1987 Developmental Stages In Human Embryos - Stage 22

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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.

Links: Embryonic Development | Carnegie Collection | Carnegie Embryos | Ronan O'Rahilly | Fabiola Müller

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 
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Pages where the terms "Historic Textbook" and "Historic Embryology" appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms and interpretations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)

Stage 22

Carnegie Collection - Stage 22 
Serial No. Size (mm) Grade Fixative Embedding Medium Plane Thinness (µm) Stain Point Score Sex Year Notes
392 E., 23 Ch., 45x45x25 Poor ... P Sagittal 50 Al. coch. 42 Female 1907 Brödel Collection. Injected
405 E., 26 Good Formol C Sagittal 40 Carmine 42.5 Male 1907
464 E.,26 Ch., 45x40x30 Good Formol? alc? P Sag. 100 Al. coch. 44.5 Male 1910
584A E.,25 Ch., 50x42x40 Poor Formol P Sagittal 50 Al. coch. 41 ? 1913
630 E., 25 Poor Formol P Transverse 100 Al. coch. 46 Male 1913
840 E, 24.8 Good Formol P Transverse 50 Al. coch. 44.5 Female 1914
875 E, 27 Ch., 40x28x22 Good Formol P Sagittal 40 Al. coch. 45 Male 1914
895 E., 26 Ch., 67x62x54 Good Formol P Transverse 25 Al. coch. 46.5 Female 1914
1315 E.,25 Good Formol P Sagittal 50 Al. coch. 40.5 Female 1915 Spina bifida and anencephaly
1458 E., 27.5 Ch, 45x45x30 Exc. Formol C Sagittal 50 (Stain - Haematoxylin Eosin) aur, or. G. 45.5 Male 1916
1894 E, 24.6 Good Formol c Sagittal 40,80 (Stain - Haematoxylin Eosin) aur, or. G. 41 Female 1917
2206 E, 27 Ch, 50x30x18 Poor Formol p Transverse 40 (Stain - Haematoxylin Eosin) 44.5 Male 1918
3681 E, 26.3 Ch, 36x36x34 Good Formol p Transverse 25 Al. coch. 44.5 Male 1921
4304 E,25 Ch, 66x45x45 Good Bouin p Transverse 20 (Stain - Haematoxylin Eosin) 44.5 Female 1923 Injected
4339 E, 24.5 Good Formol p Transverse 15 Al. coch, Mallory 46,5 Female 1923
4476 E., 26.2 Good Bouin p Transverse 40 (Stain - Haematoxylin Eosin) 46 Female 1923 Tubal
4638 E, 23.4 Exc. Bouin p Transverse 15,20 Al. coch, or. G. 41.5 Male 1924
6701 E, 24 Poor Formol p Coronal 20 (Stain - Haematoxylin Eosin) 41 Female 1933
6832 E, 25.8 Exc. Bouin C-P Coronal 20 (Stain - Haematoxylin Eosin) 42 Female 1934
8394 E, 25.3 Ch, 48x50x34 Exc. Bouin C-P Transverse 20 (Stain - Haematoxylin Eosin), Masson 44.5 Female 1946
8948 E, 26.7 Ch, 61x51x50 Poor Formol-Zenker p Transverse 15 Ag ? ? 1952
Abbreviations
  • Size - E. is the greatest length of the embryo and Ch. is the mean diameter of the chorion.
  • Grade - total grade of the specimen and includes both its original quality and the condition of the mounted sections.
  • Embedding medium - paraffin (P) or a combination of celloidin and paraffin (C-P).
  • Fixative - formalin (Formol), alcohol and formalin (Alc, formol), Bouin (Bouin solution)
  • Stain -
  •  ? - unknown or not determined.
Stage22 bf6.jpg Stage22 bf8.jpg Stage22 bf7.jpg
middle row to be added.
Stage22 bf3.jpg Stage22 bf5.jpg Stage22 bf4.jpg


Fig. 22-1. Photographs of three embryos belonging to stage 22. The eyes are more than half covered by the eyelids. The limbs have increased in length, and the digits touch or overlap. Top row, No. 6701. Middle row, No. 6832. Bottom row, No. 8394. All views are at the same magnification.

