POSTERIOR TRIANGLE

BY DR . M.MD. MUSTAFA SHARIFF DEPT OF ANATOMY SENIOR LECTURER SRMDC & H POSTERIOR TRIANGLE

• This is a triangular depressed space present above the middle one third of and behind the sternocleidomastoid muscle. POSTERIOR TRIANGLE OFNECK • Boundaries • – Infront – posterior border of sternocleidomastoid muscle

• Behind – anterior border of

• Base – Superior surface of middle 1/3rd of clavicle

• Apex – Superior nuchal line where sternocleidomastoid and trapezius muscles meet

• Roof – Skin, superficial fascia (platysma), investing layer of STERNOCLEIDOMASTOID MUSCLE (SCM)

Origin:

• Sternal head --- manubrium • Clavicular head --- medial 1/3 of clavicle

Insertion:

• Mastoid process and lateral ½ of superior nuchal line Action: • When muscle of one side contracts, the head is tilted to the same side and chin is rotated to opposite side.

• When muscles of both side contract the head and are flexed

Nerve supply: • Spinal part accessory , ventral rami of spinal C2,C3 TRAPEZIUS MUSCLE Origin: ✓ Superior nuchal line, ext. occipital protuberance, lig. nuchae, spines of C7 – T12

Insertion: ✓ Lateral 1/3 of clavicle, , spine of scapula

Functions:

✓ Elevation of scapula (sup. fibers), ✓ Depression of scapula (inf. fibers), ✓ Retraction of scapula (middle fibers), ✓ Superior rotation of glenoid fossa of scapula (sup. + inferior fibers). ROOF OF THE POSTERIOR TRIANGLE

• The ROOF of the posterior triangle is the platysma m. and the investing layer of deep

cervical fascia. Investing layer of deep cervical fascia • The platysma is a muscle of facial expression and will be Platysma m. discussed later. Roof is pierced by : Nerves :

✓ Lesser occipital, Anterior

✓ Great auricular,Superior

✓ Transverse cutaneous nerve of the neck, Posterior

✓ , Inferior • The FLOOR of the post. Muscles of floor triangle is the Splenius capitis Levator Scapulae Splenius capitis m.

Levator scapulae m. Post., mid., & • Posterior, ant.scalene .m middle, and Anterior . CONTENT OF POSTERIOR TRIANGLE • The spinal and the lymph nodes are the true content of posterior triangle and all others are behind or front of the fascial floor.

• Inferior belly of omohyoid • Accessory nerve • Root, trunks of and their branches. • Nerve to rhomboideus • Nerve to serratus anterior • Nerve to subclavius • Supra clavicular • Greater occipital nerve • Great auricular nerve • • Transverse cervical nerve • Supraclavicular nerve • Third and fourth cervical nerve supplying trapezius

Arteries: • Occipital artery emerges from the apex. • Third part of subclavian artery and branches of subclavian artery. • Transverse cervical artery Veins: • and its tributaries.

Lymphoid nodes: • Supraclavicular lymph nodes are present along the posterior border of sternomastoid.

• Occipital lymph node CONTENT OF POSTERIOR TRIANGLE SUBDIVISION OF POSTERIOR TRIANGLE

• Inferior belly of • • Supraclavicular triangle Occipital triangle: Boundaries Floor • semispinalis capitis • Splenius capitis • Levator scapulae • S-medium and post Contents of occipital triangle:

• Spinal part of accessory nerve– C3, C4 • Dorsal scapular nerve (C5) • Four cutaneous branches • Lesser occipital nerve (C2) • Great auricular nerve (C2, C3) • Transverse cervical of neck (C2, C3) • Supraclavicular nerve (C3, C4) • Upper trunk of brachial plexus • Superficial cervical artery • Occipital artery (occasional) SUPRACLAVICULAR TRIANGLE OR (SUBCLAVIAN TRIANGLE) Boundaries Roof :

• Skin

• S/F (platysma)

• investing layer of deep cervical fascia, pierced by three diverging branches of supraclavicular nerve and external jugular vein Floor

• Outer border of 1st rib

• S. medius (near insertion)

• 1st digitation of serratus anterior.

• Usually serratus anterior overlapped by sternocleidomastoid muscle. Contents

• Third part of subclavian artery • Subclavian vein • Terminal part of external jugular vein • Trunk of brachial plexus • Dorsal scapular nerve (C5) • Long thoracic nerve (C5-C7) • Nerve to subcalvius (C5) • Supraclavicular nerve (C3, C4) • Superficial cervical, Suprascapular, dorsal scapular arteries • Posterior inferior group of deep cervical lymph nodes

EXTERNAL JUGULAR VEIN • It lies deep to the platysma.

• It is formed by union of the posterior auricular vein with the posterior division of retromandibular vein.

• It begins within the parotid gland,

• Cross the sternocleidomastoid obliquely,

• Pierce the antero inferior angle of the roof of the posterior triangle and into the subclavian vein. • As it pierce the fascia, the margins of the vein get adherent to the fascia.

• So if the vein gets cut , it cannot close and the air enters into it and causes air embolism.

• To prevent this , the deep fascia has to be cut.

Its tributaries are

• Posterior external jugular vein. • The transverse cervical vein

• The supra scapular vein

• The anterior jugular vein

• The oblique jugular vein connects the external jugular vein with the internal jugular vein across the middle one third of the anterior border of the sternocleidomastoid. CLINICAL ANATOMY • The most common swelling in the posterior triangle is due to enlargement of the supraclavicular lymph nodes.

• A swelling in this region may also be caused by a lipoma. • Left supraclavicular (Virchow’s) lymph nodes are enlarged in malignancy of testis, stomach, and other abdominal organs.

• The pressure in the external jugular vein can be recorded in the recumbent position.

• It is increased in right side heart failure and in obstruction of the superior vena cava.

• The retropharyngeal abscess may be expressed in the lower part of the posterior triangle. REFERENCES o EXAM-ORINTED ANATOMY SHOUKAT N.KAZI o TEXT BOOK OF ANATOMY HEAD NECK AND BRAIN VOL III VISHRAM SINGH o HEAD & NECK AK DATTA 5TH EDITION o GRAYS ANATOMY STUDENTS EDITION o CLINCAL ANATOMY SNELL 8TH EDITION o CLINICAL ANATOMY MOORE 5TH EDITION o HEAD & NECK BD CHAURASIA’S 4TH EDITION o HEAD & NECK DR.AS.MONI