Week 11

Embryology - 27 Feb 2026 Expand to Translate
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Key Events of Human Development during the eleventh week (week 11) following fertilization or Clinical week GA 13 (LMP).

Historic Embryology
1940 Fetus Physiology
Carnegie Fetal: 95 \| 96 \| 142 \| 145 \| 184 \| 211 \| 217 \| 300 \| 362 \| 448 \| 449 \| 538 \| 590 \| 607 \| 625 \| 662 \| 693 \| 847 \| 858 \| 922 \| 928 \| 948 \| 972 \| 1318 \| 1388 \| 1455 \| 1591 \| 1597b \| 1656 \| 1686 \| 2250a \| 2250b \| 3990 \| 5652 \| 6581 \| 7218

Day	Event
week 11	Thyroid - colloid appearance in thyroid follicles, iodine and thyroid hormone (TH) synthesis Stomach - Serotonin containing cells in both the antrum and the fundus. Integumentary - blood vessels visible in the early fetal skin, small blood vessels in the upper papillary region and larger vessels in the deep reticular dermis.^[1]
71
72
73
74
75
76
77	Week 11 - CRL 68 mm, femur length 12 mm, biparietal diameter 20 mm

Sensenig (1951) - Spinal Cord Meninges
Age Group (gestation age)	Embryo no.	Crown Rump Length	Thickness of sections (microns)	Plane of section	Illustration
11 weeks	4229	58.0	20	T
	1656	67 .0	200	S
	4291	69 .0	100	T
Number of somites given in parentheses. T. transverse; F. frontal or coronal: S. sagittal. Embryo loaned by Department of Embryology. Carnegie Institution of Washington. prepared for study on a U. S. Public Health Service Grant.
Reference: Sensenig EC. The early development of the meninges of the spinal cord in human embryos. (1951) Contrib. Embryol., Carnegie Inst. Wash. Publ. 611.

Carnegie Embryos - Sensenig (1951) - Spinal Cord Meninges
Age Group (gestation age)	Embryo no.	Crown Rump Length	Thickness of sections (microns)	Plane of section	Illustration
X (20-22 days)	2795	2.0 (5)	6	Transverse
	8244	(6)	8	Transverse
	4216	2.17 (7)	15	Transverse
XI (22-24 days)	5074	3.0 (10)	10	Transverse
	7611	2 .4 (16)	8	Transverse
	2053	3.1 (20)	10	Transverse	Fig. 1, pl. 1
XII (24-26 days)	6097	3 .4 (25)	10	Transverse
	7724	3.5 (29)	8	Sagittal
	7999	3.2 (29)	10	Transverse
XIII (26-28 days)	7889	4.2	6	Frontal
	8066	5.3	8	Transverse
	8119	5.3	8	Transverse	Fig. 2, pl. 1
XIV (28-30 days)	5787	6.8	10	Sagittal
	7829	7.0	8	Transverse
	8141	7.3	8	Frontal
XV (30-32 days)	721	9.0	15	Transverse	Figs. 3, 4, pl. 1
	3385	8.3	20	Transverse
	6504	7.5	6	Sagittal
	6506	7.5	10	Frontal
XVI (32-34 days)	792	8.0	20	Transverse
	887	9.0	40	Transverse
	6507	9 .0	8	Frontal
	6511	8.1	10	Sagittal
	6512	7 .0	10	Transverse
	6516	10.5	8	Sagittal
	6517	10.5	8	Transverse
	8112	10.9	8	Frontal
XVII (34-36 days)	6519	10.8	8	Sagittal
	6521	13.2	8	Transverse	Figs. 5, 6, pl. 1
	8101	13.0	10	Transverse
	8118	12.6	10	Frontal	Fig. 21, pi. 4
XVIII (36-38 days)	4430	14.0	15	Transverse
	6524	11 .7	10	Transverse
	6525	13.8	8	Sagittal
	6528	13 .4	8	Frontal
	7707	14.5	10	Transverse
	8172	16.5	20	Transverse	Figs. 7, 8, pl. 2
	8235	14.0	10	Sagittal
XIX (38-40 days)	1390	18.0	20	Sagittal
	4405	15.8	10	Transverse
	5609	18.0	25	Frontal
	8092	16.3	20	Transverse
XX (40-42 days)	2393	23 .1	20	Sagittal
	3527	22 .0	25	Sagittal
	4059	21.6	15	Frontal
	6426	21.5	20	Transverse
	7274	18.0	20	Transverse	Figs. 9, 10, pl. 2
	7906	19.5	20	Frontal
XXI (42-44 days)	7254	22.5	20	Transverse
	7392	22.7	20	Transverse	Figs. 11, 12, pl. 2: ﬁg. 22, pl. 4
	7864	24.0	20	Frontal
XXII (44-46 days)	4339	24.5	15	Transverse
	6701	24 .0	20	Frontal
	6832	25.8	20	Frontal	Fig. 23, pl. 4
XXIII (46-48 days)	4570	30.7	15	Transverse	Figs. 13, 14, pl. 3; fig. 24, pl. 4
	6573	31.5	20	Transverse	Figs. 15, 16, pl. 3
	7425	27.0	20	Frontal
Older embryos:
8 weeks	3669	34.0	50	Transverse
	5762	34.0	25	Sagittal
	5712	35 .0	25	Frontal
	1915	35.5	50	Transverse
	4021	38 .0	15	Transverse
9 weeks	6658	40.0	40	Sagittal
	4985	41.0	20	Transverse
	301	44 .0	20	Transverse
	1686	46.0	100	Sagittal
	4475	48.0	20	Transverse	Figs. 19, 20, pl. 4
10 weeks	3990	54.0	20	Transverse
	481	57.0	200	Frontal
11 weeks	4229	58.0	20	Transverse
	1656	67 .0	200	Sagittal
	4291	69 .0	100	Transverse
12 weeks	1455	78.5	50	Sagittal
	172	80.0	100	Transverse
	72181	80.0	20	Transverse	Figs. 17, 18, pl. 3
Number of somites given in parentheses. T. transverse; F. frontal or coronal: S. sagittal. Embryo loaned by Department of Embryology. Carnegie Institution of Washington. prepared for study on a U. S. Public Health Service Grant.
Reference: Sensenig EC. The early development of the meninges of the spinal cord in human embryos. (1951) Contrib. Embryol., Carnegie Inst. Wash. Publ. 611.

References

↑ Coolen NA, Schouten KC, Middelkoop E & Ulrich MM. (2010). Comparison between human fetal and adult skin. Arch. Dermatol. Res. , 302, 47-55. PMID: 19701759 DOI.

Sensenig EC. The early development of the meninges of the spinal cord in human embryos. (1951) Contrib. Embryol., Carnegie Inst. Wash. Publ. 611.

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Cite this page: Hill, M.A. (2026, February 27) Embryology Week 11. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Week_11

What Links Here?

[PMID19701759-1] Coolen NA, Schouten KC, Middelkoop E & Ulrich MM. (2010). Comparison between human fetal and adult skin. Arch. Dermatol. Res. , 302, 47-55. PMID: 19701759 DOI.

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