The shape of the |nose|, below the bridge, is determined by the arrangement of its various ~cartilages~. These semi-rigid plates are situated so as to surround the nasal vestibule in front and prevent its closing. The apex, or tip, of the |nose| is made up of the paired lateral alar ~cartilages~. Each lateral alar ~cartilage~ has a shape similar to a horseshoe and partially encircles the nostril. These make up the large, flat lateral wall and the inferior extension makes up the medial wall. The medial wall forms the movable |nasal septum|, which divides the nasal cavity. Two to four lesser alar ~cartilages~ (sesamoid ~cartilages~) are also found on each side of the |nose| at the back end of the lateral wall of the alar ~cartilage~.