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.
Autism is one of five types of autism spectrum disorder. Autism spectrum disorders are developmental brain disorders. These disorders are characterized by impaired social interaction and communication skills, and a limited range of activities and interests. Other types of autism spectrum disorder include:1  Asperger syndrome.utism spectrum disorders are developmental brain disorders. These disorders are characterized by impaired social interaction and communication skills, and a limited range of activities and interests. Other types of autism spectrum disorder include: 1  Asperger syndrome.