General topography and layers of the infrahyoid muscles
Anatomically, the infrahyoid muscles are localized in the anterior region of the neck. Their superior point of fixation is connected to the hyoid bone, while their inferior bundles extend to the sternum, scapula, and thyroid cartilage. The entire group is divided into two distinct layers: superficial and deep.
Superficial layer
This layer includes two main muscles whose names reflect their attachment points:
- Sternohyoid muscle (m. sternohyoideus) — connects the sternum and the hyoid bone.
- Omohyoid muscle (m. omohyoideus) — extends from the scapula to the hyoid bone.
Deep layer
Beneath the superficial muscles lies the deep muscular layer. It is also represented by two structures:
- Sternothyroid muscle (m. sternothyroideus) — fixed between the sternum and the thyroid cartilage.
- Thyrohyoid muscle (m. thyrohyoideus) — located between the thyroid cartilage and the hyoid bone.
Lateral group: Longus colli muscle
Special attention should be given to the lateral group, which includes the longus colli muscle (m. longus colli). This is a rather extensive anatomical structure structurally subdivided into three separate parts:
- Pars obliqua superior (superior oblique part) — originates from the bodies of vertebrae C3–C5 and runs superiorly to the atlas.
- Pars obliqua inferior (inferior oblique part) — originates from the bodies of thoracic vertebrae Th1–Th3 and attaches to the transverse processes of cervical vertebrae C5–C6.
- Pars recta (straight part) — stretches vertically from the bodies of vertebrae C5–Th3 to the bodies of the upper cervical vertebrae.
Functional significance: Upon bilateral contraction, this muscle flexes the neck forward. If contraction occurs unilaterally, the neck bends to the corresponding side.
Blood supply and innervation:
- Innervation: provided by branches of the cervical spinal nerves — nn. cervicales (C2–C7).
- Blood supply: provided by the vertebral arteries (aa. vertebrales) and deep cervical arteries (aa. cervicales profundae).
To memorize the infrahyoid muscles, pay attention to the logic of their Latin names: the first word always indicates the lower attachment point (sterno- sternum, omo- scapula, thyro- thyroid cartilage), and the second indicates the upper one (-hyoideus — hyoid bone).
Class and exam questions
Between which structures are the infrahyoid muscles located?
They are located between the hyoid bone superiorly and the sternum, scapula, and thyroid cartilage inferiorly.
Which muscles form the superficial layer of this group?
The superficial layer includes the sternohyoid (m. sternohyoideus) and omohyoid (m. omohyoideus) muscles.
What is the function of the longus colli muscle?
It flexes the neck forward upon bilateral contraction, and bends it to the side upon unilateral contraction.
Where do the parts of the longus colli muscle originate?
The superior oblique part originates from the bodies of C3–C5, the inferior oblique part from the bodies of Th1–Th3, and the straight part from the bodies of C5–Th3.
What else to study on this topic
- Detailed topography of the superficial layer and cervical fascia
- Features of m. sternothyroideus attachment to the thyroid cartilage
- Syntopy of m. longus colli parts with the vertebral column
- Arterial network of the neck: branches of aa. vertebrales and cervicales profundae
- Mechanism of unilateral and bilateral contraction of the lateral group muscles
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