The Muscles of Facial Expression
The muscles of facial expression are located in the subcutaneous tissue, originating
from bone or fascia, and inserting onto the skin. By contracting, the muscles pull on
the skin and exert their e ects. They are the only group of muscles that insert into
skin.
These muscles have a common embryonic origin – the 2nd pharyngeal arch. They
migrate from the arch, taking their nerve supply with them. As such, all the muscles
of facial expression are innervated by the facial nerve.
The facial muscles can broadly be split into three groups:
orbital,
nasal
oral.
Orbital Group
o The orbital group of facial muscles contains two muscles associated with the
eye socket.
o These muscles control the movements of the eyelids, important in protecting
the cornea from damage. They are both innervated by the facial nerve.
Orbicularis Oculi
The orbicularis oculi muscle surrounds the eye socket and extends into the eyelid. It
has three distinct parts – palpebral, lacrimal, and orbital.
, Attachments – Originates from the medial orbital margin, the medial palpebral
ligament, and the lacrimal bone. It then inserts into the skin around the margin of
the orbit, and the superior and inferior tarsal plates.
Actions:
Palpebral part – gently closes the eyelids.
Lacrimal part – involved in the drainage of tears.
Orbital part – tightly closes the eyelids.
Innervation – Facial nerve (CN VII, temporal and zygomatic branches)
Corrugator Supercilii
The corrugator supercilii is a much smaller muscle and is located posteriorly to the
orbicularis oculi.
Attachments – Originates from the superciliary arch, running in a superolateral
direction. Inserts into the skin of the eyebrow.
Actions – Acts to draw the eyebrows together, creating vertical wrinkles on the
bridge of the nose.
Innervation – Facial nerve.
Fig 1: two orbital muscles of facial expression
The muscles of facial expression are located in the subcutaneous tissue, originating
from bone or fascia, and inserting onto the skin. By contracting, the muscles pull on
the skin and exert their e ects. They are the only group of muscles that insert into
skin.
These muscles have a common embryonic origin – the 2nd pharyngeal arch. They
migrate from the arch, taking their nerve supply with them. As such, all the muscles
of facial expression are innervated by the facial nerve.
The facial muscles can broadly be split into three groups:
orbital,
nasal
oral.
Orbital Group
o The orbital group of facial muscles contains two muscles associated with the
eye socket.
o These muscles control the movements of the eyelids, important in protecting
the cornea from damage. They are both innervated by the facial nerve.
Orbicularis Oculi
The orbicularis oculi muscle surrounds the eye socket and extends into the eyelid. It
has three distinct parts – palpebral, lacrimal, and orbital.
, Attachments – Originates from the medial orbital margin, the medial palpebral
ligament, and the lacrimal bone. It then inserts into the skin around the margin of
the orbit, and the superior and inferior tarsal plates.
Actions:
Palpebral part – gently closes the eyelids.
Lacrimal part – involved in the drainage of tears.
Orbital part – tightly closes the eyelids.
Innervation – Facial nerve (CN VII, temporal and zygomatic branches)
Corrugator Supercilii
The corrugator supercilii is a much smaller muscle and is located posteriorly to the
orbicularis oculi.
Attachments – Originates from the superciliary arch, running in a superolateral
direction. Inserts into the skin of the eyebrow.
Actions – Acts to draw the eyebrows together, creating vertical wrinkles on the
bridge of the nose.
Innervation – Facial nerve.
Fig 1: two orbital muscles of facial expression
