Thousands of microvilli form a structure called the brush border that is found on the apical surface of some epithelial cells, such as the small intestines. (Microvilli should not be confused with intestinal villi, which are made of many cells.
Autism spectrum disorder has no single known cause. Given the complexity of the disorder, and the fact that symptoms and severity vary, there are probably many causes. Both genetics and environment may play a role. 1  Genetic problems. 2  Several different genes appear to be involved in autism spectrum disorder.
Itâs suggested that the social impairment characteristic of autism spectrum disorders may be related to a lack of a type of spindle neurons called Von Economo neurons. These neurons are only found in very social species, such as the great apes, elephants, and whales and Â­dolphins, and are found only in the frontoinsular and anterior cingulate cortex.