RT Book, Section A1 Aslam, Arif A1 Aasi, Sumaira Z. A2 Kang, Sewon A2 Amagai, Masayuki A2 Bruckner, Anna L. A2 Enk, Alexander H. A2 Margolis, David J. A2 McMichael, Amy J. A2 Orringer, Jeffrey S. SR Print(0) ID 1161346440 T1 Cutaneous Surgical Anatomy T2 Fitzpatrick's Dermatology, 9e YR 2019 FD 2019 PB McGraw-Hill Education PP New York, NY SN 9780071837798 LK dermatology.mhmedical.com/content.aspx?aid=1161346440 RD 2024/10/11 AB AT-A-GLANCEThe superficial musculoaponeurotic system (SMAS) is a fibromuscular layer connecting the facial muscles. Incisions and undermining within the subcutaneous fat above SMAS will not result in damage to motor nerves.When planning reconstruction, the surgeon should consider cosmetic units, junctional lines, and resting skin tension lines to optimize the final aesthetic result.The three branches of the trigeminal nerve (cranial nerve V) provide sensory innervation to the face.The three main danger zones are areas where the temporal and marginal mandibular branches of the facial nerve and spinal accessory nerve lie superficial and can be easily injured. Damage to the temporal branch of the facial nerve may result in an ipsilateral eyebrow ptosis and obscuring of the superolateral visual field. The marginal mandibular branch of the facial nerve is vulnerable to damage along the inferior edge of the body of the mandible. Damage to the marginal mandibular branch of the facial nerve results in an asymmetrical smile. The spinal accessory nerve lies in the posterior triangle of the neck and may be identified by Erb’s point.The rich vascular supply to the face from both the external and internal carotid ensures the reliable healing potential and viability of flaps and grafts in head and neck surgery.