Size And Age

The middle group of embryos of this stage measure 25–27 mm in length.

The age is believed to be approximately 54 postovulatory days.

External Form

The eyelids, which have been thickening gradually, are now rapidly encroaching upon the eyes. The formation of the auricle has progressed noticeably: the tragus and antitragus especially are assuming a more definite form. The superficial vascular plexus of the head extends upward about three-quarters of the way above the eye-ear level. The hands extend further out in front of the body of the embryo, and the fingers of one hand may overlap those of the other.

Features for Point Scores

  1. Cornea. The cellular invasion of the postepithelial layer is complete centrally in some eyes (fig. 17)[1]. A scleral condensation is now definite.[2]
  2. Optic nerve. The mesenchyme surrounding the optic nerve forms a definite sheath.
  3. Cochlear duct. The tip of the duct points “upward” for the second time (fig. 19-6).
  4. Adenohypophysis. Remnants of the incomplete stalk are present at each end (fig. 19-7).
  5. Vomeronasal organ. The appearances are intermediate between those of stages 21 and 23 (fig. 19-9).
  6. Submandibular gland. The duct shows secondary branches. It is practically solid but a suggestion of a lumen can be found in its oral part (fig. 19-10).
  7. Metanephros. A few large glomeruli are present (fig. 19-12).
  8. Humerus. Cartilaginous phases 1–4 are still present (figs. 3 and 15–17)[3]. The formation of osteoblasts is beginning. A bony collar appears in the humerus, radius, ulna, and femur and tibia during stages 22 and 23.[4]

Additional Features

  • Blood vascular system. The aortic arch system has been illustrated by Boyd (1937 fig. 1).[5]
  • Heart. Reconstructions of the atrial region were reproduced by Licata (1954, figs. 4 and 5). Chordae tendineae begin to form at stages 22 and 23.[6].
  • Paramesonephric ducts. The paramesonephric ducts lie side-by-side caudally and show rostral vertical, middle transverse, and caudal vertical portions.
  • Brain. A general view of the organ was given by Hochstetter (1919, fig. 42).[7] The superior and inferior colliculi of the midbrain are indicated by their lamination.[8] The epithalamus is individualized by the presence of the sulcus dorsalis. In the hemispheres the cortical plate begins to appear.

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.

Links: Embryonic Development | Carnegie Collection | Carnegie Embryos | Ronan O'Rahilly | Fabiola Müller

  1. Streeter, G. L. 1951. Developmental horizons in human embryos. Description of age groups XTX, XX, XXI, XXII, and XXIII, being the fifth issue of a survey of the Carnegie Collection (prepared for publication by C. H. Heuser and G. W. Corner). Carnegie Instn. Wash. Publ. 592, Contrib. Embryol., 34, 165-196.
  2. Gilbert, P. W. 1957. The origin and development of the human extrinsic ocular muscles. Carnegie Instn. Wash. Publ. 611, Contrib. Embryol., 36, 59-78.
  3. Streeter, G. L. 1949. Developmental horizons in human embryos (fourth issue). A review of the histogenesis of cartilage and bone. Carnegie Instn. Wash. Publ. 583, Contrib. Embryol., 33, 149-169.
  4. <pubmed>5042780</pubmed>
  5. Boyd, J. D. 1937. The development of the human carotid body. Carnegie Instn. Wash. Publ. 479, Contrib. Embryoi, 26, 1-31.
  6. <pubmed>3729012</pubmed>
  7. Hochstetter, F. 1919. Beitrage zur Entwicklungsgeschicbte desmenschlichen Gehirns.1. Teil. Deuticke, Vienna.
  8. Bartelmez, G. W., and Dekaban, A. S. 1962. The early development of the human brain. Carnegie Instn. Wash. Publ. 621, Contrib. Embryoi, 37, 13-32.


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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 
Mark Hill.jpg
Pages where the terms "Historic Textbook" and "Historic Embryology" appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms and interpretations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)



Cite this page: Hill, M.A. (2019, June 20) Embryology 1987 Developmental Stages In Human Embryos - Stage 22. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/1987_Developmental_Stages_In_Human_Embryos_-_Stage_22

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