Fetal brain - 12 weeks
![Cortical neurons (brain cells) of an embryonic rat (200x) [source]](http://25.media.tumblr.com/tumblr_lhmzbjkUOA1qa6reco1_1280.jpg)
Cortical neurons (brain cells) of an embryonic rat (200x) [source]
![Human Embryo: 6 - 7 weeks
This is an approximately 6-7 week estimated gestational age 19mm embryo from conception, 8-9 weeks from LMP. Features include finger rays and cerebral hemispheres.
[Human development, on flickr]
—->Like fuckyeahnervoussystem? Recommend me in Science here! (:](http://24.media.tumblr.com/tumblr_lg02cfXgbq1qa6reco1_1280.jpg)
Human Embryo: 6 - 7 weeks
This is an approximately 6-7 week estimated gestational age 19mm embryo from conception, 8-9 weeks from LMP. Features include finger rays and cerebral hemispheres.
[Human development, on flickr]
—->Like fuckyeahnervoussystem? Recommend me in Science here! (:
Fetal brain (22 weeks)
![Sagittal section through a 16 week old female foetus, revealing the internal organs. At this stage it measures around 14 centimetres from head to rump. The brain (white) is surrounded by the still soft bones of the skull. The spinal cord runs from the brain, down through the vertebrae of the backbone. [source]](http://24.media.tumblr.com/tumblr_lejnqqDzLV1qa6reco1_400.jpg)
Sagittal section through a 16 week old female foetus, revealing the internal organs. At this stage it measures around 14 centimetres from head to rump. The brain (white) is surrounded by the still soft bones of the skull. The spinal cord runs from the brain, down through the vertebrae of the backbone. [source]
![Mouse embryonic spinal cord
[source]](http://25.media.tumblr.com/tumblr_legewmB75O1qa6reco1_400.jpg)
Mouse embryonic spinal cord
[source]
Embryo spinal cord. Coloured light micrograph of a section through the spinal cord of a 6-week-old human embryo. This spinal cord precursor is known as the neural tube.
The central canal (white) is surrounded by structures that will form the grey matter of the central nervous system. The pale pink region around these features will become white matter. The red regions are somites, structures that form skin, muscle and vertebrae (backbones).
Invagination of the midline ectoderm forms the neural tube—the precursor of the spinal cord and brain. When this process fails to take place normally—as may occur when the mother is severely deficient in folic acid during early pregnancy—severe neurological conditions such as spina bifida or anencephaly (absence of most of the brain) may result.
Closure of the neuropore A pencil drawing showing the sequence of events, which lead to the closure of the embryonic neuropore. The neuropore refers to the opening (anterior or posterior) of the developing neural tube.
“Whole-mount X-gal staining of sensory axons innervating the limbs of an embryonic day 15.5 mouse carrying the LacZ gene driven by the sensory neuron promoter of Brn3a. For more information, see the article by Schoenmann et al. in this issue (pages 6375–6386).”
Mouse embryo stained to reveal developing nerves.
A human embryo at 7 weeks gestation (Image: Ralph Hutchings / Visuals Unlimited / Getty)
Developing neural tube
“A 12.5 dpc developing mouse embryo, stained with an antibody that recognises Hepatic Nuclear Factor 3b (HNF3b). This is a transcription factor that is required for the expression of sonic hedgehog (Shh) in the notochord and in the floor plate of the developing neural tube. It is also expressed in the midbrain and important for normal neural development. This image was produced using immunohistochemistry techniques imaged with Optical Projection Tomography (OPT) to show the position of the HNF3b staining within the embryo.”
Foetal brain. Lateral (side) view of the right hand side and coronal (top) view of the brain of a 24-week-old foetus. Although at this stage of development the foetal brain shows active auditory and visual responses, it is yet to develop the characteristic folds.
In humans, cerebral convolutions appear at about 5 months and take at least into the first year after birth to fully develop.
Embryologic formation of the neural tube
“I grew up reading Marvel Comic books — The Amazing Spiderman, The Incredible Hulk, Fantastic Four… One thing I liked before they invented movie special effects was showing transformations on paper. Like when Bruce Banner transforms into the Hulk, or when Curt Connors becomes the Lizard. That’s the kind of effect I’ve always strived for in making my reviewers for my science subjects — if I can draw it the way it’s supposed to happen sequentially, then I can understand it. “
