Carnegie stage 7

Embryology - 1 Dec 2023        Expand to Translate
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Introduction

Facts Human embryonic stage 7 occurs during week 3 between 15 to 17 days. The embryo is now 0.4 mm diameter in size. The initial images are displayed unlabeled to allow you to explore the embryo for yourself, linked labeled versions are also available for some images. Summary Gastrulation is continuing as cells migrate from the epiblast, continuing to form mesoderm. Mesoderm lies between the ectoderm and endoderm as a continuous sheet except at the buccopharyngeal and cloacal membranes. These membranes have ectoderm and endoderm only and will lie at the rostral (head) and caudal (tail) of the gastrointestinal tract. From the primitive node a tube extends under the ectoderm in the opposite direction to the primitive streak. This tube forms first the axial process then notochordal process, then finally the notochord. The notochord is a key to embryonic folding and regulation of ectoderm and mesoderm differentiation. It lies in the rostrocordal axis and the embryonic disc will fold either side ventrally, pinching off a portion of the yolk sac to form the lining of the gastrointestinal tract. See also Events

Week:	1	2	3	4	5	6	7	8
Carnegie stage:	1 2 3 4	5 6	7 8 9	10 11 12 13	14 15	16 17	18 19	20 21 22 23

Carnegie Stages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | About Stages | Timeline

Bright Field Lateral

Scanning EM

Human embryonic disc epiblast layer, dorsal view primitive streak (left) connecting stalk (far left) amniotic sac removed	Human embryonic disc epiblast layer, dorsolateral view primitive streak (left) connecting stalk (far left) amniotic sac removed
	Primitive streak detail (left)
Human embryonic disc epiblast layer, dorsal view primitive streak (bottom) connecting stalk (bottom) amniotic sac removed

See also human ectopic embryos (stage 7) images.

Kyoto Collection

View: embryonic disc, showing the epiblast viewed from the amniotic (dorsal) side. Head to tail orientation is Cranial (image top) and Caudal (image bottom).

Features: embryonic disc, primitive node, primative streak, primative groove, connecting stalk Alternate View: embryonic disc, probably from from the ventral side. Showing the connecting stalk to the left.

Image source: The Kyoto Collection images are reproduced with the permission of Prof. Kohei Shiota and Prof. Shigehito Yamada, Anatomy and Developmental Biology, Kyoto University Graduate School of Medicine, Kyoto, Japan for educational purposes only and cannot be reproduced electronically or in writing without permission.

Carnegie Collection

Surface view of implantation site

Surface lateral view of implantation site

Carnegie Collection - Stage 7
Serial No.	Grade	Fixative	Embedding Medium	Thinness (µm)	Stain	Year	Notes
7802	Exc.	Alc. & Bouin	C-P	6	(Stain - Haematoxylin Eosin)	1940	Heuser et al. (1945)
8206	Good	p	C-P	6	(Stain - Haematoxylin Eosin)	1943
8361	Good	Bouin	C-P	10	p	1946	Abnormal
8602	Exc.	Alc.	C-P	8	(Stain - Haematoxylin Eosin)	1948
8752	Exc.	?	C-P	10	(Stain - Haematoxylin Eosin)	1950
8755	Exc.	Formol	C-P	10	(Stain - Haematoxylin Eosin)	1950
9217	Exc.	p	P	10	(Stain - Haematoxylin Eosin)	1954
Abbreviations 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) ? - unknown or not determined.

iBook - Carnegie Embryos

iTunes link | iBook Store Description - Imagine the excitement of seeing this incredible early period of human development for the first time. Now consider that much of our initial understanding of human development is based upon study of historic embryo collections. You can now look at these historic images of the first 8 weeks after fertilisation and explore for yourself the changes that occur in human development during this key period. This current book is designed as an atlas of the Carnegie embryo stages with some brief notes and additional information covering the first 8 weeks of development. These images are from from the beginning of last century and are one of the earliest documented series of human embryos collected for basic research and medical education on development. I hope you enjoy learning about the amazing early events that begin to make and shape us. This is the second book in a series of educational releases from UNSW Embryology. Release: First Edition - Mar 12, 2012 ISBN 978-0-7334-3148-7 Print Length 82 Pages, 25.8 MB Language English. PDF Preview version 3.87 MB (Read the associated information, this is an edited educational preview version with many features not functioning). The current website also includes numerous embryo images from this textbook (see Embryonic Development and Carnegie Embryos).

