Neck 1 & 2: surface anatomy, fascians and spaces, triangles & superficial structures

Question 1

General considerations

Answer 1

neck is bounded by the skull above and the thoracic inlet below and is supported in between by seven cervical vertebrae

a visceral compartment exists which provides communication between nasal and oral cavities and the thoracic components of the digestive and respiratory systems

a system of muscles and associated fascias exist which control skull and neck movements, strengthen skeletal support and protect, while at the same time, mobilize the visceral compartment

Question 2

Occiput

Answer 2

external occipital protuberance and superior nuchal lines

Question 3

mastoid process

Answer 3

of temporal bone

Question 4

mandible

Answer 4

ramus, angle, and inferior margin to midline (symphysis menti)

Question 5

Hyoid bone

Answer 5

body is palpable anteriorly immediately superior to the prominence of the thyroid cartilage (opposite the third cervical vertebra) laterally its greater horn is palpable

Question 6

thyroid cartilage

Answer 6

located opposite the fourth and fifth cervical vertebrae, the superior thyroid notch and laryngeal prominence are easily palpable anteriorly

Question 7

cricoid cartilage

Answer 7

located anterior to the sixth cervical vertebra this “signet” ring shaped cartilage is palpable directly inferior to the thyroid cartilage

Question 8

tracheal rings

Answer 8

inclomplete, “D”-shaped cartilages, their open areas face posteriorly.

NOTE: the thyroid isthmus is usually palpable across the level of hte 2nd, 3rd, and 4th tracheal rings

Question 9

Other surface anatomy

Answer 9

sternal (jugular) notch
sternocleidomastoid- large oblique muscle seen anteriolaterally

clavicle at root of neck from the sternoclavicular joint to the acromioclavicular joint

Platysma- corrugated “turtle neck” appearance of cutaneous muscle seen anteriorly and laterally upon straining

contour lateral border of trapezius

Spinous processes of CV 1-7

Question 10

Cervical fascias: general considerations

Answer 10

the importance of the cervical fascial layers is several fold. They bind deeper structures thereby giving them strength and continuity while at the same time allowing movement to take place. THey also allow movement of visceral components during swallowing independent of movements of the neck and help to isolate the spread of infection, although we will see later that infection can penetrate these fascial layers following the paths of blood and lymph vessels and communicate inferiorly with compartments located within the thorax.

Question 11

Superficial fascia

Answer 11

connective tissue & fatty later that fills in the space between the skin and deep fascia covering muscles. NOTE: the platysma muscle is located within the superficial fascia layer.

Question 12

Platysma muscle

Answer 12

O; superficial fascia covering the pectoralis major and deltoid
I: Inferior margin of the mandible, skin and subcutaneous tissues of the lower portion of the face and corner of the mouth
A: draws corner of mouth downward, depresses mandible, elevates skin of chest
N: cervical branch of facial n. (CN VII)

Question 13

Investing fascia

Answer 13

1st layer of deep fascia
a cylinder of fascia attached above and below to bony prominences, surrounds the entire neck from above downward and posterior to anterior, provides a roof for the anterior and posterior triangles and invests (surrounds entirely) the trapezius and SCM muscles.

Question 14

Attachments of investing fascia

Answer 14

Superior: external occipital protuberance, superior nuchal line, mastoid process and inferior margin of the mandible

Posterior: external occipital protuberance, spinous processes CV1-CV7 via the nuchal ligament

Inferior: a line connecting the inferior attachments of cervical investing fascia would connect the spinous process of CV7, spine of the scapula, acromion, clavicle and manubrium. It blends with the inferior attachments of the SCM an dtrapezius and attaches to the interveneing middle 1/3 of the clavicle. Where the laminae from both surfaces of the SCM fail to fuse anteriorly and inferiorly they form a small suprasternal space which is normally filled with fat and contains a vein which communicates with the inferior protion of the anterior jugular veins.

