The serosa is the outermost layer of the intraperitoneal organs (it's also considered the visceral peritoneum). In most alimentary canal organs, its made up of areolar connective tissue covered with mesothelium, a single layer of squamous epithelial cells
Both flagella and pili are extensions from the bacterial cell body. Flagella are like a whip or a tail while pili are best described as hairlike.A pilus is a hairlike appendage found on the surface of many bacteria.
