Unit 8 - Posterior Triangle, Root of Neck

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SLUSOM 2015, Human Anatomy, 10/11/2011

What features form the superior border of the neck?

1) Lower border of the mandible
2) Mastoid process of skull
3) Superior nuchal line
4) External occipital protuberance

mental symphysis

The midline of the chin where the left and right halves of the mandible join together

Name the landmarks of the mandible

1) Body of mandible
2) Mental symphysis
3) Masseter muscle (external surface of the mandible)
4) Facial artery

Where is the facial artery located?

Inferior border of the mandible near the anterior border of the masseter

What features form the inferior border of the neck?

Anteriorly: jugular/suprasternal notch, sternoclavicular joint, clavicle
Posteriorly: spine of CV7

Describe the features of the clavicle

1) Medial end is large and knoblike while lateral end is flattened
2) Anteriorly, medial half is convex while lateral half is concave

What part of the vertebral column is the clavicle level with?

Intervertebral disc between T2 and T3

Name the major landmarks of the neck

1) Superior border (at mandible)
2) Inferior border (at clavicle and spine of CV7)
3) Hyoid bone
4) Thyroid cartilage
5) Sternocleidomastoid muscle
6) 6-8 palpable tracheal rings of cartilage

Location and features of the hyoid bone

1) Unpaired and doesn't articulate with any other bone (suspended by muscles and ligaments)
2) Inferior to inferior aspect of mandible
3) Consists of central body and lesser and greater horns (cornua) on either side
4) Lies in the anterior neck at level of CV3

What is the purpose of the hyoid bone?

Origin and insertion point for several muscles in the anterior neck

thyrohyoid membrane

Suspends larynx from the hyoid bone

Name the location and features of the thyroid cartilage

1) Unpaired cartilage of the larynx
2) Consists of two laminae that join at the laryngeal prominence
3) Greater/superior and lesser/inferior horn postero-laterally on each side

laryngeal prominence

aka Adam's apple. Located at the midline of the thyroid cartilage where its two laminae meet and fuse

greater/superior horn of the thyroid cartilage

Point at which the thyroid cartilage is suspend from the hyoid bone

lesser/inferior horn of the thyroid cartilage

Articulates inferiorly with the cricoid cartilage

Location of cricoid cartilage

Level of CV6, inferior to the thyroid cartilage

What boundary is marked by the cricoid cartilage?

Division between larynx and trachea

What structures in the neck are found at the level of CV6?

1) Junction between larynx and trachea
2) Junction of pharynx and esophagus
3) Middle cervical sympathetic ganglion
4) Vertebral artery where it first enters the transverse foramen

What structures form the boundaries of the posterior triangle of the neck?

Anterior: posterior border of the sternocleidomastoid muscle
Posterior: anterior border of the trapezius
Inferior: clavicle

What structures form the boundaries of the anterior triangle of the neck?

Medial: midline of the neck
Lateral: anterior border of the sternocleidomastoid muscle
Superior: inferior border of the mandible

sternocleidomastoid muscle

Separates anterior and posterior triangles of the neck

What nerve does the sternocleidomastoid muscle overlie?

Spinal accessory nerve, at the midpoint of the posterior border of the muscle

What nerves innervate the skin of the neck?

C2, C3, C4

superficial cervical fascia

1) Fascia that encircles the neck
2) Contains fat, cutaneous nerves, muscles of facial expression, and their nerves and veins

Name the nerves that make up the cutaneous components of the cervical plexus

1) Lesser occipital
2) Great auricular
3) Transverse cervicals
4) Supraclaviculars

Root and path of the lesser occipital nerve

C2
Follows posterior border of sternocleidomastoid muscle superiorly to the head

What structures does the lesser occipital nerve innervate?

Skin of the neck and scalp posterosuperiorly to the auricle of the ear

Roots and path of the great auricular nerve

C2, C3
Climbs vertically on the surface of the sternocleidomastoid muscle

What structures does the great auricular nerve innervate?

1) Skin of the parotid region and auricle
2) Skin of the angle of the mandible to the mastoid process

Roots and path of the transverse cervical nerves

C2, C3
1) Crosses the sternocleidomastoid horizontally
2) Joins carotid branch of the facial nerve inferior to the parotid gland

What structures do the transverse cervical nerves innervate?

