainstem at the retro-olivary sulcus
✔ Traverses the cerebellomedullary cistern as it approaches the jugular foramen
✔ Has 2 ganglia within the jugular foramen - the superior and inferior (petrosal) ganglia
✔ Sends off its tympanic branch (tympanic nerve of Jacobson) before it exits the foramen. This Jacobson nerve has:
- GSA fibers from the tympanic membrane and Eustachian tube
- preganglionic parasympathetic GVE fibers to parotid gland (revisit the pathways of innervation to parotid gland)
[Diagram: Course and branches of CN IX]

46
Q

extracranial course and branches of CN IX

A

✔ exits the skull via the jugular foramen in a separate dural sheath (pars nervosa of the jugular foramen. Other nerves exiting through the jugular foramen exit with vessels through pars vascularis part of it)
✔ pass between ICA and IJV, then winds around styloid process & stylopharyngeus muscle, then pierce the pharyngeal wall
✔ Branches:
~ carotid branch (Hering’s nerve) - GVA
~ muscular branch to stylopharyngeus - SVE
~ pharyngeal branch to the pharyngeal plexus formed by vagus nerve - GSA
~ lingual branches - GSA and SVA
~ tonsillar branches - GSA

[Diagram: Course and branches of CN IX]

47
Q

Functional components of vagus nerve?

A

Nucleus ambiguus - SVE to 6th arch muscles; intrinsic laryngeal musculature
Dorsal vagal nucleus (motor nucleus of vagus) - gives preganglionic parasympathetic GVE fibers to the several visceral organs
Gustatory nucleus - receives SVA fibers from the area around epiglottis
Sensory nucleus of trigeminal - GSA fibres from the ear, dura and larynx
Nucleus of solitary tract - GVA from aortic arch baroreceptors and from carotid body and sinus

48
Q

Intracranial course and branches of vagus nerve?

A

✔ Exits the brainstem at the retro-olivary sulcus
✔ Traverses the cerebellomedullary cistern as it approaches the jugular foramen
✔ The superior (jugular) ganglion is within the jugular foramen (cell bodies of GSA fibers)
✔ Joined by some fibers from cranial accessory nerve at the level of the jugular ganglion
✔ Gives off 2 general sensory branches within the foramen:
~ meningeal branches to posterior cranial dura
~ auricular branch (Arnold’s nerve) to the ear
[Diagram: How accessory nerve joins vagus nerve]

49
Q

Extracranial course and branches of the vagus nerve.

A

✔ Exits the cranial cavity via the jugular foramen
✔ The inferior (nodose) ganglion is just below the jugular foramen (cell bodies of SVA and GVA)
✔ Joined by more fibers from cranial accessory nerve at the level of the inferior ganglion
✔ Travels within the carotid sheath
✔ Gives off the following branches in the neck:
~ pharyngeal branch, to the pharyngeal plexus (supplies 4th pharyngeal arch. You may trace them back to cranial accessory)
~ carotid body branches
~ superior laryngeal nerve giving off internal and external laryngeal nerves. External laryngeal supplies cricothyroid. Internal laryngeal supplies mucosa of larynx including and below the vocal cord, thyrohyoid membrane
~ recurrent laryngeal nerve supplying all intrinsic laryngeal musculature except cricothyroid
~ superior cardiac branches

[Diagram: How accessory nerve joins vagus nerve]

50
Q

State the origin, functional component and intracranial course of the hypoglossal nerve.

A

Origin and Functional component:
Nucleus of origin: hypoglossal nucleus in the medulla oblongata, which lies deep to the hypoglossal trigone
GSE function:
extrinsic [genioglossus, hyoglossus, styloglossus] and intrinsic muscles of the tongue
[palatoglossus is an extrinsic muscle of the tongue but it is supplied by the vagus nerve]

Intracranial course:
✔ Its rootlets emerge from the pre-olivary sulcus of the medulla oblongata
✔ Fibers join to form the common trunk, which exits the cranial cavity via hypoglossal canal.
✔ Has the meningeal branch of C1 (note that this is not a branch of the hypoglossal nerve).

51
Q

Extracranial course and branches of hypoglossal nerve.