NOTE: the investing fascia is continuous superiorly with the parotid fascia in the soft tissue interval between the mastoid and angle of the mandible. It also forms a connective tissue capsule for the submandibular gland.

Question 15

Infrahyoid fascia

Answer 15

2nd layer of deep fascia
beginning at the hyoid bone and thyroid cartilage, this fascia forms two definite layers which invest the infrahyoid muscles.

1. Superficial layer- invests the sternohyoid and omohyoid muscles and is prolonged inferiorly to attach to the posterior surface of the manubrium. Laterally this fascia fuses with the periosteum of the clavicle and first rib where it forms a sling for the intermediate tendon of the omohyoid muscle.
2. Deep layer- invests the sternothyroid and thyrohyoid muscles and is prolonged inferiorly to attach to the posterior surface of the manubrium.

Question 16

Cervical visceral fascias

Answer 16

encircle the visceral structures of the neck, i.e. pharynx, esophagus, larynx, trachea and thyroid gland, and are composed of two separate anterior and posterior occurring fascias which meet and fuse laterally.
pre-tracheal (3rd layer of deep fascia)
buccopharyngeal (4th layer of deep fascia)

Question 17

Pre-tracheal fascia

Answer 17

3rd layer of deep fascia- located anterior to the larynx and trachea, it is attached to the hyoid bone superiorly, blends laterally with the buccopharyngeal fascia, splits to enclose the thyroid gladn and is prolonged inferiorly where it attaches to the adventitia of the aortic arch and fuses with the fibrous pericardiium.

Question 18

Buccopharyngeal fascia

Answer 18

4th layer of deep fascia- atttaches superiorly to the base of the skull, covers the buccinator and pharyngeal constrictor muscles on their external surface, fuses laterally with the pre-tracheal fascia at the muscular attachment sites of the pharyngeal constrictors and at the posteromedial border of the thyroid gland and is prolonged inferiorly for an indeterminable distance where it fuses with the adventitia of the esophagus.

Question 19

Pre-vertebral fascia

Answer 19

5th layer of deep fascia

continuous with nuchal fascia posteriorly; both then encircle the vertebral column and its associated musculature.

Question 20

Attachments of pre-vertebral fascia:

Answer 20

superior: base of the skull anterior and lateral to the vertebral column (specifically to the basilar portion of the occipital, jugular foramen and carotid canal)
anterior: covers the prevertebral musculature and extends inferiorly into the posterior mediastinum
lateral: attaches to cervical transverse processes and FORMS THE FLOOR OF THE POSTERIOR CERVICAL TRIANGLE where it covers the scalenes, levator scapulae, splenius and semispinalis muscles

posterior (nuchal fascia)- from the nuchal lines and mastoid processes to cervical spinous processes; inferiorly fuses with the thoracolumbar fascia of the deep back.

Question 21

Specializations of pre-vertebral fascia

Answer 21

Sibson’s fascia (suprapleural membrane)- the prevertebral layer of fascia is continued onto the UNDERSIDE of the scalene muscles and reinforces the dome of cervical pleura thereby forming the suprapleural membrane.

Axillary sheath- continuation of prevertebral fascia reflected from teh scalene muscles LATERALLY along the subclavian and axillary vessels and brachial plexus as they pass through the scalene triangle

Question 22

Alar fascia

Answer 22

6th layer of deep fascia
anteriorly the pre-vertebral fascia bifurcates to form the alar fascia which attaches to the midline of the buccopharyngeal fascia, bilaterally blends with the carotid sheath adn inferiorly blends with the adventitia of the esophagus in the superior mediastinum between CV7 and TV3

Question 23

Carotid sheath

Answer 23

(neurovascular component of deep fascia)- surrounds the common and internal carotid arteries, the internal jugular vein and the vagus nerve. It is attached superiorly to the base of the skull at the margins of the jugular foramen and carotid canal. Inferiorly it fuses with the adventitias of the great vessels (aorta, pulmonary trunk, superior vena cava) and the fibrous pericardium.

