Lab 1 - Posterior Cervical Triangle

Question 1

In anatomical terms, state the relative position of the angle of the mandible with respect to the mastoid process.

Answer 1

The angle of the mandible is situated inferior, medial, and ventral to the mastoid process.

Question 2

How would the relationship between structures change if the cadaver were turned into the prone position?

Answer 2

The relationship of any two structures does not change with the orientation of the body, since relationships are always defined as they exist in the anatomical position.

Question 3

List cartilaginous structures in the neck that can be palpated through the skin.

Answer 3

Thyroid cartilage, cricoid cartilage, tracheal cartilages.

Question 4

The laryngeal prominence is a feature of which of the skeletal components of the larynx?

Answer 4

It is a median projection from the anterior surface of the thyroid cartilage and is situated at the superior end of the junction of the two laminae of the thyroid cartilage.

Question 5

In what layer of the neck is the platysma muscle located?

Answer 5

Tela subcutanea

Question 6

What is another term for tela subcutanea?

Answer 6

Superficial fascia

Question 7

What layer envelops the sternocleidomastoid muscle?

Answer 7

Investing cervical fascia.

Question 8

From what structure does the platysma muscle take origin?

Answer 8

The tela subcutanea overlying the upper part of the pectoralis major muscle.

Question 9

Where does the platysma muscle insert?

Answer 9

The inferior border of the mandible and into the corner of the mouth.

Question 10

How does the platysma muscle receive motor innervation?

Answer 10

Through the cervical branch of the facial nerve, which enters the deep surface of the muscle below the angle of the mandible.

Question 11

How is the facial nerve classified?

Answer 11

The facial nerve is a cranial nerve; specifically, it is the seventh in the series and may be designated by its name or roman numeral (VII).

Question 12

How is the platysma muscle related to the investing fascia of the neck?

Answer 12

The platysma is superficial to the cervical investing fascia.

Question 13

How is the external jugular vein related to the platysma muscle, and how are these two structures related to the investing fascia of the neck?

Answer 13

In the highest part of the neck the external jugular vein lies posterolateral to the platysma. Somewhat lower, where they are in contact, the vein is deep to the muscle; here the vessel is superficial to the investing fascia, but low in the neck the fascia is penetrated by the vein, near its junction with the subclavian vein.

Question 14

How does the external jugular vein typically begin?

Answer 14

By the junction of the posterior auricular vein with the posterior division (branch) of the retromandibular vein.

Question 15

What does the accessory nerve supply?

Answer 15

The accessory nerve provides motor innervation for the sternocleidomastoid and trapezius muscles.

Question 16

What is the location of cell bodies of nerve fibers in the accessory nerve?

Answer 16

In the ventral gray column of the upper cervical segments of the spinal cord.

Question 17

Where does the accessory nerve arise?

Answer 17

The accessory nerve arises from rootlets attached to the side of the upper segments of the spinal cord. Because it usually lacks connections with dorsal or ventral roots at these levels, this nerve may be thought of as an “accessory” spinal nerve. Nevertheless, the accessory is classified as a cranial nerve (XI). The course of this nerve takes it into the cranial cavity (by passing through the foramen magnum), where some nerve filaments arising with the vagus nerve may be added from the brainstem. As it exits the cranial cavity through the jugular foramen, the nerve fibers the accessory nerve acquired from the brainstem are shifted back to the vagus nerve and the accessory nerve proceeds through the neck to innervate the sternocleidomastoid and trapezius muscles.

Question 18

How do the sternocleidomastoid and trapezius muscles receive afferent and sympathetic innervation?

Answer 18

Through branches of the cervical plexus.

Question 19

The great auricular, transverse cervical, lesser occipital, and supraclavicular nerves are branches from what structure in the neck?

Answer 19

The cervical plexus, which is formed from the ventral primary rami of the first four cervical spinal nerves.

Question 20

What structures are innervated by these four branches of the cervical plexus?

Answer 20

These branches of the cervical plexus supply skin in the anterolateral part of the neck. Specifically, the supraclavicular nerves supply the lower part of the neck, the transverse cervical nerve innervates skin of the upper part of the anterior cervical triangle, and the great auricular nerve supplies skin of the upper part of the posterior triangle. The lesser occipital nerve is distributed to skin behind the ear.

Question 21

Be able to name the types of fibers in nerves encountered in this dissection and give the location of the cells of origin for each fiber type.

Answer 21

Example: the great auricular nerve – (1) afferent fibers from C2 and C3 spinal ganglia; and (2) postganglionic efferent fibers from the superior cervical sympathetic ganglion.

Question 22

What are the boundaries of the posterior cervical triangle?

