The Immune System Alisa, Pratik and Sarita
Define the term pathogen • - A bacterium, virus, or other microorganism that can cause disease
Role of the skin in defence against pathogens • The surface is protected by a layer called the epidermis, the epidermis is broken (by a cut, or needle etc) invasive microbes may enter. • The normal floral of the skin metabolizes substances secreted on the skin which produces end products that colonize the skin by potential pathogens
Role of the mucous membrane in defense against pathogens • It is heavily colonized with bacteria in which moist secretions they survive. • Mucous contains a number of types of anti-microbial compounds including lysozyme and antibodies. • Phagocytes patrol mucosal surfaces (e.g. in the lower respiratory tract) • Most infectious agents interrupt on the skin or mucous membranes of the oral cavity, respiratory tract and these sites most infections occurs. • Damage to the epithelial cells caused by toxic products of these bacteria may play a role.
Outline how phagocytic leukocytes ingest pathogens in the blood and in body tissues • Phagocyte is a type leukocyte (white blood cells). They are group of immune cells that is specialized in finding and "eating" bacteria, viruses, and dead or injured body cells. • Process: • When phagocytes recognizes pathogens • They starts to engulf them by endocytosis • Enzyme within the phagocytes (lysosomes) digests pathogens • Phagocytes ingest pathogens in the blood and within body tissue (as they can pass through the pores of capillaries and into these tissues)
Describe the process of blood clotting • The process by which the body prevents blood loss is referred to as coagulation. • Coagulation involves the formation of a blood clot (thrombus) that prevents further blood loss from damaged tissues, blood vessels or organs. • A blood clot functions to seal a wound injured, preventing further invasions by bacteria. • Clotting begins when the wall of a blood vessel is damaged. There are many different clotting factors involved including; platelets, prothrombin, and fibrinogen. • Platelets are produced in the bone marrow at a rate of 200 billion a day; the bloodstream carries more than a trillion. • Fibrinogen and prothrombin are proteins manufactured and deposited in blood by the liver. • Vitamin K is necessary for the production of prothrombin. • When a blood vessel is damaged, platelets clump at the site of the puncture and partially seal the leak. • The platelets and the damaged tissues release a clotting factor called thrombokinase, which converts prothrombin to thrombin. This reaction requires calcium ions. • Thrombin, in turn, acts as an enzyme that severs 2 short amino acid chains from each fibrinogen molecule. These activated fragments then join end to end, forming long threads of fibrin, which is insoluble. • Fibrin threads wind around the platelet plug in the damaged area of the blood vessel and red blood cells get trapped within the fibrin threads, making the clot appear red.
References • http://www.google.com/search?q=define+pathogens&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a#hl=en&safe=off&client=firefox-a&hs=qE&rls=org.mozilla:en-US:official&q=pathogen&tbs=dfn:1&tbo=u&sa=X&ei=ka12TunuCcuwiQftoa3BDQ&ved=0CCEQkQ4&bav=on.2,or.r_gc.r_pw.&fp=63cdb7912cfe8baf&biw=1135&bih=661 • http://textbookofbacteriology.net/innate_3.html • http://www.nobelprize.org/educational/medicine/immunity/immune-detail.html • http://www.ibguides.com/biology/notes/defence-against-infectious-diseases • http://click4biology.info/c4b/6/hum6.3.htm • http://www.med.illinois.edu/hematology/PDF%20Files/Hemostasis.pdf • http://www.medicinenet.com/blood_clots/article.htm