1. The Neck:
Cutaneous Innervation, Muscles, Anterior and Posterior Cervical Triangles and their Subdivisions

2. Objectives
Name the nerves that provide sensory innervation to the skin of the neck and describe the origin, course, and distribution of the cutaneous branches of the cervical plexus
Describe the origin, insertion, action, and nerve supply of the superficial, infrahyoid, suprahyoid, lateral vertebral and anterior vertebral muscles of the neck
Describe the formation of the ansa cervicalis and list the muscles it innervates
List the muscles located in the posterior part of the neck
Name the layers of the deep cervical fascia and describe their arrangement
Describe the boundaries of the anterior and posterior triangles of the neck and their subdivisions and list their main contents

3. Neck
extends from base of cranium and inferior border of mandible to superior thoracic aperture
cranium: strictly speaking consists of skull without mandible
divided into 2 main regions:
anterolateral neck: extends from anterior midline to anterior border of trapezius
posterior neck: extends from anterior border of trapezius to posterior midline

4. Musculature of the Neck

5. Muscle Groups of the Anterolateral Neck
superficial muscles
infrahyoid muscles
suprahyoid muscles
lateral vertebral muscles
anterior vertebral muscles
Superficial Muscles
platysma
sternocleidomastoid

6. Platysma thin muscle embedded in superficial fascia of neck
Origin: deep fascia that covers upper parts of pectoralis major and deltoid muscles
Insertion: fibers pass superficial to clavicle and run superiorly over side of neck  some fibers insert into lower border of body of mandible  other fibers enter face and blend with muscles of lower lip and angle of mouth
Nerve supply: cervical branch of facial nerve
Actions:
tenses skin of neck
helps to depress mandible
draws down lower lip and angle of mouth

7. Sternocleidomastoid
Origin: anterior surface of manubrium of sternum (sternal head) and superior surface of medial third of clavicle (clavicular head)
Insertion: 2 heads of origin join  muscle passes superiorly, posteriorly, and laterally  inserts into mastoid process and lateral part of superior nuchal line
Nerve supply: accessory nerve (motor) and branches from ventral rami of C2 and C3 spinal nerves (proprioceptive)
divides anterolateral part of neck into anterior and posterior triangles

8. Sternocleidomastoid Actions
unilateral contraction:
lateral flexion of head and neck to same side of contracting muscle
rotation of head and neck to opposite side of contracting muscle
bilateral contraction:
draw head forward
flexion of head and neck against resistance (rising from supine position)
if head is fixed, it can act as an accessory muscle of inspiration

11. Infrahyoid Muscles: Depresses hyoid and stabilizes larynx for phonation and swallowing.
sternohyoid
omohyoid
sternothyroid
thyrohyoid
thin, strap-like muscles:

13. Sternohyoid
located superficially, medial to superior belly of omohyoid
Origin: posterior surfaces of manubrium of sternum and sternal end of clavicle
Insertion: body of hyoid
Nerve supply: ansa cervicalis (ventral rami of C1-C3)
Action: depresses hyoid bone

14. Omohyoid
has inferior and superior bellies connected by an intermediate tendon
inferior belly attaches to superior border of scapula, just medial to suprascapular notch  passes anteriorly and superiorly, across lower part of posterior triangle of neck  passes deep to sternocleidomastoid  ends in intermediate tendon
superior belly begins at intermediate tendon  ascends almost vertically in anterior triangle of neck  attaches to body of hyoid, just lateral to sternohyoid
Nerve supply: ansa cervicalis (ventral rami of C1-C3)
Action: depresses hyoid bone

15. Sternothyroid located deep to sternohyoid
Origin: posterior surface of manubrium of sternum
Insertion: oblique line of thyroid cartilage
Nerve supply: ansa cervicalis (ventral rami of C1-C3)
Action: depresses larynx

16. Thyrohyoid upward continuation of sternothyroid
Origin: oblique line of thyroid cartilage
Insertion: runs superiorly over thyrohyoid membrane  inserts into greater horn and body of hyoid
Nerve supply: C1 fibers via hypoglossal nerve
Action: depresses hyoid bone or elevates larynx

