Fig. 8. Otic capsule developmental stages 205, 210, 290, 345, 345 mm Fetus and Newborn Infant
Drawings of developmental stages concluded. X 6.6. (a) 205 mm. (23 week) fetus (Wisconsin series 129, slide 20, section 3); (b) 210 mm. (23 week) fetus (Wisconsin series 51, slide 38, section 5); (C) 290 mm. (32 week) fetus (Wisconsi11 series 59, slide 36, section 5); (d) 345 mm. (38 week), fetus (Wisconsin series 61, slide 42, section 1); (e) newborn infant (Wisconsin series 315. slide 20', section 8). Parts a, b and d are from sections through the vestibular oriﬁce of the ﬁssula; (C) and (e), from sections at the fenestral oriﬁce.
The cartilage which surrounds the ﬁssula ante fenestram in the 202 mm. specimen (ﬁg. 6b) as a thick chondral layer, bordered by spicules of intrachondrial bone, undergoes rapid reduction in bulk to become, at the vestibular extremity, an osseous shell lined by a thin stratum of persistent cartilage or by a perichondrium (205 and 210 mm., a and b). Cartilage still persists at the cochlear extremity of the ﬁssula as a considerable mass (205 mm., a); similarly, it still remains at the fenestral extremity, where the ﬁssular cartilage is still continuous with similar tissue which lines the vestibular window (290 mm., c). While the cartilage is being gradually reduced in bulk, the marrow space, which everywhere surrounds the ﬁssula, becomes occupied by endochondral bone. At first, spicules of_intrachondrial bone are sparsely distributed in the area between plates of perichondrial bone (205 and 210 mm., a and b); endochondral bone next forms around these spicules (290 mm., C), ﬁnally converting the capsule into a petrous structure (345 mm., d; newborn, 9). Thus, in the newborn (c), the capsule has acquired an adult appearance, as has the stapes.
Anson BJ. and Cauldwell EW. Stapes, fissula ante fenestram and associated structures in man: V . From the fetus of 160 mm to term. (1948) 48(3): 263-300.
Cite this page: Hill, M.A. (2019, July 23) Embryology Anson1948 fig08.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Anson1948_fig08.jpg
- © Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
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