Carnegie stage 21

Embryology - 1 Dec 2023 Expand to Translate
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Introduction

Facts

Week 8, 53 - 54 days, 22 - 24 mm

Gestational age GA week 10

Summary

Ectoderm: sensory placodes, nasal pits moved ventrally, fourth ventricle of brain
Mesoderm: heart prominence, ossification continues
Head: nose, eye, external acoustic meatus
Body: straightening of trunk, heart, liver, umbilical cord
Limb: upper limbs longer and bent at elbow, foot plate with digital rays begin to separate, wrist, hand plate with webbed digits

Features

scalp vascular plexus, eylid, eye, nose, auricle of external ear, arm, elbow, wrist, knee, notch between digital rays, umbilical cord
Identify: straightening of trunk, pigmented eye, eyelid, nose, external acoustic meatus, scalp vascular plexus, webbed digits, liver prominance, thigh, ankle, foot plate, umbilical cord

Historic Papers: 1897 Coelom | 1911 Larynx | 1954 Stage 19-23

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

Virtual Embryo Slides

Stage 21 - Left Lateral

‎‎Mobile | Desktop | Original

Stage 21 | Embryo Slides

Kyoto Collection

View: This is a dorsolateral view of embryo. Amniotic membrane removed.

Central Nervous System

left lateral view	medial view
scale bar = 1mm

Kyoto embryo 940 Histology
sagittal 1
sagittal 2
sagittal 3
sagittal 4
upper
upper
upper
upper
lower
lower
lower
lower

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

Eye and Optic Nerve^[1]

Carnegie Collection - Stage 21
Serial No.	Size (mm)	Grade	Fixative	Embedding Medium	Plane	Thinness (µm)	Stain	Point Score	Sex	Year	Notes
22	E, 20 Ch, 35x30x30	Good	Alc.	P	Transverse	50	Al. coch.	34.5	Female	1895
57	E, 23 Ch., ca. 30	Poor	Alc.	P	Sagittal	50	Al. coch.	36	Male	1896
128	E, 20 Ch., 50x43	Good	Formalin	P	Coronal	50	Al. coch.	33	Female	1898
229	E, 19	Poor	Alc.	P	Sagittal	50	Al. coch.	33	Female	1903
349	E, 24	Good	Zenker	C	Coronal	250	Unstained	36	?	1905	Double vascular injection
455	E, 24 Ch., 42x34x20	Good	Alc.	P	Transverse	30	(Stain - Haematoxylin Eosin)	36.5	Male	1910
632	E, 24 Ch., 60x50x30	Good	Bichlor. acetic	P	Sagittal	40, 100, 250	Al. coch.	33	Female	1913	Injected
903C	E, 23.5	Good	Formalin	P	Transverse	40	Al. coch.	38.5	Female	1914
1008	E, 26,4	Good	Formalin	P	Sagittal	40	Al. coch.	39	??	1914
1358F	E, 23	Good	Formalin	P	Sagittal	40	Al. coch.	37.5	Female	1916
2937	E,, 24.2	Good	Bouin	P	Transverse	50	(Stain - Haematoxylin Eosin) aur., or. G.	39	Female	1920
3167	E., 24.5 Ch., 60x50x40	Poor	Bichlor, acetic, formol	P	Transverse	20	Al. coch.	32	Male	1920
4090	E, 22.2 Ch.. 66x46x30	Good	Formalin	P	Transverse	40	Al. coch.	30	Female	1922
4160	E,25	Poor	Formalin	P	Sagittal	25	(Stain - Haematoxylin Eosin)	39	Male	1923	Tubal
4960	E.22 Ch,, 47x42x28	Good	Formalin	P	Transverse	15	Al. coch., Mallory	31.5	Female	1925
5??6	E. 215	Good	Formalin	P	Sagittal	20	(Stain - Haematoxylin Eosin)	34	Female	1927
6531	E,22	Poor	Glacial acetic,	C-P	Transverse	10	(Stain - Haematoxylin Eosin)	31.5	Female	1931	Leitz Collection
7254	E,225	Exc	Bouin	C-P	Transverse	20	(Stain - Haematoxylin Eosin)	33.5	Male	1936
7592	E,22->	Exc.	Bouin	C-P	Transverse	20	(Stain - Haematoxylin Eosin)	36	Female	1937
7864	E., 24	Exc,	Formalin	C-P	Frontal	20	(Stain - Haematoxylin Eosin)	32.5	Male	1941
8553	E., 22	Exc	Bouin	C-P	Transverse	12	(Stain - Haematoxylin Eosin)	38	Female	1947
9614	E,,22 5	Exc	Bouin	P	Coronal	10 &15	Azan	?	?	1958	Rubella. Hysterectomy
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.

