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Fig. 35 Diagrammatic Section through the Cephalic region of an embryo, showing the origin of the Auditory System

The Structures which form the Organ of Hearing.— In figure 35 is shown diagrammatically the derivation of the five elements which unite together to make up the organ of hearing. The five elements are :

  1. The otocyst — an area of epiblast (epithelial covering of embryo) above the first branchial cleft which becomes invaginated in a saccular form, and forms the epithelial lining of the membranous labyrinth. Some of its lining cells become differentiated into the auditory epithelium.
  2. A ganglion derived from the " neural crest " of the hind brain (Fig. 35). The nerve cells form the cochlear and vestibular ganglia. Each cell sends out two processes, one to become connected with the auditory epithelium of the otocyst, the other to end in groups of nerve cells in the floor of the 4th ventricle, their collective fibres forming the auditory nerve. The development of the auditory nerve thus resembles that of the posterior or sensory root of a spinal nerve.
  3. The otocyst (membranous labyrinth) becomes surrounded by a capsule of cartilage — the periotic capsule. This ossifies from several centres, and forms the bony labyrinth and petro-mastoid.
  4. The dorsal end of the first visceral cleft. — The inner recess of the 1st cleft forms the Eustachian tube, the tympanum and antrum of the mastoid ; the external cleft depression, the external auditory meatus; while out of the cleft membrane is formed the membrana tympani.
  5. The malleus is derived from the upper end of Meckel's cartilage, the incus from the posterior end of the palato-quadrate bar (cartilaginous skeleton of maxillary process), while the stapes is an independent formation developed round the stapedial artery. It may be derived, in part at least, from the upper end of the cartilage of the hyoid arch.

Development of the Organ of Hearing: Fig. 35. Cephalic region of an embryo, showing the origin of the Auditory System | Fig. 36 A. Adult External Auditory Meatus | Fig. 36 B. External Auditory Meatus at Birth | Fig. 37. Tubercles round the First Visceral Cleft to form the External Ear | Fig. 38. Part of the Adult Ear formed by each Tubercle | Fig. 39. Auditory Organs 6th week human fetus | Fig. 40. Cavities from the Inner Recess of the First Cleft | Fig. 41. The temporal bone at birth | Fig. 42. Walls of the Antrum | Fig. 43. Outer aspect of the Petro-mastoid at birth | Fig. 44. Membranous Labyrinth | Fig. 45. The Otocyst in an Embryo of five weeks | Fig. 46. Nerve Structures Sense of Hearing | Figures

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Human Embryology and Morphology (1902): Development or the Face | The Nasal Cavities and Olfactory Structures | Development of the Pharynx and Neck | Development of the Organ of Hearing | Development and Morphology of the Teeth | The Skin and its Appendages | The Development of the Ovum of the Foetus from the Ovum of the Mother | The Manner in which a Connection is Established between the Foetus and Uterus | The Uro-genital System | Formation of the Pubo-femoral Region, Pelvic Floor and Fascia | The Spinal Column and Back | The Segmentation of the Body | The Cranium | Development of the Structures concerned in the Sense of Sight | The Brain and Spinal Cord | Development of the Circulatory System | The Respiratory System | The Organs of Digestion | The Body Wall, Ribs, and Sternum | The Limbs | Figures | Embryology History


Keith A. Human Embryology and Morphology. (1902) London: Edward Arnold.

Cite this page: Hill, M.A. (2024, April 20) Embryology Keith1902 fig035.jpg. Retrieved from

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