1. POSTERIOR & ANTERIOR TRIANGLE OF NECK
Dr. H.A.Jaafar
Al-Nahrain University-
college of Medicine
Dept. Of Anatomy

2. Objectives:
At the end of this lecture we should be able to know :
The boundaries, roof, floor & contents of Anterior triangle
The boundaries, contents of posterior triangle
The role of Sternomastoid muscle in main anatomical division of the neck.
What are the careful and careless area of posterior triangle
What are the importance of diagastric and omohyoid muscles as a land marks for subdivision of the two triangular regions of neck.

5. Posterior triangle

6. A. Posterior triangle Is bounded by : roof ………formed by :
posterior border of sternocleidomastoid muscle,
anterior border of trapezius muscle,
superior border of clavicle.
roof ………formed by :
platysma
investing (superficial) layer of deep cervical fascia.
floor :…….formed by :
splenius capitis
levator scapulae muscles
anterior, middle, posterior scalene muscles.

7. Posterior cervical triangle
Sternocleidomastoid
Trapezius
Posterior cervical triangle

8. Is divided into :……. by omohyoid posterior belly occipital triangle.
subclavian (supraclavicular) triangle.
Contains:
accessory nerve,
cutaneous branches of cervical plexus,
external jugular vein,
transverse cervical
suprascapular vessels,
subclavian vein & artery,
Inferior belly of omohyoid,
roots and trunks of brachial plexus.
nerve to subclavius
dorsal scapular,
suprascapular,
long thoracic nerves.

9. Triangles of posterior (lateral) region of neck

10. Triangles of posterior (lateral) region of neck
trapezius muscle
Sternomastoid muscle

11. Triangles of posterior (lateral) region of neck
clavicle
Sternomastoid muscle

12. Triangles of posterior (lateral) region of neck
Occipital triangle
supraclavicular triangle
(greater supraclavicular fossa)

13. Triangles of posterior (lateral) region of neck
Occipital triangle
supraclavicular triangle
(greater supraclavicular fossa)

15. Sternomastoid muscle

16. Sternomastoid muscle
trapezius muscle

17. Sternomastoid muscle
trapezius muscle
clavicle

18. Omohyoidmuscle
Sternomastoid muscle
trapezius muscle
clavicle

19. Omohyoidmuscle Sternomastoid muscle trapezius muscle clavicle
Scalenus anterior muscle

20. Omohyoidmuscle Sternomastoid muscle trapezius muscle clavicle
Scalenus medius muscle
clavicle

21. Omohyoidmuscle Sternomastoid muscle trapezius muscle clavicle
Sterno thyroid m
clavicle

22. Omohyoidmuscle Sternomastoid muscle trapezius muscle clavicle
thyrohyoid m
clavicle

23. Omohyoidmuscle Sternomastoid muscle trapezius muscle clavicle
Sternohyoid m
clavicle

24. apex
trapeziusmuscle
Investing layer of deep fascia roof
Sternomastoid muscle
Middle 1/3 of clavicle – base

25. Nerves in posterior triangle
1-Cervical plexus
2-Brachial plexus
3- spinal root of accessory nerve (11th cranial nerve )
1- four muscular branches
2- four cutaneous branches
Roots , trunks and their branches
1- dorsal scapular nerve –c5(nerve to rhomboids )
2- nerve to subclavius – c5 &c6
3- nerve to serratus anterior –c5,6 &7
Suprascapular nerve –c5&6
It is the most important structure in the occipital triangle

26. Spinal part of accessory nerve

27. Platysma

29. Cutaneous nerves and superficial veins
Lesser occipital n.
External jugular vein
Greet auricular n.
Transverse nerve of neck
Supraclavicular n.
Anterior jugular vein

30. Anterior triangle

31. Anterior triangles Suprahyoidmuscles Infrrahyoidmuscles
Scalene muscles
Prevertebral muscles

32. anterior border of sternocleidomastoid, anterior midline of neck,
B. Anterior triangle
Is bounded by:
anterior border of sternocleidomastoid,
anterior midline of neck,
inferior border of mandible.
roof :……formed by:
platysma
investing layer of deep cervical fascia.
Is further divided by :
omohyoid superior belly
digastric anterior and posterior bellies
into :
digastric (submandibular),
submental (suprahyoid),
carotid,
muscular (inferior carotid) triangles.