Manchester Collection

Manchester No. 1285

Described by Florian and Hill (1935).

• Specimen is housed in Department of Anatomy, University of Manchester.
• Hysterectomy.
• Chorionic cavity, 4.28 x 3.28 mm.
• Embryonic disc (narrow type), 0.87 x 0.625 mm.
• Primitive streak, 0.39 mm, and node, 0.05 mm.
• Notochordal process, 0.125 mm. Prechordal plate, 0.03 mm.
• Connecting stalk attached to chorion at decidua capsularis (suggesting polar variety of velamentous insertion of umbilical cord).

Dorsal and median projections published (Hill and Florian, 1931b, figs. 5 and 13; Florian and Hill, 1935, figs. 1-3; Mazanec, 1959, fig. 52).

• Text Figures
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  1. Graphic reconstruction of the dorsal view of the embryonal shield

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  2. Graphic reconstruction of the median section

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  3. Idealised Median Section

• Plate 1
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  Fig. 1. Section 49

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  Fig. 2. Section 43

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  Fig. 3. Section 40

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  Fig. 4. Section 37

• Plate 2
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  Fig. 5. Section 32

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  Fig. 6. Section 79

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  Fig. 7. Section 97

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  Fig. 8. Section 75

• Plate 3
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Fig.9. Section 122

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Fig. 10. Section 23

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Fig.11. Section 99

Photograph

Image: Dr Ed Uthman (Houston, Texas) - other pathology images section of ectopic (tubal) pregnancy.

Image Links: Original full image | Trilaminar embryo excerpt | Villi excerpt 1 | Villi excerpt 2

Full Image versions: ExtraLarge 1712x1206px | Large 1024x721px | Medium 500x352px

Embryo Virtual Slide

Stage 7 - Implanted Conceptus  ‎‎Mobile | Desktop | Original Stage 7 | Embryo Slides

Stage 7 - Embryonic Disc  ‎‎Mobile | Desktop | Original Stage 7 | Embryo Slides

Stage 7 Images

Bright Field Images: Stage7-bf1.jpg | Stage7-bf2.jpg | Stage7-bf3.jpg | Stage7-bf4.jpg

Scanning Electron Images: Embryonic Disc 1 | Embryonic Disc 2 | Embryonic Disc 3 | Primitive Streak

Events

• gastrulation
• notochord

Historic Stage 7 Embryos

Historic stage 7 embryo data modified from O'Rahilly and Müller (1987).

By Length of Notochordal Process

HEB-37 - Summarized by Mazanec (1959). Chorionic cavity, 2.25 x 1.29 x 0.4 mm. Embryonic disc, 0.4 mm. Primitive streak, 0.104 mm, and node, 0.04 mm. Notochordal process, 0.032 mm. Stalk of umbilical vesicle (ibid., fig. 77). Median projection published (ibid., fig. 45).

H.R. 1. (Hesketh Roberts) - Described by Johnston (1940), who believed that a notochordal process (0.04 mm) and a prechordal plate (0.075 mm) were present. Florian in an appendix to the article disagreed, and his interpretation is followed here (see stage 6).

Biggart (Prof. JH. Biggart) - Described by Morton (1949). Curettage. Embryonic disc (narrow type), 0.27 x 0.16 mm. Primitive streak and node, 0.059 mm. A notochordal process is not referred to in the text but is mapped on a dorsal projection of the embryo (ibid., fig. 2) and is approximately 0.04 mm in length. The specimen is said to resemble the Yale embryo.

