🥇 PLEXO CERVICAL, Anatomía (Superficial y Profundo). Fácil, Rápido y Sencillo

Introduction to Neck Anatomy and Innervation

Overview of Cervical Plexus

• The cervical plexus is described as a network formed by the anterior branches of spinal nerves, specifically from C1 to C4.

• It is divided into two parts: the superficial cervical plexus, which provides sensory innervation, and the deep cervical plexus, responsible for motor innervation.

Superficial Cervical Plexus

• The superficial plexus supplies cutaneous (sensory) innervation to the neck through four main nerves:

• Occipital minor

• Greater auricular nerve

• Transverse cervical nerve

• Supraclavicular nerve

Deep Cervical Plexus

• In contrast, the deep cervical plexus provides motor innervation to neck muscles and includes significant structures such as:

• The ansa cervicalis

• Phrenic nerve

• It also gives rise to specific muscular branches for key muscles like sternocleidomastoid and trapezius.

Detailed Examination of Superficial Cervical Plexus

Sensory Functions

• The superficial plexus is purely sensory; it does not control muscle movement but rather conveys sensations such as pain or temperature from the skin of the neck.

Nerve Distribution

• These nerves emerge behind important structures like the internal jugular vein and are located superficially at specific points on the sternocleidomastoid muscle.

Key Nerves in Detail

• Occipital Minor: Provides sensory innervation to lateral head regions and part of the ear's cranial surface. Also known as mastoid branch in some texts.

• Greater Auricular Nerve: Supplies sensation to areas around the mastoid process and both surfaces of the ear.

• Transverse Cervical Nerve: Innervates skin over anterior and lateral aspects of the neck.

• Supraclavicular Nerve: Divides into three branches that supply sensation over clavicle, shoulder, and upper pectoral region.

Conclusion on Cervical Plexuses

Summary Insights

Understanding the Cervical Plexus

Overview of the Cervical Plexus

• The cervical plexus consists of nerves from C1 to C3, including the lesser occipital nerve, greater auricular nerve, and transverse cervical nerve. These nerves emerge from the union of spinal roots C2, C1, and C3.

• The supraclavicular nerve arises from the junction of C3 and C4, indicating that these structures are part of the cervical plexus. The shaded area represents regions innervated by superficial cervical plexus nerves.

Deep Cervical Plexus Functions

• The deep cervical plexus is primarily motor in function (efferent), contrasting with the sensory role of the superficial plexus. It comprises two main structures and several muscular branches.

• The "ansa cervicalis" is formed by two roots: a superior root (C1-C2) known as the descending branch of hypoglossal and an inferior root (C2-C3). This structure plays a crucial role in muscle innervation in the neck region.

Ansa Cervicalis Details

• The superior root connects with cranial nerve XII (hypoglossal), but it does not form it; rather, they join temporarily before separating again for functional purposes. This distinction clarifies misconceptions about its origin.

• The inferior root originates from C2-C3 and contributes to innervating most infrahyoid muscles except for one significant exception: the thyrohyoid muscle which has different innervation pathways involving branches from both C1 and C2 directly associated with hypoglossal nerve functions.

Thyrohyoid Muscle Innervation

• There is confusion regarding thyrohyoid muscle innervation; while some sources attribute it to hypoglossal nerve contributions, current understanding indicates it receives direct input from anterior rami of spinal nerves rather than through ansa cervicalis pathways. This highlights evolving knowledge based on modern electromyography studies.

Phrenic Nerve Functionality

• The phrenic nerve is critical for diaphragm function and arises mainly from anterior rami of spinal nerves C3-C5, with primary contributions coming from C4; however, its formation can vary among individuals due to accessory fibers sometimes present or absent in certain cases.

Nervio Frénico y Plexo Cervical

Anatomía del Nervio Frénico

• El nervio frénico se forma a partir de la unión de las raíces C5, C4 y C3, perforando el tórax y conectándose con la pleura parietal.

• Se menciona que el músculo escaleno anterior está ubicado en la parte frontal del nervio frénico, lo que indica su relación anatómica.

Ramas Musculares del Plexo Cervical

• Las ramas musculares del plexo cervical incluyen conexiones directas a músculos como el esternocleidomastoideo (C2 y C3), trapecio (C3 y C4), y los músculos escalenos.

• Se discute que algunos libros sugieren que los músculos escalenos están relacionados por sus fibras con las raíces C5 y C6.

Infrahiodeos e Inervación

• Los músculos prevertebrales son inervados por ramas anteriores desde C1 hasta C4, incluyendo todos los infrahiodeos a través del asa cervical (C1-C3).

• Se destaca que el tiroides es una excepción en su inervación, recibiendo impulsos directamente de las raíces anteriores de C1 y C2.

Función del Nervio Frénico