Correctly Label The Following Muscles Of The Neck

The human neck, a marvel of biological engineering, is a complex structure supporting the head and facilitating a wide range of movements. Understanding the intricate network of muscles within the neck is crucial for healthcare professionals, athletes, and anyone interested in human anatomy. Correctly labeling these muscles not only aids in comprehending their functions but also in diagnosing and treating various conditions affecting the neck. This comprehensive guide will delve into the major muscles of the neck, their origins, insertions, functions, and clinical significance.

Anatomy of the Neck: An Overview

Before diving into the individual muscles, it is essential to understand the overall structure of the neck. The neck, or cervical region, connects the head to the torso and houses vital structures such as the spinal cord, blood vessels, nerves, and the trachea. The muscles of the neck can be broadly categorized into anterior, lateral, and posterior groups based on their location. These muscles work in synergy to enable head movements such as flexion, extension, rotation, and lateral flexion.

Key Anatomical Terms

To accurately label and understand the muscles of the neck, familiarity with the following anatomical terms is helpful:

• Origin: The point where the muscle attaches to a stationary bone.
• Insertion: The point where the muscle attaches to a moving bone.
• Action: The movement produced by the muscle when it contracts.
• Innervation: The nerve that supplies the muscle, providing the signal for contraction.

Anterior Neck Muscles

The anterior neck muscles are located at the front of the neck and are primarily involved in flexion of the head and neck, as well as assisting in swallowing and speech.

1. Sternocleidomastoid (SCM)

The sternocleidomastoid is one of the most prominent and easily identifiable muscles in the neck. It is a thick, superficial muscle that runs obliquely across the side of the neck.

• Origin: It has two heads: the sternal head, which originates from the manubrium of the sternum, and the clavicular head, which originates from the medial third of the clavicle.
• Insertion: Mastoid process of the temporal bone and the superior nuchal line.
• Action:
  • Unilateral contraction: Lateral flexion of the neck to the same side and rotation of the head to the opposite side.
  • Bilateral contraction: Flexion of the neck.
  • Accessory muscle of respiration: Elevates the sternum and clavicle during forced inspiration.
• Innervation: Accessory nerve (CN XI) and branches from the cervical plexus (C2-C3).

Clinical Significance: The SCM is often involved in conditions such as torticollis (wry neck), where it becomes shortened or contracted, causing the head to tilt to one side.

2. Suprahyoid Muscles

The suprahyoid muscles are a group of muscles located above the hyoid bone. They primarily elevate the hyoid bone and assist in swallowing.

• Digastric:
  • Origin: Anterior belly from the digastric fossa of the mandible, posterior belly from the mastoid notch of the temporal bone.
  • Insertion: Hyoid bone via an intermediate tendon.
  • Action: Elevates the hyoid bone and depresses the mandible.
  • Innervation: Anterior belly by the mylohyoid nerve (branch of the inferior alveolar nerve from the trigeminal nerve CN V3), posterior belly by the facial nerve (CN VII).
• Stylohyoid:
  • Origin: Styloid process of the temporal bone.
  • Insertion: Hyoid bone.
  • Action: Elevates and retracts the hyoid bone.
  • Innervation: Facial nerve (CN VII).
• Mylohyoid:
  • Origin: Mylohyoid line of the mandible.
  • Insertion: Hyoid bone and the median raphe.
  • Action: Elevates the hyoid bone and the floor of the mouth.
  • Innervation: Mylohyoid nerve (branch of the inferior alveolar nerve from the trigeminal nerve CN V3).
• Geniohyoid:
  • Origin: Inferior mental spine of the mandible.
  • Insertion: Hyoid bone.
  • Action: Elevates the hyoid bone and depresses the mandible.
  • Innervation: C1 spinal nerve via the hypoglossal nerve (CN XII).

3. Infrahyoid Muscles

The infrahyoid muscles are located below the hyoid bone. They depress the hyoid bone and larynx during swallowing and speech.

• Sternohyoid:
  • Origin: Manubrium of the sternum and the medial end of the clavicle.
  • Insertion: Hyoid bone.
  • Action: Depresses the hyoid bone.
  • Innervation: Ansa cervicalis (C1-C3).
• Omohyoid:
  • Origin: Superior border of the scapula.
  • Insertion: Hyoid bone.
  • Action: Depresses the hyoid bone.
  • Innervation: Ansa cervicalis (C1-C3).
• Sternothyroid:
  • Origin: Manubrium of the sternum.
  • Insertion: Oblique line of the thyroid cartilage.
  • Action: Depresses the larynx.
  • Innervation: Ansa cervicalis (C1-C3).
• Thyrohyoid:
  • Origin: Oblique line of the thyroid cartilage.
  • Insertion: Hyoid bone.
  • Action: Depresses the hyoid bone and elevates the larynx.
  • Innervation: C1 spinal nerve via the hypoglossal nerve (CN XII).

4. Scalene Muscles

The scalene muscles are a group of three muscles located on the lateral aspect of the neck. They are important for both neck movement and respiration.

