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.
Shigella infection is typically by ingestion (fecalâoral contamination); depending on age and condition of the host, fewer than 100 bacterial cells can be enough to cause an infection. Shigella causes dysentery that results in the destruction of the epithelial cells of the intestinal mucosa in the cecum and rectum.Some strains produce the enterotoxin shiga toxin, which is similar to the verotoxin of E. coli O157:H7 and other verotoxin-producing E. coli.higella species are classified by four serogroups 1  : Serogroup A: S. dysenteriae (15 serotypes). 2  Serogroup B: S. flexneri (six serotypes). 3  Serogroup C: S. boydii (19 serotypes). 4  Serogroup D: S. sonnei (one serotype).