Skin of anterior triangle of the neck

Roots and path of the supraclavicular nerves

C3, C4
Crosses the clavicle

What structures do the supraclavicular nerves innervate?

1) Skin of the inferior half of the posterior triangle of the neck
2) Skin of the upper thoracic and deltoid regions

Function of the platysma muscle

1) Facial expression
2) Covers anterior surface of the neck

Location of the platysma muscle

1) Extends from fascia in the thoracic region to the inferior aspect of the mandible
2) Superficial to the external jugular veins and the trunks of the cutaneous nerves

What innervates the platysma muscle?

Facial nerve (cranial nerve VII)

What kind of nerve fibers does the cervical plexus contain?

Sensory and motor

Which nerves contribute to the ansa cervicalis?

Cranial nerves I-III

What nerves contribute to the phrenic?

Cranial nerves III-V

Which vessels join to form the external jugular vein?

1) Retromandibular vein
2) Posterior auricular veins

What is the path of the external jugular vein?

Runs vertically across sternocleidomastoid muscle from the parotid region to the antero-inferior area of the posterior triangle?

What vessel does the external jugular vein drain into?

Subclavian vein

deep cervical fascia

1) Encircles the neck
2) Major fascia of the neck

Name the parts of the deep cervical fascia

1) Investing/anterior layer of deep cervical fascia
2) Prevertebral fascia (posterior layer of deep cervical fascia)

What is the role of the investing layer of deep fascia?

1) Covers superficial and deep surface of the trapezius and sternocleidomastoid muscles (invests the muscles)
2) Forms the roof of the anterior and posterior triangles of the neck

What is the role of the prevertebral fascia?

Surrounds the vertebral column and the muscles closely related to it

What is the function of the visceral fascia?

Surrounds the viscera of the neck (pharynx, esophagus, larynx, trachea, thyroid gland)

What is the function of the carotid sheath?

Surrounds and contains carotid vessels, internal jugular vein, vagus nerve

What is the function of the middle cervical fascia?

Surrounds and contains the infrahyoid strap muscles

cervicoaxillary canal

1) Bounded by muscles and fascia
2) Connects posterior triangle with the axilla

What structures form the roof of the posterior triangle?

Investing layer of deep cervical fascia as it attaches to
1) Adjacent borders of the trapezius and sternocleidomastoid muscles
2) Superior nuchal line
3) Clavicle

What structures form the floor of the posterior triangle?

Muscles covered by the prevertebral fascia
1) Splenius capitis
2) Splenius cervicis
3) Levator scapulae
4) Scalenus posterior
5) Scalenus medius
6) Scalenus anterior

What structures form the carpet of the posterior triangle?

Prevertebral fascia

What structures lie between the investing and prevertebral layers of deep fascia?

1) Spinal accessory nerve (cranial nerve XI)
2) Inferior belly of the omohyoid muscle
3) Transverse cervical vessels
4) Cutaneous nerves from the cervical plexus

What structures does the spinal accessory nerve innervate?

1) Trapezius
2) Sternocleidomastoid muscles

What is the spinal accessory nerve also known as?

Cranial nerve XI

Where is the spinal accessory nerve located?

Just beneath the investing layer of the deep cervical fascia

What structures lie between the carpet and floor of the posterior triangle?

1) Dorsal scapular nerve
2) Long thoracic nerve
3) Phrenic nerve
4) Proximal portion of the brachial plexus
5) Third part of the subclavian artery

Root and target of innervation of the dorsal scapular nerve

C5
Rhomboids and levator scapulae

Roots and target of innervation of the long thoracic nerve

C5, C6, C7
Serratus anterior

Roots and target of innervation of the phrenic nerve

C3, C4, C5
Diaphragm

Origin and insertion of the sternocleidomastoid muscle

Origin: 2 heads, one on manubrium and on medial end of the calvicle
Insertion: mastoid process

Functions of the sternocleidomastoid muscles

1) Contraction of muscle on one side turns the head in the opposite direction
2) Contraction of both muscles action together flexes the neck
3) Accessory muscle of respiration

Innervation of the sternocleidomastoid muscles

Spinal accessory nerve and branches of C2 and C3

How many scalene muscles are there and what are their names?