17. Suprahyoid Muscles: Elevate hyoid and depress mandible.
digastric
stylohyoid
mylohyoid

18. Digastric
consists of posterior and anterior bellies connected by an intermediate tendon
posterior belly attaches to digastric (mastoid) notch (medial to mastoid process)  runs anteriorly and inferiorly  becomes continuous with intermediate tendon
intermediate tendon pierces stylohyoid and runs in fibrous sling connected to body and greater horn of hyoid  becomes continuous with anterior belly
anterior belly runs anteriorly and superiorly  attaches to digastric fossa of mandible
Nerve supply: posterior belly  facial nerve; anterior belly  nerve to mylohyoid (branch of inferior alveolar nerve, from V3)
Actions: depresses mandible and elevates hyoid bone

19. Stylohyoid Origin: styloid process
Insertion: passes anteriorly and inferiorly, along superior border of posterior belly of digastric  inserts into hyoid bone at junction of body and greater horn
it is pierced near its insertion by intermediate tendon of digastric
Nerve supply: facial nerve
Action: elevates hyoid bone

20. Mylohyoid lies superior to anterior belly of digastric
2 mylohyoid muscles form muscular floor of oral cavity
Origin: mylohyoid line of mandible
Insertion: most posterior fibers attach to body of hyoid bone  rest of fibers terminate in midline raphe extending from mandible to hyoid
Nerve supply: nerve to mylohyoid
Actions: elevates floor of mouth and tongue during swallowing, elevates hyoid bone, depresses mandible

23. Lateral flexion of the neck
Lateral Neck Muscles:
Lateral flexion of the neck
Elevation of the 1st & 2nd ribs (accessory muscles of inspiration
scalenus anterior
scalenus medius
scalenus posterior

24. Scalenus Anterior Origin: transverse processes of C3 to C6 vertebrae
Insertion: superior surface of 1st rib and scalene tubercle (bony prominence on medial border of 1st rib)
Relations:
anterior to scalenus anterior  subclavian vein, phrenic nerve, superficial (transverse) cervical and suprascapular arteries (branches of thyrocervical trunk), and terminal part of thoracic duct (on left side)
posterior to scalenus anterior  brachial plexus and subclavian artery (pass through interscalene triangle  bounded by scalenus anterior, scalenus medius, and 1st rib)

25. Scalenus Medius Scalenus Posterior
largest and longest of scalene muscles
Origin: transverse processes of C2 to C7 vertebrae
Insertion: superior surface of 1st rib, between costal tubercle and groove for subclavian artery
Scalenus Posterior
smallest of scalene muscles
Origin: transverse processes of C4 to C6 vertebrae
Insertion: outer surface of 2nd rib

26. Anterior Vertebral Muscles: Flexion of the Head
longus capitis
longus colli
rectus capitis anterior
rectus capitis lateralis

27. Longus Capitis Origin: transverse processes of C3 to C6 vertebrae
Insertion: inferior surface of basilar part of occipital bone
Nerve supply: branches from ventral rami of C1 to C3 spinal nerves
Action: flexion of head and neck

28. Longus Colli
consists of 3 parts: inferior oblique, superior oblique, and vertical
inferior oblique part: extends from bodies of first 2 or 3 thoracic vertebrae to transverse processes of C5 and C6 vertebrae
superior oblique part: extends from transverse processes of C3 to C5 vertebrae to anterior tubercle of atlas
vertical part: extends from bodies of upper 3 thoracic and lower 3 cervical vertebrae to bodies of C2 to C4 vertebrae
Nerve supply: branches from ventral rami of C2 to C6 spinal nerves
Action: flexion of neck

29. Rectus Capitis Anterior
located posterior to upper part of longus capitis
Origin: anterior surface of lateral mass of atlas and root of its transverse process
Insertion: inferior surface of basilar part of occipital bone, immediately anterior to occipital condyle
Nerve supply: branches from loop between ventral rami of C1 and C2 spinal nerves
Action: flexion of head

30. Rectus Capitis Lateralis
Origin: upper surface of transverse process of atlas
Insertion: inferior surface of jugular process of occipital bone (just lateral to occipital condyle)
Nerve supply: branches from loop between ventral rami of C1 and C2 spinal nerves
Action: lateral flexion of head to same side of contracting muscle

