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What is Tympanic membrane develops from: and explain in detail?
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 (Sphlanchnopleuric)Lung: EndodermEnamel: Ectoderm