3
1) Scalenus anterior/anterior scalene
2) Scalenus medius/middle scalene
3) Scalenus posterior/posterior scalene

Actions and innervations of the scalene muscles

1) When acting together, are muscles of inspiration
2) Act on vertebral column of neck
Innervation: cervical nerves

Which scalene muscle is a landmark in the floor of the neck?

Scalenus anterior

Origin and insertion of scalenus anterior

Origin: anterior tubercle of transverse processes of CV3-6
Insertion: scalene tubercle of first rib between the grooves for the subclavian vessels

Innervation of scalenus anterior

C5, C6, C7

Where does the phrenic nerve cross the scalenus anterior muscle?

Anterior surface of the muscle deep to the prevertebral fascia, before entering the superior thoracic aperture

What structure crosses scalenus anterior, anterior to its insertion?

Subclavian vein

What structures are located between scalenus anterior and scalenus medius?

1) Subclavian artery
2) Ventral primary rami that form the brachial plexus

What is the largest of the scalene muscles?

Scalenus medius

Origin and insertion of scalenus medius

Origin: posterior tubercle of transverse processes of CV2-7
Insertion: superior surface of the first rib immediately posterior to the brachial plexus and subclavian artery

Innervation of scalenus medius

C3-8

What is the smallest of the scalene muscles?

Scalenus posterior

Origin and insertion of scalenus posterior

Origin: posterior tubercle of transverse processes of CV5-7
Insertion: second rib

Innervation of scalenus posterior?

C7, C8

What structures do the ventral primary rami of the brachial plexus pass between when they leave the vertebral canal?

1) Anterior and posterior tubercles of the cervical vertebrae
2) Scalenus anterior and scalenus medius

axillary fascia/sheath

Continuation of the prevertebral fascia

omohyoid muscle

1) One of the infrahyoid muscles
2) Consists of superior and inferior bellies connected by an intermediate tendon

What region of the neck is the inferior belly of the omohyoid located?

Posterior triangle

What region of the neck is the superior belly of the omohyoid located in?

Anterior triangle

Where is the intermediate tendon of the omohyoid located?

Underneath the sternocleidomastoid muscle

Origin and insertion of omohyoid muscle

Origin: upper border of scapula
Insertion: lower border of hyoid bone

Innervation of the omohyoid muscle

Ansa cervicalis

What structures lie superficial to scalenus anterior?

1) Prevertebral fascia
2) Subclavian vein
3) Phrenic nerve
4) Transverse cervical artery
5) Suprascapular artery
6) Omohyoid muscle

Name the structures that lie immediately above the first rib, from anterior to posterior

1) Subclavian vein
2) Scalenus anterior
3) Subclavian artery
4) Lower portion of brachial plexus
5) Scalenus medius

brachial plexis

Plexus of nerves that are formed from the ventral primary rami of C5-T1

Name the parts of the brachial plexus found in the posterior triangle of the neck

1) Ventral rami
2) Trunks
3) Divisions of the upper trunk
4) Suprascapular nerve
5) Nerve to the subclavius muscle
6) Dorsal scapular nerve
7) Long thoracic nerve
8) Phrenic nerve

sternoclavicular joint

Gliding joint between the medial end of the clavicle and the manubrium

articular disk

Divides the joint cavity into two separate spaces

Name the ligaments of the sternoclavicular joints

1) Articular capsule
2) Anterior sternoclavicular ligament
3) Posterior sternoclavicular ligament
4) Interclavicular ligament
5) Costoclavicular ligament

What vessels does of the subclavian arteries branch off of?

Left: aortic arch
Right: brachiocephalic trunk, which branches from the aorta

At what point does the subclavian artery become the axillary artery?

Lateral border of the first rib

What are the 3 sections of the subclavian artery, from proximal to distal?

1) Before it crosses scalenus anterior
2) Where it crosses posterior to scalenus anterior
3) After it cross scalenus anterior but before it reaches the first rib

Name the branches of the first part of the subclavian artery

1) Internal thoracic artery
2) Vertebral artery
3) Thyrocervical trunk

Where does the internal thoracic artery branch from and where does it go?