31. Posterior Muscles of the Neck: Extension & Lateral Flexion of the Head
trapezius
levator scapulae
splenius cervicis and capitis
iliocostalis cervicis
longissimus cervicis and capitis
semispinalis cervicis and capitis
multifidus
rotatores
interspinales
intertransversarii
suboccipital muscles (rectus capitis posterior major, rectus capitis posterior minor, obliquus capitis superior, obliquus capitis inferior)

32. Anatomical Divisions of the Anterior Neck
Anterior Triangle
Posterior Triangle

33. Posterior Triangle of the Neck
boundaries:
anteriorly  posterior border of sternocleidomastoid
posteriorly  anterior border of trapezius
inferiorly  middle ⅓ of clavicle
covered by skin, superficial fascia, platysma, and investing layer of deep cervical fascia
floor  splenius capitis, levator scapulae, scalenus posterior, and scalenus medius (all covered by prevertebral layer of deep cervical fascia)  small part of scalenus anterior may be present, but it is usually hidden by sternocleidomastoid
inferior belly of omohyoid crosses inferior part of posterior triangle  divides posterior triangle into occipital triangle (above it) and supraclavicular (omoclavicular or subclavian) triangle (below it)

34. Contents of the Posterior Triangle of the Neck
arteries: subclavian artery (3rd part), superficial (transverse) cervical artery, suprascapular artery, dorsal scapular artery, occipital artery
veins: external jugular vein and its tributaries, subclavian vein (occasionally)
nerves: brachial plexus and branches arising from its roots and trunks, accessory nerve, branches of cervical plexus
some cervical lymph nodes (along course of accessory nerve and superficial/transverse cervical vessels)
inferior belly of omohyoid muscle

35. Anterior Triangle of the Neck
boundaries:
anteriorly: midline of neck
posteriorly: anterior border of sternocleidomastoid
superiorly: inferior border of body of mandible
subdivisions:
submandibular (digastric) triangle
carotid triangle
muscular triangle
submental triangle

36. Submandibular Triangle
boundaries:
anteriorly: anterior belly of digastric
posteriorly: posterior belly of digastric and stylohyoid
superiorly: inferior border of body of mandible
floor: mylohyoid and hyoglossus muscles
contents:
submandibular gland (superficial part)
facial vessels (a. and v.)
submandibular lymph nodes
hypoglossal nerve
mylohyoid nerve and vessels (a. and v.)

37. Carotid Triangle boundaries:
anteriorly and superiorly: posterior belly of digastric
anteriorly and inferiorly: superior belly of omohyoid
posteriorly: anterior border of sternocleidomastoid
contents:
arteries: common carotid, initial segments of external and internal carotid, some branches of external carotid
veins: internal jugular and some of its tributaries
nerves: vagus, accessory, hypoglossal, ansa cervicalis, internal and external laryngeal
deep cervical lymph nodes

38. Muscular Triangle boundaries: anteriorly: anterior midline of neck
posteriorly and superiorly: superior belly of omohyoid
posteriorly and inferiorly: anterior border of sternocleidomastoid
contents:
sternohyoid and sternothyroid muscles
viscera of neck (e.g.: thyroid and parathyroid glands, larynx, trachea)

39. Submental Triangle only unpaired neck triangle boundaries:
laterally: anterior bellies of digastric muscles
inferiorly: body of hyoid
floor: mylohyoid muscles
contents:
submental lymph nodes
small veins that join to form anterior jugular veins

40. Muscles of the Scalp & Face

41. Muscles of the Scalp occipitofrontalis (epicranius):
consists of 4 bellies (2 frontal and 2 occipital) connected by a broad, intermediate fibrous sheet  epicranial aponeurosis (galea aponeurotica)
occipital bellies originate from occipital bone above superior nuchal lines and terminate in epicranial aponeurosis
frontal bellies originate from epicranial aponeurosis and terminate in skin of forehead above eyebrows
draws scalp back; frontal bellies raise eyebrows (surprise), producing transverse wrinkles in forehead
auricular muscles: anterior, superior and posterior  provide little movement in man

44. Parotid Gland largest of major salivary glands
located anterior and inferior to external acoustic meatus in deep hollow between ramus of mandible and sternocleidomastoid muscle
wedge-shaped on lateral view (base above, toward zygomatic arch, and apex below, posterior to angle of mandible)
wedge-shaped in horizontal section (base lateral and apex medial, toward pharyngeal wall)
parotid duct  originates from anterior part of gland  passes anteriorly, superficial to masseter and inferior to zygomatic arch  at anterior border of masseter turns medially and pierces buccal pad of fat and buccinator  opens into vestibule of oral cavity opposite upper 2nd molar tooth