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).

Hinrichsen Collection

frontal section	respiratory excerpt

Image source: The Hinrichsen Collection images are reproduced with the permission of Prof. Beate Brand-Saberi, Head, Department of Anatomy and Molecular Embryology, Ruhr-Universität Bochum. Images are for educational purposes only and cannot be reproduced electronically or in writing without permission.

Digital Embryology Consortium - Hinrichsen Collection

Madrid Collection

Madrid Collection Embryos
Carnegie Stage	Embryo	Days	CRL (mm)	Section thickness	Staining	Section plane
21	GV 7	51	22	10	(Stain - Haematoxylin Eosin)	sagittal

Events

hearing - tip of the cochlea is recurved.
vision - (stage 19 -22) the eyelid folds develop into the eyelids and cover more of the eye as the palpebral fissure takes shape. The upper and the lower eyelids meet at the outer canthus in Stage 19.^[2]
smell - the structure of the olfactory bulb is evident. ^[3] primitive olfactory bulb
Musculoskeletal
- Mandible bone-formation has taken place and formed a plate on the lateral side of Meckel's cartilage; this plate is in the substance of, and is surrounded by, that mesodermal condensation which outlines the mandible and precedes the formation of bone. The plate of bone is confined to the region of what approximately corresponds to the future body of the mandible, but the mesodermal condensation can be traced further backwards, always, of course, on the lateral side of Meckel's cartilage and the associated branches of the mandibular nerve. The condensation admittedly becomes gradually much less sharply defined but is still distinguishable from the surrounding tissue. Finally, some distance beyond the limit of bone-formation, the lateral pterygoid muscle can be seen running into and out- lining the terminal part of the mesodermal condensation. This is the first indication of the condylar process in my series (P1. 1, fig. 1). Meckel's cartilage with the inferior dental and lingual nerves on its upper surface lies medial to this rudimentary condylar area and inferior to the lateral pterygoid muscle.^[4]
Joint - knee posterior cruciate ligament present.^[5]
Cardiovascular
- Cerebral artery the formation of the anterior communicating artery.^[6]
Endocrine System Development^[7]
- Hypophysis - the pharyngeal stalk becomes fragmented (Jirfisek 1980).
- Adrenal Cortex - the cellular "capsule" becomes covered by a layer of fibrous tissue.^[8]
meninges (spinal cord) - cavity formation in the meninx primitiva has progressed, and the rudimentary ventral dura is more distinct. Ventral to the medial edge of the ganglia, this dense dural rudiment is separated from the lateral extremities of the centra and intervertebral disks. Within this space a large longitudinal venous channel is developing. The dura can be identiﬁed around the spinal ganglia, which are now shifting into the intervertebral foramina, but becomes less distinct as it passes dorsad. The ventral dura can be followed throughout the cervical, thoracic, and lumbar segments, but in the sacral segments it can be identiﬁed only on the dorsal surfaces of the intervertebral disks.^[9]
genital^[10]
- testis has a flattened surface epithelium, with an underlying tunica albuginea. Precursor cords of the seminiferous tubules appear branching and anastomosing and the rete is invading the mesonephros.^[11]

submandibular gland - Simple, stubby primary branching of duct.^[1]

palate - levator veli palatini muscle starts to develop beneath the aperture of the auditory tube to the pharynx. Same authors suggest levator veli palatini may be derived from the second branchial arch.^[12]

limb - neural stage 21 the upper limb nerves are in an orientation and arrangement similar to those in the adult.^[13]

