Diseases of the nose and throat, comprising affections of the trachea and oesophagus / by Sir St. Clair Thomson.

  • Thomson, St. Clair, 1859-1943.
Date:
1912
Catalogue details

Licence: In copyright

Credit: Diseases of the nose and throat, comprising affections of the trachea and oesophagus / by Sir St. Clair Thomson. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    the notochord-placed a little distance behind the junction of stomodaeum and foregut. . , , , , \ study of Fig. 2 will explain the origin of the thyro-glossal duct the appearance of cysts in the middle line over the front of the thyroid cartilage {sse p. 706 and Fig. 269), and the occurrence of accessory thyroid growths at the base of the tongue {see p. 387). The lingual tonsil is formed around this thyro-glossal diver- ticulum. /v.c/i. rh 0.0. Figs. 1 and 2.—The embryological air-passage. StoDi.. stomodaeum; y^, foregut; />-R:: pouch of Rathke; /yj infundibjlum ; T/uG.D., thyro- glossal duct; A.C., anterior cerebral vesicle; M.C., middle cerebral vesicle; P.C., posterior cerebral vesicle; D.S., first cephalic flexure; A'.C//., notochord; .S/i.O.. postsphenoid, and S/>./'.. presphenoid developmental centres, from which respectively develop () the bones of the cranial base as far for»vard as the sella turcica (i.e. the spheno-occipital portion of the basis cranii), and {/') the presphenoid or spheno-ethmoid portion ; A', the investing mass of Rathke. {Kindly lent by Dr. IVatson IVilliaws.) The nose and mouth in early foetal life constitute one chamber. About the eighth week a maxillaiy process gi^ows horizontally inwards from each lateral wall of this oro-nasal cavity, so as to form a partition between the nose and the mouth. On each side a median fronto-nasal plate descends from the frontal region, their lower ends dividing to form the primitive nasal pits (Fig. 3). These pits at first correspond to the vestibule, and are closed at the bottom by a layer of involuted epithelium. Failure of this fleshy septum to disappear would leave a membranous obstmo- tion between the vestibule and the nasal chamber proper (cf. p. 109). Imperfect union of the fronto-nasal plates in the middle line