Answer 22

The posterior border of the sternocleidomastoid, the anterior border of the trapezius, and the middle third of the clavicle form the anterior, posterior, and inferior boundaries, respectively. This “triangle” is a three-dimensional space bounded superficially by the investing layer of cervical fascia, while the prevertebral fascia and underlying muscles make up its deep limit.

Question 23

Name the subsidiary triangles contained within the posterior cervical triangle and give the boundaries of each.

Answer 23

There are two: (a) the supraclavicular (omoclavicular or subclavian) triangle, bounded by the clavicle and two muscles – the inferior belly of the omohyoid and part of the sternocleidomastoid; and (b) the occipital triangle, bounded by the remainder of the sternocleidomastoid, the inferior belly of the omohyoid, and the trapezius muscles.

Question 24

State the origin and insertion of the omohyoid muscle and give any other attachments of this muscle to bone.

Answer 24

The omohyoid is a compound muscle, consisting of superior and inferior bellies connected by an intermediate tendon. The muscle arises from the upper border of the scapula and inserts into the hyoid bone. Although not a true muscle attachment, a fascial sling fastens the intermediate tendon of this muscle to the clavicle and changes the direction of pull of the muscle.

Question 25

Name the muscles that underlie the fascial component of the

floor of the posterior cervical triangle, anteroinferior to the accessory nerve.

Answer 25

Part of the levator scapulae, the posterior scalene, the middle scalene, and the anterior scalene muscles.

Question 26

What structures pass between the anterior and middle scalene muscles?

Answer 26

The trunks of the brachial plexus and the subclavian artery.

Question 27

What is the brachial plexus?

Answer 27

The nerve plexus that innervates the upper limb. It arises from combinations of ventral primary rami of spinal nerves C5 through T1. These “roots” of the plexus join in a standard pattern to form three trunks: superior, middle, and inferior, which emerge between the anterior and middle scalene muscles above the subclavian artery. Each trunk splits into anterior and posterior “divisions,” which combine in various ways to form three cords (medial, lateral, and posterior, named for their relationship to the axillary artery), from which large named branches arise that innervate specific regions of the upper limb.

Question 28

How are the structures that pass between the anterior and middle scalene muscles related to the fascia covering the muscular component of the floor of the posterior triangle?

Answer 28

This (prevertebral) fascia covers the subclavian artery and the roots of the brachial plexus and extends outward along them as the axillary sheath.

Question 29

What is the origin of the long thoracic nerve?

Answer 29

Although this nerve (a.k.a., nerve to the serratus anterior m.) appears by emerging through the middle scalene muscle, it is derived from the upper root (C5 & 6,) and the middle root (C 7) of the brachial plexus.

Question 30

What is the innervation of the levator scapulae muscle?

Answer 30

The dorsal scapular nerve, arising from the ventral primary ramus of C5.

Question 31

What important neurovascular structures are found posterosuperior to the accessory nerve within the posterior cervical triangle?

Answer 31

None.

Question 32

Describe the course and distribution of the transverse cervical artery.

Answer 32

The artery crosses the lower part of the posterior cervical triangle, passing laterally in front of the anterior scalene muscle, deep to the omohyoid muscle, and superficial to the brachial plexus. This artery usually divides into superficial and deep branches to supply muscles on the back of the shoulder region (the trapezius and the levator scapulae and rhomboid muscles, respectively).

Question 33

Where does the transverse cervical artery arise?

Answer 33

From the thyrocervical trunk, a branch of the first part of the subclavian artery.

Question 34

From what vessel is the suprascapular artery a branch?

Answer 34

Also the thyrocervical trunk.

Question 35

Where is the usual location of the suprascapular artery?

Answer 35

This artery courses laterally in front of the anterior scalene muscle, very low in the posterior cervical triangle, often passing immediately posterior to the middle third of the clavicle.

Question 36

What is the dorsal scapular artery?

Answer 36

As a commonly-occurring variation of the arterial pattern supplying blood to muscles in the upper part of the back, when present this artery arises from the third part of the subclavian artery, courses through the trunks of the brachial plexus, and supplies blood to the levator scapulae and rhomboid muscles, and sometimes also to the trapezius. In some cases the dorsal scapular artery replaces, totally or in part, the transverse cervical artery. In other cases both arteries may be present.

Question 37

What are the major structures that cross the posterior cervical triangle?

Answer 37

The inferior belly of the omohyoid muscle; the subclavian, suprascapular, and transverse cervical (and sometimes, dorsal scapular) arteries; the trunks of the brachial plexus; the supraclavicular, suprascapular, dorsal scapular, long thoracic, and accessory nerves. Note also that parts of the transverse cervical, great auricular, and lesser occipital nerves lie within the triangle.