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3D Internal Anatomy


 

This section showcases a dynamic 3D anatomy model:


Understand 3D Anatomy: Visualising the 3D course of nerves and their anatomical relations is crucial for accurate and safe regional anaesthesia.


Immersive 360° Exploration: Rotate the model using the interactive slider, offering full control over your perspective for detailed examination from every angle.


Enhanced Spatial Understanding: Gain a deeper comprehension of the spatial relationships between anatomical structures, providing a clearer and more interactive learning experience than traditional flat images.


Realistic and Practical Insights: The lifelike 3D model enhances understanding of anatomy, providing essential visualisation needed for precision in performing nerve block techniques safely and accurately.

 

Intermediate Cervical Plexus Block




Cervical plexus

Formation: The cervical plexus is formed by the anterior rami (ventral divisions) of the cervical spinal nerves C1 to C4.

Anatomical Position: Situated in the posterior triangle of the neck, the cervical plexus lies halfway up the sternocleidomastoid muscle, enveloped within the prevertebral layer of the cervical fascia.

 

Superficial Branches: 

Responsible for sensory innervation to the skin of the neck and certain areas of the head.


Lesser Occipital Nerve (C2)

Origin: The lesser occipital nerve arises from the C2 spinal nerve, specifically from the anterior rami.

Pathway: After emerging from the cervical plexus, the nerve ascends along the posterior border of the sternocleidomastoid muscle. It travels superiorly and posteriorly, following the muscle's edge as it moves towards the scalp.

Innervation: The nerve continues its course towards the scalp, where it supplies the skin of the upper third of the auricle and the area just behind the ear. This innervation includes part of the posterior scalp, extending slightly into the occipital region.


Great Auricular Nerve (C2 and C3)

Origin: The great auricular nerve is formed by fibres from the C2 and C3 spinal nerves, combining within the cervical plexus.

Pathway: This nerve emerges from the posterior border of the sternocleidomastoid muscle at the midpoint of the muscle. It then ascends diagonally across the muscle, travelling towards the angle of the mandible. As it continues its course, it divides into anterior and posterior branches.

Innervation: The anterior branch supplies the skin over the parotid gland and the area in front of the ear, including the angle of the jaw. The posterior branch innervates parts of the auricle, particularly the earlobe and skin overlying the mastoid process.


Transverse Cervical Nerve (C2 and C3)

Origin: The transverse cervical nerve is composed of fibres from the C2 and C3 spinal nerves.

Pathway: After emerging from the cervical plexus, this nerve runs transversely across the neck. It passes horizontally across the sternocleidomastoid muscle, moving towards the anterior aspect of the neck.

Innervation: As it reaches the anterior triangle of the neck, the transverse cervical nerve supplies the skin in this region, specifically the skin covering the anterior and lateral parts of the neck.


Supraclavicular Nerves (C3 and C4)

Origin: The supraclavicular nerves arise from the C3 and C4 spinal nerves within the cervical plexus.

Pathway: These nerves emerge from beneath the posterior border of the sternocleidomastoid muscle and then descend toward the clavicle. They split into three distinct branches—medial, intermediate, and lateral—each taking a slightly different path as they move inferiorly.

Innervation: The medial branch crosses over the clavicle and innervates the skin over the upper sternum and the manubrium. The intermediate branch also crosses the clavicle and supplies the skin over the middle part of the clavicle and the upper chest. The lateral branch extends further down over the shoulder, supplying the skin over the lateral part of the clavicle and the shoulder, including the acromion.

 

Deep Branches: 

Primarily motor nerves and innervating muscles of the anterior neck.


Direct Branches (C1 to C4): Innervate prevertebral muscles such as the rectus capitis anterior, rectus capitis lateralis, longus capitis, and longus colli.


Ansa Cervicalis: Formed by superior (C1) and inferior (C2 and C3) roots, innervating the infrahyoid muscles except the thyrohyoid.


Phrenic Nerve (C3 to C5): It is primarily responsible for motor innervation to the diaphragm, making it essential for respiration. It originates from the cervical plexus, with its major contribution coming from the C4 spinal nerve, supplemented by fibres from C3 and C5.

Course: After its formation, the phrenic nerve descends along the anterior surface of the anterior scalene muscle in the neck, running deep to the prevertebral fascia. It then travels vertically, posterior to the sternocleidomastoid muscle, and passes over the subclavian artery while lying anterior to the subclavian vein. Continuing its descent, the nerve enters the thoracic cavity by passing through the thoracic inlet. Once in the thorax, it runs along the mediastinum, between the pleura and the pericardium, to reach the diaphragm.

Innervation: The phrenic nerve supplies motor fibres to the diaphragm, allowing it to contract and facilitate breathing. Additionally, it provides some sensory fibres to the pericardium, pleura, and diaphragmatic peritoneum. This nerve's function is critical for voluntary and involuntary breathing, with injury to the phrenic nerve often resulting in diaphragmatic paralysis, leading to significant respiratory compromise.

 

Cervical Fascia: The cervical plexus is closely associated with the cervical fascia, which is composed of multiple layers that provide structure and protection to the neck. The cervical fascia is divided into superficial and deep layers, with the cervical plexus primarily lying within the deep cervical fascia.

The superficial cervical fascia contains cutaneous nerves, superficial veins, and lymph nodes, while the deeper layers encase vital structures like muscles, blood vessels, and nerves.

The prevertebral layer of the deep cervical fascia surrounds the cervical plexus, including its superficial and deep branches. These branches arise from the prevertebral fascia and travel beneath the sternocleidomastoid muscle (SCM) before emerging at Erb’s point. Erb’s point, located at the posterior border of the SCM, serves as a key anatomical landmark where the superficial sensory branches of the cervical plexus become accessible for clinical procedures. The layered structure of the cervical fascia plays an essential role in guiding the distribution of the cervical plexus, influencing how superficial and deep branches reach their target areas for sensory and motor innervation.

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