Serosa

[L. serum - whey]. 1) In histology, the term is used to mean a serous membrane such as the peritoneum, pleura, and pericardium. A serous membrane is composed of a layer of epithelium with a thin layer of connective tissue. Synonym: tunica serosa. 2) In embryology, the term is used to mean the most exterior extraembryonic membrane. It consists of ectoderm and somatic mesoderm (somatopleure) and encloses all other extraembryonic membranes including the amnion, allantois, and yolk sac. Synonym: chorion.