NOTE: ALL deep fascias of the neck blend laterally with the CAROTID SHEATH. Therefore, care must be exercised during dissection because these interwoven fascias are tough yet structures embedded within these, i.e. ansa cervicalis, are very delicate and can be easily excised.

Question 24

Clinical note re: deep fascias

Answer 24

Since all deep fascias of the neck communicate with and help form the carotid sheath, infections within the pretracheal, retrovisceral and danger spaces can invade the carotid sheath involving the structures located within the sheath as well as dissect inferiorly within the sheath to involve the aorta causing aortitis.

Question 25

Cervical fascial spaces: General considerations

Answer 25

potential spaces which exist between layers of fascia previously described have been identified as having clinical importance.

Question 26

4 spaces

Answer 26

Suprasternal
Pre-tracheal or visceral
retropharyngeal (& retrovisceral, retroesophageal)
“Danger” space

Question 27

Pre-tracheal or visceral space

Answer 27

located between the deepest layer of the infrahyoid fascia and the pre-tracheal fascia

Extends from the level of the attachment of the infrahyoid muscles to the hyoid bone and thyroid cartilage above, to the attachment of the pericardium to the roots of the major vessels in the superior mediastinum below.

Question 28

Retropharyngeal spaces

Answer 28

two in number

located between the buccopharyngeal, pre-vertebral and alar fascias

extend from the base of the skull to the posterior mediastinum where the pre-vertebral fascia continues over the vertebral column

closed laterally by the carotid sheath.

Space 3: retrovisceral, retropharyngeal, retroesophageal space: a smaller, more anterior space located between teh buccopharyngeal and alar fascias extending from the base of the skull above to a point approximately opposite CV7-TV3 where the alar fascia blends with the esophagus in the neck or as far inferior as the superior mediastinum.

Question 29

Danger space

Answer 29

Space 4.

A larger, more posterior space is located btween the pre-vertebral and alar/ buccopharyngeal fascias extending from teh base of the skull to the diaphragm between the vertebral column and the esophagus.

Question 30

Clinical correlations re: spaces

Answer 30

of extreme clinical importance is the containment and/ or spread of infection from one compartment to another. Infections occuring within the anterior visceral copartment (pre-tracheal space) can dissect into the superior mediastinum leading to inflammation of the brachiocephalic veins, aorta, and pericardium. Infections occurring within the “danger space” can lead to retropharyngeal abscess which can lead to dysphagia and sysarthria and can dissect into the posterior aspect of the superior and posterior mediastinum ie. chronic tonsillitis can lead to mediastinal abscess, thereby leading to inflammation of the esophagus as far distally as the diaphragm.

Question 31

Boundaries of the neck

Answer 31

Anterior: line drawn from teh symphysis menti to the sternal notch
Posterior- trapezius (anterior) border
superior: indefinite line that connects teh superior nuchal line, mastoid process and inferior margin of the mandible to the symphysis menti
inferior: superior margin of the clavicle, sternoclavicular joint and sternal notch

Question 32

SCM

Answer 32

O: Sternal head: manubrium (anterior surface), Clavicular head: proximal 1/3 of clavicle (superior surface)

I: mastoid process (lateral surface), superior nuchal line (lateral half)

A: Unilaterally acting: rotates head toward side opposite while elevating chin (side bends)
Bilaterally acting: flexes head; limited etension of the atlanto-occipital joint; functions as an accessory muscle of respiration

N: Spinal accessory n. (CN XI) and cervical spinal nervs C2 and C3

Question 33

Torticollis

Answer 33

wry neck
congenital or acquired
results in a shortening of the SCM which places the patient’s head in a position side bent to the same side and rotated to the side oppoite of the affected muscle

Question 34

What does the SCM create?

Answer 34

Anterior and posterior triangles of the neck

Question 35

Posterior triangular subdivisions

Answer 35

posterior triangle- bounded by the trapezius posteriorly, the SCM anteriorly and the clavicle inferiorly, it is subdivided by the passage of the inferior belly of the omohyoid muscle into: occipital triangle and omoclavicular (subclavian or supraclavicular) triangle.