33. Omohyoidmuscle
Sternomastoid muscle

34. Omohyoidmuscle
Sternomastoid muscle

35. Omohyoidmuscle
Sternomastoid muscle

36. Omohyoidmuscle
Sternomastoid muscle

37. apex
trapeziusmuscle
Investing layer of deep fascia roof
Sternomastoid muscle
Middle 1/3 of clavicle – base

38. Anterior triangles Suprahyoidmuscles Infrrahyoidmuscles
Prevertebral muscles
Scalene muscles

39. Posterior belly of digastric
Stylohyoid
Anterior belly of digastric muscle
Sternohyoid muscle

40. Digastric triangle
Above …………….lower border of mandible Below & infront …..anterior belly of Digastric muscle Below & behind …..posterior belly of Digastric & stylohyoid muscles . Floor : Anteriorly : ……..mylohyoid muscle Posteriorly ………part of hyoglossus muscle

41. Contents of Digastric triangle
submandibular salivary gland
submandibular lymph nodes
lie on the surface of the gland
facial artery
deep to posterior end of submandibular salivary gland
facial vein
lies superficial to submandibular salivary gland
hypoglossal nerve
nerve to mylohyoid muscle

42. d Anterior belly of digastric Digastric triangle
Posterior belly of digastric
Mylohyoid muscle forms the floor of the mouth

43. Hyoid bone

44. C. Hyoid bone……..Is a U-shaped bone
consisting of :
a median body,
lesser horns (cornua) laterally, …………. paired
greater horns (cornua) posteriorly……… paired
1. Body
Provides for attachments for :
Geniohyoid muscle,
mylohyoid, muscle
Omohyoid muscle,
sternohyoid muscle.
2. Greater horn
Provides attachments for :
middle constrictor,
hyoglossus,
digastric (anterior and posterior) bellies,
stylohyoid,
thyrohyoid muscle.
3. Lesser horn
Provides attachment for :
stylohyoid ligament,
which runs from styloid process to lesser horn

45. Styloid process

46. D. Styloid process Gives origin to :
Is a slender projection of variable length
extends downward & forward from temporal bone.
Gives origin to :
three muscles:
stylohyoid,
styloglossus,
Stylopharyngeus
two ligaments :
stylohyoid
stylomandibular.

47. Carotid triangle boundary : Behind : …………..sternomastoid muscle
Infront & above : posterior belly of digastric muscle
Infront&below : superior belly of omohyoid muscle
Floor : infont : hyoglossus muscle ( above ) and the thyrohyoid muscle (below)
Behind: the middle constrictor muscle of the pharynx (above ) and the inferior constrictor muscle of the pharynx (below )

48. d
Posterior belly of digastric
Carotid triangle

49. apex
trapeziusmuscle
Investing layer of deep fascia roof
Sternomastoid muscle
Middle 1/3 of clavicle – base

50. Internal carotid artery
External carotid artery
Common carotid artery

51. Contents of the Carotid triangle
1- The carotid sheath and its contents :
- common carotid artery : in the lower part of the triangle .
- internal carotid artery : in the upper part of the triangle .
Internal jugular vein : lateral
Vagus nerve : between the artery and the vein but in a more posterior plane .

52. 2- the external carotid artery : gives most of its branches in the carotid triangle ( superior thyroid artery ,lingual artery ,facial artery , ascending pharyngeal artery and occipital artery )
3- hypoglossal nerve
4- Descendes cervicalis (C2,3) anterior to carotid sheath.
5- sympathetic trunk adherent to the posterior wall of carotid sheath

53. Contents of the Muscular triangle
It contains the infrahyoid muscle

54. Contents of the Submental triangle
1- submental lymph nodes
2- beginning of the anterior jugular vein

55. The infrahyoid muscles
They are strap like muscles occupy each side of the midline of the neck , from the hyoid bone to the manubrium sterni .
They consist of 4 muscles arranged into 2 layers :
1- superficial layer : a- sternohyoid
B- omohyoid
2- deep layer: a- sternothyroid
B- thyrohyoid

56. Suprahyoid muscles 1- digastric muscle 2- mylohyoid muscle
3- hyoglossus muscle
4- geniohyoid muscle
5- stylohyoid muscle

57. Geniohyoid muscle
Hyoglossus

58. Submendibular gland
Digastric
Accessory n.
Hypoglossal n.
Superior thyroid a.
Cervical plexus
Ansa cervicalis
Sternothyroid
Phrenic n.
Sternohyoid
Omohyoid
Vagus n.

