File:Anson1948 fig05.jpg

Fig. 5. Otic capsule developmental stages 160 mm and 170 mm fetus

Drawings, continued, of the stapes and the adjacent fissular region of the otic capsule, depicting developmental stages; X 6.6. Parts a to c are from a 160 mm. (19.5 week) fetus (Wisconsin series 41: (a) slide 19, section 4; (b) slide 18, section 8; (c) slide 17, section 9). d to f, from a 170 mm. (20 week) fetus (Wisconsin series 131: (d) slide 25, section 5; (e) slide 21, section 10; (f) slide 20, section 8). Here, a is taken at the level of the tympanic orifice of the fissula ante fenestram; 19, through the middle of the fissular tract and the posterior crus of the stapes; c, through the vestibular orifice of the fissula, and d to- f, from sections of the 170 mm. fetus which pass through similar levels of the fissula and ossicle (in succession, the tympanic extremity, the body and the vestibular extremity of the fisstula).

In the 160 mm specimen destruction of cartilage is under way; bone is formed on the obturator aspect of the base and crus of the stapes and on the tympanic and vestibular walls of the otic capsule. Concurrently, the cartilage of the fissula has become partially separated; while almost detached at its cochlear end, the fissular cartilage is still broadly continuous with similar tissue at the vestibular window.

In the 170 mm fetus newly formed bone is present on both aspects of the crus as a complete shell externally, as a foraminous wall internally (i. e., toward the obturator foramen).

Reference

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. (2024, April 27) Embryology Anson1948 fig05.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Anson1948_fig05.jpg

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