Question 36

occipital triangle

Answer 36

larger, more superior triangle bounded by the trapezius, SM and inferior belly of the omohyoid

Question 37

omoclavicular (subclavian or supraclavicular) triangle

Answer 37

smaller, more inferior triangle bounded by the inferior belly of the omohyoid, clavicle and SCM

Question 38

Anterior triangle

Answer 38

bounded by the SCM posteriorly, the angle and inferior margin of the mandible superiorly and an imaginary line mid-sagitttally, it is subdivided by the passage of the digastric and omohyoid muscles to form the following triangles: digastric, submental, carotid and muscular triangles.

Question 39

Digastric (submandibular) triangle

Answer 39

bounded superiorly by the inferior margin of the mandible, inferiorly by the two bellies of the digastric muscle

Question 40

Submental triangle

Answer 40

bounded laterally by the two opposing anterior bellies of the digastric muscles and the hyoid bone.

Question 41

carotid triangle

Answer 41

bounded superiorly by the posterior belly of the digastric, anteriorly by the superior belly of the omohyoid and posteriorly by the SCM

Question 42

Muscular triangle

Answer 42

bounded posterior-superiorly by the superior belly of the omohyoid, posterior-inferiorly by the SCM and anteriorly by the median line of the neck to the hyoid bone.

Question 43

External Jugular Veins

Answer 43

paired left and right
Formation: union of the posterior division of the retromandibular and the posterior auricular veins at the angle of the mandible.

Course: descends from its formation SUPERFICIAL to the SCM, pierces the investing fascia to gain the root of the neck behind the clavicle where it terminates in the subclavian vein.

Tributaries: posterior external jugular v. (from lateral occiput)
transverse cervical v.
Suprascapular v.
Anterior jugular v.

NOTE: a portion of the superficial cervical lymph nodes lie along the path of the external jugular vein.

Question 44

Clinical notes re external jugular v.

Answer 44

Prominence of the external jugular v. beyond normal can reveal much about the health status of the individual. Increased filling is an indication of increased resistance to flow in such conditions as heart failure, SVC obstruction, enlarged supraaclavicular lymph nodes or increased intrathoracic pressure.

Laceration of the external jugular v. along the posterior border of the SCM can lead to AIR EMBOLISM due to negative intrathoracic pressure which sucks in air through the open vein. This is evidenced by hearing a bruit upon auscultation of the thoracic wall, cyanosis of mucous membranes, reduced flow of blood through the right atrium due to accumulated air, and dyspnea.

Question 45

Anterior jugular veins

Answer 45

paired right and left

Formation: small veins in the submental and submandibular regions coalesce at the level of the hyoid bone to form the anterior jugular vein.

Course: Descends from the level of the hyoid bone to the medial inferior most extent of the anterior triangle, pierces the investing fascia and continues inferiorly within the suprasternal space where it communicates with its opposite fellow via the JUGULOVENOUS ARCH. It then turns laterally coursing deep to the SCM to join the external jugular vein.

Question 46

common facial vein

Answer 46

in the submandibular region the facial vein joins with anterior division of the retromandibular vein to form the common facial vein before piercing the carotid sheath to join the internal jugular vein. Often, the union of the retromandibular and facial veins also forms a communicating vein which follows the anterior border of the SCM to communicate with the anterior jugular system.

Question 47

clinical note re: anastamoses

Answer 47

The anastomoses of the anterior and posterior divisions of the retromandibular v. provide an important route for returning blood from inside the skull to the thorax. Should the internal jugular v. (most important venous drainage of the brain & skull) become blocked at its origin, emissary vv. and opthalmic vv. draining through the scalp and orbit, respectively, provide blood to the retromandibular and facial vv. The previously described anastomoses with the posterior auricular v. forming the external jugular v. and the formation of the common facial v. through the anastomosis of the facial v. and anterior division of the retromandibular v. ultimately return blood to the internal jugular v. DISTAL to the blockage allowing blood to return to the heart without increasing intracranial blood pressure.

