Gross and histological description of the epidermal membrane found on normal neonatal piglets

The structure and composition of fetal and placental tissues vary among different species of placental mammals. Some mammals, including camelids and pigs, possess an epidermal membrane during the fetal stage, called the epithelion, that is absent from other domestic mammals. Because neonatal piglets are a common animal model for many research techniques, it is important that researchers correctly identify this tissue and recognize its lack of pathological consequence when working with fetal and neonatal piglets. Here, the authors describe gross and histological examinations of the epithelion, comparing this tissue with other extra-fetal tissues and coatings.