Superficial muscular aponeurotic system
Superficial muscular aponeurotic system (or superficial musculoaponeurotic system<ref name=":02">Template:Citation</ref>) (SMAS) is a thin yet tough<ref name=":0">Template:Cite book</ref>Template:Rp unitary tissue plane of the face<ref name=":332">Template:Cite book</ref> formed by facial fasciae, subcutis connective tissue, and facial muscles.<ref name=":0" />Template:Rp Its composition varies, containing muscle fibres in some areas, and fibrous or fibroaponeurotic tissue in others.<ref name=":332" /> It connects to the dermis via vertical septa.Template:Citation needed 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).<ref name=":332" />
Superiorly, the SMAS extends to the galea aponeurotica ofTemplate:Citation needed the scalp,<ref name=":0" />Template:Rp becoming continuous with temporoparietal fascia<ref name=":02"/><ref name=":02"/> (at the zygomatic arch<ref name=":02"/>) and galea.Template:Citation needed It becomes continuous with the platysma muscle inferiorly (inferior to the inferior border of the mandible), and indistinct laterally (inferior to the zygomatic arch). Anteromedially, it blends with the epimysium of some facial muscles;<ref name=":332" /> a link between facial muscles and the skin of the face is thereby established, enabling facial expression.<ref name=":0" />Template:Rp Over the parotid gland, the SMAS is firmly united with the superficial layer of parotid fascia.<ref name=":33">Template:Cite book</ref>
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.<ref name=":0" />Template:Rp