Question 48

Cutaneous Nerves: Dorsal Rami

Answer 48

C1 spinal nerve has no dorsal root in 50% of individuals; when present, it has a much reduced dorsal root ganglion. Its cutaneous distribution has been taken over by the greater occipital n. (C2). What small amount of GSA innervation that remains comes from the dura lining the posterior cranial fossa.

C2 (greater occipital nerve)- pierces the semispinalis capitis and trapezius ascends to innervate the skin over the vertex and posterolateral area of the skull.

C3-C6 dorsal rami pierce the deep musculature to reach subcutaneous areas near the dorsal midline and extend laterally to cutaneous areas over the trapezius.

Question 49

Ventral Rami

Answer 49

C1-C4 Ventral rami form the cervical plexus.

C2-C4 ventral rami (of the cervical plexus) participate in cutaneously innervating the pinna (outer ear) as well as the region directly behind and in front of the ear, lateral and anterior areas of the neck, upper anterior thorax and prominence of the shoulder.

Question 50

Lesser occipital n.

Answer 50

C2,3

ascends the posterior border of the SCM to innervate the medial surface of the ear as well as the skin behind the ear.

Question 51

Great auricular n.

Answer 51

C2,3
ascends the lateral surface of the upper half of the SCM toward the angle of the mandible paralleling the external jugular vein. En route it provides branches to the skin covering the mastoidi process, lower portion of both surfaces of the ear and the inferior portion of the angle of the mandible and parotid region.

Question 52

Transverse cervical n.

Answer 52

C2,3
crosses the lateral surface of the SCM inferior to the great auricular nerve and deep to the external jugular vein. Within the anterior triangle, it travels deep to the platysma where it divides into two branches (superior and inferior) which pierce the platysma to innervate the skin and subcutaneous tissue of the anterior triangle from the mandible to the sternum. Often, the transverse cervical n. and the cervical branch of the facial n. unite to form the ansa cervialis superificialis (function unknown)

Question 53

Supraclavicular nn.

Answer 53

(C3, 4)

arise from a common trunk which crosses the inferior portion of the posterior triangle where it divides into three branches:

a. medial supraclavicular nn- cross the inferior portion of the SCM to provide branches to the skin at the base of the neck, upper sternum and sternoclavicular joint.
b. intermediate supraclavicular nn.- cross the clavicle to innervate the skin over the pectoralis major as far inferior as the third rib
c. lateral supraclavicular nn.- cross the clavicle in the area of the acromioclavicular joint (which they supply and provide cutaneous innervation to the prominence of the shoulder.

Question 54

Clinical note re cutaneous branches of the cervical plexus

Answer 54

are locally anesthetized (cervical nerve block) during the normal course of surgical approaches to superficial or deeper areas of the neck, i.e. radical neck dissection of cancerous lymph nodes, etc. Concomitantly, the phrenic n. shares spinal cord levels of innervation (C3-4) with the spinal cord levels of origin of the cervical plexus and therefore the ipsilateral hemidiaphragm will also be paralyzed. Care must be taken to not utilize this procedure on patietns with significant respiratory or cardiac disease. (

Question 55

Lymphatics- superficial

Answer 55

Superficial cervical lymph nodes include sumental, submandibular, external jugular, and anterior jugular.

Receive lymph from the lower portion of the ear and parotid region, the facial region, portions of the oral cavity, submandibular and sublingual salivary glands, skin of the anterior neck and muscles of hte infrahyoid region.

Nodes of this system drain to the deep cervical lymph nodes that parallel the internal jugular vein.

NOTE: lymph drainage from areas of the head not mentioned in b. above drains to deep cervical lymph nodes which will be considered with the carotid sheath. AS A GENERAL RULE, lymphatic drainage from the superficial structures of the head and neck drain via superficial cervical nodes to the deep cervical nodes which also receive lymph from the deeper areas of hte face, head and viscera of the neck.