• Anterior Scalene:
  • Origin: Anterior tubercles of the transverse processes of C3-C6 vertebrae.
  • Insertion: Scalene tubercle on the inner border of the first rib.
  • Action:
    • Unilateral contraction: Lateral flexion of the neck to the same side.
    • Bilateral contraction: Elevates the first rib during inspiration.
  • Innervation: Cervical spinal nerves (C4-C6).
• Middle Scalene:
  • Origin: Posterior tubercles of the transverse processes of C2-C7 vertebrae.
  • Insertion: Superior surface of the first rib, posterior to the subclavian groove.
  • Action:
    • Unilateral contraction: Lateral flexion of the neck to the same side.
    • Bilateral contraction: Elevates the first rib during inspiration.
  • Innervation: Cervical spinal nerves (C3-C8).
• Posterior Scalene:
  • Origin: Posterior tubercles of the transverse processes of C5-C7 vertebrae.
  • Insertion: Outer surface of the second rib.
  • Action:
    • Unilateral contraction: Lateral flexion of the neck to the same side.
    • Bilateral contraction: Elevates the second rib during inspiration.
  • Innervation: Cervical spinal nerves (C6-C8).

Clinical Significance: The scalene muscles are closely related to the brachial plexus and subclavian artery. Tightness or hypertrophy of these muscles can lead to thoracic outlet syndrome, causing compression of these structures and resulting in pain, numbness, and weakness in the upper limb.

Lateral Neck Muscles

While the scalenes are located laterally, they are often grouped with the anterior muscles due to their function and location. Other muscles that contribute to the lateral aspect of the neck include the platysma, though it is primarily a muscle of facial expression, it does extend into the neck region.

1. Platysma

• Origin: Arises from the fascia covering the superior parts of the pectoralis major and deltoid muscles.
• Insertion: Inserts into the mandible, skin, and subcutaneous tissue of the lower face.
• Action:
  • Tenses the skin of the neck.
  • Depresses the mandible.
  • Assists in drawing down the lower lip and corner of the mouth, expressing tension or strain.
• Innervation: Facial nerve (CN VII).

Posterior Neck Muscles

The posterior neck muscles are located at the back of the neck and are primarily involved in extension, rotation, and lateral flexion of the head and neck. These muscles can be divided into superficial, intermediate, and deep layers.

1. Superficial Layer

• Trapezius:
  • Origin: Superior nuchal line, external occipital protuberance, nuchal ligament, spinous processes of C7-T12 vertebrae.
  • Insertion: Lateral third of the clavicle, acromion, and spine of the scapula.
  • Action:
    • Upper fibers: Elevate the scapula.
    • Middle fibers: Retract the scapula.
    • Lower fibers: Depress the scapula.
    • Together, they rotate the scapula upward.
    • Also assists in neck extension and lateral flexion.
  • Innervation: Accessory nerve (CN XI) and cervical spinal nerves (C3-C4).

2. Intermediate Layer

• Splenius Capitis:
  • Origin: Spinous processes of C7-T3 vertebrae and the lower half of the nuchal ligament.
  • Insertion: Mastoid process of the temporal bone and the occipital bone just inferior to the superior nuchal line.
  • Action:
    • Unilateral contraction: Lateral flexion and rotation of the head to the same side.
    • Bilateral contraction: Extension of the head and neck.
  • Innervation: Cervical spinal nerves (C3-C6).
• Splenius Cervicis:
  • Origin: Spinous processes of T3-T6 vertebrae.
  • Insertion: Transverse processes of C1-C3 vertebrae.
  • Action:
    • Unilateral contraction: Lateral flexion and rotation of the neck to the same side.
    • Bilateral contraction: Extension of the neck.
  • Innervation: Cervical spinal nerves (C3-C6).

3. Deep Layer

The deep layer of posterior neck muscles includes the suboccipital muscles and the deep cervical extensors.

Suboccipital Muscles

These four muscles are located deep in the posterior neck, just below the occipital bone. They are primarily involved in precise movements of the head.

• Rectus Capitis Posterior Major:
  • Origin: Spinous process of the axis (C2).
  • Insertion: Inferior nuchal line of the occipital bone.
  • Action: Extension and ipsilateral rotation of the head.
  • Innervation: Suboccipital nerve (dorsal ramus of C1).
• Rectus Capitis Posterior Minor:
  • Origin: Posterior tubercle of the atlas (C1).
  • Insertion: Inferior nuchal line of the occipital bone.
  • Action: Extension of the head.
  • Innervation: Suboccipital nerve (dorsal ramus of C1).
• Obliquus Capitis Superior:
  • Origin: Transverse process of the atlas (C1).
  • Insertion: Occipital bone between the superior and inferior nuchal lines.
  • Action: Lateral flexion and extension of the head.
  • Innervation: Suboccipital nerve (dorsal ramus of C1).
• Obliquus Capitis Inferior:
  • Origin: Spinous process of the axis (C2).
  • Insertion: Transverse process of the atlas (C1).
  • Action: Ipsilateral rotation of the head.
  • Innervation: Suboccipital nerve (dorsal ramus of C1).

