Anatomy of the posterior triangle of the neck-The neck is limited above by the lower border of the body of the mandible and an imaginary line drawn from the angle of the mandible to the mastoid process. Below it is limited by the upper border of the clavicle. Posteriorly , by the anterior border of the trapezius muscles.

1. Posterior Triangle
PRESENTED BY DR. SHOVITA MONDAL
DEPARTMENT OF ORAL AND MAXILLOFACIAL SURGERY
AWADH DENTAL COLLEGE AND HOSPITAL

2. OBJECTIVES
INTRODUCTION
BOUNDARIES
SUBDIVISIONS
CONTENTS
APPLIED ANATOMY

3. INTRODUCTION
 The neck is limited above by the lower border of the body of the mandible and an
imaginary line drawn from the angle of the mandible to the mastoid process.
 Below it is limited by the upper border of the clavicle.
 Posteriorly , by the anterior border of the trapezius muscles.

4. POSTERIOR TRIANGLE
 Posterior triangle is a space on the side of the neck situated behind the
sternocleidomastoid muscle.
BOUNDARIES
Anterior: Posterior border of sternocleidomastoid
Posterior: Anterior border of trapezius
Inferior : Middle one third of clavicle
Apex: lies on the superior nuchal line

5. Roof:
 Roof of the posterior triangle is formed by
Skin
Superficial fascia
platysma muscle
investing layer of deep cervical fascia
FLOOR
is formed by prevertebral layer layer of deep cervical fascia covering the following muscles
Splenius Capitis
Levator scapulae
Anterior scalene
Middle Scalene

6. SUBDIVIDION OF POSTERIOR TRIANGLE
 Inferior belly of Omohyoid divides the triangle into two parts- Upper larger part
which is also known as Occipital Triangle and the small part is Subclavian
triangle.

7. Contents:
 Nerve supply-

8. LYMPH NODES

9. Clinical Anatomy
 The most common swelling in posterior triangle is due to enlargement of the
supraclavicular lymph nodes. These nodes are commonly enlarged in tuberculosis,
hodgekins disease and in malignant growths of the brest, arm or chest.
 Dysphagia Lusoria.

10. EXTERNAL JUGULAR VEIN :

11. CLINICAL ANATOMY:
 As external jugular vein pierces the fascia , the margins of the vein get adherent to
the fascia. So if the vein get cut, it can not close and air is sucked in due to
negative intrathoracic pressure, that causes air embolism.

12. Sternocleidomastoid Muscle
 Also known as Sternomastoid, one of the large superficial muscle of the neck .
supplied by spinal root of accessory nerve.
 ORIGIN:
Sternal Head- The sternal head is tendinous and arises from the superolateral
part of the front of the manubrium sterni.
The Clavicular head is arises form medial one third of the superior surface of
the clavicle.
INSERTION : It is inserted by thick tendon into the lateral surface of mastoid process.

13. Nerve supply
 Spinal accessory nerve provides the motor supply.

14. Blood Supply
 Two branches from the occipital artery , one branch from superior thyroid artery
one from suprascapular artery.

15. Actions:
 When one muscle contracts it turns the chin to the opposite side.
 When both muscles contracts together they draw the head forwards, as in eating
and in lifting the head from a pillow.
 It also helps in forced inspiration.

16. CLINICAL ANATOMY
 TORTICOLLIS: It is a deformity in which the head is bent to one side and the
chin point to another side,. This is a result of spasm or contracture of the muscles
supplied by the spinal accessory nerve.

17. TRAPEZIUS MUSCLE :
 The trapezius is a broad flat, superficial muscle extending from the cervical to thoracic region on
the posterior aspect of the neck and trunk. The muscle is divided into 3 parts – descending.
Ascending and middle part.

18. Origin
 The muscle attaches to the middle third of superior nuchal line, external occipital
protuberance, and spinous process of c7- t12 vertebrae.
 INSERTION : The muscle inserts on the lateral third of clavicle.
 NERVE SUPPLY : Spinal root of accessory nerve and cervical nerve (c3 and c4)
 Blood Supply: transverse cervical artery.

19. Dia 0.5o

20. Clinical Anatomy :
The accessory nerve can be injured more distally in the neck by trauma or by
surgical exploration in the posterior triangle. If the accessory nerve is sacrificed as a
part of radical neck dissection , and the innervation of trapezius is lost the patients
develops INTRACTABLE NEURALGIA due to traction on the branchial plexus .

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