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TRIANGLES OF THE NECK

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Introduction

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  • The side of the neck presents a somewhat quadrilateral outline .
  • It 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.
  • Medially, by the midline of the neck.
  • Posteriorly, by the anterior border of the Trapezius muscle .

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Quadrilateral outline in the neck

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Sternocleidomastoid Muscle

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Sternocleidomastoid Muscles

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  • This quadrilateral space is divided by the Sternocleidomastoid muscle into two main triangles .
  • It passes obliquely upwards and backwards from its site of origin at the clavicle and sternum to its point of insertion on the mastoid process and the occipital bone .
  • The triangle in front of this muscle is the anterior triangle and the one behind it is the posterior triangle .

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Anterior Triangle

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Posterior triangle

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THE ANTERIOR TRIANGLE

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ANTERIOR TRIANGLE

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  • BOUNDARIES
    • Anterior border of the SCM muscle
    • midline of the neck
    • inferior border of the mandible
  • ROOF
    • Skin
    • Superfacial fascia and platysma muscle
    • Investing layer of deep cervical fascia

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SUBDIVISIONS OF THE ANTERIOR TRIANGLE

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  • The anterior triangle is divided into four

smaller triangles:

    • SUBMENTAL TRIANGLE
    • SUBMANDIBULAR TRIANGLE
    • CAROTID TRIANGLE
    • MUSCULAR TRIANGLE

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SUBMENTAL TRIANGLE

  • Borders
    • Body of hyoid
    • Anterior digastric on right
    • Anterior digastric on left
  • Floor : Mylohyoid
  • Roof is made of the:
    • Skin
    • Superficial fascia with platysma
    • Deep cervical fascia
  • Submental triangle is unpaired
  • Content: Anterior Jugular vein and sub-mental lymph

nodes

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SUBMANDIBULAR TRIANGLE

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  • Borders
    • Inferior border of the mandible
    • Posterior digastric
    • Anterior digastric
  • Floor of the triangle
    • Hyoglossus
    • Mylohyoid
    • Middle constrictor
  • Roof is made of the:
    • Skin
    • Superficial fascia with platysma
    • Deep cervical fascia
  • Submandibular triangle is paired

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SUBMANDIBULAR TRIANGLE

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  • Lesser’s triangle is a small subdivision of the submandibular triangle, which aids in identifying the lingual artery (especially for ligation)
  • Boundaries of Lesser’s triangle:
    • Hypoglossal nerve
    • Anterior digastric
    • Posterior digastric

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SUBMANDIBULAR TRIANGLE

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SUBMANDIBULAR

TRIANGLE: Content

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  • Arteries
    • Facial
    • Sublingual
    • Submental
  • Veins: same as arteries
  • Nerves : Mylohyoid and hypoglossal
  • Structures
    • Submandibular gland
    • Inferior portion of parotid gland
    • Submandibular lymph node

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CAROTID TRIANGLE

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  • Named because parts of all three carotid arteries are located within it
  • Borders of the carotid triangle:
    • Anterior border of the sternocleidomastoid
    • Posterior digastric
    • Superior omohyoid
  • Floor of the triangle is composed of the:
    • Hyoglossus
    • Thyrohyoid
    • Middle constrictorInferior constrictor
  • Roof
    • Skin
    • Superficial fascia with platysma
    • Deep cervical fascia
  • Carotid triangle is paired

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CAROTID TRIANGLE

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CAROTID TRIANGLE

  • Arteries
  • Common carotid (with carotid body)
  • Internal carotid (with carotid

sinus)

  • Superior thyroid (with superior Superior thyroid
  • Lingual
  • Facial
  • Ascending pharyngeal
  • Occipital
  • Vein
  • Internal Jugalar vein
  • Common facial vein
  • Lingual Vein
  • Superior Thyroid vein
  • Middle thyroid vein
  • Nerves

– Vagus

  • External laryngeal
  • Internal laryngeal
  • Spinal Acessory
  • Hypoglossal
  • Ansa cervicalos
  • Sympathetic trunk
  • Structures
    • Larynx
    • Thyroid

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MUSCULAR TRIANGLE

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  • Borders
    • Anterior border of the sternocleidomastoid
    • Superior omohyoid
    • Midline
  • Floor
    • Sternohyoid
    • Sternothyroid
  • Roof
    • Skin
    • Superficial fascia with platysma
    • Deep cervical fascia
  • Muscular triangle is paired

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MUSCULAR TRIANGLE

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MUSCULAR TRIANGLE:

Content

  • Arteries
    • Superior thyroid
  • Veins
    • Inferior thyroid
    • Anterior jugular
  • Nerves: Ansa cervicalis
  • Structures
    • Strap muscles: Sternohyoid, Sternothyroid, Thyrohyoid
    • Thyroid gland
    • Parathyroid gland
    • Larynx
    • Trachea

– Esophagus

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MUSCULAR TRIANGLE:

Content

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Posterior triangle

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  • Boundaries
    • SCM anteriorly
    • Trapezius muscle, posteriorly.
    • Clavicle, inferiorly.
  • The apex of the triangle is formed by the occipital bone.
  • The ROOF of the posterior triangle is formed by:
    • Skin
    • Superficial fascia
    • Platysma muscle
    • Investing layer of the deep cervical fascia

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FLOOR

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Formed by the following muscles from above downwards:

  • Splenius Capitis
  • Levator scapulae
  • Posterior scalene
  • Middle scalene
  • Anterior scalene

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Subdivisions of the posterior triangle

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  • The posterior triangle is further divided into two smaller triangles by the Inferior belly of the Omohyoid muscle.
  • Supraclavicular triangle
    • Inferior belly of the Omohyoid
    • the Clavicle,
    • Sternocleidomastoid muscle
  • Occipital triangle
    • Inferior belly of the Omohyoid
    • Trapezius muscle
    • Sternocleidomastoid muscle

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CONTENTS: NERVES

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  • Spinal acessory nerve.
  • Branches of Cervical plexus
    • Lesser occipital
    • Transverse cervical
    • Great auricular
    • Supraclavicular
  • Roots and trunks of brachial plexus.
  • Dorsal scapular
  • Long thoracic
  • Phrenic

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VESSELS

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  • Arteries
    • Subclavian artery
    • Transverse Cervical artery
    • Suprascapular artery
  • Vein
    • External jugular vein (terminal part)
  • Lymph Nodes
    • Occipital
    • Supraclavicular

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CLINICAL SIGNIFICANCE OF THE POSTERIOR TRIANGLE

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  • The Accessory Nerve may be damaged, while taking lymph node biopsy.
  • The External Jugular Vein is present in a superficial location here and this makes it vulnerable to injury.

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