Video: Muscles of the anterior neck
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Fancy a game of Charades? Just guess what I am. I promise I'll make it easy. So, let's see. We've got lots of head and neck movements. Those neck muscles are working very hard to move this…chicken'... Read more
Fancy a game of Charades? Just guess what I am. I promise I'll make it easy. So, let's see. We've got lots of head and neck movements. Those neck muscles are working very hard to move this…chicken's big head! So, we're pretty good at Charades, but how are we when it comes to the anatomy of the muscles of the anterior neck? Well, don't worry because after this tutorial, you'll be a pro.
In today's tutorial, we will take a look at the muscles of the anterior neck which are divided into five main groups – the superficial, scalene, suprahyoid, infrahyoid, and prevertebral muscles of the neck. Within each of these groups, we'll explore the attachments and innervation of each muscle as well as their actions which occur on contraction. Finally, to finish off, we'll take a look at a clinical note to help consolidate and apply our knowledge. So time to flex those anterior neck muscles, put your head down, and get learning about the muscles of the anterior neck.
We'll begin with the superficial muscles of the neck which consist of the thin platysma muscle and the strong sternocleidomastoid muscle. The platysma muscle is a thin muscular sheet located in the subcutaneous tissue of the anterior neck. It arises from the fascia that covers the clavicle, the acromial region, and the superior portions of the pectoralis major and deltoid muscles. From here, it ascends through the anterolateral sides of the neck.
The fibers of the platysma muscle have numerous insertion points. Its medial fibers insert onto the lower border of the mandible or the skin of the lower lip while its lateral fibers attach to the skin and the subcutaneous tissue of the perioral region and the muscles surrounding the mouth. Here, the platysma blends with the depressor anguli oris and depressor labii inferioris muscles and reinforces their actions.
The most medially located fibers of the platysma interlace across the midline with their contralateral muscle fibers forming an inverted V. This muscle fiber interlacing occurs at the level of the thyroid cartilage. Due to its insertion point on the mouth, the platysma muscle contributes to facial expression on contraction. It is also a weak depressor of the mandible and tenses the skin of the lower face and anterior neck. Innervation of this muscle is supplied by the cervical branch of the facial nerve.
The sternocleidomastoid muscle is a large two-headed muscle of the neck. It has both a sternal head and a clavicular head. The sternal head arises from the anterior surface of the manubrium of the sternum as its name suggests while the clavicular head originates from the medial third of the clavicle. This muscle ascends posterosuperiorly to insert onto the lateral aspect of the mastoid process of the temporal bone and to the lateral third of the superior nuchal line of the occipital bone. Fibers from the sternal portion mainly attach to the occipital bone while fibers from the clavicular portion typically attach to the mastoid process.
On unilateral contraction, this muscle flexes the cervical vertebral column to the same side and rotates the head to the opposite side. Bilateral contraction elevates the head by dorsally extending the upper cervical joints. It also flexes the lower cervical column causing an overall bending of the neck towards the chest. Finally, if the head is in a fixed position, it also elevates the sternum and clavicle and thus expands the thoracic cavity acting as an accessory muscle of inspiration. Providing the innervation to this muscle is the accessory nerve and branches of the cervical plexus which arise from C2 to C3 nerve roots.
The next group of muscles of the anterior neck is composed of three muscles collectively known as the scalene muscles. They comprise the scalenus anterior, the scalenus medius, and scalenus posterior muscles which are named according to their relative position. The scalenus anterior muscle is the anteriormost of the three scalene muscles and arises from the anterior tubercles of the transverse processes of vertebrae C3 to C6. Muscle fibers descend almost vertically towards the thoracic cage and form a long thin tendon which inserts onto the scalene tubercle and superior surface of the first rib.
The scalenus anterior acts on the cervical vertebral joints and elicits flexion of the neck on bilateral contraction. Unilateral contraction causes ipsilateral flexion of the neck. Due to its costal attachment, the scalenus anterior muscle also contributes to the elevation of the first rib and thereby contributes to forced inspiration during breathing movements. The scalenus anterior receives its nerve supply from the anterior rami of spinal nerves C4 to C6.