46. Parotid Gland
structures within parotid gland from lateral (superficial) to medial (deep):
facial nerve
retromandibular vein
external carotid artery
anatomic relations:
superficial (lateral): skin, superficial fascia, branches of great auricular nerve
posterior: mastoid process, sternocleidomastoid, posterior belly of digastric, styloid process with attached muscles, carotid sheath with its contents
anterior: ramus of mandible, masseter, medial pterygoid
deep (medial): pharynx

50. Vasculature of the Head & Neck

52. Common Carotid Artery
right common carotid artery originates from brachiocephalic trunk (artery), posterior to right sternoclavicular joint
left common carotid artery originates from aortic arch in superior mediastinum
common carotid artery ascends in neck within carotid sheath to upper border of thyroid cartilage, where it divides into external and internal carotid arteries
within carotid sheath, internal jugular vein lies lateral to common carotid artery and vagus nerve lies between common carotid artery and internal jugular vein, posteriorly

53. Subclavian Artery
right subclavian artery is a branch of brachiocephalic trunk (artery)  begins posterior to right sternoclavicular joint
left subclavian artery is a branch of aortic arch  begins in superior mediastinum
subclavian artery is divided into 3 parts by scalenus anterior muscle:
1st part  from origin to medial border of scalenus anterior
2nd part  posterior to scalenus anterior
3rd part  from lateral border of scalenus anterior to lateral border of 1st rib, where it becomes continuous with axillary artery

55. Subclavian Artery branches of 1st part: vertebral artery
thyrocervical trunk
internal thoracic artery
branches of 2nd part:
costocervical trunk (may originate from 1st part)
3rd part gives rise to dorsal scapular artery or may have no branches

56. Vertebral Artery originates from 1st part of subclavian artery
course is divided into 4 parts:
1st (prevertebral) part  runs superiorly and posteriorly from subclavian artery to transverse foramen of C6, between longus colli muscle (medial to artery) and scalenus anterior muscle (lateral to artery)  inferior cervical sympathetic ganglion (or cervicothoracic/stellate ganglion) lies posterior to 1st part of vertebral artery
2nd (cervical) part  ascends through transverse foramina of C6 to C1, anterior to ventral rami of corresponding spinal nerves

57. 4th (intracranial) part
3rd (atlantic) part
2nd (cervical) part
1st (prevertebral) part

58. Vertebral Artery parts (cont.):
3rd (atlantic) part  runs medially, posterior to lateral mass of atlas, and enters vertebral canal passing under posterior atlanto-occipital membrane  it lies in a groove on superior surface of posterior arch of atlas and it is a content of suboccipital triangle
4th (intracranial) part  pierces dura mater and arachnoid, and ascends into cranial cavity (within subarachnoid space) via foramen magnum  anastomoses with vertebral artery of opposite side to form basilar artery

59. 3rd (atlantic) part
2nd (cervical) part

61. Thyrocervical Trunk
originates from 1st part of subclavian artery, just medial to scalenus anterior muscle, and opposite origin of internal thoracic artery
after a short course, it divides into inferior thyroid, superficial (transverse) cervical and suprascapular arteries
inferior thyroid artery:
contributes to supply larynx, trachea, pharynx, esophagus, thyroid and parathyroid glands
ascends to level of cricoid cartilage and then arches medially, posterior to carotid sheath, to reach lower part of lobe of thyroid gland  as it approaches thyroid gland, it is closely related to recurrent laryngeal nerve

63. Thyrocervical Trunk inferior thyroid artery (cont.):
ascending cervical artery  originates from inferior thyroid artery as it arches medially  ascends on scalenus anterior muscle  supplies adjacent muscles and gives 1 or 2 spinal branches
superficial (transverse) cervical artery  runs laterally and posteriorly, passing anterior to scalenus anterior, phrenic nerve, and brachial plexus  supplies superficial muscles of upper back
suprascapular artery  runs parallel and inferior to superficial (transverse) cervical artery  as it approaches scapula, it is joined by suprascapular nerve  supplies muscles on posterior aspect of scapula

