serosa

noun, plural se·ro·sas, se·ro·sae [si-roh-see, -zee] /sɪˈroʊ si, -zi/.

1. Embryology, Zoology.
   1. the chorion.
   2. a similar membrane in insects and other lower invertebrates.
2. serous membrane.

noun

1. another name for serous membrane
2. one of the thin membranes surrounding the embryo in an insect’s egg

n. pl. se•ro•sas

1. serous membrane
2. The chorion of a bird or reptile embryo.