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Practical Plastic Surgery - part 7

giữa crura tiếp tục từ phần trước nhất của crura trung gian đối với đầu mũi và bắt đầu chuyển sang hai bên để tạo thành một phần của genu (tức là, đường cong) của sụn bên dưới. Crura bên bao gồm phần còn lại của genu bằng cách tiếp tục sang hai bên, phía sau và hơi cephalically. | 396 Practical Plastic Surgery 64 middle crura which continue from the most anterior portion of the medial crura towards the tip of the nose and begin the turn laterally to form part of the genu i.e. curve of the lower lateral cartilages. The lateral crura comprise the remainder of the genu by continuing laterally posteriorly and slightly cephalically. It is important to note that as one traces the lateral crura from the tip posterolaterally the crura project more cephalically Fig. 64.1 . Hence the lateral crura provide structural support to the nasal rim predominantly at their medial portions leaving the very lateral portions of the nasal alae devoid of cartilage. This portion of the nose is comprised of fibrofatty tissue covered by overlying skin. The nasal septum is composed of three structures the perpendicular plate of the ethmoid posteriorly and cephalically the vomer posteriorly and caudally and the quadrangular i.e. cartilaginous septum anteriorly. The septum functions as a support structure for the mid-portion of the nose and it also comprises the medial component of the internal nasal valve completed posteriorly by the nasal floor and laterally by the upper lateral cartilages . The average internal valve angle is 12 . The arterial anatomy of the nose is important to consider for several reasons. While the blood supply to the nose is abundant making tissue necrosis a rare complication the potential for clinically significant bleeding exists. Bleeding can be significant in that it can compromise tissue due to compression e.g. septal hematoma or compromise visualization during the rhinoplasty. Again beginning cephalically the blood supply to the dorsal nose is derived from the dorsal nasal artery and the external nasal branches of the anterior ethmoidal artery. The lateral nasal artery which arises from the angular artery supplies blood flow to the nasal sidewalls and the caudal nasal dorsum and tip. The columellar branches of the superior labial artery .