1) Arises from the antero-inferior aspect of the subclavian artery
2) Descends posterior to the sternal end of the clavicle to enter thorax

Where does the vertebral artery branch from?

Arises from postero-superior aspect of the subclavian artery

Trace the path of the vertebral artery once it branches from the subclavian artery

1) Enters transverse foramen of CV6
2) Ascends through succeeding transverse foramina
3) Runs along the superior aspect of the atlas
4) Enters skull via the suboccipital triangle

What structures does the vertebral artery supply?

Brain and the brain stem

Where does the thyrocervical trunk branch from?

Superior aspect of subclavian artery

Name the branches of the thyrocervical trunk

1) Inferior thyroid artery
2) Suprascapular artery
3) Transverse cervical artery

Trace the path of the inferior thyroid artery once it branches from the thyrocervical trunk

1) Passes superiorly along medial border of scalenus anterior to about the level of C6
2) Turns medially and branches

What structure does the ascending cervical artery run parallel to?

Phrenic nerve

What structure does the inferior laryngeal artery accompany?

Recurrent/inferior laryngeal nerve

Name the branches of the inferior thyroid artery

1) Ascending cervical artery
2) Inferior laryngeal artery

Trace the path of the suprascapular artery once it branches from the thyrocervical trunk

1) Passes anterior to scalenus muscle and posterior to sternocleidomastoid muscle
2) Travels behind clavicle to reach scapular notch
3) Crosses above the transverse scapular ligament

Trace the path of the transverse cervical artery once it branches from the thyrocervical trunk

1) Passes between the scalenus anterior and sternocleidomastoid muscles
2) Turns posteriorly and crosses posterior triangle
2) Divides into superficial and deep branches

What structure does the superficial branch of the transverse cervical artery accompany?

Spinal accessory nerve, on the deep surface of the trapezius muscle

What structure does the deep branch of the transverse cervical artery accompany?

Dorsal scapular nerve, on the deep surface of the levator scapulae and rhomboid muscles

superficial cervical artery

Instead of branching off of the transverse cervical artery, the superficial branch may arise from the thyrocervical trunk separately as this artery

dorsal scapular artery

Instead of branching off of the transverse cervical artery, the deep branch may arise from the third party of the subclavian artery separately as this artery

What branches are located in the second part of the subclavian artery?

Costocervical trunk

What are the branches of the costocervical trunk?

1) Deep cervical artery
2) Highest intercostal artery

What structures does the deep cervical artery supply?

Deep muscles on the back of the neck

What structures does the highest intercostal artery supply?

First two intercostal spaces

The third part of the subclavian artery has no branches. What is the exception to this rule?

Instead of having a deep branch of the transverse cervical artery, will have a separate branch off of the third part called the dorsal scapular artery

Where is the subclavian vein located?

1) Begins at lateral border of first rib
2) Anterior to scalenus anterior muscle
3) Ends posterior to medial end of clavicle (at the sternoclavicular joint)

What vessels form the brachiocephalic vein?

1) Subclavian vein
2) Internal jugular

Where do the subclavian and internal jugular veins join?

Poster to the medial end of the clavicle (at the sternoclavicular joint)

Where do the thoracic ducts drain into the venous system?

Left: junction of the subclavian and internal jugular veins
Right: right subclavian vein

Where is the internal jugular vein located?

1) Begins at the jugular foramen at the base of the skull
2) Within the carotid sheath, deep to the sternocleidomastoid muscle
3) Ends posterior to medial end of the clavicle (at the sternoclavicular joint)

What is the function of the anterior jugular vein?

Drains anterior triangle of the neck into the jugular arch

Location of the jugular arch

Above jugular notch of the sternum

What does the jugular arch empty into?

External jugular vein and internal jugular vein (to a lesser extent)

Where is the phrenic nerve located?

Anterior to the subclavian artery, medial to the phrenic nerve

Where does the right recurrent laryngeal nerve branch from?

Right vagus nerve as it passes the subclavian artery

Define the root of the neck

Base of cervical region that is
1) Superior to manubrium and transitions into the superior mediastinum
2) Anterior to the muscles of the prevertebral region and the scalene muscles
3) Lateral to the visceral compartment of the neck

Where does the superior cardiac branch arise from?

Right vagus nerve

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