The scalenus medius muscle is the largest and longest of the scalenus muscles and sits sandwiched between the scalenus anterior and posterior muscles. It arises from the posterior tubercles of the transverse processes of vertebrae C2 to C7 via muscular slips. Muscle fibers extend inferolaterally to form a tendon which inserts onto the superior surface of the first rib. Contraction of this muscle elicits strong ipsilateral flexion of the neck and similar to its anterior counterpart, this muscle also raises the first rib during forced inspiration. The scalenus medius muscle is also active during regular inspiration, even during quiet breathing. The anterior rami of cervical spinal nerves C3 to C8 provides innervation to this muscle.
The smallest of the scalene muscles is the scalenus posterior muscle which arises from the posterior tubercles of the transverse processes of C5 to C7. It extends inferolaterally and tapers into a thin tendon which inserts onto the external surface of the second rib. When the costal attachment of this muscle is fixed, ipsilateral flexion of the neck occurs on unilateral contraction. This muscle also helps to stabilize or elevate the second rib during respiration. Allowing these movements to occur by innervating this muscle is the anterior rami of spinal nerves C6 to C8.
Moving on to the next group of muscles of the anterior neck, we meet the suprahyoid muscles. As its name suggests, these muscles are all located above or superior to the hyoid bone and are made up of the digastric, stylohyoid, mylohyoid, and geniohyoid muscles. This group of muscles contributes to the formation of the floor of the mouth and works together to elevate the hyoid bone with some muscles additionally depressing the mandible.
The digastric muscle is composed of two bellies – an anterior and posterior belly – joined together by an intermediate tendon. The anterior belly arises from the digastric fossa of the mandible while the posterior belly arises from the mastoid notch of the temporal bone. The digastric muscle inserts onto the body and greater horn of the hyoid bone via its intermediate tendon. A fascial sling derived from the pretracheal layer of the deep cervical fascia allows the intermediate tendon to slide in an anterior and posterior fashion as the muscle bellies contract. Subsequently, the digastric muscle elevates and stabilizes the hyoid bone during swallowing and speaking and depresses the mandible against resistance.
This muscle receives its innervation from two separate nerves. The anterior belly is innervated by the nerve to the mylohyoid, a branch of the inferior alveolar nerve, while the posterior belly receives its innervation from the digastric branch of the facial nerve.
The stylohyoid muscle is a narrow strap muscle which extends from the base of the temporal bone to the hyoid bone. Specifically, this thin muscle of the anterior neck originates from the posterior aspect of the styloid process of the temporal bone and extends in an anteroinferior direction to insert onto the body of the hyoid bone. As a result, the stylohyoid muscle elevates the hyoid bone and pulls it posteriorly on contraction. The stylohyoid muscle receives its innervation from the stylohyoid branch of the facial nerve.
Moving on to the next muscle of the suprahyoid region, we come to the mylohyoid muscle. The paired mylohyoid muscle forms the muscular floor of the oral cavity and separates the sublingual space of the oral cavity from the submandibular space. It arises from the mylohyoid line on the internal surface of the mandible. Medially, the anterior two-thirds of the mylohyoid muscle join with its counterpart along a midline fibrous raphe. Posteriorly, its fibers extend inferiorly to attach to the anterior surface of the body of the hyoid bone, as we can see from this lateral view.
On contraction, the mylohyoid muscle elevates the floor of the mouth, hyoid bone, and tongue during swallowing and speaking. It can also depress the mandible. It receives its innervation from the nerve to the mylohyoid, a branch of the inferior alveolar nerve.
The final muscle of the suprahyoid muscle group is the geniohyoid muscle. The geniohyoid muscle is a paired muscle located superior to the medial portion of the mylohyoid muscle. It arises from the inferior mental spines of the mandible and extends in a posteroinferior direction to insert onto the anterior surface of the body of the hyoid bone. On contraction, the geniohyoid muscle pulls the hyoid bone in an anterosuperior direction and depresses the mandible at the temporomandibular joint. The geniohyoid muscle receives its innervation from the geniohyoid branch of the hypoglossal nerve.