Clinical Significance: The suboccipital muscles are often implicated in tension headaches and cervicogenic headaches. Their close proximity to the dura mater and vertebral artery makes them important to consider in manual therapy and headache management.

Deep Cervical Extensors

These muscles are located deeper and run along the cervical spine, primarily contributing to extension and stabilization of the neck.

• Semispinalis Capitis:
  • Origin: Transverse processes of C7-T6 vertebrae.
  • Insertion: Occipital bone between the superior and inferior nuchal lines.
  • Action: Extension of the head and neck, and contralateral rotation.
  • Innervation: Dorsal rami of cervical spinal nerves.
• Semispinalis Cervicis:
  • Origin: Transverse processes of T1-T6 vertebrae.
  • Insertion: Spinous processes of C2-C5 vertebrae.
  • Action: Extension of the neck and contralateral rotation.
  • Innervation: Dorsal rami of cervical spinal nerves.
• Multifidus:
  • Origin: Sacrum, ilium, transverse processes of vertebrae.
  • Insertion: Spinous processes of vertebrae 2-4 segments above.
  • Action: Stabilizes the spine and assists in extension and rotation.
  • Innervation: Dorsal rami of spinal nerves.
• Rotatores:
  • Origin: Transverse processes of vertebrae.
  • Insertion: Spinous process of the vertebra above.
  • Action: Stabilizes the spine and assists in rotation.
  • Innervation: Dorsal rami of spinal nerves.

Clinical Relevance

Understanding the muscles of the neck is crucial for diagnosing and treating various conditions, including:

• Torticollis: As mentioned earlier, this condition involves shortening or contraction of the sternocleidomastoid muscle.
• Whiplash: A neck injury caused by a sudden forward and backward movement of the head, often resulting in muscle strains and ligament sprains.
• Cervicogenic Headaches: Headaches originating from the neck, often due to muscle tension or dysfunction in the cervical spine and associated muscles.
• Thoracic Outlet Syndrome: Compression of the brachial plexus and subclavian artery due to tight scalene muscles or other anatomical abnormalities.
• Muscle Strains: Overuse or sudden injury can lead to strains in the neck muscles, causing pain and limited range of motion.
• Poor Posture: Weakness or imbalance in the neck muscles can contribute to poor posture, leading to chronic neck pain and stiffness.

Palpation of Neck Muscles

Palpation is an essential skill for healthcare professionals to assess the condition of the neck muscles. It involves using touch to feel and examine the muscles for tenderness, tightness, or abnormalities.

Tips for Palpation

• Sternocleidomastoid (SCM): Have the patient rotate their head to the opposite side. This will make the SCM more prominent and easier to palpate.
• Trapezius: Palpate the upper fibers by having the patient shrug their shoulders.
• Scalenes: Palpate deep to the SCM in the lateral neck region. Have the patient take a deep breath to feel the muscles contract.
• Suboccipital Muscles: These are deep and difficult to palpate directly. Palpate in the suboccipital region just below the occipital bone, using gentle pressure.
• Splenius Capitis and Cervicis: Palpate in the posterior neck region, deep to the trapezius.

Exercises for Neck Muscles

Strengthening and stretching the neck muscles can help prevent injuries, improve posture, and relieve pain. Here are some exercises that can be beneficial:

Stretching Exercises

• Neck Flexion Stretch: Gently drop your chin to your chest and hold for 15-30 seconds.
• Neck Extension Stretch: Gently tilt your head back and look up towards the ceiling, holding for 15-30 seconds.
• Lateral Flexion Stretch: Gently tilt your head to one side, bringing your ear towards your shoulder, and hold for 15-30 seconds. Repeat on the other side.
• Neck Rotation Stretch: Gently turn your head to one side, looking over your shoulder, and hold for 15-30 seconds. Repeat on the other side.

Strengthening Exercises

• Chin Tucks: Gently tuck your chin towards your chest, keeping your head level. Hold for 5 seconds and repeat 10-15 times.
• Isometric Neck Flexion: Place your hand on your forehead and gently push forward, resisting the movement with your neck muscles. Hold for 5 seconds and repeat 10-15 times.
• Isometric Neck Extension: Place your hands on the back of your head and gently push backward, resisting the movement with your neck muscles. Hold for 5 seconds and repeat 10-15 times.
• Isometric Lateral Flexion: Place your hand on the side of your head and gently push towards your shoulder, resisting the movement with your neck muscles. Hold for 5 seconds and repeat 10-15 times on each side.

Conclusion

The muscles of the neck are a complex and interconnected network that enables a wide range of movements and supports vital functions. Correctly labeling these muscles is essential for understanding their roles in maintaining posture, facilitating movement, and contributing to overall health. By understanding the origins, insertions, actions, and clinical significance of the anterior, lateral, and posterior neck muscles, healthcare professionals and individuals alike can better diagnose and manage conditions affecting this crucial region of the body. Regular exercise, proper posture, and awareness of potential risk factors can help maintain the health and function of the neck muscles, ensuring a pain-free and active life.