exists and is an alternate of . The sperm that reach the egg swim into it and attempt to penetrate the zona pelluca, which is the semi permeable outer membrane of the egg. Some sperm have a shape which makes this relatively easy, and others which are poorly formed are likely to have more difficulty.
1 Shigellosis is an infectious disease caused by a group of bacteria called Shigella. 2  Symptoms of Shigella infection include diarrhea (often bloody), fever, and stomach cramps starting a day or two after exposure to the bacteria. 3  Shigellosis usually resolves in 5 to 7 days.
What causes Shigellosis? Causes: Shigellosis: Shigella bacterial infection of the digestive tract. The disease is caused when virulent Shigella organisms attach to, and penetrate, epithelial cells of the intestinal mucosa. After invasion, they multiply intracellularly, and spread to contiguous epitheleal cells resulting in tissue destruction.