• Biggart Embryo
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  embryo in situ

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  duct part of yolk-sac

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  distal expansion of yolk-sac

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  embryonic rudiment

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  opening of duct part into distal expansion of yolk-sac

Guá (Guálberto) - Described by Lordy (1931). Hysterectomy. Chorionic cavity, 8 x 7.5 mm. Embryonic disc, 0.776 x 0.0465 mm. Primitive streak, 0.09 mm. Notochordal process, 0.045 mm. Possible notochordal canal. Said to resemble Hugo embryo. Probably belongs either to stage 7 or to stage 8.

Carnegie No. 7802 - (figs. 7-4 to 7-12). An important specimen described and illustrated by Heuser, Rock, and Hertig (1945). Hysterectomy. Chorion, 3.75 x 2.35 x 2.2 mm. Chorionic cavity, 2.3 x 1.4 x 1.1 mm. Embryonic disc (broad type), 0.42 x 0.35 x 0.05 mm. Primitive streak, 0.11 mm, and node, 0.03 mm. Notochordal process, 0.048 mm. Presumed age, 16 days. Median projection published (ibid., plate 6; Mazanec, 1959, fig. 46) and dorsal projection has been prepared by the present writers.

• 7802 Embryo
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  Hertig1946 Fig. 5

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  Hertig1946 Fig. 5a

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  Hertig1946 Fig. 5b

• 
• 
• 
• 

P.M. - Described by Meyer (1924). Curettage. Measurements have been criticized by Stieve (1926) but defended by Mazanec (1959). Chorion, 3.9 x 3.77 x 2.5 mm. Chorionic cavity, 2.7 x 2.6 x 2.1 mm. Embryonic disc (circular), 0.41 x 0.41 mm. Primitive streak, 0.12 mm, and node, 0.02 mm. Notochordal process, 0.06 mm, acknowledged by Mazanec (1959) although denied by Fahrenholz (1927). No notochordal canal. Median projection published (Mazanec, 1959, fig. 47).

Hugo - Described by Stieve (1926), who reproduced a photomicrograph of every second section. Hysterectomy. Surrounded by 942 chorionic villi ranging in length from 0.3 to 1 mm. Chorion, 6.4 x 5.9 x 5.6 mm. Chorionic cavity, 4.7 x 4.4 x 3.8 mm. Embryonic disc (broad type), 0.635 (Florian, 1931) x 0.63 mm. Primitive streak, 0.245 mm, and node, 0.05 mm. Notochordal process, 0.07 (0.11?) mm. (Florian, 1934c). No notochordal canal. Prechordal plate probably not yet developed (Hill and Florian, 1931a). Dorsal and median projections published (Florian, 1934c, fig. 1; Hill and Florian, 1931b, figs. 44 and 11; Mazanec, 1959, fig. 49).

Robertson, O’Neill, and Chappell (1948) described a hysterectomy specimen that possessed a chorion of 3.816 x 3.639 x 2.687 mm. Chorionic cavity, 2.718 x 2.239 x 1.679 mm. Embryonic disc (broad type), 0.462 x 0.485 mm. Primitive streak, 0.138 mm, and node (situated halfway), 0.03 mm. Notochordal process, 0.072 mm. Suggestion of notochordal canal in one or two sections. Assigned to horizon VIII by authors but probably belongs to stage 7. Median projection published (ibid., fig. 12).

D’Arrigo (1961) described an embryonic disc of 0.47 mm, which showed a notochordal process of 0.075 mm. Canalization of the process is “doubtful,” but the presence of a prechordal plate is “probable.” The specimen “could be recorded in Streeter’s horizon VII.”

Goodwin - Described by Kindred (1933). Tubal. Chorion, 5.8 x 2.72 x 2.25 mm. Chorionic cavity, 2.44 x 2.25 x 0.75 mm. Embryonic disc, 0.588 mm in width. Primitive streak, 0.215 mm, and node, 0.078 mm. Notochordal process, 0.078 mm. No notochordal canal and no prechordal plate.

