Anatomy of Neck Triangles: Structures and Boundaries
Apr 24, 2023
Anatomy of neck triangles is an important topic for NEET PG preparation. This blog post will help you understand what are Neck Triangles, the Anatomy of Neck Triangles, their structures and boundaries in detail. So, let’s get started!
Q. All of the following are in the anterior triangle of neck EXCEPT
Digastric
Subclavian
Muscular
Submental
Subclavian is in the posterior triangle
Explanation
Posterior triangle has two parts
Occipital
Subclavian
Anterior triangle has 3 parts
Digastric
Muscular
Submental
Posterior triangle
Anterior triangle
Boundary - Sternocleidomastoid
Origin from sternum and clavicle
Inserted into mastoid
Posterior triangle
Boundaries
Anteriorly - sternocleidomastoid
Posteriorly - trapezius muscle
Base - middle 1/ 3 of clavicle
Omohyoid has superior or anterior belly and inferior or posterior belly
Inferior belly of omohyoid divides posterior triangle into
Larger occipital triangle
Smaller subclavian triangle
Occipital triangle - near occipital bone
Subclavian triangle
Block can be given in posterior triangle of neck - subclavian triangle
Third part of subclavian artery can be blocked here
Cervical plexus block
Brachial plexus block
Anterior triangles
Carotid triangle - bounded by superior belly of omohyoid
Common carotid artery bifurcation
All 3 arteries - common carotid, external and internal carotid arteries are contents
Digastric triangle
bounded by anterior and posterior belly of digastric
In Reynaud’s phenomenon → the periphery becomes pale → severe ischemia → gangrene
Anterior triangle - carotid triangle
In front of sternomastoid
Contents
Common carotid artery
Internal jugular vein
CN X
Ansa cervicalis
Sympathetic trunk (stellate ganglion block )
CN XII
Posterior triangle
Occipital triangle and Subclavian triangle
Contents
Subclavian artery
External jugular vein
Cervical plexus (nerve block)
Brachial plexus trunk
Phrenic nerve
CN XI
Three blocks can be given in posterior triangle
Brachial plexus can be blocked - multiple fracture of upper limb
Lateral to scalenus anterior in subclavian triangle
Cervical plexus block
Subclavian artery block
Cervical plexus block
Posterior border of sternomastoid
In the midpoint of sternomastoid
Gives 4 branches
Greater auricular nerve
Lesser occipital nerve
Transverse cervical nerve
Supraclavicular nerve
Spinal accessory nerve - supply sternomastoid and trapezius
While draining an abscess in the posterior triangle - be careful
Surface mark the spinal accessory nerve
To avoid iatrogenic injury to 11th nerve
This paralyzes trapezius → difficulty in shrugging the shoulder
The Sternomastoid is spared
Because in nerve injury → only distal part is affected
Sternomastoid is already supplied
Phrenic nerve should never be blocked - difficulty breathing respiratory muscle paralysis
Subclavian artery block
Superior surface of first rib
Third part of subclavian artery blocked using thumb
Lateral to sternomastoid and scalenus anterior
Subclavian artery third part can be blocked in neck region
Subclavian artery continue as axillary artery in axilla
Posterior border of sternomastoid - Midpoint - cervical plexus block
Brachial plexus block
Scalenus anterior inserted into inner border of first rib - carotid tubercle
Scalenus medius is also attached to first rib - superior surface
Interscalene triangle - between scalenus anterior and scalenus medius
Both blocks are given here
Subclavian artery block and brachial plexus block
Third part distal to scalenus anterior
Artery is compressed on superior surface of first rib
Trunks of brachial plexus in neck
Cords are in axilla
Scalenus anterior and medius inserted to first rib
In between the scalene muscles - interscalene triangle
Brachial plexus and subclavian artery can be blocked in interscalene triangle
Axillary sheath covers brachial plexus and axillary artery
Axillary vein is outside the sheath
Subclavian artery crosses first rib to become axillary artery
Similarly, Axillary vein becomes subclavian vein
Subclavian artery and vein sandwich scalenus anterior muscle
Subclavian artery becomes axillary artery
Axillary vein - outside axillary sheath
Becomes subclavian vein in neck
Brachial plexus pass behind clavicle
Trunk of brachial plexus in interscalene triangle
Covered by prevertebral fascia
Prevertebral fascia
At the floor of posterior triangle
Covers scalenus medius
Extends into axilla and form axillary sheath
As Brachial plexus pull the fascia into axilla
Axillary sheath - continuation of prevertebral fascia in the axilla
Contents - axillary vein and brachial plexus
Axillary vein is outside
Cervical plexus blocked in occipital triangle
Posterior border of sternomastoid
Midpoint of sternomastoid
Phrenic nerve
Branch of cervical plexus
Anterior surface of scalenus anterior muscle
Motor supply to diaphragm
Sensory to
central diaphragm
Mediastinum - pleura, pericardium, Peritoneum
Cervical plexus nerve block
Behind sternomastoid
Block given during surgery around the region
Posterior border of sternomastoid- midpoint of sternomastoid
Phrenic nerve cannot be blocked → respiratory paralysis
Three things blocked in posterior triangle
3rd part of subclavian triangle - interscalene triangle - subclavian triangle
Cervical plexus - occipital triangle- posterior border, midpoint of sternomastoid
Trunk of brachial plexus -subclavian triangle
11th nerve - spinal accessory nerve
Supply sternomastoid and trapezius
Could be damaged iatrogenically during drainage in posterior triangle
Spares sternomastoid
Trapezius paralyzed - cannot shrug shoulder
Q. If there is superficial cut in the region of middle part of posterior triangle of neck, patient will experience problem in
Adduction of arm
Protraction of scapula
Shrugging of shoulder
Overhead abduction of arm
Explanation
Trapezius help in shrugging of shoulder - which is paralyzed so cannot shrug the shoulder
Though trapezius help in overhead abduction, serratus anterior is required along with trapezius for overhead abduction
Sternomastoid is spared during the injury
We hope you have understood Neck Triangles in detail through this detailed article. For more informative articles like this, keep following our blog and download the PrepLadder app to access high-yield content.
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