MUC16 is a transmembrane mucin expressed at the apical surface of uterine epithelia. They commonly have basal and/or apical appendages. The dorsal scales are overlapping, strongly keeled and have apical pits. Two lateral ungual spines project proximally from the apical tuft. Initiation of primordia in apical meristems is correlated to heightened auxin levels. Branching occurs to form new apical meristems. Also, a lack of differentiation between apical and basal structures exists. Light activates photo-receptors and triggers signal cascades in plant cells of apical or lateral meristems. Basque has a distinction between laminal and apical articulation for the alveolar fricatives and affricates. May be terminal (apical), subapical, lateral, gynobasic, or subgynobasic. They are known to regulate axillary bud growth and apical dominance. Secretion is directly onto the apical surface. Such new plants can be grown from shoot cuttings that contain an apical meristem. Another model studied in apical dendrite development is the rat. Proplastids are commonly found in an adult plant's apical meristems.