Carnegie stage 23
Embryology - 15 Jun 2024 Expand to Translate |
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Introduction
This is the final Carnegie stage of embryonic development in Week 8. After this development is considered fetal for the remainder of the pregnancy.
Facts
Week 8, 56 - 60 days, 27 - 31 mm
Gestational age GA week 10
Summary
- Ectoderm:
- Mesoderm: ossification continues
- Head: eyelids, external ears, rounded head
- Body: straightening of trunk, intestines herniated at umbilicus
- Limbs: hands and feet turned inward
See also Carnegie stage 23 Events
Features
- scalp vascular plexus, eylid, eye, nose, auricle of external ear, mouth, shoulder, arm, elbow, wrist, toes separated, sole of foot, umbilical cord
- hearing - cochlea shows nearly 21/2 turns. otic capsule cartilage separated from the semicircular ducts by a pre cartilaginous zone. Labyrinth has practically completed its gross development and ductus reuniens is well defined.[1]
- Links: Week 8 | System Development | Lecture - Limb | Lecture - Head Development | Lecture - Sensory | Science Practical - Head | Science Practical - Sensory | Science Practical - Urogenital | Category:Carnegie Stage 23 | Fetal Development
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
Kyoto Collection
View: This is a dorsolateral view of embryo. Amniotic membrane removed.
Image source: Embryology page Created: 19.03.1999
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
- Carnegie stage 23: 4570 right | 4570 anterior | 4570 left | 4570 posterior | 4570 large right | 4570 large left | Rotation | Carnegie Embryos
iBook - Carnegie Embryos | |
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Hill Collection
Hill HH12 | |
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- Links: Hill Collection
Events
- Vision
- The retina comprises the pigmented layer, external limiting membrane, proliferative zone, external neuroblastic layer, transient fiber layer, internal neuroblastic layer, nerve fiber layer, and internal limiting membrane. Eyelids closure is complete (Note - shown as still open in the Kyoto embryo).[3]
- The cornea now comprises the anterior epithelium and its basement membrane, the substantia propria, and the posterior epithelium (Streeter, 1951, fig. 18, and O’Rahilly, 1966, figs. 51 and 59).
- Optic nerve a vascular canal is present and sheath in the more advanced specimens (O’Rahilly, 1966, fig. 55).
- Joint - knee cavity, anterior cruciate ligament and posterior cruciate ligament present[4]
- Hearing - Cochlear duct tip now points “downward” for the second time (fig. 19-6). The duct is coiled to nearly its final extent of 2½ turns.
- Pituitary - adenohypophysis loss of the stalk and lobules of epithelium project into the mesodermal component of the gland, and oriented epithelial follicles are present (Streeter, 1951, plate 2). Abundant angioblasts and capillaries are found.
- Vomeronasal organ. A narrow canal is seen in the long, tapering duct. The sac is beginning to shrink and retrogress (fig. 19-9).
- Submandibular gland. Lumina are found in many terminal branches of the duct (fig. 19-10). Orientation of the epithelial tree is beginning, and angiogenesis is commencing around the epithelium. A mesodermal sheath is beginning to form around the gland.
- Renal - Metanephros secretory tubules are changing from short to long, and becoming more convoluted. The epithelium in some tubules is high. Renal tubules of fourth and fifth orders are present. Large glomeruli are numerous (fig. 19-12).
- Humerus. All five cartilaginous phases are now present (Streeter, 1949, figs. 3 and 18).
References
- ↑ Template:Ref-Streeter1906
- ↑ 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.
- ↑ <pubmed>7364662</pubmed>
- ↑ <pubmed>9185992</pubmed>
Additional Images
Historic Images
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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) |
- 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
Cite this page: Hill, M.A. (2024, June 15) Embryology Carnegie stage 23. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Carnegie_stage_23
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G