Mbbs triangles of neck anatomy

Triangles of Neck

Dr.R.Arulmoli

Learning objectives

Name the triangles of neck.

Describe the boundaries, contents & clinical importance of posterior triangle of neck.

Describe the boundaries, divisions, contents & clinical importance of anterior triangle of neck.(submental,digastric and carotid)

Neck-boundaries

Anterior- anterior median line.

Posterior-anterior border of trapezius.

Superior-base of the mandible to the mastoid process.

Inferior-clavicle.

Bony Structures

mandible

skull base

sella

C1

C2

C3

C4

C5

C6

C7

hyoid

Deep cervical fascia(fascia colli)

Deep fascia of neck – 4 modifications:

1. Investing layer- encloses 2 muscles (trapezius & sternocleidomastoid), 2 salivary glands (parotid & submandibular).

2. Pretracheal fascia - in front of the trachea & encloses thyroid gland.

3. Carotid sheath- encloses common carotid artery, internal carotid artery, internal jugular vein & vagus nerve.

4. Prevertebral fascia- forms the floor of posterior triangle encloses prevertebral muscles.

Deep cervical fascia

Investing layer

Pretracheal layer

Carotid sheath

Prevertebral layer

Triangles of neck

The sternocleidomastoid muscle divides the side of the neck into anterior and posterior triangles.

Triangles of neck

Posterior triangle of neck

Posterior triangle- boundaries

Anterior – Posterior border of sternocleidomastoid

muscle.

Posterior – Anterior border of trapezius muscle.

Inferior – Middle 1/3 of clavicle.

Posterior triangle- boundaries

Posterior triangle- Divisions

The inferior belly of omohyoid muscle divides the posterior triangle into 2 triangles.

1. Occipital triangle- larger upper one.

2. Supraclavicular triangle- smaller lower one.

Posterior triangle - Roof

Skin.

Superficial fascia containing :

- Platysma

- External jugular vein

- Cutaneous nerves arising from cervical plexus

- Lymph vessels

Investing layer of deep cervical fascia.

Platysma

Platysma

Origin: Arise from the pectoral fascia (deep fascia).Insertion:Ascends up and inserted into the base of the mandible and skin of the face. Nerve supply: Facial nerve (cervical branch) Action:Depresses the mandible and pulls down the angle of mouth in horror or surprise.

External jugular vein

Ext. Jugular Vein

Formation:Formed by the union of posterior auricular vein and the posterior branch of retromandibular vein.Course :Descends in the superficial fascia across the sternocleidomastoid.Termination: Pierces the deep fascia,descends behind the clavicle and drains into the subclavian vein.

External jugular vein - termination

EXT.JUGULAR VEIN

SUBCLAVIAN VEIN

External jugular vein-clinical significance

External jugular vein is distended in cardiac failure.

Injury to the vein in the region where it pierces the deep fascia, may lead to air embolism.

Cutaneous nerves - cervical plexus

Formation: Ventral rami of C1-C4.

Branches:

Cutaneous -

1.Lesser occipital (C2)

2.Great auricular (C2,3)

3.Anterior or transverse cutaneous nerve of neck (C2,3)

4.Supraclavicular nerve(C3,4)

Cervical plexus- Cutaneous Nerves

Cervical plexus- Cutaneous Nerves

Posterior Triangle - Floor

Prevertebral layer of deep cervical fascia.

Prevertebral muscles –

Semispinalis capitis-inconstant

Splenius capitis

Levator scapulae

Scalenus posterior

Scalenus medius

Scalenus anterior

Posterior triangle - Floor

Scalene muscles

Scalenus anterior

Scalenus medius

Scalenus posterior

Posterior triangle - Contents

1.Spinal Accessory Nerve – XI cranial nerve

2.Cutaneous nerves of cervical plexus – -Lesser occipital nerve - Great auricular nerve - Transverse cutaneous nerve of neck - Supra clavicular nerves.

3. Muscular branches to - - Levator scapulae - Rhomboides - Serratus anterior - Subclavius

4. Trunks of brachial plexus

5. Third part of subclavian artery and vein.

6. Transverse cervical artery and vein

7. Lymph nodes- occipital & supraclavicular nodes.

Posterior triangle - Contents

Accessory nerve

Accessory nerve

Posterior triangle - Contents

Trunks of brachial plexus

Sternocleidomastoid

Origin- Sternal head from front of manubrium sterni & Clavicular head from medial 1/3 of clavicle. Insertion- Mastoid process & lateral half of superior nuchal line.

