Superficial muscular aponeurotic system (or superficial musculoaponeurotic system
) (SMAS) is a thin yet tough
unitary tissue plane of the face
formed by facial fasciae, subcutis connective tissue, and facial muscles.
Its composition varies, containing muscle fibres in some areas, and fibrous or fibroaponeurotic tissue in others.
It connects to the dermis via vertical septa. It does not attach to bone. In most areas, a distinct plane can be defined deep to the SMAS (continuous with that formed between the platysma and underlying
investing layer of deep cervical fascia
The investing layer of deep cervical fascia is the most superficial part of the deep cervical fascia, and encloses the whole neck.
It is considered by some sources to be incomplete or nonexistent.
Attachments
It surrounds the neck like a collar, ...
).
Superiorly, the SMAS extends to the
galea aponeurotica of the scalp,
becoming continuous with
temporoparietal fascia (at the
zygomatic arch
In anatomy, the zygomatic arch (colloquially known as the cheek bone), is a part of the skull formed by the zygomatic process of temporal bone, zygomatic process of the temporal bone (a bone extending forward from the side of the skull, over the ...
) and galea. It becomes continuous with the
platysma muscle inferiorly (inferior to the inferior border of the mandible), and indistinct laterally (inferior to the
zygomatic arch
In anatomy, the zygomatic arch (colloquially known as the cheek bone), is a part of the skull formed by the zygomatic process of temporal bone, zygomatic process of the temporal bone (a bone extending forward from the side of the skull, over the ...
). Anteromedially, it blends with the
epimysium of some facial muscles;
a link between facial muscles and the skin of the face is thereby established, enabling
facial expression
Facial expression is the motion and positioning of the muscles beneath the skin of the face. These movements convey the emotional state of an individual to observers and are a form of nonverbal communication. They are a primary means of conveying ...
.
Over the parotid gland, the SMAS is firmly united with the superficial layer of
parotid fascia.
Clinical significance
The SMAS is clinically important in
facial plastic surgery for
rhytidectomy (facelift procedure). During this procedure, the SMAS is accessed through an arch-shaped incision anterior to the ear; a portion of the SMAS is then excised and the remaining SMAS is stretched by drawing it posterior-ward and suturing it, thus making the skin of the face which overlies the SMAS taut.
References
External links
Facelift, SMAS Plication
Plastic surgery
Oral and maxillofacial surgery
Otorhinolaryngology
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