The infrahyoid muscles are a group of ribbon-like muscles that include the sternohyoid, omohyoid, thyrohyoid, and sternothyroid. These muscles are arranged in superficial and deep layers and attach to both the hyoid bone and thyroid cartilage, allowing them to depress or elevate these structures. Specifically, the sternohyoid and omohyoid are superficial muscles that depress the hyoid bone, while the sternothyroid and thyrohyoid are deep muscles with actions including depressing the larynx or elevating it through attachment to the hyoid bone.

1. Infrahyoid Muscles /
Ribbon Muscles

2. The infrahyoid muscles are:
a. Sternohyoid
b. Sternothyroid
c. Thyrohyoid
d. Omohyoid.
These ribbon muscles have the following general
features.
a. They are arranged in two layers, superficial
(sternohyoid and omohyoid) and deep (sternothyroid
and thyrohyoid).
b. All of them are supplied by the ventral rami of
first, second and third cervical spinal nerves.
c. Because of their attachment to the hyoid bone and
to the thyroid cartilage, they move these structures.
d. Sternohyoid, superior belly of omohyoid,
sternothyroid lie superficial to the lateral or
superficial convex surface of the thyroid gland.
e. The anterior surface of isthmus of thyroid gland
is covered by right and left sternothyroid and
sternohyoid muscles.

3. Muscle Proximal Attachment Distal Attachment Nerve Supply Action
Sternohyoid
a. Posterior surface of manubrium
sterni
b. Adjoining pafts of the clavicle and
the posterior
sternoclavicular ligament
medial part of lower border of hyoid
bone
Ansa Cervicalis
Depresses the hyoid bone following
its elevation during
swallowing and during
vocal movements
Sternothyroid:
It lies deep to the
sternohyoid
a. Posterior surface
of manubrium sterni
b. Adjoining part of
first costal cartilage
Oblique line on the
lamina of the thyroid
cadilage
Ansa cervicalis
C1, C2, C3
Depresses the larynx
after it has been elevated
in swallowing and in
vocal movements
Thyrohyoid:
It lies deep to the
sternohyoid
Oblique line of thyroid
cartilage
Lower border of the
body and the greater
cornua of the hyoid
bone
C1 through
hypoglossal nerve
a. Depresses the hyoid
bone
b. Elevates the larynx when the hyoid
is fixed by the suprahyoid muscles
Omohyoid:
lt has an inferior belly, a common
tendon and a superior belly. lt
arises by the inferior belly, and is
inserted through the superior belly
a. Upper border of scapula near the
suprascapular
notch
b. Adjoining part of suprascapular
ligament
Lower border of body of hyoid bone
lateral to the sternohyoid. The central
tendon lies on the internal jugular
vein at the level of the cricoid
cartilage and is bound to the clavicle
by a fascial pulley
Superior belly by the superior root of
the ansa cervicalis, and inferior belly
by inferior root of
ansa cervicalis
Depresses the hyoid
bone following itelevation during
swallowing or in vocal movements