Superficial muscular aponeurotic system
Superficial muscular aponeurotic system is a thin yet tough unitary tissue plane of the face formed by facial fasciae, subcutaneous 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.
Superiorly, the SMAS extends to the galea aponeurotica of the scalp, becoming continuous with temporoparietal fascia and galea. It becomes continuous with the platysma muscle inferiorly, and indistinct laterally. 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. Over the parotid gland, the SMAS is firmly united with the superficial layer of parotid fascia.