Nerve supply- Motor- Spinal part of accessory nerve. Sensory- Ventral ramus of C2.

Action - Turns the face to opposite side & tilt the head towards the shoulder(one muscle).

Draw the head forwards (both muscles).

Sternocleidomastoid: Torticollis or Wry Neck

Deformity where head is bent to one side and chin points to opposite side.

Due to spasm of muscles supplied by accessory nerve- (sternocleidomastoid & trapezius).

Posterior triangle - Clinical Importance

Common swellings in the posterior triangle:

- Enlarged supraclavicular lymph nodes.

- Lipoma.

- Cystic hygroma.

Enlarged left supraclavicular node (Virchow’s node)- occurs in cancer of stomach & testis.

Anterior triangle of Neck

Anterior triangle of Neck

Boundaries:

Superior - Inferior margin of Mandible

Anterior - Midline of Neck

Posterior - Sternocleidomastoid muscle

Anterior triangle of Neck

Anterior triangle - subdivision

1. Submental triangle

2. Digastric triangle

3. Carotid triangle

4. Muscular triangle

Anterior triangle- subdivision

Submental triangle

Submental triangle

Boundaries:

Side - Anterior belly of digastric muscle.

Base - Body of hyoid bone.

Apex- Chin.

Roof :

Skin,superficial fascia,

deep fascia.

Floor: Mylohyoid muscles.

Contents:

• Submental lymph nodes.

• Submental vein.

Submental triangle - floor

Digastric triangle

Digastric triangle (submandibular triangle)

Boundaries :

Antero inferior- Anterior belly of digastric.

Postero inferior- Posterio belly of digastric.

Superior (Base) - Base of the mandible.

Roof :

Skin,

Superficial fascia with platysma,

Cervical branch of facial nerve,

Transverse cut. nerve of neck.

Floor :

Mylohyoid & hyoglossus muscle.

Digastric triangle

Digastric triangle

Digastric triangle - contents

Submandibular salivary gland

Facial vein

Facial artery

Submandibular lymph nodes

Mylohyoid nerve & vessels

Hypoglossal nerve

External carotid artery

Glossopharyngeal nerve.

PROFESSOR: Who talks in someone else's sleep.

Carotid triangle

Carotid triangle

Boundaries:

Superior- Posterior belly of digastric & stylohyoid.

Anteroinferior- Superior belly of omohyoid.

Posterior- Anterior border of sternocleidomastoid.

Carotid triangle

Boundaries:

Superior- posterior belly of digastric & stylohyoid.

Anteroinferior- superior belly of omohyoid.

Posterior- anterior border of sternocleidomastoid

Carotid triangle

Roof :

Skin, superficial fascia with platysma & investing layer of deep cervical fascia.

Floor :

Thyrohyoid muscle

Hyoglossus muscle

Middle constrictor muscle

Inferior constrictor muscle.

Carotid triangle

Contents:

Arteries – common carotid artery, internal carotid artery & external carotid artery with its branches, superior thyroid, lingual, facial, ascending pharyngeal,occipital

Veins - Internal jugular vein, common facial vein, lingual vein.

Nerves - Vagus nerve, superior laryngeal nerve, spinal accessory nerve, hypoglossal nerve, ansa cervicalis, sympathetic chain.

Lymph nodes- Deep cervical nodes:jugulo-digastric & jugulo-omohyoid.

Carotid triangle- contents

Carotid triangle- contents - Ansa cervicalis

Thin nerve loop embedded in the anterior wall of carotid sheath.

Formation:

- Superior root – C1 fibres pass along hypoglossal nerve.

- Inferior root – C2 & C3.

Carotid triangle- contents - Ansa cervicalis

Ansa cervicalis

Carotid triangle- contents

Muscular triangle

Muscular triangle

Boundaries:

Anterior- Midline of neck from hyoid bone to sternum.

Posterosuperior-Superior belly of omohyoid.

Posteroinferior-Anterior border of sternocleidomastoid.

Contents :• Infrahyoid muscles - Sternohyoid - Omohyoid - Sternothyroid - Thyrohyoid

Muscular triangle - contents

Infra hyoid muscles

Sterno hyoid

Summary

Hodgkin’s lymphoma Submandibular abscess

Thyroid nodule

Any questions ?

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