File:Streeter1922-fig12.jpg

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Fig. 12. Reconstruction model of an embryo 18 mm long

No. 1390 Carnegie Collection. X 12.3.


In embryos 16 to 18 mm. long the relations are such as are shown in figure 12, which is a drawing of a model posed similarly to those shown in figures 9 and 11.

Owing to the foreshortening in a three-quarter view of this kind, one is apt to get a false impression as to the height of the head; in a true profile view the distance between the eye or ear and the dorsal midline over the midbrain or cerebellum would be much greater. At this time the auricular hillocks, except those continued as the tragus and antitragus, have lost their identity and have been molded into the early form of the definitive parts of the auricle. The beginning helix can be definitely outlined, and less distinctly the crus, the former being entirely a derivative of the hyoid bar, the latter a derivative of the mandibular bar. A fact of interest is that, whereas the crus and tragus form a relatively small part of those adult surface structures that are derived from the mandibular bar, the scapha-helix and antitragus (eventually, also, the anthelix and lobule) constitute the only permanent surface representatives of the hyoid bar.


The embryo external appearance and dimensions suggest that it is a Carnegie stage 19 embryo (Week 7, 48 - 51 days, 16 - 18 mm).


Plate 1. Ventrolateral view of the head in a series of human embryos Fig. 9. Embryo 6 mm | Fig. 10. Embryo 12 mm | Fig. 11. Embryo 14 mm | Fig. 12. Embryo 18 mm

Ventrolateral view of the head in a series of human embryos, showing the change in topography of the auricle in the course of its development. The surface area of the mandibular and hyoid bars entering into the formation of the auricular primordium is colored blue. These figures show the lateral and dorsal migration of the auricle coincident with the formation of the mandible.


In-text Figures: Figure 1 and 2 | Figure 3 and 4 | Figure 5 | Figure 6 and 7 | Figure 8 | Text | Glossary
Plates: Plate 1 | Plate 2 | Plate 3 | Plate 4 | Plate 5 | Plate 6 | Plates | Glossary
Figures: 1. Auricle cartilage | 2. External ear | 3. Agnathia | 4. Agnathia+cyclopia | 6. Auricular cartilage embryo 21, 32 and 43 mm | 7. Auricular cartilage 50 mm fetus | 9. Embryo 6 mm | 10. Embryo 12 mm | 11. Embryo 14 mm | 12. Embryo 18 mm | 13. Embryo 1380, 5 mm | 14. Embryo 1767, 11 mm | 15. Embryo 1461, 10 mm | 16. Embryo 562, 13 mm | 17. Embryo 1232, 14 mm | 18. Embryo 475, 15 mm | 19. Embryo 899, 13 mm | 20. Embryo 434, 15 mm | 21. Embryo 492, 16.8 mm | 22. Embryo 576, 17 mm | 23. Embryo 547, 18 mm | 24. Embryo 955, 17 mm | 25. Embryo 1584, 18 mm | 26. Embryo 1134e, 21.3 mm | 27. Embryo 1358b, 33.2 mm | 28. Embryo 1535, 28 mm | 29. Embryo 2163, 36 mm | 30. Embryo 1980, 37 mm | 31. Embryo 1840a, 38.5 mm | 32. Embryo 2075, 40 mm | 33. Embryo 2144, 45.5 mm | 34. Embryo 642, 49 mm | 35. Embryo 2170, 50 mm | 36. Embryo 2095, 52 mm | 37. Embryo 2095, 52 mm | 38. Embryo 2066, 53 mm | 39. Embryo 2079, 56.5 mm. | 40. Embryo 1561, 57 mm | 41. Embryo 218, 62.5 mm. (R.) | 42. Embryo 1724, 66.2 mm | 43. Embryo 2328, 65 mm | 44. Embryo 2118, 69 mm | 45. Embryo 981, 85 mm | 46. Embryo 1845, 87 mm | 47. Embryo 1449, 87.3 mm | 48. Embryo 2003, 103.5 mm | 49. Embryo 1858, 100 mm | 50. Embryo 2274, 113 mm | 51. Embryo 2185, 113.5 mm. | 52. Embryo 9526, 114 mm. | 53. Embryo 1811, 114 mm | 54. Embryo 1716, 119 mm. Fig. 59. 1742, 191.2 mm | 55. Embryo 19576, 119 mm. | 56. Embryo 1782, 135.6 mm | 57. Embryo 1702, 150 mm | 58. Embryo 1708, 154 mm | 59. Embryo 1742, 191.2 mm | Figures


Related Notes: Outer Ear Development | Carnegie Contributions to Embryology

Reference

Streeter GL. Development of the auricle in the human embryo. (1922) Carnegie Instn. Wash. Publ. 277, Contrib. Embryol., 14: 111-138.



Cite this page: Hill, M.A. (2024, April 12) Embryology Streeter1922-fig12.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Streeter1922-fig12.jpg

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current10:45, 27 January 2013Thumbnail for version as of 10:45, 27 January 2013667 × 1,000 (103 KB)Z8600021 (talk | contribs)==Fig. 12. Reconstruction model of an embryo 18 mm long== No. 1390 Carnegie Collection. X 12.3. Plate 1. Ventrolateral view of the head in a series of human embryos Ventrolateral view of the head in a series of human embryos, showing the change in top