The next group of muscles of the anterior neck are the infrahyoid muscles, and as their name suggests, these muscles are located inferior to or below the hyoid bone. This group of muscles are also known as the strap muscles due to their flat ribbon-like appearance. They comprise the sternohyoid, sternothyroid, thyrohyoid, and omohyoid muscles. The infrahyoid muscles are arranged into a superficial plane which include the sternohyoid and omohyoid muscles and a deep plane made up of the sternothyroid and thyrohyoid muscles. Let's begin with taking a closer look at the muscles of the superficial plane of infrahyoid muscles beginning with the sternohyoid muscle.
The paired sternohyoid muscle arises from both the sternal end of the clavicle and posterior surface of the manubrium of the sternum. From its origin point, it extends in a superior direction to insert onto the inferior border of the body of the hyoid bone. On contraction, the sternohyoid muscle depresses the hyoid bone after elevation during swallowing and is supplied by the sternohyoid branch of the ansa cervicalis.
The next muscle of the superficial plane of infrahyoid muscles is the paired omohyoid muscle. Similar to the digastric muscle of the suprahyoid muscle group, the omohyoid muscle is composed of two bellies – a superior and inferior belly – connected by an intermediate tendon. The inferior belly of the omohyoid muscle originates from the superior border of the scapula, medial to the superior scapular notch. It joins with the superior belly at the intermediate tendon which is attached to the clavicle by a fascial sling. From the intermediate tendon, the superior belly ascends to insert onto the inferior aspect of the body of the hyoid bone lateral to the attachment of the sternohyoid muscle. On contraction, the omohyoid muscle depresses, retracts, and stabilizes the hyoid bone. It is innervated by the anterior rami of C1 to C3 through the ansa cervicalis.
Now let's turn our attention to the muscles of the deep plane of the infrahyoid muscles beginning with the thyrohyoid muscle.
The thyrohyoid muscle lies deep to the superior portion of the omohyoid and sternohyoid muscles and originates from the oblique line on the lamina of the thyroid cartilage. It ascends from its origin point to insert onto the inferior border of the greater horn and body of the hyoid bone. This muscle generally acts to depress the hyoid bone; however, when the hyoid is fixed, it raises the larynx. The anterior ramus of C1 supplies this muscle through the thyrohyoid branch of the hypoglossal nerve.
Finally, we meet the sternothyroid muscle, which lies deep to the sternohyoid muscle. It arises from the costal cartilage of the first rib and the posterior surface of the manubrium of the sternum just deep to the attachment of the sternohyoid muscle. It ascends to insert onto the oblique line of the thyroid cartilage of the larynx and depresses the larynx after it has been elevated on contraction. Allowing for this action to occur is the sternothyroid branch of the ansa cervicalis, which carries fibers from the anterior rami of C1 to C3.
Moving on to the final group of muscles of the anterior neck, we meet the prevertebral muscles, which are a group of deep cervical muscles located at the upper vertebral column. Muscles of this region include the rectus capitis anterior, rectus capitis lateralis, longus colli, and longus capitis muscles. We'll take a quick look at each of these muscles now.
The rectus capitis anterior muscle is a short muscle which arises from the anterior aspect of the lateral mass of the atlas and its transverse process. It courses superiorly to attach to the basilar part of the occipital bone. The primary function of this muscle is to flex the head at the atlantooccipital joints. It also functions to stabilize the atlantooccipital joint and is innervated by the anterior rami of spinal nerves C1 and C2.
The rectus capitis lateralis muscle is located lateral to the rectus capitis anterior muscle and the cranial end of the longus capitis. It arises from the superior surface of the transverse process of the atlas and extends superiorly to insert onto the inferior surface of the jugular process of the occipital bone. The primary function of the rectus capitis lateralis muscle is to stabilize the atlantooccipital joint during movement. Unilateral contraction of this muscle produces ipsilateral flexion of the neck. Allowing for these movements to occur are the branches of the anterior rami of the first 2 cervical spinal nerves.
The longus colli is a paired muscle located on the anterior aspect of the vertebral column that spans the entire cervical spine and the first 3 thoracic vertebrae. This muscle consists of three parts – a superior oblique part, vertical intermediate part, and inferior oblique part – which are attached to the vertical column via tendinous slips.