A

✔ exits its canal and enters the carotid sheath
✔ joined by the C1 root of the cervical plexus
✔ loops under the occipital artery and lateral to the external carotid artery
✔ enters the digastric triangle of the neck
✔ Branches of the hypoglossal nerve:
✨ Meningeal branch: anterior wall of posterior cranial dura (predominantly C1 fibers)
✨ Descendens hypoglossi: C1 fibers that leave hypoglossal nerve; form the superior root of ansa cervicalis
✨ Nerves to thyrohyoid and geniohyoid
✨ Nerves to: styloglossus, genioglossus, hyoglossus

[Diagram]
[Cadaveric image: Extracranial course of hypoglossal nerve]

52
Q

Briefly discuss the cervical sympathetic chain.
Formation? Location? Postganglionic fibres from the ganglia do what?

A

✓ Consist of 3 interconnected sympathetic ganglia — superior, middle and inferior cervical ganglia.
✓ Superior cervical ganglion:
✨lies at C2-C3 level; cell bodies of C1-C4
✓ Middle cervical ganglion: lies at C6 level; cell bodies of C5-C6
✓ Inferior cervical ganglion: lies at the neck of the first rib behind the vertebral artery; cell bodies of C7-C8.
✓ The first thoracic ganglion often fuses with the inferior cervical ganglion to form the stellate ganglion. If they do not fuse, then it’s the first thoracic ganglion that is referred to as the stellate ganglion.
✓ Lies on the prevertebral fascia behind carotid sheath.
✓ Receives preganglionic fibers from upper thoracic spinal nerves, mainly T1, T2, T3.
✓ Postganglionic fibers from the ganglia may:
✨ join the cervical spinal nerves
✨ join some cranial nerves
✨ hitch hike on surrounding arteries
✨ may form distinct nerves that travel to their targets
✓ Disruption of the cervical sympathetic chain leads to Horner’s syndrome (recall the symptoms)

53
Q

What ganglia form the ansa subclavia?

A

Middle and inferior cervical ganglia.

54
Q

Briefly discuss Level I cervical lymph nodes.

A

✔ comprise submental and submandibular lymph nodes
✔ territory of drainage: oral cavity, anterior nasal cavity, submandibular gland, and soft tissues of mid-face
Level Ia: submental nodes; are limited by the anterior bellies of digastric
Level Ib: submandibular nodes; located within the submandibular triangle

55
Q

Briefly discuss Level II cervical lymph nodes.

A

✔ comprise the upper jugular (deep cervical) chain of lymph nodes
✔ territory of drainage: face, 3 major salivary glands, nose, pharynx, larynx, ear
✔ receive lymphatics from retropharyngeal, submandibular and submental lymph nodes [Level I nodes drain into Level II nodes]
Level IIa: anteror upper jugular lymph nodes; includes jugulodigastric nodes
Level IIb: posterior upper jugular nodes; behind the internal jugular vein, and separate from it

Further notes:
Some authorities use the vertical plane of the spinal accessory nerve to divide level IIa and IIb nodes intraoperatively.

56
Q

Breifly discuss Level III cervical lymph nodes.

A

✔ comprise the middle jugular (deep cervical) chain of lymph nodes
✔ territory of drainage: base of tongue, tonsils, larynx, hypopharynx and thyroid gland
✔ receive efferent lymphatics from levels II and V, and from preteracheal, retropharyngeal and recurrent laryngeal nodes

57
Q

Briefly discuss Level IV cervical lymph nodes.

A

✔ they comprise the lower jugular (deep cervical) chain and medial supraclavicular lymph nodes
✔ territory of drainage: hypopharynx, larynx, thyroid gland and the cervical esophagus
✔ are divided into 2 by an imaginary line at 2 cm above the sternoclavicular joint
Level IVa: lower jugular nodes
Level IVb: medial supraclavicular node
✔ includes the Virchow’s nodes

58
Q

Briefly discuss Level V cervical lymph nodes.

A

✔ comprise the posterior triangle lymph nodes
✔ territory of drainage: nasopharynx, oropharynx, posterior scalp, and thyroid gland
Level Va: lymph nodes of occipital triangle esp. those around and above spinal accessory nerve
Level Vb: lymph nodes of occipital triangle, below level of cricoid cartilage; some authorities include the lateral supraclavicular nodes
Level Vc: other authorities recognize the supraclavicluar lymph nodes as a separate group; Vc about 2 cm above the level of the manubrium

59
Q

Briefly discuss Level VI cervical lymph nodes.

