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.
What is autism spectrum disorder? Autism spectrum disorder, also called ASD, is the name used for a specific set of behavioural and developmental problems and the challenges that go with them. There is no medical cure for the differences in the brain that cause ASD.