64. Costocervical Trunk
usually originates from 2nd part of subclavian artery
passes posteriorly, over cervical pleura, toward neck of 1st rib, where it divides into supreme (superior) intercostal and deep cervical arteries
supreme (superior) intercostal artery  descends in front of neck of 1st and 2nd ribs  gives off posterior intercostal arteries of upper 2 intercostal spaces
deep cervical artery  passes posteriorly, between transverse process of C7 and neck of 1st rib  ascends between semispinalis capitis and semispinalis cervicis muscles  ends by anastomosing with a branch of occipital artery  it supplies deep muscles of back of neck

66. Veins of the Neck

67. Internal Jugular Vein collects most venous blood from head and neck
begins in jugular foramen, as a continuation of sigmoid sinus  ends posterior to corresponding sternoclavicular joint, where it joins subclavian vein to form brachiocephalic vein
lies within carotid sheath, lateral to internal carotid artery (in upper neck), and lateral to common carotid artery (in lower neck)
deep cervical lymph nodes lie alongside internal jugular vein
upper and lower ends of internal jugular vein are dilated (superior and inferior bulbs)

69. Internal Jugular Vein tributaries:
inferior petrosal sinus  leaves cranial cavity via jugular foramen and drains into superior bulb
lingual vein(s)
pharyngeal veins
facial vein
superior and middle thyroid veins
occipital vein (sometimes)

72. Subclavian Vein
begins at lateral border of 1st rib, as a continuation of axillary vein
passes over 1st rib, anterior and slightly inferior to subclavian artery (separated from it by scalenus anterior muscle)
ends posterior to sternoclavicular joint by joining internal jugular vein to form brachiocephalic vein
has only one constant tributary  external jugular vein

75. Stop

76. Dorsal Scapular Artery
may originate from transverse cervical artery or directly from subclavian artery (usually 3rd part)
runs through brachial plexus (above or below middle trunk)  passes deep to levator scapulae to reach superior angle of scapula  descends along medial border of scapula, deep to rhomboid muscles, with dorsal scapular nerve  supplies neighboring muscles and anastomoses with branches of suprascapular artery (branch of thyrocervical trunk) and subscapular artery (branch of axillary artery)

77. External Carotid Artery
begins at upper border of thyroid cartilage  ascends in carotid triangle  leaves carotid triangle as it passes deep (medial) to posterior belly of digastric and stylohyoid  terminates within substance of parotid gland, posterior to neck of mandible, dividing into superficial temporal and maxillary arteries
branches:
anterior branches: superior thyroid, lingual and facial arteries
posterior branches: occipital and posterior auricular arteries
medial branch: ascending pharyngeal artery
terminal branches: superficial temporal and maxillary arteries

78. Superior Thyroid Artery
originates from initial part of external carotid artery
descends almost vertically to reach upper pole of lobe of thyroid gland
supplies thyroid and parathyroid glands, infrahyoid muscles and larynx
Lingual Artery
originates from external carotid artery opposite tip of greater horn of hyoid
initial segment is crossed superficially (laterally) by hypoglossal nerve  passes deep to hyoglossus muscle
gives off branches that supply tongue, palatine tonsil, soft palate, sublingual gland, mylohyoid muscle and mucosa of floor of mouth

79. Facial Artery
originates immediately above lingual artery (sometimes by a common trunk with it)
first ascends medial (deep) to posterior belly of digastric and stylohyoid muscles  arches laterally over these two muscles and submandibular gland  curves around inferior border of mandible, anterior to masseter, to enter face (area where its pulse can be felt)
before it enters face, it gives off branches that contribute to supply pharynx, soft palate, palatine tonsil, submandibular gland and neighboring muscles

80. Occipital Artery
originates from posterior aspect of external carotid artery, close to inferior border of posterior belly of digastric
passes posteriorly and superiorly, deep (medial) to posterior belly of digastric and mastoid process  reaches back of scalp  its terminal branches accompany branches of greater occipital nerve and supply posterior part of scalp
along its curse, it gives off branches that supply auricle, middle ear, mastoid air cells, cranial dura mater and neighboring muscles