A

✔ comprise the central compartment (anterior cervical) nodes
Level VIa: the superficially located nodes around the anterior jugular veins
Level VIb: between medial borders or the common carotid arteries. Include: pre-layngeal nodes, pretracheal nodes, paratracheal/recurrent laryngeal nodes
Delphian lymph node: a pre-laryngeal or pre-cricoid level VIa node located between the cricothyroid muscles

60
Q

5 major [potential] spaces of the infrahyoid neck

A
  1. Visceral space
  2. Carotid space
  3. Retropharyngeal space
  4. Posterior cervical spce
  5. Perivertebral space

Further notes:
Some of these spaces are continuous with suprahyoid spaces or the mediastinum.
[Radiograph: Infrahyoid neck spaces]

61
Q

Differentiate between the clinical procedures of cricothyrotomy and tracheostomy.

A
62
Q

Describe the formation, location and distribution of the ansa cervicalis.

A

Formation
✔ formed by union of two roots: superior and inferior roots
✔ superior root (descendens hypoglossi) is formed by the descending branch of the hypoglossal nerve carrying C1 spinal nerve fibres
✔ inferior root (descendens cervicalis) is derived from C2 and C3 spinal nerves

Location
✔ in the carotid triangle, embedded in the anterior wall of the carotid sheath

Distribution
It supplies all the infrahyoid muscles except the thryohyoid:
✔ omohyoid [gives two separate branches for the superior and inferior bellies]
✔ sternothyroid
✔ sternohyoid
[Diagram: Cervical Plexus]

63
Q

State the boundaries of the vertebral triangle aka. scalenovertebral triangle.

A

Medial: lower oblique part of longus colli
Lateral: medial border of scalenus anterior
Apex: transverse process of C6 vertebra
Base: first part of subclavian artery
Roof: carotid sheath
Floor: From above downwards it is formed by:
✔ transverse process of C7 vertebra
✔ ventral ramus of C8
✔ neck of first rib
✔ cupola of cervical pleura
[Diagram] [Cadaveric image]

64
Q

State the contents of the vertebral triangle aka. scalenovertebral triangle.

A

✔ first part of the vertebral artery and accompanying veins
✔ thyrocervical trunk and inferior thyroid artery
✔ sympathetic chain with stellate ganglion (inf. cervical ganglion)
✔ thoracic duct
ansa subclavia

65
Q

State the boundaries of the thoracic outlet.

A

Anteriorly: superior border of manubrium sterni
Posteriorly: anterior border of the superior surface of the body of T1 vertebra
Laterally: medial border of 1st rib and its cartilage

66
Q

State the contents of the thoracic outlet in terms of muscles and nerves.

A

Muscles:
✔ longus colli
✔ sternothryoid
✔ sternohyoid

Nerves:
✔ right and left phrenic nerves
✔ right and left vagus nerves
✔ left recurrent laryngeal nerves
✔ right and left symphathetic chains

67
Q

State the contents of the thoracic outlet in terms of veins, arteries and lymphatics.

A

Veins:
✔ right and left brachiocephalic veins
✔ right and left 1st posterior intercostal veins
✔ inferior thyroid veins

Arteries:
✔ right and left internal thoracic arteries
✔ brachiocephalic artery
✔ left common carotid artery
✔ left subclavian artery
✔ right and left superior intercostal arteries

Lymphatics
✔ thoracic duct

68
Q

State the non-neurovascular/non-muscular contents of the thoracic outlet.

A

✔ esophagus
✔ trachea
✔ right and left apices of lungs
✔ right and left cervical pleura

69
Q

(a) What is suprapleural membrane/Sibson’s fascia?
(b) Where is it attached?
(c) What are its functions?

A

(a) It is a fibrous structure that partly separates thoracic inlet from the neck and covers the apex of lung and cervical pleura. It is triangular in shape.
(b) Apex: Transverse process of C7 vertebra
Base: Inner border of 1st rib and costal cartilage
(c) Functions:
✓ protect underlying pleura and apex of lung
✓ resist intrathoracic pressure and prevent neck from puffing up during respiration

[Diagram 1] [Diagram 2]