1

MA 607C

NECK- II

Anterior ! Contents and Root of Neck:

Reading: Moore and Agur 596-612

M.Pizzimenti, Ph.D.

LEARNING OBJECTIVES:

• Know the function and nerve supply of muscles of anterior and post. triangles of neck.

• Describe the principal motor nerves of the neck indicating their source and muscles

innervated.

• Explain the important results of injury to individual motor nerves of the neck.

• Sketch the arterial tree from the superior mediastinum through the neck. Outline the branches

of the subclavian and external carotid aa.

• Sketch the tributaries of retromandibular, external and internal jugular veins

• Know the boundaries and contents of root of the neck.

• Outline the sub-triangles of the neck and describe the anatomy found within each.

• How a patient might present if he/she suffered a lesion of the following nerves: spinal

accessory nerve; vagus; hypoglossal; ansa cervicalis; sympathetic chain.

• Describe what knowledge of anatomy would be necessary to successfully perform: an

interscalene block; catheter placement into the subclavian v. and IJV

Arterial Pathways Through the Neck

Subclavian artery

• On the left side it arises directly from the arch of the

aorta. On the right side it is a branch of the

brachiocephalic trunk.

• It is divided into three parts by the scalenus anterior

muscle

- 1st part: from the origin of the vessel to the

medial margin of ant. scalenus

- 2nd part: posterior to the muscle

- 3rd part: from the lateral margin of the muscle

to the first rib

• Branches

- Vertebral artery: passes through the transverse

foramina of vertebra C1-C6 and continues

through foramen magnum into the cranial cavity.

- Thyrocervical trunk: arises from the first part of

the subclavian artery and divides into the following arteries:

! Suprascapular artery: passes ant. to ant. scalene muscle inf. to the transverse

cervical artery. Supplies ____________________ mm.

! Transverse cervical artery: Course

! Inferior thyroid artery - ascends to reach thyroid gland

- Internal thoracic artery

2

MA 598C

Common Carotid Artery

• On the right side, the common carotid artery arises from the brachiocephalic trunk.

• On the left side, it arises from the arch of the aorta.

• At the level of the upper border of the thyroid cartilage, it divides into external and internal

carotid arteries.

• Receptors

! Carotid sinus: dilated portion that functions as a baroreceptor, stimulated by changes in

blood pressure. Physical massage of the carotid sinus (for 5-10 seconds) is occasionally

performed in the diagnosis of tachycardia (an elevated heartbeat rate).

! Carotid body: ovoid body located at the bifurcation of the common carotid artery. It

functions as a chemoreceptor- sensitive to PO2. Innervated by the glossopharyngeal

nerve (afferent).

Internal Carotid artery

• Does Not supply branches in the neck

• It supplies most of cerebrum, and the tissues of orbital cavities, forehead, and nose.

External Carotid

• It ends in the body of the parotid gland at the level of neck of the mandible by dividing into

maxillary and superficial temporal arteries.

• Branches:

- Superior thyroid artery

! Found near the level of the

greater horn of the hyoid

bone.

! Descends deep to the

infrahyoid muscles and

supplies thyroid gland.

! Supplies larynx via the

superior laryngeal a.

(piercing the thyrohyoid

membrane)

- Lingual artery

! Found near the tip of the

greater horn of the hyoid

bone.

! Passes deep to the

hyoglossus muscle to reach

the tongue.

! It gives blood supply to the

tongue.

- Facial artery

! Usually arises just above the

3

GA 741

GD 178

lingual artery.

! Hooks around the lower border of the mandible and travels through the face

! It gives rise to ascending palatine artery, tonsillar artery and submental artery.

- Ascending pharyngeal artery

! It ascends between the

internal carotid artery and

the wall of the pharynx

! Supplies pharynx, palate,

ear and meninges.

- Occipital artery

! Supplies branches to

sternocleidomastoid

muscle.

! Travels through the

superior part of the

posterior triangle of the

neck and emerges to

appear on the skin and

above the occipital

triangle.

- Posterior auricular artery

! Arises near posterior

belly of digastric m.

! Travels posteriorly between auricle and mastoid process.

! Maxillary artery ! Arises behind the neck of the mandible and it is the larger terminal branch of the

external carotid artery.

! Runs deep to the neck of the mandible to enter the infratemporal fossa. Branches

of the maxillary artery are discussed in the lecture

of infratemporal fossa.

- Superficial temporal artery

! Small terminal branch of the external carotid

artery.

Nerves

• Spinal Accessory Nerve (CN XI)

- Originates from two sources; 1) brain stem, and 2)

spinal roots arising from the spinal cord.

- The cranial component joins the vagus nerve, while the

spinal component pierces the deep surface of

sternocleidomastoid muscle supplying this muscle and

trapezius muscle.

• Cervical plexus

- C1-C4 ventral rami

- Sensory branches already discussed

4

MA 607B

GD 179

- Ansa cervicalis

! Loop

! Superior root of the loop formed from C1 and C2: runs with hypoglossal n. (CN

XII)

! Inferior root also known as from C2 and C3.

! C1 supplies motor fibers to geniohyoid and thyrohyoid muscles.

