1987 Developmental Stages In Human Embryos - Stage 10: Difference between revisions
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==Stage 10== | ==Stage 10== | ||
[[Carnegie stage 10]] | [[Carnegie stage 10]] | ||
* Approximately 1.5–3 mm in length | |||
* Approximately 22 ± 1 postovulatory days | |||
* Characteristic feature: 4–12 pairs of somites | |||
==Summary== | |||
External: 4–12 pairs of somites; fusion of neural folds is imminent or in progress; the optic sulcus may have appeared; pharyngeal arch 1 begins to be visible on the surface. | |||
Internal: the cardiac loop is appearing; the laryngeotracheal sulcus develops; the intermediate mesoderm becomes visible. | |||
==Size and Age== | |||
The chorion generally has a diameter of 8–15 mm. The greatest length of the embryo, although not of great informational value (Bartelmez and Evans, 1926), is usually 1.5–3 mm. | |||
The age is approximately 22 postovulatory days. A brief review of stage 10 was published by Heuser and Corner (1957), and a detailed investigation of this stage was undertaken by Müller and O'Rahilly (1985), who provided graphic reconstructions. Both of these publications contain an appropriate bibliography. | |||
==External Form== | |||
(figs. 10-1 and 10-2) | |||
The criterion for stage 10 is the presence of 4–12 pairs of somites. This stage is particularly important because, during it,the neural tube first begins to be formed from the neural folds and groove. In the less advanced specimens the neural groove is open throughout its whole length, whereas by the end of the stage the groove is closed from the rhombencephalon to below the level of the last somites present. | |||
The embryo is becoming longer, and the umbilical vesicle continues to expand. The rostral portion of the neural folds becomes elevated, a caudal fold begins to appear, and the whole embryo comes to rise beyond the level of the umbilical vesicle (i.e., a variable degree of lordosis usually becomes evident). By the end of the stage the cardiac region has become a prominent feature of the external form (Boyden, 1940). | |||
Representative specimens of this stage are illustrated in figures 10-3 and 10-4. These outlines, showing the dorsal aspect of a median section of each specimen, are enlarged to the same scale. As pointed out by Bartelmez and Evans (1926), the mesencephalic flexure is present in all embryos of this period. A dorsal flexure may or may not be found. The curvature of the dorsal profile varies from a gentle convexity through all degrees of concavity (lordosis) from the least possible curve to a deep, sharp kink. Bartelmez and Evans (1926) and Streeter (1942) have discussed the significance of this variation as seen in human and rhesus embryos of early somitic stages. On the whole, the evidence indicates that, whereas extreme dorsal flexion should be regarded as an artifact, anything from a gentle convexity to a moderate dorsal concavity can be considered normal. | |||
The optic sulcus develops in the forebrain and, toward the end of the stage, an indication of invagination of the otic disc is found. During stage 10, swellings begin to appear for the mandibular arch (Politzer, 1930, fig. 5), and the hyoid arch and probably the maxillary process become identifiable (Bartelmez and Evans, 1926, fig. 6). Pharyngeal cleft 1 becomes visible (Corner, 1929, figs. 4 and 10).The future ectodermal ring (O'Rahilly and Müller, 1985) is beginning to form as a thick area overlying pharyngeal arch 1. An indication of an intermediate band is present and represents the future intermembral part of the ectodermal ring. | |||
==References== | ==References== | ||
Revision as of 16:07, 27 June 2015
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O'Rahilly R. and Müller F. Developmental Stages in Human Embryos. Contrib. Embryol., Carnegie Inst. Wash. 637 (1987).
| Online Editor Note |
|---|
| O'Rahilly R. and Müller F. Developmental Stages in Human Embryos. Contrib. Embryol., Carnegie Inst. Wash. 637 (1987).
