A line or stripe.
- angioid s's — red to black irregular bands in the ocular fundus running outward from the optic disk.
- s. canal — the papillary duct, the canal between the exterior and the lactiferous sinus within the teat of a ruminant.
- primitive s. — a faint white trace at the caudal end of the embryonic disk, formed by movement of cells at the onset of mesoderm formation, providing the first evidence of the embryonic axis.
