Plate 49 Establishment of Disease

Skin Epithelium – outer part of skin Epi: “on” Theli: “tissue” Densely packed cells protect body from invading pathogens

Skin Connective tissue – provides cohesion and support to internal structure of the body Fibers provide flexibility and form

How do bacteria get into your skin?

Phagocytes After a foreign substance has ruptured the skin, phagocyte cells migrate to the site Phagein: “to eat” Cyte: “cell” Phagocytes – group of immune cells specialized in “eating” potential pathogens Pus from an infection is primarily dead phagocytes

Phagocytosis hill.com/sites/ /student_view0/ch apter2/animation__phagocytosis.html hill.com/sites/ /student_view0/ch apter2/animation__phagocytosis.html

Bacterial Enzymes Bacteria use enzymes to help establish themselves in the body: – Coagulase – Hyaluronidase – Streptokinase – Hemolysis

Coagulase Coagulase is secreted by some bacteria (ex: Staphylococcus) Causes proteins in blood to clot Commonly found in Gram positive bacteria Blood clot surrounds bacteria and protects against phagocytes

Hyaluronidase Hyaluronic acid (hyaluronan) is found in epithelial and connective tissues and acts as a “goo” in tissue repair Bacteria (ex: Clostridium) secrete hyaluronidase enzyme to breakdown hyaluronic acid It allows bacteria to infiltrate skin barrier Fun fact: sperm secrete hyaluronidase when they come into contact with an egg

Streptokinase Some bacteria (ex: Streptococcus) secrete streptokinase enzyme to dissolve blood clots Allows bacteria to spread past the location of initial infection Also used in heart attack victims to dissolve arterial blood clots in the heart

Hemolysin Some bacteria secrete hemolysin that breakdown cell membranes of red blood cells Lowers oxygen levels in blood, improving conditions for anaerobic bacteria (ex: Clostridium) Lowers activity of white blood cells and protects bacteria Can result in anemia (low levels of RBC)