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Fig. 46. Showing the Nerve Structures concerned in the Sense of Hearing

It has already been shown (Fig. 35) that the mass of nerve cells which come in contact with the otocyst arise from the neural crest of the hind brain in the same manner as the ganglion of a posterior nerve root. The mass of nerve cells is divided into three groups (A, B, C, see Fig. 46).

A becomes the geniculate ganglion

n the formation of the petro-mastoid it is included in the aqueductus Fallopii. Its cells give rise to the great superficial petrosal nerve and chorda tympani in the same manner as the ganglion of a posterior root produces the sensory fibres of a spinal nerve (Dixon).- The pars intermedia, in part at least, represents the afferent or ingrowing root of the ganglion.


B The second or cochlear group gives rise to :

  1. The spiral ganglion situated in the lamina spiralis;
  2. To the cells in the floor of the internal auditory meatus which become connected with the saccule and posterior semicircular canal ;
  3. Another part remains stranded on the restiform body as the accessory and lateral root ganglia (Fig. 46).


Each cell of the ventral acoustic ganglion (group B) sends efferent processes to the organ of Corti in the cochlea and the acoustic cells of the saccule and posterior semicircular canal and afferent fibres which form the dorsal or lateral root of the auditory nerve and run to the nerve cells in the opposite side of the medulla oblongata. Some of these fibres form the striae acousticae.

C The third group of cells (Fig. 46) forms the vestibular ganglion in the fundus or floor of the internal auditory meatus.

Its cells send efferent fibres to the utricle, external and superior semicircular canals, and afferent fibres which form the mesial root of the auditory nerve. This root passes beneath the restiform body (Fig. 46) to terminate in the nerve cells of the acoustic tubercle and trigone in the floor of the 4th ventricle. These nerve cells and fibres are in no sense auditory, but concerned with the balancing of the body.


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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Pages where the terms "Historic Textbook" and "Historic Embryology" appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms and interpretations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)

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

Reference

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


Cite this page: Hill, M.A. (2019, March 20) Embryology Keith1902 fig046.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Keith1902_fig046.jpg

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