develops from develops from embryonic structure yolk yolk syncytial layer periblast This class was sourced from an external ontology (teleost_anatomy). Its definitions, naming conventions and relationships may need to be checked for compatibility with uberon YSL Peripheral layer of the yolk cell including nuclei and non-yolky cytoplasm. Kimmel et al, 1995. ZFA:0000088 UBERON:2000088