Figure 6

Proposed mechanism of dynamic pulling forces of the muscles attached to the fMCs. (A) Contractions of the DSN and OOr (yellow and green) attached to the bases and posterior surfaces of the fMCs may rotate fMCs and cause the nasal tip downward. (B) The crossing fibers of the DSN and OOr attached to the fMCs can increase the length of the fibers pulling the fMCs and assist in changing the pulling direction toward the nasal tip. Bilateral crossing fibers of the DSN and OOr could pull the nasal tip downward in a more-medial direction. The crossing fibers of the DSN and OOr attached to the fMCs and their adjacent vestibular skin may increase tension in the nasolabial area below the fMCs, causing the nasal tip to droop and the upper lip to shorten. (C) Distinctive unilateral crossing fibers may cause imbalance of the pulling force toward the nasal tip. (D) The unilateral crossing fibers of the DSN were often observed with connecting fibers (red) in an arched shape between both the DSNs. These connecting fibers may modify the downward force in a more-medial direction, reducing asymmetric forces on the nasal tip. (E) When the DSN and OOr with crossing fibers attached to the fMCs pull the fMCs and nasal tip downward, the depressor alae nasi muscle (blue) located lateral to the DSN may pull the vestibular skin of the nostril sill adjacent to the fMCs downward. The crossing fibers of the OOr attached to the vestibular skin adjacent to the fMCs may assist in pulling the nose downward (purple). Yellow and green arrows indicate directions of the contraction forces of the DSN and OOr. White and red arrows indicate the pulling direction toward the nasal tip. Blue arrows indicate directions of the contraction forces of the DAN. Purple arrows indicate directions of the contraction forces of the crossing fibers of the OOr attached to the vestibular skin adjacent to the fMCs.