81. Posterior Auricular Artery
arises from posterior aspect of external carotid artery at upper border of posterior belly of digastric
passes posteriorly and superiorly to reach notch between cartilage of external acoustic meatus and mastoid process  it supplies auricle, middle ear, scalp above and behind ear, parotid gland and neighboring muscles
Ascending Pharyngeal Artery
smallest branch of external carotid artery  arises near its origin
ascends along pharyngeal wall toward cranial base, medial to internal carotid artery
supplies pharynx, soft palate, palatine tonsil, middle ear and cranial dura mater

82. Superficial Temporal Artery
upward continuation of external carotid artery
ascends anterior to ear with auriculotemporal nerve and superficial temporal vein  passes superficial (lateral) to root of zygomatic process of temporal bone (area where pulse can be felt)
superior to zygomatic process of temporal bone, it divides into anterior (frontal) and posterior (parietal) branches  supply frontal, temporal and parietal regions of scalp
also gives branches to parotid gland, external ear, face and temporomandibular joint

83. Maxillary Artery
largest of 2 terminal branches of external carotid artery
passes anteriorly, deep to neck of mandible  runs through infratemporal fossa, and terminates in pterygopalatine fossa
gives off branches that supply external and middle ear, cranial dura mater, upper and lower teeth and gingiva, muscles of mastication, face, hard and soft palate, palatine tonsil and nasal cavity

87. Scalp
part of head that extends from superciliary arches (anteriorly) to external occipital protuberance and superior nuchal lines (posteriorly)  on each side extends inferiorly to zygomatic arch
layers (first 3 layers are tightly bound together and move as a unit):
Skin (thick and hair bearing with numerous sebaceous glands)
Connective tissue (dense with numerous arteries, veins and nerves)
Aponeurosis (epicranial aponeurosis, galea aponeurotica)  connects frontal and occipital bellies of occipitofrontalis
Loose connective tissue (allows movement of 3 superficial layers over skull)
Pericranium (periosteum covering outer surface of bones of calvaria)

88. Arterial Supply of the Scalp
main arteries lie in connective tissue deep to skin and freely anastomose with each other  arteries are accompanied by corresponding veins (freely anastomose with each other and are connected to diploic veins and intracranial venous sinuses via emissary veins)
arteries:
supratrochlear artery (from ophthalmic artery)
supraorbital artery (from ophthalmic artery)
zygomaticotemporal artery (from ophthalmic artery)
superficial temporal artery (from external carotid artery)
posterior auricular artery (from external carotid artery)
occipital artery (from external carotid artery)

89. Subclavian Vein
begins at lateral border of 1st rib, as a continuation of axillary vein
passes over 1st rib, anterior and slightly inferior to subclavian artery (separated from it by scalenus anterior muscle)
ends posterior to sternoclavicular joint by joining internal jugular vein to form brachiocephalic vein
has only one constant tributary  external jugular vein

92. Innervation of the Head, Face & Neck
Cranial Nerves
Sensory Nerves

93. Cutaneous (Sensory) Innervation of the Head & Neck
skin of back of scalp and back of neck is supplied by dorsal rami of spinal nerves C2-C5 (dorsal rami of C1 and C6-C8 normally have no cutaneous distribution)
skin of anterior and lateral aspects of neck is supplied by ventral rami of C2-C4 spinal nerves via cutaneous branches of cervical plexus  emerge from underneath posterior border of sternocleidomastoid muscle
cutaneous branches of cervical plexus:
lesser occipital nerve (C2)  follows posterior border of sternocleidomastoid  supplies skin over lateral part of occipital region and upper part of medial surface of auricle

94. Cutaneous Innervation of the Head & Neck
cutaneous branches of cervical plexus (cont.):
great auricular nerve (C2, C3)  ascends superficial to sternocleidomastoid, parallel to external jugular vein  supplies skin over angle of mandible and parotid gland, and both surfaces of lower part of auricle
transverse cervical nerve (C2, C3)  runs anteriorly, superficial to sternocleidomastoid  supplies skin of anterior and lateral aspects of neck
supraclavicular nerves (C3, C4)  arise by a common trunk, which divides into medial, intermediate, and lateral supraclavicular nerves  descend across side of lower neck  supply skin at base of neck and skin that covers upper parts of pectoralis major and deltoid muscles

96. Putting It All Together