<prompt> Tympanic membrane develops from:EctodermEndodermMesodermAll  <response>: Ans: d All Ref.: Human Embryology, IB Singh, 6th ed,p. 350Tympanic membrane develops from all three layers, i.e., ectoderm, endoderm and mesoderm 1st ectodermal cleft - Ectodermal Tubotympanic recess - Endodermal Connective tissue - MesodermalAnatomical structures and their origin in general:ECTODERM:ENDODERM:Structures meeting the external environment are ectodermal in origin Skin Mucous covering of outer parts, like Oral cavity Anal canal Vagina UrethraEpithelial lining of structures meetingthe alimentary canal are endodermal in origin GIT Ducts and acini of salivary glands except parotid Eustachian tube and middle ear Biliary system Parenchyma of the liver Respiratory system Ducts and acini of the pancreasMESODERM:Serous lining of body cavities and endotheliallining of CVS, lymphatics and lymph nodes are mesodermal in origin Bone, muscle, cartilage Connective tissue of skin BloodvesselsSPECIAL POINTS: Eye:PituitaryExtraocular muscles: MesodermNeurohypophysis: NeuroectodermAdenohypophysis: EctodermDilator sphincter pupillae,ciliary muscle: Neural crestLens: Surface ectodermSalivary glands:Parotid: EctodermSubmandibular, sublingual glands: EndodermRetina: NeuroectodermMeninges:Dura mater: Mesoderm Pia and Arachnoid mater: Neural crestEar: Pinna, EAC: EctodermTympanic membrane: all 3 layersMiddle ear, eustachian tube: EndodermCochlea, Semicircular canals: EctodermAdrenals:Cortex: MesodermMedulla: Neural crestThyroid and Parathyroid. EndodermAbdomen:Parafollicular C cells: Neural crestLiver, pancreas: EndodermSpleen, testis, ovary: MesodennThorax:Heart: Mesoderm SphlanchnopleuricLung: EndodermEnamel: Ectoderm 