! C1, C2, and C3 supply the infrahyoid muscles: sternohyoid, omohyoid and

sternothyroid muscles.

• Vagus Nerve (CN X)

" What do we already know about this CN?

- Branches

! Pharyngeal branches- (parasympathetic motor)

supply carotid body, pharynx and a part of the

palate.

! Superior laryngeal nerve bifurcates into internal

and external laryngeal nerves. Internal laryngeal

nerve supplies mucous membrane of larynx above

the vocal cords (sensory). External laryngeal

supplies cricothyroid muscle of the larynx and

gives branches to the pharyngeal plexus.

! Left recurrent

! Right recurrent

• Sympathetic Trunk

- No white rami communicans in neck

- Receive preganglionic fibers from

spinal rami (T-1 to T-5)

- Preganglionic fibers synapse with the

postganglionic neurons in the cervical

ganglion.

- Post-ganglionic fibers pass to cervical

spinal nerves, plexuses on the

external and internal carotid arteries

to reach blood vessels and viscera in

head and neck and heart

- Found posterior to carotid sheath

• Phrenic nerve

- derived from C3, C4, and C5 fibers

- Lies on the anterior surface of scalenus anterior muscle, passes to thorax deep to the

subclavian vein

- supplies the diaphragm, pericardium and mediastinal pleura.

5

GA 741B

N 27

MA 600

• Hypoglossal n. (CN XII)

- Motor supply to tongue and

muscles with “glossus” in name

(except palatoglossus m.)

- Exits hypoglossal canal of skull

- Travels lateral to ext carotid, found

in submandibular ! near tendon of

digastric m.

Veins

• Facial

• Retromandibular

• Communicating

• Anterior jugular

• External jugular

• Internal jugular

• Superior Thyroid

Clinical Note:

Jugular Pulse:

• Normally, blood fills only lower parts of jugular veins

• Pulse strength is related to pressure, thus jugular vein can be

used as a monometer of right atrial pressure

• Obvious when head is inferior to feet (Trendelenburg position)

IJV Access:

Heads of sternocleidomastoid serve as landmark.

Note the carotid a. position (N Engl J Med 356:e21, May 24, 2007 Videos in Clinical Medicine)

" Why would access on right side be preferred?

6

MA 587C

MA 596

Component Triangles of Anterior Cervical

Triangle • Submental triangle:

• Submandibular (digastric) triangle:

! Bounded by digastrics and mandible

! Contents: submandibular gland, facial

artery and vein, hypoglossal nerve, and

nerve to the mylohyoid muscle.

• Carotid triangle:

! Bounded by SCM, posterior belly of

digastric and omohyoid.

! Contents: Common carotid artery, external

carotid artery and its branches, internal carotid

artery, internal jugular vein, internal and external

laryngeal nerve situated deep in the carotid

triangle.

- Carotid Sheath:

! sheath of deep cervical fascia that

envelops the common and internal carotid

arteries, the internal jugular vein, the

vagus nerve

! Cervical part of the sympathetic trunks lie

embedded in loose connective tissue directly posterior to the carotid sheath

• Muscular triangle:

- Boundaries- median line,

SCM and omohyoid

- Content: infrahyoid

muscles, larynx, pharynx,

thyroid gland and trachea.

Root of the neck:

Boundaries

• Anteriorly- manubrium of the

sternum

• Laterally- 1st rib

• Posteriorly- T1 vertebra.

Contents:

The brachiocephalic trunk,

subclavian arteries, subclavian

Liebgott-2001

MA 607

7

MA 608

MA 609

vein, thoracic duct, sympathetic trunk, cervical viscera (thyroid gland). The subclavian artery,

vagus n. and sympathetic trunks are described above.

Subclavian Vein:

Thoracic Duct:

Thyroid Gland

Function • Controls rate of metabolism by

secreting thyroid hormone

• Controls calcium metabolism by

secreting calcitonin

Description and Location

• Right and left lobes united by

isthmus

• Found ant. to 2nd and 3rd tracheal

rings

Blood supply

• Superior and inf. Thyroid a.

• Thyroid ima in 10 % from

brachiocephalic trunk

Thryoid plexus of vv.

• Superior, middle : drain into IJV

• inf. thyroid vv.: drain into

brachiocephalic vv.

Parathyroid Glands

• Parathormone: control metabolism

of phosphorus and calcium

• (Usually) 4 in number

• found on the posterior medial aspect of thyroid gland

8

N 130

MA = Moore, KL and Agur, AMR. 2007. Essential Clinical Anatomy (3rd Ed), Lippincott Williams & Wilkins

MD = Moore, KL and Dalley, A. 1999. Clinically Oriented Anatomy (4th Ed), Lippincott Williams & Wilkins

GD = Tank, PW. 2005. Grant’s Dissector (13th Ed), Lippincott Williams & Wilkins

GA = Agur AMR and Dalley, A 2005. Grant’s Atlas of Anatomy (11th Ed), Lippincott Williams & Wilkins

N = Netter, FH. 2003, Atlas of Human Anatomy (3rd

Ed), Icon Learning Systems

Unlabelled images © LifeArt