The original 1987 publication text, figures and tables have been altered in formatting, addition of internal online links, and links to PubMed. Original Document - Copyright © 1987 Carnegie Institution of Washington.
|
- 1987 Stages: Introduction | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | References | Appendix 1 | Appendix 2 | Historic Papers | Embryonic Development
| Historic Disclaimer - information about historic embryology pages |
|---|
 |
Stage 10
- Approximately 1.5–3 mm in length
- Approximately 22 ± 1 postovulatory days
- Characteristic feature: 4–12 pairs of somites
Summary
External: 4–12 pairs of somites; fusion of neural folds is imminent or in progress; the optic sulcus may have appeared; pharyngeal arch 1 begins to be visible on the surface.
Internal: the cardiac loop is appearing; the laryngeotracheal sulcus develops; the intermediate mesoderm becomes visible.
Size and Age
The chorion generally has a diameter of 8–15 mm. The greatest length of the embryo, although not of great informational value (Bartelmez and Evans, 1926), is usually 1.5–3 mm.
The age is approximately 22 postovulatory days. A brief review of stage 10 was published by Heuser and Corner (1957), and a detailed investigation of this stage was undertaken by Müller and O'Rahilly (1985), who provided graphic reconstructions. Both of these publications contain an appropriate bibliography.
External Form
(figs. 10-1 and 10-2) The criterion for stage 10 is the presence of 4–12 pairs of somites. This stage is particularly important because, during it,the neural tube first begins to be formed from the neural folds and groove. In the less advanced specimens the neural groove is open throughout its whole length, whereas by the end of the stage the groove is closed from the rhombencephalon to below the level of the last somites present.
The embryo is becoming longer, and the umbilical vesicle continues to expand. The rostral portion of the neural folds becomes elevated, a caudal fold begins to appear, and the whole embryo comes to rise beyond the level of the umbilical vesicle (i.e., a variable degree of lordosis usually becomes evident). By the end of the stage the cardiac region has become a prominent feature of the external form (Boyden, 1940).
Representative specimens of this stage are illustrated in figures 10-3 and 10-4. These outlines, showing the dorsal aspect of a median section of each specimen, are enlarged to the same scale. As pointed out by Bartelmez and Evans (1926), the mesencephalic flexure is present in all embryos of this period. A dorsal flexure may or may not be found. The curvature of the dorsal profile varies from a gentle convexity through all degrees of concavity (lordosis) from the least possible curve to a deep, sharp kink. Bartelmez and Evans (1926) and Streeter (1942) have discussed the significance of this variation as seen in human and rhesus embryos of early somitic stages. On the whole, the evidence indicates that, whereas extreme dorsal flexion should be regarded as an artifact, anything from a gentle convexity to a moderate dorsal concavity can be considered normal.
The optic sulcus develops in the forebrain and, toward the end of the stage, an indication of invagination of the otic disc is found. During stage 10, swellings begin to appear for the mandibular arch (Politzer, 1930, fig. 5), and the hyoid arch and probably the maxillary process become identifiable (Bartelmez and Evans, 1926, fig. 6). Pharyngeal cleft 1 becomes visible (Corner, 1929, figs. 4 and 10).The future ectodermal ring (O'Rahilly and Müller, 1985) is beginning to form as a thick area overlying pharyngeal arch 1. An indication of an intermediate band is present and represents the future intermembral part of the ectodermal ring.
References
| Online Editor Note |
|---|
| O'Rahilly R. and Müller F. Developmental Stages in Human Embryos. Contrib. Embryol., Carnegie Inst. Wash. 637 (1987).
The original 1987 publication text, figures and tables have been altered in formatting, addition of internal online links, and links to PubMed. Original Document - Copyright © 1987 Carnegie Institution of Washington.
|
Search Pubmed
- 1987 Stages: Introduction | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | References | Appendix 1 | Appendix 2 | Historic Papers | Embryonic Development
| Historic Disclaimer - information about historic embryology pages |
|---|
|
Cite this page: Hill, M.A. (2024, April 26) Embryology 1987 Developmental Stages In Human Embryos - Stage 10. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/1987_Developmental_Stages_In_Human_Embryos_-_Stage_10
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
