has part has part has_part characteristic of part of has modifier thymus development abnormal thymus morphology abnormal thymus development abnormal thymic development MPheno.ontology anomaly in the formation and/or differentiation of the thymus abnormal thymus organogenesis abnormal development of the thymus MP:0000704 in mouse, the parathyroid glands develop with the thymus from two common parathyroid/thymus primordia originating from the third pharyngeal pouch endoderm; the third pharyngeal pouches are formed at E9.5-E10 and are patterned into dorsal/anterior parathyroid and ventral/posterior thymus domains; the third pouch endoderm proliferates to form bilateral parathyroid/thymus common primordia at E11-E11.5; each primordium separates into one parathyroid gland and one thymus lobe at E12.5-E13.5, which then migrate to their eventual adult locations by about E14.5; the parathyroids locate adjacent to, or sometimes embedded within, the thyroid gland; the thymus migrates further caudally into the thorax, where the two lobes meet at the midline just above the heart; embryonic thymic remnants can give rise to ectopic thymic tissue in the neck, thyroid, and parathyroid glands; the thymus is the first of the lymphoid organs to be formed and grows considerably immediately after birth in response to postnatal antigen stimulation and the demand for large numbers of mature T cells; in rats and mice, the thymus reaches maximal size by sexual maturity and then gradually involutes abnormal gland development abnormal immune system development quality abnormal