References

↑ ^1.0 ^1.1 Streeter GL. Developmental Horizons In Human Embryos Description Or Age Groups XIX, XX, XXI, XXII, And XXIII, Being The Fifth Issue Of A Survey Of The Carnegie Collection. (1957) Carnegie Instn. Wash. Publ. 611, Contrib. Embryol., 36: 167-196.
↑ Pearson AA. The development of the eyelids. Part I. External features. (1980) J. Anat.: 130(1): 33-42. PMID 7364662 PDF
↑ Bossy J. Development of olfactory and related structures in staged human embryos. (1980) Anat. Embryol., 161(2);225-36 PMID 7469043
↑ SYMONS NB. (1952). The development of the human mandibular joint. J. Anat. , 86, 326-32. PMID: 12980883
↑ Mérida-Velasco JA, Sánchez-Montesinos I, Espín-Ferra J, Mérida-Velasco JR, Rodríguez-Vázquez JF & Jiménez-Collado J. (1997). Development of the human knee joint ligaments. Anat. Rec. , 248, 259-68. PMID: 9185992
↑ Menshawi K, Mohr JP & Gutierrez J. (2015). A Functional Perspective on the Embryology and Anatomy of the Cerebral Blood Supply. J Stroke , 17, 144-58. PMID: 26060802 DOI.
↑ O'Rahilly R. The timing and sequence of events in the development of the human endocrine system during the embryonic period proper. (1983) Anat. Embryol., 166: 439-451. PMID 6869855
↑ Crowder RE. The development of the adrenal gland in man, with special reference to origin and ultimate location of cell types and evidence in favor of the "cell migration" theory. (1957) Contrib. Embryol., Carnegie Inst. Wash. 36, 193-210.
↑ Sensenig EC. The early development of the meninges of the spinal cord in human embryos. (1951) Contrib. Embryol., Carnegie Inst. Wash. Publ. 611.
↑ O'Rahilly R. (1983). The timing and sequence of events in the development of the human reproductive system during the embryonic period proper. Anat. Embryol. , 166, 247-61. PMID: 6846859
↑ Wilson KM. Origin and development of the rete ovarii and the rete testis in the human embryo. (1926) Carnegie Instn. Wash. Publ. 362, Contrib. Embryol., Carnegie Inst. Wash., 17:69-88.
↑ Kishimoto H, Yamada S, Kanahashi T, Yoneyama A, Imai H, Matsuda T, Takeda T, Kawai K & Suzuki S. (2016). Three-dimensional imaging of palatal muscles in the human embryo and fetus: Development of levator veli palatini and clinical importance of the lesser palatine nerve. Dev. Dyn. , 245, 123-31. PMID: 26509917 DOI.
↑ Shinohara H. Naora H. Hashimoto R. Hatta T. and Tanaka O. Development of the innervation pattern in the upper limb of staged human embryos. (1990) Acta Anat (Basel) 138: 265-269. PMID 2389673

Additional Images

Heart atria
External ear Stages 14-23 and adult
Limbs Stage 20-23
Stage 21 Optical Projection Tomography
Head Stage 17-23

Historic Images

Historic Disclaimer - information about historic embryology pages
Pages where the terms "Historic" (textbooks, papers, people, recommendations) 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, interpretations and recommendations may not reflect our current scientific understanding. (More? Embryology History \| Historic Embryology Papers)

1909 Liver
1921 Embryo
1911 Frontal section of human thyreoid cartilage
1911 Frontal section of human laryngeal muscles and cartilages.
1911 Frontal section of human cricoid cartilage
1911 Graphic reconstruction of cricoid cartilage posterior view
1911 Graphic reconstruction of cricoid cartilage, lateral view
1911 Embryo no. 22 choudrification
1911 Graphic reconstruction thyreoid cartilage
1911 Graphic reconstruction of laryngeal cartilages
F1911 Cross section of human superior laryngeal nerve and nerve recurrens.
1911 Cross section of human M. interarytaenoideus and aryepiglotticus
1911 Cross section low in laryngeal region
1911 Cross section of human thyreoid cartilage, cricoid cartilage, and hyoid bone
1911 Graphic reconstruction of nerve recurrens and its branches
1911 Graphic reconstruction of motor branch of superior laryngeal nerve
1911 Graphic reconstructions of laryngeal muscles, and cartilages, and their relations
1911 Wax model of laryngeal muscles and nerves
1911 Wax model of laryngeal region from below
1911 Wax model of laryngeal region from the left side
1911 Wax model of laryngeal region from below