Back | Carnegie Staging Criteria
|
Carnegie Stage |
Post ovulatory days |
Weeks post conception | Somite Number |
Greatest length (mm) [mean] |
Morphological land marks |
---|---|---|---|---|---|
9 |
19 - 21 |
3 |
1 - 3* |
1.4 - 2.5 |
Head fold present. Neural folds may be apposed but are not yet fused at any point. No visible pharyngeal arch. *May be more than 3 somites and may not be paired. |
10 |
22 |
4 |
4 - 12 |
1.5 - 3.6 |
Neural tube closing ie closed/fused at least at closure point 1. First and, possibly, second pharyngeal arches visible. Looped heart tube visible. |
24 |
4 |
13 - 20 |
1.4 - 5.0 |
Rostral neuropore closing. Otic placodes present. Optic vesicles formed. No limb buds. |
|
26 |
4 |
21 - 29 |
3.0 - 5.4 |
Rostral neuropore closed. Caudal neuropore closing. Upper limb buds appear. Optic vesicles clearly visible. Three pairs of pharyngeal arches visible. Otic pits present. May have thin tail. |
|
28 |
4 |
30 or more |
3.9 - 6.0 |
Caudal neuropore closed. Upper limb buds clearly visible. Lower limb buds appear. Lens placodes distinct. Four pairs of pharyngeal arches visible. Thin tail present. Otic vesicles present. |
|
32 |
5 |
More than 30 |
4.9 - 8.2 |
Four clearly visible limb buds - upper limbs tapering with no hand plate. Nasal pits visible. Optic cups present and optic fissure may be visible. |
|
33 |
6 |
6 - 11 |
Hand plates formed. Nasal pits prominent. Future cerebral hemispheres distinct. |
||
37 |
6 |
7 - 12.2 |
Foot plates formed. No/unclear digital rays in handplate. Pigment visible in retina. |
||
41 |
6 |
10 - 14.5 |
Digital rays clearly visible in hand plates. Trunk beginning to straighten. Cerebral vesicles prominent. |
||
44 |
7 |
11.7 - 17.2 |
Notches between the digital rays in the hand. Elbow region visible. Toe rays begin to appear in foot plates. |
||
47.5 |
7 |
15.5 - 21.5 |
Five distinct toe rays but interdigital notches have not yet appeared. Limbs extend ventrally/forward. Trunk elongating and straightening. Midgut herniation prominent. |
||
50.5 |
8 |
18 - 23 |
Fingers distinct but webbed. Notches between the digital rays in the feet. Upper limbs longer and bent at elbows. Scalp vascular plexus appears. |
||
52 |
8 |
20 - 26.4 |
Fingers free and longer. Toes distinct but webbed. Hands and feet approach each other. Stubby tail present. Scalp vascular plexus forms a line at somewhat more than half the distance from eye-ear level to the vertex. |
||
54 |
8 |
23.4 - 27.5 |
Toes free and longer. Fingers longer and overlap, scalp vascular plexus at ¾ up head. Eyelids and auricles (external ears) more developed. |
||
56 |
8 |
23 - 32.2 |
Forehead more prominent and head shows human characteristics. Scalp vascular plexus at vertex. Limbs longer and more developed. Distinct bulge still present in umbilical cord caused by herniation of intestines. |
The updated HDBR staging guide is largely based on a) O'Rahilly R, Müller F (2001) Human Embryology and Teratology 3rd Edition (ISBN-10: 0471382256) b) O'Rahilly R, Müller F (2010) Developmental stages in human embryos: revised and new measurements. Cells Tissues Organs. 192:73-84. PMID: 20185898. In addition, the experience of HDBR staff in viewing and staging embryos refined the staging criteria to only include features that are visible externally in unfixed material. |