@biomedicalephemera / biomedicalephemera.tumblr.com
Skeleton of anencephalic fetus with complicated spina bifada
Cranial deformation is due to failure of skull to form bony material. Kerckringii proposes that this was an effect of the spina bifada.
Specilegium Anatomicum nec non Anthropogeniae Ichnographiam. Theodori Kerckringii, 1717.
Exencephaly, Pseudocephaly, and Anencephaly
In exencephaly, the brain is formed without the brain casing - the cranium. It is generally missing the forebrain (the prefrontal lobe), but is otherwise mostly formed. Despite this, the spinal cord is rarely formed with the brain, as there is a disconnect between the telencephalon and the hindbrain during very early development, and only the midbrain is formed.
In pseudoencephaly (a term rarely used in medicine nowadays), the midbrain and spinal cord are formed, but the forebrain is not.
In anencephaly, the most common of the three conditions, the brain and spinal cord are only tiny specs of what they should be. Curiously, despite them being a literal extension of the brain, the eyeballs sometimes fully form, though with no receptors to process the information they receive, even if the fetus were to survive, they would not see anything.
Human Monstrosities, Part IV. Barton Cooke Hirst and George A. Piersol, 1893.
I have a very vivid memory from my childhood of one of my family cats giving birth to a kitten with its brain exposed. It survived at least a day too. The image is permanently burned in to my brain. I believe the term for this anencephaly. Anywho, it'd be appreciated if you posted anything you have about animals, and especially cats specifically, being born with anencaphaly.
Ahh, yes, that's fun. Anyway, I do have some stuff with anencephaly already, but just like cyclopia, it's a fascinating and sometimes horrifying deformity that always demands more attention. I actually have some really old cat deformity illustrations, one of which looks like anencephaly, so I'll try to get that up when I have a chance!
Anencephaly in the skeleton and whole fetus
Anencephaly is the congenital absence of the skull and neocortex, due to a neural tube defect between the 23rd and 26th day of pregnancy. At that point, the embryo is basically a tube with a thickened top, and when that top end doesn't close properly, the part of the brain known as the telencephalon (the largest part of the brain, which includes the cerebral hemispheres and basically everything that allows us to experience the world and live life) doesn't form, and because that doesn't form, the skull above it isn't triggered to form, either.
Anencephalic fetuses still develop some of the lower facial bones, the mandible, and the rest of their body, but the neural network of the spinal cord terminates at the brain-stem, and the condition is necessarily terminal, if the fetus even makes it to term. This is one of the few conditions that is often allowed to undergo late-term (generally second trimester) abortion - as these fetuses generally die in utero, and late-term fetal death is often very problematic in terms of infection and partial delivery, it's much safer to induce labor and expel the fetus before this occurs.
Studies in mice have shown that folic acid supplementation (already common in females of child-bearing age) can drastically reduce one of the primary causes of anencephaly in humans (expression of the CART1 gene). However, as the condition is so rare in humans, and the supplementation of folic acid is already highly recommended to prevent other neural tube defects in fetuses (such as spina bifida), no studies with the same hypothesis have been, or will probably ever be, performed on humans.
Human Monstrosities, Part II. Barton Cooke Hearst and George A. Piersol, 1892.
Craniorachischisis totalis
This open neural tube defect occurs very early in pregnancy, like all deformities and malformations of the neural tube.
I won’t get into the (actually very interesting, if complicated) specifics of the notochord and neural plates and the gene signaling going on, but around the third week of development a groove forms down the back of the embryo. This is called the neural groove, and it will form the canal that the spinal cord and spine will develop within. One of the most critical phases of development is the closure of that grove to form a tube, and much can go wrong.
Though an embryo may have such a malformation that they’re unable to sustain life independently, the genes and cells in other parts of the body don’t know that, and since they continue to receive blood and nutriment from the mother, they continue doing their thing and forming other structures. That’s how such a catastrophic defect from so early on can end up at this stage - fully formed except for the critical neural regions.
Manual of Pathology. W. M. Late Coplin, 1905.
Isodore Geoffroy Saint-Hilaire. Histoire Générale et Particuliere des Anomalies de l’Organisatoin Chez l’Homme, et les Animaux mummy.
Craniorachischisis totalis
This open neural tube defect occurs very early in pregnancy, like all deformities and malformations of the neural tube.
I won't get into the (actually very interesting, if complicated) specifics of the notochord and neural plates and the gene signaling going on, but around the third week of development a groove forms down the back of the embryo. This is called the neural groove, and it will form the canal that the spinal cord and spine will develop within. One of the most critical phases of development is the closure of that grove to form a tube, and much can go wrong.
Though an embryo may have such a malformation that they're unable to sustain life independently, the genes and cells in other parts of the body don't know that, and since they continue to receive blood and nutriment from the mother, they continue doing their thing and forming other structures. That's how such a catastrophic defect from so early on can end up at this stage - fully formed except for the critical neural regions.
Manual of Pathology. W. M. Late Coplin, 1905.
Skeleton of anencephalic fetus with complicated spina bifada
Cranial deformation is due to failure of skull to form bony material. Kerckringii proposes that this was an effect of the spina bifada.
Specilegium Anatomicum nec non Anthropogeniae Ichnographiam. Theodori Kerckringii, 1717.
Isodore Geoffroy Saint-Hilaire. Histoire Générale et Particuliere des Anomalies de l’Organisatoin Chez l’Homme, et les Animaux mummy.