Pha I - Described by Mazanec (1949). Chorionic cavity, 7.872 x 5.475 x 2.032 mm. Embryonic disc, 0.66 x 0.52 mm. Primitive streak, 0.145 mm, and node, 0.06 mm. Notochordal process, 0.09 mm. No prechordal plate. Median projection published (ibid., fig. 51).

H. Schm. 10 - (H. Schmid). Described briefly by Grosser (1931c). Embryonic disc (almost circular), 0.51 x 0.58 mm. Primitive streak, 0.14 mm, and node, 0.1 mm. Notochordal process, 0.1 mm. Probably belongs to stage 7, although a cavity in one section was thought to represent “Lieberkühn’s canal.”

Bi 24 (Bittmann) - Described by Hill and Florian (1931b). Chorionic cavity, 3.05 x 3.036 x 3.029 mm. Embryonic disc (narrow type), 0.62 x 0.39 mm. Primitive streak, 0.28 mm, and node (Mazanec, 1959, fig. 105), 0.05 mm. Notochordal process, 0.105 mm, consists of median chord and lateral mesoblastic wings. Prechordal plate, 0.03 mm. Possible primordial germ cells in endoderm of region of cloacal membrane and in endoderm of umbilical vesicle caudally (Florian, 1931). Politzer (1933) counted 41 germ cells in the region of the allanto-enteric diverticulum in this embryo, and 19 such cells in another presomite specimen (Bi 25). Dorsal and median projections published (Hill and Florian, 1931b, figs. 4 and 12; Florian, 1945, plate 5, fig. 43; Mazanec, 1959, fig. 50).

Manchester No. 1285 (fig. 7-1). Described by Florian and Hill (m̩). Hysterectomy. Chorionic cavity, 4.28 x 3.28 mm. Embryonic disc (narrow type), 0.87 x 0.625 mm. Primitive streak, 0.39 mm, and node, 0.05 mm. Notochordal process, 0.125 mm. Prechordal plate, 0.03 mm. Connecting stalk attached to chorion at decidua capsularis (suggesting polar variety of velamentous insertion of umbilical cord). Dorsal and median projections published (Hill and Florian, 1931b, figs. 5 and 13; Florian and Hill, 1935, figs. 1-3; Mazanec, 1959, fig. 52). Specimen is housed in Department of Anatomy, University of Manchester.

Pha II. - Summarized by Mazanec (1959). Chorionic cavity, 4.985 x 3.882 x 3.52 mm. Embryonic disc, 0.895 x 0.62 mm. Primitive streak, 0.37 mm, and node, 0.06 mm. Notochordal process, 0.13 mm. No prechordal plate. Median projection published (ibid., fig. 53).

Thompson and Brash (1923) described a specimen that showed a notochordal process of 0.3 mm. It is described in the present work under stage 8.

By Year of Publication

No measurements of notochordal process available for the following historic embryos.

Debeyre (1912) described in detail a specimen that possessed a chorionic cavity of 5.6 x 2.1 mm. Embryonic disc, 0.9 x 0.6 x 0.95 mm. Primitive streak stated to be 0.54 mm in length. Chorionic villi (0.4-1.6 mm) showed some branching. Unsuitable plane of section makes it impossible to assess the specimen precisely.

Carnegie No. 1399 Mateer - Described by Streeter (1920). Hysterectomy. Angiogenesis in villi described by Hertig (1935). Chorion, 9 x 8 x 3.5 mm. Chorionic cavity, 6.1 x 5.6 x 2.5 mm. Embryonic disc, 1 x 0.75 mm. Primitive streak and groove present. Although the notochordal process was originally thought probably to be absent, Hill and Florian (1931b) have no doubt that it is present. More advanced than Hugo (Florian and Völker, 1929). A very small twin embryo was originally described but that “interpretation has become open to doubt” (Corner, 1955). Drawing of every section reproduced by Turner (1920). A median drawing (Davis, 1927, fig. 5A) and a projection have been published (Mazanec, 1959, fig. 56).