59. III. Nerves

60. Has both spinal and cranial portions, traverse jugular foramen,
A. Accessory nerve
Is formed by union of :
cranial &
spinal roots.
Has both spinal and cranial portions,
traverse jugular foramen,
they interchange fibers.
cranial roots :
arise from medulla oblongata below roots of vagus.
spinal roots :
arise from lateral aspect of cervical segment of spinal cord
between C1 – C5
unites to form a trunk
ascends between dorsal & ventral roots of spinal nerves in vertebral canal
passes through foramen magnum.

61. cranial portion
contains motor fibers .. join vagus nerve
innervate soft palate, pharyngeal constrictors, & larynx.
spinal portion
innervates sternocleidomastoid & trapezius muscles.
Lies on levator scapulae in posterior cervical triangle
passes deep to trapezius.

62. B. Cervical plexus Is formed by ventral primary rami of C1 to C4.
1. Cutaneous branches
a- Lesser occipital nerve (C2)
Ascends along posterior border of sternocleidomastoid to scalp
behind auricle.
b- Great auricular nerve (C2-C3)
Ascends on sternocleidomastoid
innervate skin behind auricle & on parotid gland.
C- Transverse cervical nerve (C2-C3)
Turns around posterior border of sternocleidomastoid
innervates skin of anterior cervical triangle.
D-Supraclavicular nerve (C3-C4)
Emerges as a common trunk from under sternocleidomastoid
divides into anterior, middle, & lateral branches to skin over clavicle &shoulder.

63. Ansa cervicalis………………Is a nerve loop
2. Motor branches
Ansa cervicalis………………Is a nerve loop
formed by union of :
superior root (C1) descendens hypoglossi
inferior root (C2--C3; descendens cervicalis.
Lies superficial to carotid sheath
in anterior cervical triangle.
Innervates infrahyoid (strap) muscles:
omohyoid,
sternohyoid,
sternothyroid muscles,
with exception of thyrohyoid muscle,
innervated by C1 via hypoglossal nerve.

65. Arises from chiefly from 4th cervical nerve; contains : motor,
Phrenic nerve (C3-C5)
Arises from chiefly from 4th cervical nerve;
contains :
motor,
sensory,
sympathetic nerve fibers;
Provides:
motor supply to diaphragm
sensation to its central part.
Descends on anterior surface of anterior scalene muscle
under cover of sternocleidomastoid muscle.
Passes between subclavian artery & vein at root of neck
enters thorax by crossing in front of origin of internal thoracic artery,
it joins pericardiacophrenic branch of this artery.
Passes anterior to root of lung
between mediastinal pleura & fibrous pericardium
supply sensory fibers to these structures.
longus capitis and cervicis or colli,
sternocleidomastoid,
trapezius,
levator scapulae,
scalene muscles.

66. descends lateral to phrenic nerve,
Accessory phrenic nerve (C5)
arises as a contribution of :
C5 to phrenic nerve or
a branch of nerve to subclavius (C5),
descends lateral to phrenic nerve,
enters thorax by passing posterior to subclavian vein,
joins phrenic nerve below first rib to supply diaphragm.

67. Is formed by union of ventral primary rami of C5 to T1
C. Brachial plexus
Is formed by union of ventral primary rami of C5 to T1
passes between anterior scalene & middle scalene muscles.
1. roots give rise to :
Dorsal scapular nerve (C5)
Emerges from behind anterior scalene muscle
runs downward and backward through middle scalene muscle
deep to trapezius.
Passes deep to levator scapulae
descends along with dorsal scapular artery on deep surface of rhomboid muscles
along medial border of scapula,
Innervating:
levator scapulae
rhomboid muscle.
Long thoracic nerve (C5--C7)
Pierces middle scalene muscle,
descends behind brachial plexus,
enters axilla
innervate ……..serratus anterior.

68. infraspinatus muscles
C. Brachial plexus
2. Iupper trunk gives rise to :
Suprascapular nerve (C5-C6)
Passes deep to trapezius
joins suprascapular artery in a course toward shoulder.
Passes through scapular notch under transverse scapular ligament.
Supplies :
supraspinatus
infraspinatus muscles
Nerve to subclavius muscle (C5)
Descends in front of plexus and behind clavicle
innervate subclavius.
Communicates with phrenic nerve as accessory phrenic nerve

76. Omohyoidmuscle
Sternomastoid muscle

77. apex
trapeziusmuscle
Investing layer of deep fascia roof
Sternomastoid muscle
Middle 1/3 of clavicle – base

78. Posterior belly of digastric
Stylohyoid
Anterior belly of digastric muscle
Sternohyoid muscle