The superior oblique part arises from the anterior tubercles of transverse processes of the third, fourth, and fifth cervical vertebrae and extends in a superomedial direction to terminate on the anterior tubercle of the anterior arch of the atlas. The intermediate vertical part arises from the anterior surfaces of the bodies of the lower three cervical and superior three thoracic vertebrae. This muscle section inserts onto the anterior surface of the bodies of the second, third, and fourth cervical vertebrae. The inferior oblique part is the smallest section of the longus colli muscle and arises from the anterior surfaces of the bodies of the first 3 thoracic vertebrae. It ascends superolaterally terminating onto the anterior tubercles of the transverse processes of the fifth and sixth cervical vertebrae.
Bilateral contraction of the muscle causes flexion of the neck. Unilateral contraction especially of the inferior oblique part also results in weak ipsilateral flexion and contralateral rotation of the neck. The longus colli muscle receives its innervation from the anterior rami of the second to sixth cervical spinal nerves.
The final prevertebral muscle and final muscle of the anterior neck is the longus capitis muscle. This flat muscle runs up the length of the cervical spine adjacent to the vertebral bodies. It originates as four small muscle straps that run from the anterior tubercles of the transverse processes of C3 to C6. Its muscle fibers extend in a superomedial direction converging into a single broad muscle belly which inserts onto the basilar part of the occipital bone.
The longus capitis muscle works together with the rest of the prevertebral muscles to produce flexion of the head at the cervical spine when the muscle contracts in a bilateral fashion. When the head is in an extended position, the longus capitis muscle returns the head into a neutral position. Unilateral contraction rotates the head ipsilaterally. Allowing these movements to occur are the anterior rami of spinal nerves C1 to C3, and occasionally, C4.
Now that you have a good understanding of these muscles of the anterior neck, it's time to apply this knowledge to a clinical scenario.
Longus colli tendinitis is an inflammation of the tendinous slips of the longus colli muscle. It is a frequent contributor to neck pain and may be caused by calcium deposits in the tendons of the longus colli muscle resulting in an aseptic inflammatory response. Following this etiology, the pathology is known as acute calcific tendinitis of the longus colli. Symptoms include fever, neck pain or stiffness, a sensation of a lump in your throat otherwise known as globus sensation, and dysphagia or swallowing problems. Calcifications may be observed on radiographs; however, a diagnosis of calcific tendinitis of the longus colli is generally achieved through MRI or CT imaging. In this image, we can see calcification of a musculotendinous slip of the longus colli muscle. Conservative treatment using nonsteroidal anti-inflammatory drugs is usually sufficient with symptoms typically resolving within a number of weeks.
And that's a wrap on the muscles of the anterior neck. But before you go, let's take some time to quickly go over what we learned today.
We began this tutorial by exploring the superficial muscles of the anterior neck which consists of the thin platysma muscle and the large, strong sternocleidomastoid muscle. The platysma muscle facilitates movements of facial expression while the sternocleidomastoid muscle functions to ventrally and laterally flex the neck. Next we met the scalene muscles which comprise the scalenus anterior, scalenus medius, and scalenus posterior muscles. These muscles function to flex and rotate the neck.
The suprahyoid muscles of the anterior neck are all located above the hyoid bone and include the digastric, stylohyoid, mylohyoid, and geniohyoid muscles. This group of muscles contributes to the formation of the floor of the mouth and works together to elevate the hyoid bone. Located below the hyoid bone are the next group of muscles known as the infrahyoid muscles of the anterior neck. Muscles of this group include the sternohyoid, sternothyroid, thyrohyoid, and omohyoid muscles. Most of the infrahyoid muscles are responsible for depressing the hyoid bone.
Finally, we met the prevertebral muscles which occupy the anterior and lateral portions of the upper cervical spine. This group of muscles includes the rectus capitis anterior, the rectus capitis lateralis, the longus colli, and longus capitis muscles. They generally function to flex the cervical column. To finish today's tutorial, we explored the cause, symptoms, diagnosis, and treatment of the calcific tendinitis of the longus colli muscle.
And that brings us to the end of the tutorial. We hope you enjoyed learning about the muscles of the anterior neck, and happy studying.