• 1399 Embryo
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  Streeter Plate 1

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  Streeter Plate 2

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  Streeter Plate 3

Ho (Hodiesne) - Described by Fahrenholz (1927). Abortion. Chorionic cavity, 6.5 x 6 x 3 mm. Embryonic disc (deformed), 0.6 mm (0.725 mm by flexible scale). Primitive streak, 0.22 mm (0.345 mm by flexible scale). Notochordal process just beginning (“undoubtedly present,” Hill and Florian, 1931b). Possible prechordal plate claimed (disputed by Waldeyer, 1929a, but supported by Hill and Florian, 1963). “Lieberkühn’s canal” (0.065 mm) is an artificial folding of the embryonic disc (Hill and Florian, 1931b). Dorsal and median projections published (Fahrenholz, 1927, figs. 32, 6 and 7; Mazanec, 1959, fig. 54).

Debeyre (1933) described a specimen (0.9 mm) that possessed a primitive streak and probably belonged to stage 6 or stage 7. Large cells near the opening of the allantois were identified as primordial germ cells.

Falkiner - Described by Martin and Falkiner (1938). Curettage. Embryo damaged and not in good condition. Measurements seem too small (see Mazanec, 1959). Chorionic cavity, 1.5 x 1.4 mm. Embryonic disc, 0.15 x 0.29 mm. Primitive streak, 0.07 mm. Notochordal process contains “no definite lumen.” Cells rostral to notochordal process are “probably” the prechordal plate. Development “agrees most closely” with that of Bi I. Median projection published (Martin and Falkiner, 1938, fig. 8; Mazanec, 1959, fig. 39).

• Falkiner Embryo
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  Fig. 1

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  Fig. 2

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  Fig. 3

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  Fig. 4

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  Fig. 5

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  Fig. 6

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  Fig. 7

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  Fig. 8 Reconstruction

Gar (Green-Armytage) - Described by West (1952). Hysterectomy. Chorionic cavity, 3 x 2.6 x 2 mm. Embryonic disc (broad type), 0.56 x 0.69 mm. Primitive streak, node, and groove present. Short notochordal process. No notochordal plate. Said to resemble Hugo embryo. Trophoblast described by Hamilton and Boyd (1960).

Mal (Maliphant) - Described by West (1952). Hysterectomy. Chorionic cavity, 3 x 1.8 mm. Embryonic disc (broad type), 0.45 x 0.6 mm. Primitive streak, node, and groove present. Notochordal process present (Mazanec, 1959); small cavity in node (West, 1952) or in notochordal process (Mazanec, 1959) “hardly sufficient to warrant the name chorda canal.” No prechordal plate. Belongs either to stage 7 or to stage 8 (said to resemble Jones-Brewer I, which is in stage 8).

Carnegie No. 8602 - Photomicrograph reproduced by Hertig, Rock, and Adams (1956) (plate 10, fig. 53). Chorion, 2.73 x 2.43 mm. Chorionic cavity, 1.83 x 1.33 mm. Embryonic disc, 0.3 x 0.06 mm. Presumed age, 16-17 days.

• 8602 Embryo
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• 

Missen - Trophoblast described by Hamilton and Boyd (1960). Curettage. Chorion, 1.66 x 1.43 mm. Embryonic disc, 0.28 x 0.214 mm. Primitive streak and node. Notochordal process. Said to resemble No. 7801 and Edwards Jones-Brewer (stage 6). Presumed age, about 14 days.

Other embryos probably belonging to stage 7 include Fitzgerald, Fitzgerald-Brewer II, and Jones-Brewer II (Brewer and Fitzgerald, 1937).

Additional Images

Carnegie Stages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | About Stages | Timeline

Glossary Links

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Cite this page: Hill, M.A. (2023, December 1) Embryology Carnegie stage 7. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Carnegie_stage_7

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© Dr Mark Hill 2023, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G