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Often the head will appear dome-shaped, and the open fontanelle is noticeable as a "soft spot" on the top of the dog's head. The fluid-filled spaces within the brain, known as ventricles, also become swollen. The increased pressure damages or prevents the development of brain tissue. [12] Not all open fontanelles are connected with hydrocephalus.
The face and neck development of the human embryo refers to the development of the structures from the third to eighth week that give rise to the future head and neck.They consist of three layers, the ectoderm, mesoderm and endoderm, which form the mesenchyme (derived form the lateral plate mesoderm and paraxial mesoderm), neural crest and neural placodes (from the ectoderm). [1]
Anencephaly is the absence of a major portion of the brain, skull, and scalp that occurs during embryonic development. [1] It is a cephalic disorder that results from a neural tube defect that occurs when the rostral (head) end of the neural tube fails to close, usually between the 23rd and 26th day following conception. [2]
Only a comparatively small part of the head at term is represented by the face. The rest of the head is composed of the firm skull, which is made up of two frontal, two parietal, and two temporal bones, along with the upper portion of the occipital bone and the wings of the sphenoid. These bones are separated by membranous spaces, or sutures.
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This abnormality appears during the beginning or end of the fourth week of the fetus's development. An absence of the skull is needed in order to make a diagnosis. A presence of brain tissue will confirm the diagnosis of acrania and differentiate it from other developmental problems such as anencephaly. [2]
In prenatal development of the fetus, the laminae of the septum pellucidum separate to form a small cavity – the cave of septum pellucidum. This is an important normal structure to identify in the sonographic assessment of the fetal brain. In post-natal life, the laminae of the septum pellucidum usually fuse, which obliterates the cavum.
A 7-month-old baby born in New Jersey is being considered the first to ever survive his rare condition past birth.