Weller reported that the thymus and the parathyroids are formed by the third and fourth endodermal pharyngeal pouches that migrate laterally in surrounding mesenchyme

Pahwa et al., Thymus 1:27-58, 1979

International Union of Immunological SocietiesUniversity of South AfricaInstitute of Infectious Disease and Molecular MedicineElizabeth Glazer Pediatric Aids FoundationStellenbosch University